PLT-7503: Create Message Export Scheduled Task and CLI Command (#7612)

* Created message export scheduled task

* Added CLI command to immediately kick off an export job

* Added email addresses for users joining and leaving the channel to the export

* Added support for both MySQL and PostgreSQL

* Fixing gofmt error

* Added a new ChannelMemberHistory store and associated tests

* Updating the ChannelMemberHistory channel as users create/join/leave channels

* Added user email to the message export object so it can be included in the actiance export xml

* Don't fail to log a leave event if a corresponding join event wasn't logged

* Adding copyright notices

* Adding message export settings to daily diagnostics report

* Added System Console integration for message export

* Cleaned up TODOs

* Made batch size configurable

* Added export from timestamp to CLI command

* Made ChannelMemberHistory table updates best effort

* Added a context-based timeout option to the message export CLI

* Minor PR updates/improvements

* Removed unnecessary fields from MessageExport object to reduce query overhead

* Removed JSON functions from the message export query in an effort to optimize performance

* Changed the way that channel member history queries and purges work to better account for edge cases

* Fixing a test I missed with the last refactor

* Added file copy functionality to file backend, improved config validation, added default config values

* Fixed file copy tests

* More concise use of the testing libraries

* Fixed context leak error

* Changed default export path to correctly place an 'export' directory under the 'data' directory

* Can't delete records from a read replica

* Fixed copy file tests

* Start job workers when license is applied, if configured to do so

* Suggestions from the PR

* Moar unit tests

* Fixed test imports

41 files changed, 1446 insertions, 59 deletions

diff --git a/app/app.go b/app/app.go
index 7bd4c561b..fd313c9c9 100644
--- a/app/app.go
+++ b/app/app.go
@@ -48,6 +48,7 @@ type App struct {
 	Elasticsearch    einterfaces.ElasticsearchInterface
 	Emoji            einterfaces.EmojiInterface
 	Ldap             einterfaces.LdapInterface
+	MessageExport    einterfaces.MessageExportInterface
 	Metrics          einterfaces.MetricsInterface
 	Mfa              einterfaces.MfaInterface
 	Saml             einterfaces.SamlInterface
@@ -198,6 +199,12 @@ func RegisterJobsDataRetentionJobInterface(f func(*App) ejobs.DataRetentionJobIn
 	jobsDataRetentionJobInterface = f
 }
 
+var jobsMessageExportJobInterface func(*App) ejobs.MessageExportJobInterface
+
+func RegisterJobsMessageExportJobInterface(f func(*App) ejobs.MessageExportJobInterface) {
+	jobsMessageExportJobInterface = f
+}
+
 var jobsElasticsearchAggregatorInterface func(*App) ejobs.ElasticsearchAggregatorInterface
 
 func RegisterJobsElasticsearchAggregatorInterface(f func(*App) ejobs.ElasticsearchAggregatorInterface) {
@@ -222,6 +229,12 @@ func RegisterLdapInterface(f func(*App) einterfaces.LdapInterface) {
 	ldapInterface = f
 }
 
+var messageExportInterface func(*App) einterfaces.MessageExportInterface
+
+func RegisterMessageExportInterface(f func(*App) einterfaces.MessageExportInterface) {
+	messageExportInterface = f
+}
+
 var metricsInterface func(*App) einterfaces.MetricsInterface
 
 func RegisterMetricsInterface(f func(*App) einterfaces.MetricsInterface) {
@@ -267,6 +280,9 @@ func (a *App) initEnterprise() {
 			}
 		})
 	}
+	if messageExportInterface != nil {
+		a.MessageExport = messageExportInterface(a)
+	}
 	if metricsInterface != nil {
 		a.Metrics = metricsInterface(a)
 	}
@@ -289,6 +305,9 @@ func (a *App) initJobs() {
 	if jobsDataRetentionJobInterface != nil {
 		a.Jobs.DataRetentionJob = jobsDataRetentionJobInterface(a)
 	}
+	if jobsMessageExportJobInterface != nil {
+		a.Jobs.MessageExportJob = jobsMessageExportJobInterface(a)
+	}
 	if jobsElasticsearchAggregatorInterface != nil {
 		a.Jobs.ElasticsearchAggregator = jobsElasticsearchAggregatorInterface(a)
 	}
diff --git a/app/channel.go b/app/channel.go
index 16c5dd084..caaacea06 100644
--- a/app/channel.go
+++ b/app/channel.go
@@ -49,12 +49,19 @@ func (a *App) JoinDefaultChannels(teamId string, user *model.User, channelRole s
 	} else {
 		townSquare := result.Data.(*model.Channel)
 
-		cm := &model.ChannelMember{ChannelId: townSquare.Id, UserId: user.Id,
-			Roles: channelRole, NotifyProps: model.GetDefaultChannelNotifyProps()}
+		cm := &model.ChannelMember{
+			ChannelId:   townSquare.Id,
+			UserId:      user.Id,
+			Roles:       channelRole,
+			NotifyProps: model.GetDefaultChannelNotifyProps(),
+		}
 
 		if cmResult := <-a.Srv.Store.Channel().SaveMember(cm); cmResult.Err != nil {
 			err = cmResult.Err
 		}
+		if result := <-a.Srv.Store.ChannelMemberHistory().LogJoinEvent(user.Id, townSquare.Id, model.GetMillis()); result.Err != nil {
+			l4g.Warn("Failed to update ChannelMemberHistory table %v", result.Err)
+		}
 
 		if requestor == nil {
 			if err := a.postJoinChannelMessage(user, townSquare); err != nil {
@@ -74,12 +81,19 @@ func (a *App) JoinDefaultChannels(teamId string, user *model.User, channelRole s
 	} else {
 		offTopic := result.Data.(*model.Channel)
 
-		cm := &model.ChannelMember{ChannelId: offTopic.Id, UserId: user.Id,
-			Roles: channelRole, NotifyProps: model.GetDefaultChannelNotifyProps()}
+		cm := &model.ChannelMember{
+			ChannelId:   offTopic.Id,
+			UserId:      user.Id,
+			Roles:       channelRole,
+			NotifyProps: model.GetDefaultChannelNotifyProps(),
+		}
 
 		if cmResult := <-a.Srv.Store.Channel().SaveMember(cm); cmResult.Err != nil {
 			err = cmResult.Err
 		}
+		if result := <-a.Srv.Store.ChannelMemberHistory().LogJoinEvent(user.Id, offTopic.Id, model.GetMillis()); result.Err != nil {
+			l4g.Warn("Failed to update ChannelMemberHistory table %v", result.Err)
+		}
 
 		if requestor == nil {
 			if err := a.postJoinChannelMessage(user, offTopic); err != nil {
@@ -158,6 +172,9 @@ func (a *App) CreateChannel(channel *model.Channel, addMember bool) (*model.Chan
 			if cmresult := <-a.Srv.Store.Channel().SaveMember(cm); cmresult.Err != nil {
 				return nil, cmresult.Err
 			}
+			if result := <-a.Srv.Store.ChannelMemberHistory().LogJoinEvent(channel.CreatorId, sc.Id, model.GetMillis()); result.Err != nil {
+				l4g.Warn("Failed to update ChannelMemberHistory table %v", result.Err)
+			}
 
 			a.InvalidateCacheForUser(channel.CreatorId)
 		}
@@ -302,6 +319,9 @@ func (a *App) createGroupChannel(userIds []string, creatorId string) (*model.Cha
 			if result := <-a.Srv.Store.Channel().SaveMember(cm); result.Err != nil {
 				return nil, result.Err
 			}
+			if result := <-a.Srv.Store.ChannelMemberHistory().LogJoinEvent(user.Id, channel.Id, model.GetMillis()); result.Err != nil {
+				l4g.Warn("Failed to update ChannelMemberHistory table %v", result.Err)
+			}
 		}
 
 		return channel, nil
@@ -520,9 +540,12 @@ func (a *App) addUserToChannel(user *model.User, channel *model.Channel, teamMem
 		l4g.Error("Failed to add member user_id=%v channel_id=%v err=%v", user.Id, channel.Id, result.Err)
 		return nil, model.NewAppError("AddUserToChannel", "api.channel.add_user.to.channel.failed.app_error", nil, "", http.StatusInternalServerError)
 	}
-
 	a.WaitForChannelMembership(channel.Id, user.Id)
 
+	if result := <-a.Srv.Store.ChannelMemberHistory().LogJoinEvent(user.Id, channel.Id, model.GetMillis()); result.Err != nil {
+		l4g.Warn("Failed to update ChannelMemberHistory table %v", result.Err)
+	}
+
 	a.InvalidateCacheForUser(user.Id)
 	a.InvalidateCacheForChannelMembers(channel.Id)
 
@@ -1069,6 +1092,9 @@ func (a *App) removeUserFromChannel(userIdToRemove string, removerUserId string,
 	if cmresult := <-a.Srv.Store.Channel().RemoveMember(channel.Id, userIdToRemove); cmresult.Err != nil {
 		return cmresult.Err
 	}
+	if cmhResult := <-a.Srv.Store.ChannelMemberHistory().LogLeaveEvent(userIdToRemove, channel.Id, model.GetMillis()); cmhResult.Err != nil {
+		return cmhResult.Err
+	}
 
 	a.InvalidateCacheForUser(userIdToRemove)
 	a.InvalidateCacheForChannelMembers(channel.Id)
diff --git a/app/channel_test.go b/app/channel_test.go
index 374b20657..d44af467d 100644
--- a/app/channel_test.go
+++ b/app/channel_test.go
@@ -1,9 +1,14 @@
+// Copyright (c) 2017-present Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
 package app
 
 import (
 	"testing"
 
 	"github.com/mattermost/mattermost-server/model"
+	"github.com/mattermost/mattermost-server/store"
+	"github.com/stretchr/testify/assert"
 )
 
