MM-11029 Adding plugin logging functionality. (#9034)

* Capturing stdout, stderr of plugins in logs.

* Cleanup go-plugin debug logs.

* Adding logging to plugin API

* Generating mocks.

* godoc convention

8 files changed, 316 insertions, 31 deletions

diff --git a/plugin/api.go b/plugin/api.go
index 842cef4f6..81a27c330 100644
--- a/plugin/api.go
+++ b/plugin/api.go
@@ -119,6 +119,30 @@ type API interface {
 	// payload is the data sent with the event. Interface values must be primitive Go types or mattermost-server/model types
 	// broadcast determines to which users to send the event
 	PublishWebSocketEvent(event string, payload map[string]interface{}, broadcast *model.WebsocketBroadcast)
+
+	// LogDebug writes a log message to the Mattermost server log file.
+	// Appropriate context such as the plugin name will already be added as fields so plugins
+	// do not need to add that info.
+	// keyValuePairs should be primitive go types or other values that can be encoded by encoding/gob
+	LogDebug(msg string, keyValuePairs ...interface{})
+
+	// LogInfo writes a log message to the Mattermost server log file.
+	// Appropriate context such as the plugin name will already be added as fields so plugins
+	// do not need to add that info.
+	// keyValuePairs should be primitive go types or other values that can be encoded by encoding/gob
+	LogInfo(msg string, keyValuePairs ...interface{})
+
+	// LogError writes a log message to the Mattermost server log file.
+	// Appropriate context such as the plugin name will already be added as fields so plugins
+	// do not need to add that info.
+	// keyValuePairs should be primitive go types or other values that can be encoded by encoding/gob
+	LogError(msg string, keyValuePairs ...interface{})
+
+	// LogWarn writes a log message to the Mattermost server log file.
+	// Appropriate context such as the plugin name will already be added as fields so plugins
+	// do not need to add that info.
+	// keyValuePairs should be primitive go types or other values that can be encoded by encoding/gob
+	LogWarn(msg string, keyValuePairs ...interface{})
 }
 
 var Handshake = plugin.HandshakeConfig{
diff --git a/plugin/client_rpc.go b/plugin/client_rpc.go
index 159d41201..f58bbd22b 100644
--- a/plugin/client_rpc.go
+++ b/plugin/client_rpc.go
@@ -9,9 +9,12 @@ import (
 	"bytes"
 	"encoding/gob"
 	"encoding/json"
+	"fmt"
 	"io/ioutil"
+	"log"
 	"net/http"
 	"net/rpc"
+	"os"
 	"reflect"
 
 	"github.com/hashicorp/go-plugin"
@@ -33,7 +36,6 @@ type HooksRPCServer struct {
 	impl         interface{}
 	muxBroker    *plugin.MuxBroker
 	apiRPCClient *APIRPCClient
-	log          *mlog.Logger
 }
 
 // Implements hashicorp/go-plugin/plugin.Plugin interface to connect the hooks of a plugin
@@ -156,24 +158,11 @@ func (g *HooksRPCClient) OnActivate() error {
 func (s *HooksRPCServer) OnActivate(args *OnActivateArgs, returns *OnActivateReturns) error {
 	connection, err := s.muxBroker.Dial(args.APIMuxId)
 	if err != nil {
-		return err // Where does this go?
+		return err
 	}
 
-	// Settings for this should come from the parent process, for now just set it up
-	// though stdout.
-	logger := mlog.NewLogger(&mlog.LoggerConfiguration{
-		EnableConsole: true,
-		ConsoleJson:   true,
-		ConsoleLevel:  mlog.LevelDebug,
-		EnableFile:    false,
-	})
-	logger = logger.With(mlog.Bool("plugin_subprocess", true))
-
-	s.log = logger
-
 	s.apiRPCClient = &APIRPCClient{
 		client: rpc.NewClient(connection),
-		log:    logger,
 	}
 
 	if mmplugin, ok := s.impl.(interface {
@@ -185,6 +174,10 @@ func (s *HooksRPCServer) OnActivate(args *OnActivateArgs, returns *OnActivateRet
 		mmplugin.OnConfigurationChange()
 	}
 
+	// Capture output of standard logger because go-plugin
+	// redirects it.
+	log.SetOutput(os.Stderr)
+
 	if hook, ok := s.impl.(interface {
 		OnActivate() error
 	}); ok {
@@ -293,7 +286,7 @@ func (g *HooksRPCClient) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		Request:              forwardedRequest,
 		RequestBodyStream:    requestBodyStreamId,
 	}, nil); err != nil {
-		mlog.Error("Plugin failed to ServeHTTP, RPC call failed", mlog.Err(err))
+		g.log.Error("Plugin failed to ServeHTTP, RPC call failed", mlog.Err(err))
 		http.Error(w, "500 internal server error", http.StatusInternalServerError)
 	}
 	return
@@ -302,7 +295,7 @@ func (g *HooksRPCClient) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 func (s *HooksRPCServer) ServeHTTP(args *ServeHTTPArgs, returns *struct{}) error {
 	connection, err := s.muxBroker.Dial(args.ResponseWriterStream)
 	if err != nil {
-		s.log.Debug("Can't connect to remote response writer stream", mlog.Err(err))
+		fmt.Fprintf(os.Stderr, "[ERROR] Can't connect to remote response writer stream, error: %v", err.Error())
 		return err
 	}
 	w := ConnectHTTPResponseWriter(connection)
@@ -312,7 +305,7 @@ func (s *HooksRPCServer) ServeHTTP(args *ServeHTTPArgs, returns *struct{}) error
 	if args.RequestBodyStream != 0 {
 		connection, err := s.muxBroker.Dial(args.RequestBodyStream)
 		if err != nil {
-			s.log.Debug("Can't connect to remote response writer stream", mlog.Err(err))
+			fmt.Fprintf(os.Stderr, "[ERROR] Can't connect to remote request body stream, error: %v", err.Error())
 			return err
 		}
 		r.Body = ConnectIOReader(connection)
diff --git a/plugin/client_rpc_generated.go b/plugin/client_rpc_generated.go
index 9880814b2..897d6be04 100644
--- a/plugin/client_rpc_generated.go
+++ b/plugin/client_rpc_generated.go
@@ -7,6 +7,8 @@
 package plugin
 