 func TestPermanentDeleteChannel(t *testing.T) {
@@ -104,3 +109,164 @@ func TestMoveChannel(t *testing.T) {
 		t.Fatal(err)
 	}
 }
+
+func TestJoinDefaultChannelsTownSquare(t *testing.T) {
+	th := Setup().InitBasic()
+	defer th.TearDown()
+
+	// figure out the initial number of users in town square
+	townSquareChannelId := store.Must(th.App.Srv.Store.Channel().GetByName(th.BasicTeam.Id, "town-square", true)).(*model.Channel).Id
+	initialNumTownSquareUsers := len(store.Must(th.App.Srv.Store.ChannelMemberHistory().GetUsersInChannelDuring(model.GetMillis()-100, model.GetMillis()+100, townSquareChannelId)).([]*model.ChannelMemberHistory))
+
+	// create a new user that joins the default channels
+	user := th.CreateUser()
+	th.App.JoinDefaultChannels(th.BasicTeam.Id, user, model.CHANNEL_USER_ROLE_ID, "")
+
+	// there should be a ChannelMemberHistory record for the user
+	histories := store.Must(th.App.Srv.Store.ChannelMemberHistory().GetUsersInChannelDuring(model.GetMillis()-100, model.GetMillis()+100, townSquareChannelId)).([]*model.ChannelMemberHistory)
+	assert.Len(t, histories, initialNumTownSquareUsers+1)
+
+	found := false
+	for _, history := range histories {
+		if user.Id == history.UserId && townSquareChannelId == history.ChannelId {
+			found = true
+			break
+		}
+	}
+	assert.True(t, found)
+}
+
+func TestJoinDefaultChannelsOffTopic(t *testing.T) {
+	th := Setup().InitBasic()
+	defer th.TearDown()
+
+	// figure out the initial number of users in off-topic
+	offTopicChannelId := store.Must(th.App.Srv.Store.Channel().GetByName(th.BasicTeam.Id, "off-topic", true)).(*model.Channel).Id
+	initialNumTownSquareUsers := len(store.Must(th.App.Srv.Store.ChannelMemberHistory().GetUsersInChannelDuring(model.GetMillis()-100, model.GetMillis()+100, offTopicChannelId)).([]*model.ChannelMemberHistory))
+
+	// create a new user that joins the default channels
+	user := th.CreateUser()
+	th.App.JoinDefaultChannels(th.BasicTeam.Id, user, model.CHANNEL_USER_ROLE_ID, "")
+
+	// there should be a ChannelMemberHistory record for the user
+	histories := store.Must(th.App.Srv.Store.ChannelMemberHistory().GetUsersInChannelDuring(model.GetMillis()-100, model.GetMillis()+100, offTopicChannelId)).([]*model.ChannelMemberHistory)
+	assert.Len(t, histories, initialNumTownSquareUsers+1)
+
+	found := false
+	for _, history := range histories {
+		if user.Id == history.UserId && offTopicChannelId == history.ChannelId {
+			found = true
+			break
+		}
+	}
+	assert.True(t, found)
+}
+
+func TestCreateChannelPublic(t *testing.T) {
+	th := Setup().InitBasic()
+	defer th.TearDown()
+
+	// creates a public channel and adds basic user to it
+	publicChannel := th.createChannel(th.BasicTeam, model.CHANNEL_OPEN)
+
+	// there should be a ChannelMemberHistory record for the user
+	histories := store.Must(th.App.Srv.Store.ChannelMemberHistory().GetUsersInChannelDuring(model.GetMillis()-100, model.GetMillis()+100, publicChannel.Id)).([]*model.ChannelMemberHistory)
+	assert.Len(t, histories, 1)
+	assert.Equal(t, th.BasicUser.Id, histories[0].UserId)
+	assert.Equal(t, publicChannel.Id, histories[0].ChannelId)
+}
+
+func TestCreateChannelPrivate(t *testing.T) {
+	th := Setup().InitBasic()
+	defer th.TearDown()
+
+	// creates a private channel and adds basic user to it
+	privateChannel := th.createChannel(th.BasicTeam, model.CHANNEL_PRIVATE)
+
+	// there should be a ChannelMemberHistory record for the user
+	histories := store.Must(th.App.Srv.Store.ChannelMemberHistory().GetUsersInChannelDuring(model.GetMillis()-100, model.GetMillis()+100, privateChannel.Id)).([]*model.ChannelMemberHistory)
+	assert.Len(t, histories, 1)
+	assert.Equal(t, th.BasicUser.Id, histories[0].UserId)
+	assert.Equal(t, privateChannel.Id, histories[0].ChannelId)
+}
+
+func TestCreateGroupChannel(t *testing.T) {
+	th := Setup().InitBasic()
+	defer th.TearDown()
+
+	user1 := th.CreateUser()
+	user2 := th.CreateUser()
+
+	groupUserIds := make([]string, 0)
+	groupUserIds = append(groupUserIds, user1.Id)
+	groupUserIds = append(groupUserIds, user2.Id)
+	groupUserIds = append(groupUserIds, th.BasicUser.Id)
+
+	if channel, err := th.App.CreateGroupChannel(groupUserIds, th.BasicUser.Id); err != nil {
+		t.Fatal("Failed to create group channel. Error: " + err.Message)
+	} else {
+		// there should be a ChannelMemberHistory record for each user
+		histories := store.Must(th.App.Srv.Store.ChannelMemberHistory().GetUsersInChannelDuring(model.GetMillis()-100, model.GetMillis()+100, channel.Id)).([]*model.ChannelMemberHistory)
+		assert.Len(t, histories, 3)
+
+		channelMemberHistoryUserIds := make([]string, 0)
+		for _, history := range histories {
+			assert.Equal(t, channel.Id, history.ChannelId)
+			channelMemberHistoryUserIds = append(channelMemberHistoryUserIds, history.UserId)
+		}
+		assert.Equal(t, groupUserIds, channelMemberHistoryUserIds)
+	}
+}
+
+func TestAddUserToChannel(t *testing.T) {
+	th := Setup().InitBasic()
+	defer th.TearDown()
+
+	// create a user and add it to a channel
+	user := th.CreateUser()
+	if _, err := th.App.AddTeamMember(th.BasicTeam.Id, user.Id); err != nil {
+		t.Fatal("Failed to add user to team. Error: " + err.Message)
+	}
+
+	groupUserIds := make([]string, 0)
+	groupUserIds = append(groupUserIds, th.BasicUser.Id)
+	groupUserIds = append(groupUserIds, user.Id)
+
+	channel := th.createChannel(th.BasicTeam, model.CHANNEL_OPEN)
+	if _, err := th.App.AddUserToChannel(user, channel); err != nil {
+		t.Fatal("Failed to add user to channel. Error: " + err.Message)
+	}
+
+	// there should be a ChannelMemberHistory record for the user
+	histories := store.Must(th.App.Srv.Store.ChannelMemberHistory().GetUsersInChannelDuring(model.GetMillis()-100, model.GetMillis()+100, channel.Id)).([]*model.ChannelMemberHistory)
+	assert.Len(t, histories, 2)
+	channelMemberHistoryUserIds := make([]string, 0)
+	for _, history := range histories {
+		assert.Equal(t, channel.Id, history.ChannelId)
+		channelMemberHistoryUserIds = append(channelMemberHistoryUserIds, history.UserId)
+	}
+	assert.Equal(t, groupUserIds, channelMemberHistoryUserIds)
+}
+
+func TestRemoveUserFromChannel(t *testing.T) {
+	th := Setup().InitBasic()
+	defer th.TearDown()
+
+	// a user creates a channel
+	publicChannel := th.createChannel(th.BasicTeam, model.CHANNEL_OPEN)
+	histories := store.Must(th.App.Srv.Store.ChannelMemberHistory().GetUsersInChannelDuring(model.GetMillis()-100, model.GetMillis()+100, publicChannel.Id)).([]*model.ChannelMemberHistory)
+	assert.Len(t, histories, 1)
+	assert.Equal(t, th.BasicUser.Id, histories[0].UserId)
+	assert.Equal(t, publicChannel.Id, histories[0].ChannelId)
+	assert.Nil(t, histories[0].LeaveTime)
+
+	// the user leaves that channel
+	if err := th.App.LeaveChannel(publicChannel.Id, th.BasicUser.Id); err != nil {
+		t.Fatal("Failed to remove user from channel. Error: " + err.Message)
+	}
+	histories = store.Must(th.App.Srv.Store.ChannelMemberHistory().GetUsersInChannelDuring(model.GetMillis()-100, model.GetMillis()+100, publicChannel.Id)).([]*model.ChannelMemberHistory)
+	assert.Len(t, histories, 1)
+	assert.Equal(t, th.BasicUser.Id, histories[0].UserId)
+	assert.Equal(t, publicChannel.Id, histories[0].ChannelId)
+	assert.NotNil(t, histories[0].LeaveTime)
+}
diff --git a/app/diagnostics.go b/app/diagnostics.go
index 513cf11f5..3f37337ab 100644
--- a/app/diagnostics.go
+++ b/app/diagnostics.go
@@ -44,6 +44,7 @@ const (
 	TRACK_CONFIG_ELASTICSEARCH  = "config_elasticsearch"
 	TRACK_CONFIG_PLUGIN         = "config_plugin"
 	TRACK_CONFIG_DATA_RETENTION = "config_data_retention"
+	TRACK_CONFIG_MESSAGE_EXPORT = "config_message_export"
 
 	TRACK_ACTIVITY = "activity"
 	TRACK_LICENSE  = "license"
@@ -470,6 +471,13 @@ func (a *App) trackConfig() {
 		"file_retention_days":     *cfg.DataRetentionSettings.FileRetentionDays,
 		"deletion_job_start_time": *cfg.DataRetentionSettings.DeletionJobStartTime,
 	})
+
+	SendDiagnostic(TRACK_CONFIG_MESSAGE_EXPORT, map[string]interface{}{
+		"enable_message_export":         *cfg.MessageExportSettings.EnableExport,
+		"daily_run_time":                *cfg.MessageExportSettings.DailyRunTime,
+		"default_export_from_timestamp": *cfg.MessageExportSettings.ExportFromTimestamp,
+		"batch_size":                    *cfg.MessageExportSettings.BatchSize,
+	})
 }
 
 func trackLicense() {
diff --git a/app/diagnostics_test.go b/app/diagnostics_test.go
index 25bc75265..9b884fd43 100644
--- a/app/diagnostics_test.go
+++ b/app/diagnostics_test.go
@@ -135,6 +135,7 @@ func TestDiagnostics(t *testing.T) {
 			TRACK_CONFIG_PLUGIN,
 			TRACK_ACTIVITY,
 			TRACK_SERVER,
+			TRACK_CONFIG_MESSAGE_EXPORT,
 			TRACK_PLUGINS,
 		} {
 			if !strings.Contains(info, item) {
diff --git a/app/license.go b/app/license.go
index 18836c571..cacc71524 100644
--- a/app/license.go
+++ b/app/license.go
@@ -89,6 +89,16 @@ func (a *App) SaveLicense(licenseBytes []byte) (*model.License, *model.AppError)
 	a.ReloadConfig()
 	a.InvalidateAllCaches()
 
+	// start job server if necessary - this handles the edge case where a license file is uploaded, but the job server
+	// doesn't start until the server is restarted, which prevents the 'run job now' buttons in system console from
+	// functioning as expected
+	if *a.Config().JobSettings.RunJobs {
+		a.Jobs.StartWorkers()
+	}
+	if *a.Config().JobSettings.RunScheduler {
+		a.Jobs.StartSchedulers()
+	}
+
 	return license, nil
 }
 
diff --git a/cmd/platform/mattermost.go b/cmd/platform/mattermost.go
index 6c015c6db..be2ff8164 100644
--- a/cmd/platform/mattermost.go
+++ b/cmd/platform/mattermost.go
@@ -36,7 +36,7 @@ func init() {
 
 	resetCmd.Flags().Bool("confirm", false, "Confirm you really want to delete everything and a DB backup has been performed.")
 
-	rootCmd.AddCommand(serverCmd, versionCmd, userCmd, teamCmd, licenseCmd, importCmd, resetCmd, channelCmd, rolesCmd, testCmd, ldapCmd, configCmd, jobserverCmd, commandCmd)
+	rootCmd.AddCommand(serverCmd, versionCmd, userCmd, teamCmd, licenseCmd, importCmd, resetCmd, channelCmd, rolesCmd, testCmd, ldapCmd, configCmd, jobserverCmd, commandCmd, messageExportCmd)
 }
 