 import (
+	"fmt"
+
 	"github.com/mattermost/mattermost-server/mlog"
 	"github.com/mattermost/mattermost-server/model"
 )
@@ -38,6 +40,8 @@ func (s *HooksRPCServer) OnDeactivate(args *OnDeactivateArgs, returns *OnDeactiv
 		OnDeactivate() error
 	}); ok {
 		returns.A = hook.OnDeactivate()
+	} else {
+		return fmt.Errorf("Hook OnDeactivate called but not implemented.")
 	}
 	return nil
 }
@@ -69,6 +73,8 @@ func (s *HooksRPCServer) OnConfigurationChange(args *OnConfigurationChangeArgs,
 		OnConfigurationChange() error
 	}); ok {
 		returns.A = hook.OnConfigurationChange()
+	} else {
+		return fmt.Errorf("Hook OnConfigurationChange called but not implemented.")
 	}
 	return nil
 }
@@ -102,6 +108,8 @@ func (s *HooksRPCServer) ExecuteCommand(args *ExecuteCommandArgs, returns *Execu
 		ExecuteCommand(args *model.CommandArgs) (*model.CommandResponse, *model.AppError)
 	}); ok {
 		returns.A, returns.B = hook.ExecuteCommand(args.A)
+	} else {
+		return fmt.Errorf("Hook ExecuteCommand called but not implemented.")
 	}
 	return nil
 }
@@ -135,6 +143,8 @@ func (s *HooksRPCServer) MessageWillBePosted(args *MessageWillBePostedArgs, retu
 		MessageWillBePosted(post *model.Post) (*model.Post, string)
 	}); ok {
 		returns.A, returns.B = hook.MessageWillBePosted(args.A)
+	} else {
+		return fmt.Errorf("Hook MessageWillBePosted called but not implemented.")
 	}
 	return nil
 }
@@ -169,6 +179,8 @@ func (s *HooksRPCServer) MessageWillBeUpdated(args *MessageWillBeUpdatedArgs, re
 		MessageWillBeUpdated(newPost, oldPost *model.Post) (*model.Post, string)
 	}); ok {
 		returns.A, returns.B = hook.MessageWillBeUpdated(args.A, args.B)
+	} else {
+		return fmt.Errorf("Hook MessageWillBeUpdated called but not implemented.")
 	}
 	return nil
 }
@@ -200,6 +212,8 @@ func (s *HooksRPCServer) MessageHasBeenPosted(args *MessageHasBeenPostedArgs, re
 		MessageHasBeenPosted(post *model.Post)
 	}); ok {
 		hook.MessageHasBeenPosted(args.A)
+	} else {
+		return fmt.Errorf("Hook MessageHasBeenPosted called but not implemented.")
 	}
 	return nil
 }
@@ -232,6 +246,8 @@ func (s *HooksRPCServer) MessageHasBeenUpdated(args *MessageHasBeenUpdatedArgs,
 		MessageHasBeenUpdated(newPost, oldPost *model.Post)
 	}); ok {
 		hook.MessageHasBeenUpdated(args.A, args.B)
+	} else {
+		return fmt.Errorf("Hook MessageHasBeenUpdated called but not implemented.")
 	}
 	return nil
 }
@@ -258,6 +274,8 @@ func (s *APIRPCServer) RegisterCommand(args *RegisterCommandArgs, returns *Regis
 		RegisterCommand(command *model.Command) error
 	}); ok {
 		returns.A = hook.RegisterCommand(args.A)
+	} else {
+		return fmt.Errorf("API RegisterCommand called but not implemented.")
 	}
 	return nil
 }
@@ -285,6 +303,8 @@ func (s *APIRPCServer) UnregisterCommand(args *UnregisterCommandArgs, returns *U
 		UnregisterCommand(teamId, trigger string) error
 	}); ok {
 		returns.A = hook.UnregisterCommand(args.A, args.B)
+	} else {
+		return fmt.Errorf("API UnregisterCommand called but not implemented.")
 	}
 	return nil
 }
@@ -312,6 +332,8 @@ func (s *APIRPCServer) CreateUser(args *CreateUserArgs, returns *CreateUserRetur
 		CreateUser(user *model.User) (*model.User, *model.AppError)
 	}); ok {
 		returns.A, returns.B = hook.CreateUser(args.A)
+	} else {
+		return fmt.Errorf("API CreateUser called but not implemented.")
 	}
 	return nil
 }
@@ -338,6 +360,8 @@ func (s *APIRPCServer) DeleteUser(args *DeleteUserArgs, returns *DeleteUserRetur
 		DeleteUser(userId string) *model.AppError
 	}); ok {
 		returns.A = hook.DeleteUser(args.A)
+	} else {
+		return fmt.Errorf("API DeleteUser called but not implemented.")
 	}
 	return nil
 }
@@ -365,6 +389,8 @@ func (s *APIRPCServer) GetUser(args *GetUserArgs, returns *GetUserReturns) error
 		GetUser(userId string) (*model.User, *model.AppError)
 	}); ok {
 		returns.A, returns.B = hook.GetUser(args.A)
+	} else {
+		return fmt.Errorf("API GetUser called but not implemented.")
 	}
 	return nil
 }
@@ -392,6 +418,8 @@ func (s *APIRPCServer) GetUserByEmail(args *GetUserByEmailArgs, returns *GetUser
 		GetUserByEmail(email string) (*model.User, *model.AppError)
 	}); ok {
 		returns.A, returns.B = hook.GetUserByEmail(args.A)
+	} else {
+		return fmt.Errorf("API GetUserByEmail called but not implemented.")
 	}
 	return nil
 }
@@ -419,6 +447,8 @@ func (s *APIRPCServer) GetUserByUsername(args *GetUserByUsernameArgs, returns *G
 		GetUserByUsername(name string) (*model.User, *model.AppError)
 	}); ok {
 		returns.A, returns.B = hook.GetUserByUsername(args.A)
+	} else {
+		return fmt.Errorf("API GetUserByUsername called but not implemented.")
 	}
 	return nil
 }
@@ -446,6 +476,8 @@ func (s *APIRPCServer) UpdateUser(args *UpdateUserArgs, returns *UpdateUserRetur
 		UpdateUser(user *model.User) (*model.User, *model.AppError)
 	}); ok {
 		returns.A, returns.B = hook.UpdateUser(args.A)
+	} else {
+		return fmt.Errorf("API UpdateUser called but not implemented.")
 	}
 	return nil
 }
@@ -473,6 +505,8 @@ func (s *APIRPCServer) CreateTeam(args *CreateTeamArgs, returns *CreateTeamRetur
 		CreateTeam(team *model.Team) (*model.Team, *model.AppError)
 	}); ok {
 		returns.A, returns.B = hook.CreateTeam(args.A)
+	} else {
+		return fmt.Errorf("API CreateTeam called but not implemented.")
 	}
 	return nil
 }
@@ -499,6 +533,8 @@ func (s *APIRPCServer) DeleteTeam(args *DeleteTeamArgs, returns *DeleteTeamRetur
 		DeleteTeam(teamId string) *model.AppError
 	}); ok {
 		returns.A = hook.DeleteTeam(args.A)
+	} else {
+		return fmt.Errorf("API DeleteTeam called but not implemented.")
 	}
 	return nil
 }
@@ -526,6 +562,8 @@ func (s *APIRPCServer) GetTeam(args *GetTeamArgs, returns *GetTeamReturns) error
 		GetTeam(teamId string) (*model.Team, *model.AppError)
 	}); ok {
 		returns.A, returns.B = hook.GetTeam(args.A)
+	} else {
+		return fmt.Errorf("API GetTeam called but not implemented.")
 	}
 	return nil
 }
@@ -553,6 +591,8 @@ func (s *APIRPCServer) GetTeamByName(args *GetTeamByNameArgs, returns *GetTeamBy
 		GetTeamByName(name string) (*model.Team, *model.AppError)
 	}); ok {
 		returns.A, returns.B = hook.GetTeamByName(args.A)
+	} else {
+		return fmt.Errorf("API GetTeamByName called but not implemented.")
 	}
 	return nil
 }
@@ -580,6 +620,8 @@ func (s *APIRPCServer) UpdateTeam(args *UpdateTeamArgs, returns *UpdateTeamRetur
 		UpdateTeam(team *model.Team) (*model.Team, *model.AppError)
 	}); ok {
 		returns.A, returns.B = hook.UpdateTeam(args.A)
+	} else {
+		return fmt.Errorf("API UpdateTeam called but not implemented.")
 	}
 	return nil
 }
@@ -607,6 +649,8 @@ func (s *APIRPCServer) CreateChannel(args *CreateChannelArgs, returns *CreateCha
 		CreateChannel(channel *model.Channel) (*model.Channel, *model.AppError)
 	}); ok {
 		returns.A, returns.B = hook.CreateChannel(args.A)
+	} else {
+		return fmt.Errorf("API CreateChannel called but not implemented.")
 	}
 	return nil
 }
@@ -633,6 +677,8 @@ func (s *APIRPCServer) DeleteChannel(args *DeleteChannelArgs, returns *DeleteCha
 		DeleteChannel(channelId string) *model.AppError
 	}); ok {
 		returns.A = hook.DeleteChannel(args.A)