 var rootCmd = &cobra.Command{
diff --git a/cmd/platform/message_export.go b/cmd/platform/message_export.go
new file mode 100644
index 000000000..fb1f4073b
--- /dev/null
+++ b/cmd/platform/message_export.go
@@ -0,0 +1,79 @@
+// Copyright (c) 2016-present Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
+package main
+
+import (
+	"errors"
+
+	"context"
+
+	"time"
+
+	"github.com/mattermost/mattermost-server/model"
+	"github.com/spf13/cobra"
+)
+
+var messageExportCmd = &cobra.Command{
+	Use:     "export",
+	Short:   "Export data from Mattermost",
+	Long:    "Export data from Mattermost in a format suitable for import into a third-party application",
+	Example: "export --format=actiance --exportFrom=12345",
+	RunE:    messageExportCmdF,
+}
+
+func init() {
+	messageExportCmd.Flags().String("format", "actiance", "The format to export data in")
+	messageExportCmd.Flags().Int64("exportFrom", -1, "The timestamp of the earliest post to export, expressed in seconds since the unix epoch.")
+	messageExportCmd.Flags().Int("timeoutSeconds", -1, "The maximum number of seconds to wait for the job to complete before timing out.")
+}
+
+func messageExportCmdF(cmd *cobra.Command, args []string) error {
+	a, err := initDBCommandContextCobra(cmd)
+	if err != nil {
+		return err
+	}
+
+	if !*a.Config().MessageExportSettings.EnableExport {
+		return errors.New("ERROR: The message export feature is not enabled")
+	}
+
+	// for now, format is hard-coded to actiance. In time, we'll have to support other formats and inject them into job data
+	if format, err := cmd.Flags().GetString("format"); err != nil {
+		return errors.New("format flag error")
+	} else if format != "actiance" {
+		return errors.New("unsupported export format")
+	}
+
+	startTime, err := cmd.Flags().GetInt64("exportFrom")
+	if err != nil {
+		return errors.New("exportFrom flag error")
+	} else if startTime < 0 {
+		return errors.New("exportFrom must be a positive integer")
+	}
+
+	timeoutSeconds, err := cmd.Flags().GetInt("timeoutSeconds")
+	if err != nil {
+		return errors.New("timeoutSeconds error")
+	} else if timeoutSeconds < 0 {
+		return errors.New("timeoutSeconds must be a positive integer")
+	}
+
+	if messageExportI := a.MessageExport; messageExportI != nil {
+		ctx := context.Background()
+		if timeoutSeconds > 0 {
+			var cancel context.CancelFunc
+			ctx, cancel = context.WithTimeout(ctx, time.Second*time.Duration(timeoutSeconds))
+			defer cancel()
+		}
+
+		job, err := messageExportI.StartSynchronizeJob(ctx, startTime)
+		if err != nil || job.Status == model.JOB_STATUS_ERROR || job.Status == model.JOB_STATUS_CANCELED {
+			CommandPrintErrorln("ERROR: Message export job failed. Please check the server logs")
+		} else {
+			CommandPrettyPrintln("SUCCESS: Message export job complete")
+		}
+	}
+
+	return nil
+}
diff --git a/cmd/platform/message_export_test.go b/cmd/platform/message_export_test.go
new file mode 100644
index 000000000..211c1ca3c
--- /dev/null
+++ b/cmd/platform/message_export_test.go
@@ -0,0 +1,65 @@
+// Copyright (c) 2016-present Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
+package main
+
+import (
+	"testing"
+
+	"io/ioutil"
+	"os"
+	"path/filepath"
+
+	"github.com/mattermost/mattermost-server/model"
+	"github.com/mattermost/mattermost-server/utils"
+	"github.com/stretchr/testify/require"
+)
+
+// There are no tests that actually run the Message Export job, because it can take a long time to complete depending
+// on the size of the database that the config is pointing to. As such, these tests just ensure that the CLI command
+// fails fast if invalid flags are supplied
+
+func TestMessageExportNotEnabled(t *testing.T) {
+	configPath := writeTempConfig(t, false)
+	defer os.RemoveAll(filepath.Dir(configPath))
+
+	// should fail fast because the feature isn't enabled
+	require.Error(t, runCommand(t, "--config", configPath, "export"))
+}
+
+func TestMessageExportInvalidFormat(t *testing.T) {
+	configPath := writeTempConfig(t, true)
+	defer os.RemoveAll(filepath.Dir(configPath))
+
+	// should fail fast because format isn't supported
+	require.Error(t, runCommand(t, "--config", configPath, "--format", "not_actiance", "export"))
+}
+
+func TestMessageExportNegativeExportFrom(t *testing.T) {
+	configPath := writeTempConfig(t, true)
+	defer os.RemoveAll(filepath.Dir(configPath))
+
+	// should fail fast because export from must be a valid timestamp
+	require.Error(t, runCommand(t, "--config", configPath, "--format", "actiance", "--exportFrom", "-1", "export"))
+}
+
+func TestMessageExportNegativeTimeoutSeconds(t *testing.T) {
+	configPath := writeTempConfig(t, true)
+	defer os.RemoveAll(filepath.Dir(configPath))
+
+	// should fail fast because timeout seconds must be a positive int
+	require.Error(t, runCommand(t, "--config", configPath, "--format", "actiance", "--exportFrom", "0", "--timeoutSeconds", "-1", "export"))
+}
+
+func writeTempConfig(t *testing.T, isMessageExportEnabled bool) string {
+	dir, err := ioutil.TempDir("", "")
+	require.NoError(t, err)
+
+	utils.TranslationsPreInit()
+	config := utils.LoadGlobalConfig("config.json")
+	config.MessageExportSettings.EnableExport = model.NewBool(isMessageExportEnabled)
+	configPath := filepath.Join(dir, "foo.json")
+	require.NoError(t, ioutil.WriteFile(configPath, []byte(config.ToJson()), 0600))
+
+	return configPath
+}
diff --git a/config/default.json b/config/default.json
index e6f9cab1b..1c13c0f09 100644
--- a/config/default.json
+++ b/config/default.json
@@ -334,6 +334,13 @@
         "FileRetentionDays": 365,
         "DeletionJobStartTime": "02:00"
     },
+    "MessageExportSettings": {
+        "EnableExport": false,
+        "DailyRunTime": "01:00",
+        "ExportFromTimestamp": 0,
+        "FileLocation": "export",
+        "BatchSize": 10000
+    },
     "JobSettings": {
         "RunJobs": true,
         "RunScheduler": true
diff --git a/einterfaces/jobs/message_export.go b/einterfaces/jobs/message_export.go
new file mode 100644
index 000000000..74b0df751
--- /dev/null
+++ b/einterfaces/jobs/message_export.go
@@ -0,0 +1,13 @@
+// Copyright (c) 2017-present Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
+package jobs
+
+import (
+	"github.com/mattermost/mattermost-server/model"
+)
+
+type MessageExportJobInterface interface {
+	MakeWorker() model.Worker
+	MakeScheduler() model.Scheduler
+}
diff --git a/einterfaces/message_export.go b/einterfaces/message_export.go
new file mode 100644
index 000000000..ba498cdfb
--- /dev/null
+++ b/einterfaces/message_export.go
@@ -0,0 +1,14 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
+package einterfaces
+
+import (
+	"context"
+
+	"github.com/mattermost/mattermost-server/model"
+)
+
+type MessageExportInterface interface {
+	StartSynchronizeJob(ctx context.Context, exportFromTimestamp int64) (*model.Job, *model.AppError)
+}
diff --git a/i18n/en.json b/i18n/en.json
index f252ebe08..60b289f88 100644
--- a/i18n/en.json
+++ b/i18n/en.json
@@ -1333,6 +1333,10 @@
     "translation": "File storage not configured properly. Please configure for either S3 or local server file storage."
   },
   {
+    "id": "api.file.move_file.copy_within_s3.app_error",
+    "translation": "Unable to copy file within S3."
+  },
+  {
     "id": "api.file.move_file.delete_from_s3.app_error",
     "translation": "Unable to delete file from S3."
   },
@@ -3851,6 +3855,18 @@
     "translation": "License does not support Data Retention."
   },
   {
+    "id": "ent.message_export.generic.license.error",
+    "translation": "License does not support Message Export."
+  },
+  {
+    "id": "ent.elasticsearch.start.create_bulk_processor_failed.app_error",
+    "translation": "Failed to create Elasticsearch bulk processor"
+  },
+  {
+    "id": "ent.elasticsearch.start.start_bulk_processor_failed.app_error",
+    "translation": "Failed to start Elasticsearch bulk processor"
+  },
+  {
     "id": "ent.elasticsearch.aggregator_worker.create_index_job.error",
     "translation": "Elasticsearch aggregator worker failed to create the indexing job"
   },
@@ -4379,6 +4395,54 @@
     "translation": "Invalid user id"
   },
   {
+    "id": "model.channel_member_history.is_valid.channel_id.app_error",
+    "translation": "Invalid channel id"
+  },
+  {
+    "id": "model.channel_member_history.is_valid.user_id.app_error",
+    "translation": "Invalid user id"
+  },
+  {
+    "id": "model.channel_member_history.is_valid.user_email.app_error",
+    "translation": "Invalid user email"
+  },
+  {
+    "id": "model.channel_member_history.is_valid.join_time.app_error",
+    "translation": "Invalid join time"
+  },
+  {
+    "id": "model.channel_member_history.is_valid.leave_time.app_error",
+    "translation": "Invalid leave time"
+  },
+  {
+    "id": "store.sql_channel_member_history.log_join_event.app_error",
+    "translation": "Failed to record channel member history"
+  },
+  {
+    "id": "store.sql_channel_member_history.log_leave_event.select_error",
+    "translation": "Failed to record channel member history. No existing join record found"
+  },
+  {
+    "id": "store.sql_channel_member_history.log_leave_event.update_error",
+    "translation": "Failed to record channel member history. Failed to update existing join record"
+  },
+  {
+    "id": "store.sql_channel_member_history.get_users_in_channel_at.app_error",
+    "translation": "Failed to get users in channel at specified time"
+  },
+  {
+    "id": "store.sql_channel_member_history.get_users_in_channel_during.app_error",
+    "translation": "Failed to get users in channel during specified time period"
+  },
+  {
+    "id": "store.sql_channel_member_history.get_all.app_error",
+    "translation": "Failed to get records"
+  },
+  {
+    "id": "store.sql_channel_member_history.purge_history_before.app_error",
+    "translation": "Failed to purge records"
+  },
+  {
     "id": "model.client.connecting.app_error",
     "translation": "We encountered an error while connecting to the server"
   },
@@ -4879,6 +4943,30 @@
     "translation": "Invalid value for write timeout."
   },
   {
+    "id": "model.config.is_valid.message_export.enable.app_error",
+    "translation": "Message export job EnableExport setting must be either true or false"
+  },
+  {
+    "id": "model.config.is_valid.message_export.daily_runtime.app_error",
+    "translation": "Message export job DailyRuntime must be a 24-hour time stamp in the form HH:MM."
+  },
+  {
+    "id": "model.config.is_valid.message_export.export_from.app_error",
+    "translation": "Message export job ExportFromTimestamp must be a timestamp (expressed in seconds since unix epoch). Only messages sent after this timestamp will be exported."
+  },
+  {
+    "id": "model.config.is_valid.message_export.file_location.app_error",
+    "translation": "Message export job FileLocation must be a writable directory that export data will be written to"
+  },
+  {
+    "id": "model.config.is_valid.message_export.file_location.relative",
+    "translation": "Message export job FileLocation must be a sub-directory of FileSettings.Directory"
+  },
+  {
+    "id": "model.config.is_valid.message_export.batch_size.app_error",
+    "translation": "Message export job BatchSize must be a positive integer"
+  },
+  {
     "id": "model.emoji.create_at.app_error",
     "translation": "Create at must be a valid time"
   },
@@ -5475,6 +5563,10 @@
     "translation": "The database schema has been upgraded to version %v"
   },
   {
+    "id": "store.sql_compliance.message_export.app_error",
+    "translation": "Failed to select message export data"
+  },
+  {
     "id": "store.sql_audit.get.finding.app_error",
     "translation": "We encountered an error finding the audits"
   },
diff --git a/jobs/jobs_watcher.go b/jobs/jobs_watcher.go
index b36a99051..f519e7cca 100644
--- a/jobs/jobs_watcher.go
+++ b/jobs/jobs_watcher.go
@@ -78,6 +78,13 @@ func (watcher *Watcher) PollAndNotify() {
 					default:
 					}
 				}
+			} else if job.Type == model.JOB_TYPE_MESSAGE_EXPORT {
+				if watcher.workers.MessageExport != nil {
+					select {
+					case watcher.workers.MessageExport.JobChannel() <- *job:
+					default:
+					}
+				}
 			} else if job.Type == model.JOB_TYPE_ELASTICSEARCH_POST_INDEXING {
 				if watcher.workers.ElasticsearchIndexing != nil {
 					select {
diff --git a/jobs/schedulers.go b/jobs/schedulers.go
index cbe5f1749..bec53a49b 100644
--- a/jobs/schedulers.go
+++ b/jobs/schedulers.go
@@ -39,6 +39,10 @@ func (srv *JobServer) InitSchedulers() *Schedulers {
 		schedulers.schedulers = append(schedulers.schedulers, srv.DataRetentionJob.MakeScheduler())
 	}
 
+	if srv.MessageExportJob != nil {
+		schedulers.schedulers = append(schedulers.schedulers, srv.MessageExportJob.MakeScheduler())
+	}
+
 	if elasticsearchAggregatorInterface := srv.ElasticsearchAggregator; elasticsearchAggregatorInterface != nil {
 		schedulers.schedulers = append(schedulers.schedulers, elasticsearchAggregatorInterface.MakeScheduler())
 	}
diff --git a/jobs/server.go b/jobs/server.go
index 40cfb1f64..777b02a26 100644
--- a/jobs/server.go
+++ b/jobs/server.go
@@ -19,6 +19,7 @@ type JobServer struct {
 	Schedulers *Schedulers
 
 	DataRetentionJob        ejobs.DataRetentionJobInterface
+	MessageExportJob        ejobs.MessageExportJobInterface
 	ElasticsearchAggregator ejobs.ElasticsearchAggregatorInterface
 	ElasticsearchIndexer    ejobs.ElasticsearchIndexerInterface
 	LdapSync                ejobs.LdapSyncInterface
diff --git a/jobs/workers.go b/jobs/workers.go
index b1d275658..3abd7131c 100644
--- a/jobs/workers.go
+++ b/jobs/workers.go
@@ -17,6 +17,7 @@ type Workers struct {
 	Watcher   *Watcher
 
 	DataRetention            model.Worker
+	MessageExport            model.Worker
 	ElasticsearchIndexing    model.Worker
 	ElasticsearchAggregation model.Worker
 	LdapSync                 model.Worker
@@ -34,6 +35,10 @@ func (srv *JobServer) InitWorkers() *Workers {
 		workers.DataRetention = srv.DataRetentionJob.MakeWorker()
 	}
 
+	if srv.MessageExportJob != nil {
+		workers.MessageExport = srv.MessageExportJob.MakeWorker()
+	}
+
 	if elasticsearchIndexerInterface := srv.ElasticsearchIndexer; elasticsearchIndexerInterface != nil {
 		workers.ElasticsearchIndexing = elasticsearchIndexerInterface.MakeWorker()
 	}
@@ -57,6 +62,10 @@ func (workers *Workers) Start() *Workers {
 			go workers.DataRetention.Run()
 		}
 
+		if workers.MessageExport != nil && *workers.Config().MessageExportSettings.EnableExport {
+			go workers.MessageExport.Run()
+		}
+
 		if workers.ElasticsearchIndexing != nil && *workers.Config().ElasticsearchSettings.EnableIndexing {
 			go workers.ElasticsearchIndexing.Run()
 		}
@@ -86,6 +95,14 @@ func (workers *Workers) handleConfigChange(oldConfig *model.Config, newConfig *m
 		}
 	}
 
+	if workers.MessageExport != nil {
+		if !*oldConfig.MessageExportSettings.EnableExport && *newConfig.MessageExportSettings.EnableExport {
+			go workers.MessageExport.Run()
+		} else if *oldConfig.MessageExportSettings.EnableExport && !*newConfig.MessageExportSettings.EnableExport {
+			workers.MessageExport.Stop()
+		}
+	}
+
 	if workers.ElasticsearchIndexing != nil {
 		if !*oldConfig.ElasticsearchSettings.EnableIndexing && *newConfig.ElasticsearchSettings.EnableIndexing {
 			go workers.ElasticsearchIndexing.Run()
@@ -120,6 +137,10 @@ func (workers *Workers) Stop() *Workers {
 		workers.DataRetention.Stop()
 	}
 
+	if workers.MessageExport != nil && *workers.Config().MessageExportSettings.EnableExport {
+		workers.MessageExport.Stop()
+	}
+
 	if workers.ElasticsearchIndexing != nil && *workers.Config().ElasticsearchSettings.EnableIndexing {
 		workers.ElasticsearchIndexing.Stop()
 	}
diff --git a/model/channel_member_history.go b/model/channel_member_history.go
new file mode 100644
index 000000000..bc71b580a
--- /dev/null
+++ b/model/channel_member_history.go
@@ -0,0 +1,12 @@
+// Copyright (c) 2017-present Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
+package model
+
+type ChannelMemberHistory struct {
+	ChannelId string
+	UserId    string
+	UserEmail string `db:"Email"`
+	JoinTime  int64
+	LeaveTime *int64
+}
diff --git a/model/config.go b/model/config.go
index e2f05d72e..1f56eb4f5 100644
--- a/model/config.go
+++ b/model/config.go
@@ -8,6 +8,7 @@ import (
 	"io"
 	"net/http"
 	"net/url"
+	"path/filepath"
 	"strings"
 	"time"
 )
@@ -1508,6 +1509,36 @@ func (s *PluginSettings) SetDefaults() {
 	}
 }
 
+type MessageExportSettings struct {
+	EnableExport        *bool
+	DailyRunTime        *string
+	ExportFromTimestamp *int64
+	FileLocation        *string
+	BatchSize           *int
+}
+
+func (s *MessageExportSettings) SetDefaults() {
+	if s.EnableExport == nil {
+		s.EnableExport = NewBool(false)
+	}
+
+	if s.FileLocation == nil {
+		s.FileLocation = NewString("export")
+	}
+
+	if s.DailyRunTime == nil {
+		s.DailyRunTime = NewString("01:00")
+	}
+
+	if s.ExportFromTimestamp == nil {
+		s.ExportFromTimestamp = NewInt64(0)
+	}
+
+	if s.BatchSize == nil {
+		s.BatchSize = NewInt(10000)
+	}
+}
+
 type ConfigFunc func() *Config
 
 type Config struct {
@@ -1538,6 +1569,7 @@ type Config struct {
 	WebrtcSettings        WebrtcSettings
 	ElasticsearchSettings ElasticsearchSettings
 	DataRetentionSettings DataRetentionSettings
+	MessageExportSettings MessageExportSettings
 	JobSettings           JobSettings
 	PluginSettings        PluginSettings
 }
@@ -1617,6 +1649,7 @@ func (o *Config) SetDefaults() {
 	o.LogSettings.SetDefaults()
 	o.JobSettings.SetDefaults()
 	o.WebrtcSettings.SetDefaults()
+	o.MessageExportSettings.SetDefaults()
 }
 
 func (o *Config) IsValid() *AppError {
@@ -1680,6 +1713,10 @@ func (o *Config) IsValid() *AppError {
 		return err
 	}
 
+	if err := o.MessageExportSettings.isValid(o.FileSettings); err != nil {
+		return err
+	}
+
 	return nil
 }
 
@@ -1998,6 +2035,35 @@ func (ls *LocalizationSettings) isValid() *AppError {
 	return nil
 }
 
+func (mes *MessageExportSettings) isValid(fs FileSettings) *AppError {
+	if mes.EnableExport == nil {
+		return NewAppError("Config.IsValid", "model.config.is_valid.message_export.enable.app_error", nil, "", http.StatusBadRequest)
+	}
+	if *mes.EnableExport {
+		if mes.ExportFromTimestamp == nil || *mes.ExportFromTimestamp < 0 || *mes.ExportFromTimestamp > time.Now().Unix() {
+			return NewAppError("Config.IsValid", "model.config.is_valid.message_export.export_from.app_error", nil, "", http.StatusBadRequest)
+		} else if mes.DailyRunTime == nil {
+			return NewAppError("Config.IsValid", "model.config.is_valid.message_export.daily_runtime.app_error", nil, "", http.StatusBadRequest)
+		} else if _, err := time.Parse("15:04", *mes.DailyRunTime); err != nil {
+			return NewAppError("Config.IsValid", "model.config.is_valid.message_export.daily_runtime.app_error", nil, err.Error(), http.StatusBadRequest)
+		} else if mes.FileLocation == nil {
+			return NewAppError("Config.IsValid", "model.config.is_valid.message_export.file_location.app_error", nil, "", http.StatusBadRequest)
+		} else if mes.BatchSize == nil || *mes.BatchSize < 0 {
+			return NewAppError("Config.IsValid", "model.config.is_valid.message_export.batch_size.app_error", nil, "", http.StatusBadRequest)
+		} else if *fs.DriverName != IMAGE_DRIVER_LOCAL {
+			if absFileDir, err := filepath.Abs(fs.Directory); err != nil {
+				return NewAppError("Config.IsValid", "model.config.is_valid.message_export.file_location.relative", nil, err.Error(), http.StatusBadRequest)
+			} else if absMessageExportDir, err := filepath.Abs(*mes.FileLocation); err != nil {
+				return NewAppError("Config.IsValid", "model.config.is_valid.message_export.file_location.relative", nil, err.Error(), http.StatusBadRequest)
+			} else if !strings.HasPrefix(absMessageExportDir, absFileDir) {
+				// configured export directory must be relative to data directory
+				return NewAppError("Config.IsValid", "model.config.is_valid.message_export.file_location.relative", nil, "", http.StatusBadRequest)
+			}
+		}
+	}
+	return nil
+}
+
 func (o *Config) GetSanitizeOptions() map[string]bool {
 	options := map[string]bool{}
 	options["fullname"] = o.PrivacySettings.ShowFullName
diff --git a/model/config_test.go b/model/config_test.go
index 86958458c..58f690165 100644
--- a/model/config_test.go
+++ b/model/config_test.go
@@ -5,6 +5,10 @@ package model
 
 import (
 	"testing"
+
+	"os"
+
+	"github.com/stretchr/testify/require"
 )
 
 func TestConfigDefaultFileSettingsDirectory(t *testing.T) {
@@ -33,3 +37,109 @@ func TestConfigDefaultFileSettingsS3SSE(t *testing.T) {
 		t.Fatal("FileSettings.AmazonS3SSE should default to false")
 	}
 }
+
+func TestMessageExportSettingsIsValidEnableExportNotSet(t *testing.T) {
+	fs := &FileSettings{}
+	mes := &MessageExportSettings{}
+
+	// should fail fast because mes.EnableExport is not set
+	require.Error(t, mes.isValid(*fs))
+}
+
+func TestMessageExportSettingsIsValidEnableExportFalse(t *testing.T) {
+	fs := &FileSettings{}
+	mes := &MessageExportSettings{
+		EnableExport: NewBool(false),
+	}
+
+	// should fail fast because message export isn't enabled
+	require.Nil(t, mes.isValid(*fs))
+}
+
+func TestMessageExportSettingsIsValidExportFromTimestampInvalid(t *testing.T) {
+	fs := &FileSettings{}
+	mes := &MessageExportSettings{
+		EnableExport: NewBool(true),
+	}
+
+	// should fail fast because export from timestamp isn't set
+	require.Error(t, mes.isValid(*fs))
+
+	mes.ExportFromTimestamp = NewInt64(-1)
+
+	// should fail fast because export from timestamp isn't valid
+	require.Error(t, mes.isValid(*fs))
+
+	mes.ExportFromTimestamp = NewInt64(GetMillis() + 10000)
+
+	// should fail fast because export from timestamp is greater than current time
+	require.Error(t, mes.isValid(*fs))
+}
+
+func TestMessageExportSettingsIsValidDailyRunTimeInvalid(t *testing.T) {
+	fs := &FileSettings{}
+	mes := &MessageExportSettings{
+		EnableExport:        NewBool(true),
+		ExportFromTimestamp: NewInt64(0),
+	}
+
+	// should fail fast because daily runtime isn't set
+	require.Error(t, mes.isValid(*fs))
+
+	mes.DailyRunTime = NewString("33:33:33")
+
+	// should fail fast because daily runtime is invalid format
+	require.Error(t, mes.isValid(*fs))
+}
+
+func TestMessageExportSettingsIsValidBatchSizeInvalid(t *testing.T) {
+	fs := &FileSettings{
+		DriverName: NewString("foo"), // bypass file location check
+	}
+	mes := &MessageExportSettings{
+		EnableExport:        NewBool(true),
+		ExportFromTimestamp: NewInt64(0),
+		DailyRunTime:        NewString("15:04"),
+		FileLocation:        NewString("foo"),
+	}
+
+	// should fail fast because batch size isn't set
+	require.Error(t, mes.isValid(*fs))
+}
+
+func TestMessageExportSettingsIsValidFileLocationInvalid(t *testing.T) {
+	fs := &FileSettings{}
+	mes := &MessageExportSettings{
+		EnableExport:        NewBool(true),
+		ExportFromTimestamp: NewInt64(0),
+		DailyRunTime:        NewString("15:04"),
+		BatchSize:           NewInt(100),
+	}
+
+	// should fail fast because FileLocation isn't set
+	require.Error(t, mes.isValid(*fs))
+
+	// if using the local file driver, there are more rules for FileLocation
+	fs.DriverName = NewString(IMAGE_DRIVER_LOCAL)
+	fs.Directory, _ = os.Getwd()
+	mes.FileLocation = NewString("")
+
+	// should fail fast because file location is not relative to basepath
+	require.Error(t, mes.isValid(*fs))
+}
+
+func TestMessageExportSettingsIsValid(t *testing.T) {
+	fs := &FileSettings{
+		DriverName: NewString("foo"), // bypass file location check
+	}
+	mes := &MessageExportSettings{
+		EnableExport:        NewBool(true),
+		ExportFromTimestamp: NewInt64(0),
+		DailyRunTime:        NewString("15:04"),
+		FileLocation:        NewString("foo"),
+		BatchSize:           NewInt(100),
+	}
+
+	// should pass because everything is valid
+	require.Nil(t, mes.isValid(*fs))
+}
diff --git a/model/job.go b/model/job.go
index 843d73fad..9a7566025 100644
--- a/model/job.go
+++ b/model/job.go
@@ -12,6 +12,7 @@ import (
 
 const (
 	JOB_TYPE_DATA_RETENTION                 = "data_retention"
+	JOB_TYPE_MESSAGE_EXPORT                 = "message_export"
 	JOB_TYPE_ELASTICSEARCH_POST_INDEXING    = "elasticsearch_post_indexing"
 	JOB_TYPE_ELASTICSEARCH_POST_AGGREGATION = "elasticsearch_post_aggregation"
 	JOB_TYPE_LDAP_SYNC                      = "ldap_sync"
@@ -50,6 +51,7 @@ func (j *Job) IsValid() *AppError {
 	case JOB_TYPE_ELASTICSEARCH_POST_INDEXING:
 	case JOB_TYPE_ELASTICSEARCH_POST_AGGREGATION:
 	case JOB_TYPE_LDAP_SYNC:
+	case JOB_TYPE_MESSAGE_EXPORT:
 	default:
 		return NewAppError("Job.IsValid", "model.job.is_valid.type.app_error", nil, "id="+j.Id, http.StatusBadRequest)
 	}
diff --git a/model/license.go b/model/license.go
index 3e42a2343..a81f882ca 100644
--- a/model/license.go
+++ b/model/license.go
@@ -55,6 +55,7 @@ type Features struct {
 	ThemeManagement           *bool `json:"theme_management"`
 	EmailNotificationContents *bool `json:"email_notification_contents"`
 	DataRetention             *bool `json:"data_retention"`
+	MessageExport             *bool `json:"message_export"`
 
 	// after we enabled more features for webrtc we'll need to control them with this
 	FutureFeatures *bool `json:"future_features"`
@@ -76,6 +77,7 @@ func (f *Features) ToMap() map[string]interface{} {
 		"elastic_search":              *f.Elasticsearch,
 		"email_notification_contents": *f.EmailNotificationContents,
 		"data_retention":              *f.DataRetention,
+		"message_export":              *f.MessageExport,
 		"future":                      *f.FutureFeatures,
 	}
 }
@@ -152,6 +154,10 @@ func (f *Features) SetDefaults() {
 	if f.DataRetention == nil {
 		f.DataRetention = NewBool(*f.FutureFeatures)
 	}
+
+	if f.MessageExport == nil {
+		f.MessageExport = NewBool(*f.FutureFeatures)
+	}
 }
 
 func (l *License) IsExpired() bool {
diff --git a/model/message_export.go b/model/message_export.go
new file mode 100644
index 000000000..b59b114d4
--- /dev/null
+++ b/model/message_export.go
@@ -0,0 +1,18 @@
+// Copyright (c) 2017-present Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
+package model
+
+type MessageExport struct {
+	ChannelId          *string
+	ChannelDisplayName *string
+
+	UserId    *string
+	UserEmail *string
+
+	PostId       *string
+	PostCreateAt *int64
+	PostMessage  *string
+	PostType     *string
+	PostFileIds  StringArray
+}
diff --git a/store/layered_store.go b/store/layered_store.go
index ecf02864c..65b4670c0 100644
--- a/store/layered_store.go
+++ b/store/layered_store.go
@@ -153,6 +153,10 @@ func (s *LayeredStore) UserAccessToken() UserAccessTokenStore {
 	return s.DatabaseLayer.UserAccessToken()
 }
 
+func (s *LayeredStore) ChannelMemberHistory() ChannelMemberHistoryStore {
+	return s.DatabaseLayer.ChannelMemberHistory()
+}
+
 func (s *LayeredStore) Plugin() PluginStore {
 	return s.DatabaseLayer.Plugin()
 }
diff --git a/store/sqlstore/channel_member_history_store.go b/store/sqlstore/channel_member_history_store.go
new file mode 100644
index 000000000..20d0d3335
--- /dev/null
+++ b/store/sqlstore/channel_member_history_store.go
@@ -0,0 +1,102 @@
+// Copyright (c) 2017-present Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
+package sqlstore
+
+import (
+	"net/http"
+
+	l4g "github.com/alecthomas/log4go"
+	"github.com/mattermost/mattermost-server/model"
+	"github.com/mattermost/mattermost-server/store"
+)
+
+type SqlChannelMemberHistoryStore struct {
+	SqlStore
+}
+
+func NewSqlChannelMemberHistoryStore(sqlStore SqlStore) store.ChannelMemberHistoryStore {
+	s := &SqlChannelMemberHistoryStore{
+		SqlStore: sqlStore,
+	}
+
+	for _, db := range sqlStore.GetAllConns() {
+		table := db.AddTableWithName(model.ChannelMemberHistory{}, "ChannelMemberHistory").SetKeys(false, "ChannelId", "UserId", "JoinTime")
+		table.ColMap("ChannelId").SetMaxSize(26)
+		table.ColMap("UserId").SetMaxSize(26)
+		table.ColMap("JoinTime").SetNotNull(true)
+	}
+
+	return s
+}
+
+func (s SqlChannelMemberHistoryStore) LogJoinEvent(userId string, channelId string, joinTime int64) store.StoreChannel {
+	return store.Do(func(result *store.StoreResult) {
+		channelMemberHistory := &model.ChannelMemberHistory{
+			UserId:    userId,
+			ChannelId: channelId,
+			JoinTime:  joinTime,
+		}
+
+		if err := s.GetMaster().Insert(channelMemberHistory); err != nil {
+			result.Err = model.NewAppError("SqlChannelMemberHistoryStore.LogJoinEvent", "store.sql_channel_member_history.log_join_event.app_error", map[string]interface{}{"ChannelMemberHistory": channelMemberHistory}, err.Error(), http.StatusInternalServerError)
+		}
+	})
+}
+
+func (s SqlChannelMemberHistoryStore) LogLeaveEvent(userId string, channelId string, leaveTime int64) store.StoreChannel {
+	return store.Do(func(result *store.StoreResult) {
+		query := `
+			UPDATE ChannelMemberHistory
+			SET LeaveTime = :LeaveTime
+			WHERE UserId = :UserId
+			AND ChannelId = :ChannelId
+			AND LeaveTime IS NULL`
+
+		params := map[string]interface{}{"UserId": userId, "ChannelId": channelId, "LeaveTime": leaveTime}
+		if sqlResult, err := s.GetMaster().Exec(query, params); err != nil {
+			result.Err = model.NewAppError("SqlChannelMemberHistoryStore.LogLeaveEvent", "store.sql_channel_member_history.log_leave_event.update_error", nil, err.Error(), http.StatusInternalServerError)
+		} else if rows, err := sqlResult.RowsAffected(); err == nil && rows != 1 {
+			// there was no join event to update
+			l4g.Warn("Channel join event for user %v and channel %v not found", userId, channelId)
+		}
+	})
+}
+
+func (s SqlChannelMemberHistoryStore) GetUsersInChannelDuring(startTime int64, endTime int64, channelId string) store.StoreChannel {
+	return store.Do(func(result *store.StoreResult) {
+		query := `
+			SELECT
+				cmh.*,
+				u.Email
+			FROM ChannelMemberHistory cmh
+			INNER JOIN Users u ON cmh.UserId = u.Id
+			WHERE cmh.ChannelId = :ChannelId
+			AND cmh.JoinTime <= :EndTime
+			AND (cmh.LeaveTime IS NULL OR cmh.LeaveTime >= :StartTime)
+			ORDER BY cmh.JoinTime ASC`
+
+		params := map[string]interface{}{"ChannelId": channelId, "StartTime": startTime, "EndTime": endTime}
+		var histories []*model.ChannelMemberHistory
+		if _, err := s.GetReplica().Select(&histories, query, params); err != nil {
+			result.Err = model.NewAppError("SqlChannelMemberHistoryStore.GetUsersInChannelAt", "store.sql_channel_member_history.get_users_in_channel_during.app_error", params, err.Error(), http.StatusInternalServerError)
+		} else {
+			result.Data = histories
+		}
+	})
+}
+
+func (s SqlChannelMemberHistoryStore) PurgeHistoryBefore(time int64, channelId string) store.StoreChannel {
+	return store.Do(func(result *store.StoreResult) {
+		query := `
+			DELETE FROM ChannelMemberHistory
+			WHERE ChannelId = :ChannelId
+			AND LeaveTime IS NOT NULL
+			AND LeaveTime <= :AtTime`
+
+		params := map[string]interface{}{"AtTime": time, "ChannelId": channelId}
+		if _, err := s.GetMaster().Exec(query, params); err != nil {
+			result.Err = model.NewAppError("SqlChannelMemberHistoryStore.PurgeHistoryBefore", "store.sql_channel_member_history.purge_history_before.app_error", params, err.Error(), http.StatusInternalServerError)
+		}
+	})
+}
diff --git a/store/sqlstore/channel_member_history_store_test.go b/store/sqlstore/channel_member_history_store_test.go
new file mode 100644
index 000000000..c1119d227
--- /dev/null
+++ b/store/sqlstore/channel_member_history_store_test.go
@@ -0,0 +1,14 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
+package sqlstore
+
+import (
+	"testing"
+
+	"github.com/mattermost/mattermost-server/store/storetest"
+)
+
+func TestChannelMemberHistoryStore(t *testing.T) {
+	StoreTest(t, storetest.TestChannelMemberHistoryStore)
+}
diff --git a/store/sqlstore/compliance_store.go b/store/sqlstore/compliance_store.go
index 3d638b1fd..a25b01548 100644
--- a/store/sqlstore/compliance_store.go
+++ b/store/sqlstore/compliance_store.go
@@ -211,3 +211,36 @@ func (s SqlComplianceStore) ComplianceExport(job *model.Compliance) store.StoreC
 		}
 	})
 }
+
+func (s SqlComplianceStore) MessageExport(after int64, limit int) store.StoreChannel {
+	return store.Do(func(result *store.StoreResult) {
+		props := map[string]interface{}{"StartTime": after, "Limit": limit}
+		query :=
+			`SELECT
+				Posts.Id AS PostId,
+				Posts.CreateAt AS PostCreateAt,
+				Posts.Message AS PostMessage,
+				Posts.Type AS PostType,
+				Posts.FileIds AS PostFileIds,
+				Channels.Id AS ChannelId,
+				Channels.DisplayName AS ChannelDisplayName,
+				Users.Id AS UserId,
+				Users.Email AS UserEmail
+			FROM
+				Posts
+				LEFT OUTER JOIN Channels ON Posts.ChannelId = Channels.Id
+				LEFT OUTER JOIN Users ON Posts.UserId = Users.Id
+			WHERE
+				Posts.CreateAt > :StartTime AND
+				Posts.Type = ''
+			ORDER BY PostCreateAt
+			LIMIT :Limit`
+
+		var cposts []*model.MessageExport
+		if _, err := s.GetReplica().Select(&cposts, query, props); err != nil {
+			result.Err = model.NewAppError("SqlComplianceStore.MessageExport", "store.sql_compliance.message_export.app_error", nil, err.Error(), http.StatusInternalServerError)
+		} else {
+			result.Data = cposts
+		}
+	})
+}
diff --git a/store/sqlstore/supplier.go b/store/sqlstore/supplier.go
index dbe4aa92c..3b9528578 100644
--- a/store/sqlstore/supplier.go
+++ b/store/sqlstore/supplier.go
@@ -62,29 +62,30 @@ const (
 )
 
 type SqlSupplierOldStores struct {
-	team            store.TeamStore
-	channel         store.ChannelStore
-	post            store.PostStore
-	user            store.UserStore
-	audit           store.AuditStore
-	cluster         store.ClusterDiscoveryStore
-	compliance      store.ComplianceStore
-	session         store.SessionStore
-	oauth           store.OAuthStore
-	system          store.SystemStore
-	webhook         store.WebhookStore
-	command         store.CommandStore
-	commandWebhook  store.CommandWebhookStore
-	preference      store.PreferenceStore
-	license         store.LicenseStore
-	token           store.TokenStore
-	emoji           store.EmojiStore
-	status          store.StatusStore
-	fileInfo        store.FileInfoStore
-	reaction        store.ReactionStore
-	job             store.JobStore
-	userAccessToken store.UserAccessTokenStore
-	plugin          store.PluginStore
+	team                 store.TeamStore
+	channel              store.ChannelStore
+	post                 store.PostStore
+	user                 store.UserStore
+	audit                store.AuditStore
+	cluster              store.ClusterDiscoveryStore
+	compliance           store.ComplianceStore
+	session              store.SessionStore
+	oauth                store.OAuthStore
+	system               store.SystemStore
+	webhook              store.WebhookStore
+	command              store.CommandStore
+	commandWebhook       store.CommandWebhookStore
+	preference           store.PreferenceStore
+	license              store.LicenseStore
+	token                store.TokenStore
+	emoji                store.EmojiStore
+	status               store.StatusStore
+	fileInfo             store.FileInfoStore
+	reaction             store.ReactionStore
+	job                  store.JobStore
+	userAccessToken      store.UserAccessTokenStore
+	plugin               store.PluginStore
+	channelMemberHistory store.ChannelMemberHistoryStore
 }
 
 type SqlSupplier struct {
@@ -130,6 +131,7 @@ func NewSqlSupplier(settings model.SqlSettings, metrics einterfaces.MetricsInter
 	supplier.oldStores.fileInfo = NewSqlFileInfoStore(supplier, metrics)
 	supplier.oldStores.job = NewSqlJobStore(supplier)
 	supplier.oldStores.userAccessToken = NewSqlUserAccessTokenStore(supplier)
+	supplier.oldStores.channelMemberHistory = NewSqlChannelMemberHistoryStore(supplier)
 	supplier.oldStores.plugin = NewSqlPluginStore(supplier)
 
 	initSqlSupplierReactions(supplier)
@@ -801,6 +803,10 @@ func (ss *SqlSupplier) UserAccessToken() store.UserAccessTokenStore {
 	return ss.oldStores.userAccessToken
 }
 
+func (ss *SqlSupplier) ChannelMemberHistory() store.ChannelMemberHistoryStore {
+	return ss.oldStores.channelMemberHistory
+}
+
 func (ss *SqlSupplier) Plugin() store.PluginStore {
 	return ss.oldStores.plugin
 }
diff --git a/store/store.go b/store/store.go
index 3c950495d..c95888c22 100644
--- a/store/store.go
+++ b/store/store.go
@@ -63,6 +63,7 @@ type Store interface {
 	Reaction() ReactionStore
 	Job() JobStore
 	UserAccessToken() UserAccessTokenStore
+	ChannelMemberHistory() ChannelMemberHistoryStore
 	Plugin() PluginStore
 	MarkSystemRanUnitTests()
 	Close()
@@ -160,6 +161,13 @@ type ChannelStore interface {
 	GetChannelUnread(channelId, userId string) StoreChannel
 }
 
+type ChannelMemberHistoryStore interface {
+	LogJoinEvent(userId string, channelId string, joinTime int64) StoreChannel
+	LogLeaveEvent(userId string, channelId string, leaveTime int64) StoreChannel
+	GetUsersInChannelDuring(startTime int64, endTime int64, channelId string) StoreChannel
+	PurgeHistoryBefore(time int64, channelId string) StoreChannel
+}
+
 type PostStore interface {
 	Save(post *model.Post) StoreChannel
 	Update(newPost *model.Post, oldPost *model.Post) StoreChannel
@@ -276,6 +284,7 @@ type ComplianceStore interface {
 	Get(id string) StoreChannel
 	GetAll(offset, limit int) StoreChannel
 	ComplianceExport(compliance *model.Compliance) StoreChannel
+	MessageExport(after int64, limit int) StoreChannel
 }
 
 type OAuthStore interface {
diff --git a/store/storetest/channel_member_history_store.go b/store/storetest/channel_member_history_store.go
new file mode 100644
index 000000000..c73a25f65
--- /dev/null
+++ b/store/storetest/channel_member_history_store.go
@@ -0,0 +1,179 @@
+// Copyright (c) 2017-present Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
+package storetest
+
+import (
+	"testing"
+
+	"github.com/mattermost/mattermost-server/model"
+	"github.com/mattermost/mattermost-server/store"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestChannelMemberHistoryStore(t *testing.T, ss store.Store) {
+	t.Run("Log Join Event", func(t *testing.T) { testLogJoinEvent(t, ss) })
+	t.Run("Log Leave Event", func(t *testing.T) { testLogLeaveEvent(t, ss) })
+	t.Run("Get Users In Channel At Time", func(t *testing.T) { testGetUsersInChannelAt(t, ss) })
+	t.Run("Purge History", func(t *testing.T) { testPurgeHistoryBefore(t, ss) })
+}
+
+func testLogJoinEvent(t *testing.T, ss store.Store) {
+	// create a test channel
+	channel := model.Channel{
+		TeamId:      model.NewId(),
+		DisplayName: "Display " + model.NewId(),
+		Name:        "zz" + model.NewId() + "b",
+		Type:        model.CHANNEL_OPEN,
+	}
+	channel = *store.Must(ss.Channel().Save(&channel, -1)).(*model.Channel)
+
+	// and a test user
+	user := model.User{
+		Email:    model.NewId() + "@mattermost.com",
+		Nickname: model.NewId(),
+	}
+	user = *store.Must(ss.User().Save(&user)).(*model.User)
+
+	// log a join event
+	result := <-ss.ChannelMemberHistory().LogJoinEvent(user.Id, channel.Id, model.GetMillis())
+	assert.Nil(t, result.Err)
+}
+
+func testLogLeaveEvent(t *testing.T, ss store.Store) {
+	// create a test channel
+	channel := model.Channel{
+		TeamId:      model.NewId(),
+		DisplayName: "Display " + model.NewId(),
+		Name:        "zz" + model.NewId() + "b",
+		Type:        model.CHANNEL_OPEN,
+	}
+	channel = *store.Must(ss.Channel().Save(&channel, -1)).(*model.Channel)
+
+	// and a test user
+	user := model.User{
+		Email:    model.NewId() + "@mattermost.com",
+		Nickname: model.NewId(),
+	}
+	user = *store.Must(ss.User().Save(&user)).(*model.User)
+
+	// log a join event, followed by a leave event
+	result := <-ss.ChannelMemberHistory().LogJoinEvent(user.Id, channel.Id, model.GetMillis())
+	assert.Nil(t, result.Err)
+
+	result = <-ss.ChannelMemberHistory().LogLeaveEvent(user.Id, channel.Id, model.GetMillis())
+	assert.Nil(t, result.Err)
+}
+
+func testGetUsersInChannelAt(t *testing.T, ss store.Store) {
+	// create a test channel
+	channel := model.Channel{
+		TeamId:      model.NewId(),
+		DisplayName: "Display " + model.NewId(),
+		Name:        "zz" + model.NewId() + "b",
+		Type:        model.CHANNEL_OPEN,
+	}
+	channel = *store.Must(ss.Channel().Save(&channel, -1)).(*model.Channel)
+
+	// and a test user
+	user := model.User{
+		Email:    model.NewId() + "@mattermost.com",
+		Nickname: model.NewId(),
+	}
+	user = *store.Must(ss.User().Save(&user)).(*model.User)
+
+	// log a join event
+	leaveTime := model.GetMillis()
+	joinTime := leaveTime - 10000
+	store.Must(ss.ChannelMemberHistory().LogJoinEvent(user.Id, channel.Id, joinTime))
+
+	// case 1: both start and end before join time
+	channelMembers := store.Must(ss.ChannelMemberHistory().GetUsersInChannelDuring(joinTime-500, joinTime-100, channel.Id)).([]*model.ChannelMemberHistory)
+	assert.Len(t, channelMembers, 0)
+
+	// case 2: start before join time, no leave time
+	channelMembers = store.Must(ss.ChannelMemberHistory().GetUsersInChannelDuring(joinTime-100, joinTime+100, channel.Id)).([]*model.ChannelMemberHistory)
+	assert.Len(t, channelMembers, 1)
+	assert.Equal(t, channel.Id, channelMembers[0].ChannelId)
+	assert.Equal(t, user.Id, channelMembers[0].UserId)
+	assert.Equal(t, user.Email, channelMembers[0].UserEmail)
+	assert.Equal(t, joinTime, channelMembers[0].JoinTime)
+	assert.Nil(t, channelMembers[0].LeaveTime)
+
+	// case 3: start after join time, no leave time
+	channelMembers = store.Must(ss.ChannelMemberHistory().GetUsersInChannelDuring(joinTime+100, joinTime+500, channel.Id)).([]*model.ChannelMemberHistory)
+	assert.Len(t, channelMembers, 1)
+	assert.Equal(t, channel.Id, channelMembers[0].ChannelId)
+	assert.Equal(t, user.Id, channelMembers[0].UserId)
+	assert.Equal(t, user.Email, channelMembers[0].UserEmail)
+	assert.Equal(t, joinTime, channelMembers[0].JoinTime)
+	assert.Nil(t, channelMembers[0].LeaveTime)
+
+	// add a leave time for the user
+	store.Must(ss.ChannelMemberHistory().LogLeaveEvent(user.Id, channel.Id, leaveTime))
+
+	// case 4: start after join time, end before leave time
+	channelMembers = store.Must(ss.ChannelMemberHistory().GetUsersInChannelDuring(joinTime+100, leaveTime-100, channel.Id)).([]*model.ChannelMemberHistory)
+	assert.Len(t, channelMembers, 1)
+	assert.Equal(t, channel.Id, channelMembers[0].ChannelId)
+	assert.Equal(t, user.Id, channelMembers[0].UserId)
+	assert.Equal(t, user.Email, channelMembers[0].UserEmail)
+	assert.Equal(t, joinTime, channelMembers[0].JoinTime)
+	assert.Equal(t, leaveTime, *channelMembers[0].LeaveTime)
+
+	// case 5: start before join time, end after leave time
+	channelMembers = store.Must(ss.ChannelMemberHistory().GetUsersInChannelDuring(joinTime-100, leaveTime+100, channel.Id)).([]*model.ChannelMemberHistory)
+	assert.Len(t, channelMembers, 1)
+	assert.Equal(t, channel.Id, channelMembers[0].ChannelId)
+	assert.Equal(t, user.Id, channelMembers[0].UserId)
+	assert.Equal(t, user.Email, channelMembers[0].UserEmail)
+	assert.Equal(t, joinTime, channelMembers[0].JoinTime)
+	assert.Equal(t, leaveTime, *channelMembers[0].LeaveTime)
+
+	// case 6: start and end after leave time
+	channelMembers = store.Must(ss.ChannelMemberHistory().GetUsersInChannelDuring(leaveTime+100, leaveTime+200, channel.Id)).([]*model.ChannelMemberHistory)
+	assert.Len(t, channelMembers, 0)
+}
+
+func testPurgeHistoryBefore(t *testing.T, ss store.Store) {
+	// create a test channel
+	channel := model.Channel{
+		TeamId:      model.NewId(),
+		DisplayName: "Display " + model.NewId(),
+		Name:        "zz" + model.NewId() + "b",
+		Type:        model.CHANNEL_OPEN,
+	}
+	channel = *store.Must(ss.Channel().Save(&channel, -1)).(*model.Channel)
+
+	// and two test users
+	user := model.User{
+		Email:    model.NewId() + "@mattermost.com",
+		Nickname: model.NewId(),
+	}
+	user = *store.Must(ss.User().Save(&user)).(*model.User)
+
+	user2 := model.User{
+		Email:    model.NewId() + "@mattermost.com",
+		Nickname: model.NewId(),
+	}
+	user2 = *store.Must(ss.User().Save(&user2)).(*model.User)
+
+	// user1 joins and leaves the channel
+	leaveTime := model.GetMillis()
+	joinTime := leaveTime - 10000
+	store.Must(ss.ChannelMemberHistory().LogJoinEvent(user.Id, channel.Id, joinTime))
+	store.Must(ss.ChannelMemberHistory().LogLeaveEvent(user.Id, channel.Id, leaveTime))
+
+	// user2 joins the channel but never leaves
+	store.Must(ss.ChannelMemberHistory().LogJoinEvent(user2.Id, channel.Id, joinTime))
+
+	// in between the join time and the leave time, both users were members of the channel
+	channelMembers := store.Must(ss.ChannelMemberHistory().GetUsersInChannelDuring(joinTime+10, leaveTime-10, channel.Id)).([]*model.ChannelMemberHistory)
+	assert.Len(t, channelMembers, 2)
+
+	// but if we purge the old data, only the user that didn't leave is left
+	store.Must(ss.ChannelMemberHistory().PurgeHistoryBefore(leaveTime, channel.Id))
+	channelMembers = store.Must(ss.ChannelMemberHistory().GetUsersInChannelDuring(joinTime+10, leaveTime-10, channel.Id)).([]*model.ChannelMemberHistory)
+	assert.Len(t, channelMembers, 1)
+	assert.Equal(t, user2.Id, channelMembers[0].UserId)
+}
diff --git a/store/storetest/compliance_store.go b/store/storetest/compliance_store.go
index 514910f6f..c5bd60f05 100644
--- a/store/storetest/compliance_store.go
+++ b/store/storetest/compliance_store.go
@@ -9,12 +9,14 @@ import (
 
 	"github.com/mattermost/mattermost-server/model"
 	"github.com/mattermost/mattermost-server/store"
+	"github.com/stretchr/testify/assert"
 )
 
 func TestComplianceStore(t *testing.T, ss store.Store) {
 	t.Run("", func(t *testing.T) { testComplianceStore(t, ss) })
 	t.Run("ComplianceExport", func(t *testing.T) { testComplianceExport(t, ss) })
 	t.Run("ComplianceExportDirectMessages", func(t *testing.T) { testComplianceExportDirectMessages(t, ss) })
+	t.Run("MessageExport", func(t *testing.T) { testComplianceMessageExport(t, ss) })
 }
 
 func testComplianceStore(t *testing.T, ss store.Store) {
@@ -316,3 +318,118 @@ func testComplianceExportDirectMessages(t *testing.T, ss store.Store) {
 		}
 	}
 }
+
+func testComplianceMessageExport(t *testing.T, ss store.Store) {
+	// get the starting number of message export entries
+	startTime := model.GetMillis()
+	var numMessageExports = 0
+	if r1 := <-ss.Compliance().MessageExport(startTime-10, 10); r1.Err != nil {
+		t.Fatal(r1.Err)
+	} else {
+		messages := r1.Data.([]*model.MessageExport)
+		numMessageExports = len(messages)
+	}
+
+	// need a team
+	team := &model.Team{
+		DisplayName: "DisplayName",
+		Name:        "zz" + model.NewId() + "b",
+		Email:       model.NewId() + "@nowhere.com",
+		Type:        model.TEAM_OPEN,
+	}
+	team = store.Must(ss.Team().Save(team)).(*model.Team)
+
+	// and two users that are a part of that team
+	user1 := &model.User{
+		Email: model.NewId(),
+	}
+	user1 = store.Must(ss.User().Save(user1)).(*model.User)
+	store.Must(ss.Team().SaveMember(&model.TeamMember{
+		TeamId: team.Id,
+		UserId: user1.Id,
+	}, -1))
+
+	user2 := &model.User{
+		Email: model.NewId(),
+	}
+	user2 = store.Must(ss.User().Save(user2)).(*model.User)
+	store.Must(ss.Team().SaveMember(&model.TeamMember{
+		TeamId: team.Id,
+		UserId: user2.Id,
+	}, -1))
+
+	// need a public channel as well as a DM channel between the two users
+	channel := &model.Channel{
+		TeamId:      team.Id,
+		Name:        model.NewId(),
+		DisplayName: "Channel2",
+		Type:        model.CHANNEL_OPEN,
+	}
+	channel = store.Must(ss.Channel().Save(channel, -1)).(*model.Channel)
+	directMessageChannel := store.Must(ss.Channel().CreateDirectChannel(user1.Id, user2.Id)).(*model.Channel)
+
+	// user1 posts twice in the public channel
+	post1 := &model.Post{
+		ChannelId: channel.Id,
+		UserId:    user1.Id,
+		CreateAt:  startTime,
+		Message:   "zz" + model.NewId() + "a",
+	}
+	post1 = store.Must(ss.Post().Save(post1)).(*model.Post)
+
+	post2 := &model.Post{
+		ChannelId: channel.Id,
+		UserId:    user1.Id,
+		CreateAt:  startTime + 10,
+		Message:   "zz" + model.NewId() + "b",
+	}
+	post2 = store.Must(ss.Post().Save(post2)).(*model.Post)
+
+	// user1 also sends a DM to user2
+	post3 := &model.Post{
+		ChannelId: directMessageChannel.Id,
+		UserId:    user1.Id,
+		CreateAt:  startTime + 20,
+		Message:   "zz" + model.NewId() + "c",
+	}
+	post3 = store.Must(ss.Post().Save(post3)).(*model.Post)
+
+	// fetch the message exports for all three posts that user1 sent
+	messageExportMap := map[string]model.MessageExport{}
+	if r1 := <-ss.Compliance().MessageExport(startTime-10, 10); r1.Err != nil {
+		t.Fatal(r1.Err)
+	} else {
+		messages := r1.Data.([]*model.MessageExport)
+		assert.Equal(t, numMessageExports+3, len(messages))
+
+		for _, v := range messages {
+			messageExportMap[*v.PostId] = *v
+		}
+	}
+
+	// post1 was made by user1 in channel1 and team1
+	assert.Equal(t, post1.Id, *messageExportMap[post1.Id].PostId)
+	assert.Equal(t, post1.CreateAt, *messageExportMap[post1.Id].PostCreateAt)
+	assert.Equal(t, post1.Message, *messageExportMap[post1.Id].PostMessage)
+	assert.Equal(t, channel.Id, *messageExportMap[post1.Id].ChannelId)
+	assert.Equal(t, channel.DisplayName, *messageExportMap[post1.Id].ChannelDisplayName)
+	assert.Equal(t, user1.Id, *messageExportMap[post1.Id].UserId)
+	assert.Equal(t, user1.Email, *messageExportMap[post1.Id].UserEmail)
+
+	// post2 was made by user1 in channel1 and team1
+	assert.Equal(t, post2.Id, *messageExportMap[post2.Id].PostId)
+	assert.Equal(t, post2.CreateAt, *messageExportMap[post2.Id].PostCreateAt)
+	assert.Equal(t, post2.Message, *messageExportMap[post2.Id].PostMessage)
+	assert.Equal(t, channel.Id, *messageExportMap[post2.Id].ChannelId)
+	assert.Equal(t, channel.DisplayName, *messageExportMap[post2.Id].ChannelDisplayName)
+	assert.Equal(t, user1.Id, *messageExportMap[post2.Id].UserId)
+	assert.Equal(t, user1.Email, *messageExportMap[post2.Id].UserEmail)
+
+	// post3 is a DM between user1 and user2
+	assert.Equal(t, post3.Id, *messageExportMap[post3.Id].PostId)
+	assert.Equal(t, post3.CreateAt, *messageExportMap[post3.Id].PostCreateAt)
+	assert.Equal(t, post3.Message, *messageExportMap[post3.Id].PostMessage)
+	assert.Equal(t, directMessageChannel.Id, *messageExportMap[post3.Id].ChannelId)
+	assert.Equal(t, user1.Id, *messageExportMap[post3.Id].UserId)
+	assert.Equal(t, user1.Email, *messageExportMap[post3.Id].UserEmail)
+}
diff --git a/store/storetest/mocks/ChannelMemberHistoryStore.go b/store/storetest/mocks/ChannelMemberHistoryStore.go
new file mode 100644
index 000000000..4ac0967f9
--- /dev/null
+++ b/store/storetest/mocks/ChannelMemberHistoryStore.go
@@ -0,0 +1,77 @@
+// Code generated by mockery v1.0.0
+
+// Regenerate this file using `make store-mocks`.
+
+package mocks
+
+import mock "github.com/stretchr/testify/mock"
+import store "github.com/mattermost/mattermost-server/store"
+
+// ChannelMemberHistoryStore is an autogenerated mock type for the ChannelMemberHistoryStore type
+type ChannelMemberHistoryStore struct {
+	mock.Mock
+}
+
+// GetUsersInChannelDuring provides a mock function with given fields: startTime, endTime, channelId
+func (_m *ChannelMemberHistoryStore) GetUsersInChannelDuring(startTime int64, endTime int64, channelId string) store.StoreChannel {
+	ret := _m.Called(startTime, endTime, channelId)
+
+	var r0 store.StoreChannel
+	if rf, ok := ret.Get(0).(func(int64, int64, string) store.StoreChannel); ok {
+		r0 = rf(startTime, endTime, channelId)
+	} else {
+		if ret.Get(0) != nil {
+			r0 = ret.Get(0).(store.StoreChannel)
+		}
+	}
+
+	return r0
+}
+
+// LogJoinEvent provides a mock function with given fields: userId, channelId, joinTime
+func (_m *ChannelMemberHistoryStore) LogJoinEvent(userId string, channelId string, joinTime int64) store.StoreChannel {
+	ret := _m.Called(userId, channelId, joinTime)
+
+	var r0 store.StoreChannel
+	if rf, ok := ret.Get(0).(func(string, string, int64) store.StoreChannel); ok {
+		r0 = rf(userId, channelId, joinTime)
+	} else {
+		if ret.Get(0) != nil {
+			r0 = ret.Get(0).(store.StoreChannel)
+		}
+	}
+
+	return r0
+}
+
+// LogLeaveEvent provides a mock function with given fields: userId, channelId, leaveTime
+func (_m *ChannelMemberHistoryStore) LogLeaveEvent(userId string, channelId string, leaveTime int64) store.StoreChannel {
+	ret := _m.Called(userId, channelId, leaveTime)
+
+	var r0 store.StoreChannel
+	if rf, ok := ret.Get(0).(func(string, string, int64) store.StoreChannel); ok {
+		r0 = rf(userId, channelId, leaveTime)
+	} else {
+		if ret.Get(0) != nil {
+			r0 = ret.Get(0).(store.StoreChannel)
+		}
+	}
+
+	return r0
+}
+
+// PurgeHistoryBefore provides a mock function with given fields: time, channelId
+func (_m *ChannelMemberHistoryStore) PurgeHistoryBefore(time int64, channelId string) store.StoreChannel {
+	ret := _m.Called(time, channelId)
+
+	var r0 store.StoreChannel
+	if rf, ok := ret.Get(0).(func(int64, string) store.StoreChannel); ok {
+		r0 = rf(time, channelId)
+	} else {
+		if ret.Get(0) != nil {
+			r0 = ret.Get(0).(store.StoreChannel)
+		}
+	}
+
+	return r0
+}
diff --git a/store/storetest/mocks/ComplianceStore.go b/store/storetest/mocks/ComplianceStore.go
index b2208ead7..fb828cd4b 100644
--- a/store/storetest/mocks/ComplianceStore.go
+++ b/store/storetest/mocks/ComplianceStore.go
@@ -61,6 +61,22 @@ func (_m *ComplianceStore) GetAll(offset int, limit int) store.StoreChannel {
 	return r0
 }
 
+// MessageExport provides a mock function with given fields: after, limit
+func (_m *ComplianceStore) MessageExport(after int64, limit int) store.StoreChannel {
+	ret := _m.Called(after, limit)
+
+	var r0 store.StoreChannel
+	if rf, ok := ret.Get(0).(func(int64, int) store.StoreChannel); ok {
+		r0 = rf(after, limit)
+	} else {
+		if ret.Get(0) != nil {
+			r0 = ret.Get(0).(store.StoreChannel)
+		}
+	}
+
+	return r0
+}
+
 // Save provides a mock function with given fields: compliance
 func (_m *ComplianceStore) Save(compliance *model.Compliance) store.StoreChannel {
 	ret := _m.Called(compliance)
diff --git a/store/storetest/mocks/LayeredStoreDatabaseLayer.go b/store/storetest/mocks/LayeredStoreDatabaseLayer.go
index c3b8bbb60..9c66c4aac 100644
--- a/store/storetest/mocks/LayeredStoreDatabaseLayer.go
+++ b/store/storetest/mocks/LayeredStoreDatabaseLayer.go
@@ -46,6 +46,22 @@ func (_m *LayeredStoreDatabaseLayer) Channel() store.ChannelStore {
 	return r0
 }
 
+// ChannelMemberHistory provides a mock function with given fields:
+func (_m *LayeredStoreDatabaseLayer) ChannelMemberHistory() store.ChannelMemberHistoryStore {
+	ret := _m.Called()
+
+	var r0 store.ChannelMemberHistoryStore
+	if rf, ok := ret.Get(0).(func() store.ChannelMemberHistoryStore); ok {
+		r0 = rf()
+	} else {
+		if ret.Get(0) != nil {
+			r0 = ret.Get(0).(store.ChannelMemberHistoryStore)
+		}
+	}
+
+	return r0
+}
+
 // Close provides a mock function with given fields:
 func (_m *LayeredStoreDatabaseLayer) Close() {
 	_m.Called()
diff --git a/store/storetest/mocks/Store.go b/store/storetest/mocks/Store.go
index 85ed10d35..40b50a554 100644
--- a/store/storetest/mocks/Store.go
+++ b/store/storetest/mocks/Store.go
@@ -44,6 +44,22 @@ func (_m *Store) Channel() store.ChannelStore {
 	return r0
 }
 
+// ChannelMemberHistory provides a mock function with given fields:
+func (_m *Store) ChannelMemberHistory() store.ChannelMemberHistoryStore {
+	ret := _m.Called()
+
+	var r0 store.ChannelMemberHistoryStore
+	if rf, ok := ret.Get(0).(func() store.ChannelMemberHistoryStore); ok {
+		r0 = rf()
+	} else {
+		if ret.Get(0) != nil {
+			r0 = ret.Get(0).(store.ChannelMemberHistoryStore)
+		}
+	}
+
+	return r0
+}
+
 // Close provides a mock function with given fields:
 func (_m *Store) Close() {
 	_m.Called()
diff --git a/store/storetest/store.go b/store/storetest/store.go
index 55545decb..367c5f441 100644
--- a/store/storetest/store.go
+++ b/store/storetest/store.go
@@ -19,29 +19,30 @@ func NewStoreChannel(result store.StoreResult) store.StoreChannel {
 
 // Store can be used to provide mock stores for testing.
 type Store struct {
-	TeamStore             mocks.TeamStore
-	ChannelStore          mocks.ChannelStore
-	PostStore             mocks.PostStore
-	UserStore             mocks.UserStore
-	AuditStore            mocks.AuditStore
-	ClusterDiscoveryStore mocks.ClusterDiscoveryStore
-	ComplianceStore       mocks.ComplianceStore
-	SessionStore          mocks.SessionStore
-	OAuthStore            mocks.OAuthStore
-	SystemStore           mocks.SystemStore
-	WebhookStore          mocks.WebhookStore
-	CommandStore          mocks.CommandStore
-	CommandWebhookStore   mocks.CommandWebhookStore
-	PreferenceStore       mocks.PreferenceStore
-	LicenseStore          mocks.LicenseStore
-	TokenStore            mocks.TokenStore
-	EmojiStore            mocks.EmojiStore
-	StatusStore           mocks.StatusStore
-	FileInfoStore         mocks.FileInfoStore
-	ReactionStore         mocks.ReactionStore
-	JobStore              mocks.JobStore
-	UserAccessTokenStore  mocks.UserAccessTokenStore
-	PluginStore           mocks.PluginStore
+	TeamStore                 mocks.TeamStore
+	ChannelStore              mocks.ChannelStore
+	PostStore                 mocks.PostStore
+	UserStore                 mocks.UserStore
+	AuditStore                mocks.AuditStore
+	ClusterDiscoveryStore     mocks.ClusterDiscoveryStore
+	ComplianceStore           mocks.ComplianceStore
+	SessionStore              mocks.SessionStore
+	OAuthStore                mocks.OAuthStore
+	SystemStore               mocks.SystemStore
+	WebhookStore              mocks.WebhookStore
+	CommandStore              mocks.CommandStore
+	CommandWebhookStore       mocks.CommandWebhookStore
+	PreferenceStore           mocks.PreferenceStore
+	LicenseStore              mocks.LicenseStore
+	TokenStore                mocks.TokenStore
+	EmojiStore                mocks.EmojiStore
+	StatusStore               mocks.StatusStore
+	FileInfoStore             mocks.FileInfoStore
+	ReactionStore             mocks.ReactionStore
+	JobStore                  mocks.JobStore
+	UserAccessTokenStore      mocks.UserAccessTokenStore
+	PluginStore               mocks.PluginStore
+	ChannelMemberHistoryStore mocks.ChannelMemberHistoryStore
 }
 
 func (s *Store) Team() store.TeamStore                         { return &s.TeamStore }
@@ -67,12 +68,15 @@ func (s *Store) Reaction() store.ReactionStore                 { return &s.React
 func (s *Store) Job() store.JobStore                           { return &s.JobStore }
 func (s *Store) UserAccessToken() store.UserAccessTokenStore   { return &s.UserAccessTokenStore }
 func (s *Store) Plugin() store.PluginStore                     { return &s.PluginStore }
-func (s *Store) MarkSystemRanUnitTests()                       { /* do nothing */ }
-func (s *Store) Close()                                        { /* do nothing */ }
-func (s *Store) DropAllTables()                                { /* do nothing */ }
-func (s *Store) TotalMasterDbConnections() int                 { return 1 }
-func (s *Store) TotalReadDbConnections() int                   { return 1 }
-func (s *Store) TotalSearchDbConnections() int                 { return 1 }
+func (s *Store) ChannelMemberHistory() store.ChannelMemberHistoryStore {
+	return &s.ChannelMemberHistoryStore
+}
+func (s *Store) MarkSystemRanUnitTests()       { /* do nothing */ }
+func (s *Store) Close()                        { /* do nothing */ }
+func (s *Store) DropAllTables()                { /* do nothing */ }
+func (s *Store) TotalMasterDbConnections() int { return 1 }
+func (s *Store) TotalReadDbConnections() int   { return 1 }
+func (s *Store) TotalSearchDbConnections() int { return 1 }
 
 func (s *Store) AssertExpectations(t mock.TestingT) bool {
 	return mock.AssertExpectationsForObjects(t,
@@ -98,6 +102,7 @@ func (s *Store) AssertExpectations(t mock.TestingT) bool {
 		&s.ReactionStore,
 		&s.JobStore,
 		&s.UserAccessTokenStore,
+		&s.ChannelMemberHistoryStore,
 		&s.PluginStore,
 	)
 }
diff --git a/utils/file_backend.go b/utils/file_backend.go
index 3469a63fb..c7a6c5591 100644
--- a/utils/file_backend.go
+++ b/utils/file_backend.go
@@ -13,6 +13,7 @@ type FileBackend interface {
 	TestConnection() *model.AppError
 
 	ReadFile(path string) ([]byte, *model.AppError)
+	CopyFile(oldPath, newPath string) *model.AppError
 	MoveFile(oldPath, newPath string) *model.AppError
 	WriteFile(f []byte, path string) *model.AppError
 	RemoveFile(path string) *model.AppError
diff --git a/utils/file_backend_local.go b/utils/file_backend_local.go
index b5e67f8f0..1367ccc1e 100644
--- a/utils/file_backend_local.go
+++ b/utils/file_backend_local.go
@@ -40,6 +40,13 @@ func (b *LocalFileBackend) ReadFile(path string) ([]byte, *model.AppError) {
 	}
 }
 
+func (b *LocalFileBackend) CopyFile(oldPath, newPath string) *model.AppError {
+	if err := CopyFile(filepath.Join(b.directory, oldPath), filepath.Join(b.directory, newPath)); err != nil {
+		return model.NewAppError("copyFile", "api.file.move_file.rename.app_error", nil, err.Error(), http.StatusInternalServerError)
+	}
+	return nil
+}
+
 func (b *LocalFileBackend) MoveFile(oldPath, newPath string) *model.AppError {
 	if err := os.MkdirAll(filepath.Dir(filepath.Join(b.directory, newPath)), 0774); err != nil {
 		return model.NewAppError("moveFile", "api.file.move_file.rename.app_error", nil, err.Error(), http.StatusInternalServerError)
diff --git a/utils/file_backend_s3.go b/utils/file_backend_s3.go
index ed88dc70c..5512b64dc 100644
--- a/utils/file_backend_s3.go
+++ b/utils/file_backend_s3.go
@@ -95,6 +95,23 @@ func (b *S3FileBackend) ReadFile(path string) ([]byte, *model.AppError) {
 	}
 }
 
+func (b *S3FileBackend) CopyFile(oldPath, newPath string) *model.AppError {
+	s3Clnt, err := b.s3New()
+	if err != nil {
+		return model.NewAppError("copyFile", "api.file.write_file.s3.app_error", nil, err.Error(), http.StatusInternalServerError)
+	}
+
+	source := s3.NewSourceInfo(b.bucket, oldPath, nil)
+	destination, err := s3.NewDestinationInfo(b.bucket, newPath, nil, s3CopyMetadata(b.encrypt))
+	if err != nil {
+		return model.NewAppError("copyFile", "api.file.write_file.s3.app_error", nil, err.Error(), http.StatusInternalServerError)
+	}
+	if err = s3Clnt.CopyObject(destination, source); err != nil {
+		return model.NewAppError("copyFile", "api.file.move_file.copy_within_s3.app_error", nil, err.Error(), http.StatusInternalServerError)
+	}
+	return nil
+}
+
 func (b *S3FileBackend) MoveFile(oldPath, newPath string) *model.AppError {
 	s3Clnt, err := b.s3New()
 	if err != nil {
@@ -107,7 +124,7 @@ func (b *S3FileBackend) MoveFile(oldPath, newPath string) *model.AppError {
 		return model.NewAppError("moveFile", "api.file.write_file.s3.app_error", nil, err.Error(), http.StatusInternalServerError)
 	}
 	if err = s3Clnt.CopyObject(destination, source); err != nil {
-		return model.NewAppError("moveFile", "api.file.move_file.delete_from_s3.app_error", nil, err.Error(), http.StatusInternalServerError)
+		return model.NewAppError("moveFile", "api.file.move_file.copy_within_s3.app_error", nil, err.Error(), http.StatusInternalServerError)
 	}
 	if err = s3Clnt.RemoveObject(b.bucket, oldPath); err != nil {
 		return model.NewAppError("moveFile", "api.file.move_file.delete_from_s3.app_error", nil, err.Error(), http.StatusInternalServerError)
diff --git a/utils/file_backend_test.go b/utils/file_backend_test.go
index 0989f783c..098f86bbd 100644
--- a/utils/file_backend_test.go
+++ b/utils/file_backend_test.go
@@ -86,6 +86,26 @@ func (s *FileBackendTestSuite) TestReadWriteFile() {
 	s.EqualValues(readString, "test")
 }
 
+func (s *FileBackendTestSuite) TestCopyFile() {
+	b := []byte("test")
+	path1 := "tests/" + model.NewId()
+	path2 := "tests/" + model.NewId()
+
+	err := s.backend.WriteFile(b, path1)
+	s.Nil(err)
+	defer s.backend.RemoveFile(path1)
+
+	err = s.backend.CopyFile(path1, path2)
+	s.Nil(err)
+	defer s.backend.RemoveFile(path2)
+
+	_, err = s.backend.ReadFile(path1)
+	s.Nil(err)
+
+	_, err = s.backend.ReadFile(path2)
+	s.Nil(err)
+}
+
 func (s *FileBackendTestSuite) TestMoveFile() {
 	b := []byte("test")
 	path1 := "tests/" + model.NewId()
diff --git a/utils/license.go b/utils/license.go
index f4775d338..54bad45b5 100644
--- a/utils/license.go
+++ b/utils/license.go
@@ -228,6 +228,7 @@ func getClientLicense(l *model.License) map[string]string {
 		props["Company"] = l.Customer.Company
 		props["PhoneNumber"] = l.Customer.PhoneNumber
 		props["EmailNotificationContents"] = strconv.FormatBool(*l.Features.EmailNotificationContents)
+		props["MessageExport"] = strconv.FormatBool(*l.Features.MessageExport)
 	}
 
 	return props