+	} else {
+		return fmt.Errorf("API DeleteChannel called but not implemented.")
 	}
 	return nil
 }
@@ -660,6 +706,8 @@ func (s *APIRPCServer) GetChannel(args *GetChannelArgs, returns *GetChannelRetur
 		GetChannel(channelId string) (*model.Channel, *model.AppError)
 	}); ok {
 		returns.A, returns.B = hook.GetChannel(args.A)
+	} else {
+		return fmt.Errorf("API GetChannel called but not implemented.")
 	}
 	return nil
 }
@@ -688,6 +736,8 @@ func (s *APIRPCServer) GetChannelByName(args *GetChannelByNameArgs, returns *Get
 		GetChannelByName(name, teamId string) (*model.Channel, *model.AppError)
 	}); ok {
 		returns.A, returns.B = hook.GetChannelByName(args.A, args.B)
+	} else {
+		return fmt.Errorf("API GetChannelByName called but not implemented.")
 	}
 	return nil
 }
@@ -716,6 +766,8 @@ func (s *APIRPCServer) GetDirectChannel(args *GetDirectChannelArgs, returns *Get
 		GetDirectChannel(userId1, userId2 string) (*model.Channel, *model.AppError)
 	}); ok {
 		returns.A, returns.B = hook.GetDirectChannel(args.A, args.B)
+	} else {
+		return fmt.Errorf("API GetDirectChannel called but not implemented.")
 	}
 	return nil
 }
@@ -743,6 +795,8 @@ func (s *APIRPCServer) GetGroupChannel(args *GetGroupChannelArgs, returns *GetGr
 		GetGroupChannel(userIds []string) (*model.Channel, *model.AppError)
 	}); ok {
 		returns.A, returns.B = hook.GetGroupChannel(args.A)
+	} else {
+		return fmt.Errorf("API GetGroupChannel called but not implemented.")
 	}
 	return nil
 }
@@ -770,6 +824,8 @@ func (s *APIRPCServer) UpdateChannel(args *UpdateChannelArgs, returns *UpdateCha
 		UpdateChannel(channel *model.Channel) (*model.Channel, *model.AppError)
 	}); ok {
 		returns.A, returns.B = hook.UpdateChannel(args.A)
+	} else {
+		return fmt.Errorf("API UpdateChannel called but not implemented.")
 	}
 	return nil
 }
@@ -798,6 +854,8 @@ func (s *APIRPCServer) AddChannelMember(args *AddChannelMemberArgs, returns *Add
 		AddChannelMember(channelId, userId string) (*model.ChannelMember, *model.AppError)
 	}); ok {
 		returns.A, returns.B = hook.AddChannelMember(args.A, args.B)
+	} else {
+		return fmt.Errorf("API AddChannelMember called but not implemented.")
 	}
 	return nil
 }
@@ -826,6 +884,8 @@ func (s *APIRPCServer) GetChannelMember(args *GetChannelMemberArgs, returns *Get
 		GetChannelMember(channelId, userId string) (*model.ChannelMember, *model.AppError)
 	}); ok {
 		returns.A, returns.B = hook.GetChannelMember(args.A, args.B)
+	} else {
+		return fmt.Errorf("API GetChannelMember called but not implemented.")
 	}
 	return nil
 }
@@ -855,6 +915,8 @@ func (s *APIRPCServer) UpdateChannelMemberRoles(args *UpdateChannelMemberRolesAr
 		UpdateChannelMemberRoles(channelId, userId, newRoles string) (*model.ChannelMember, *model.AppError)
 	}); ok {
 		returns.A, returns.B = hook.UpdateChannelMemberRoles(args.A, args.B, args.C)
+	} else {
+		return fmt.Errorf("API UpdateChannelMemberRoles called but not implemented.")
 	}
 	return nil
 }
@@ -884,6 +946,8 @@ func (s *APIRPCServer) UpdateChannelMemberNotifications(args *UpdateChannelMembe
 		UpdateChannelMemberNotifications(channelId, userId string, notifications map[string]string) (*model.ChannelMember, *model.AppError)
 	}); ok {
 		returns.A, returns.B = hook.UpdateChannelMemberNotifications(args.A, args.B, args.C)
+	} else {
+		return fmt.Errorf("API UpdateChannelMemberNotifications called but not implemented.")
 	}
 	return nil
 }
@@ -911,6 +975,8 @@ func (s *APIRPCServer) DeleteChannelMember(args *DeleteChannelMemberArgs, return
 		DeleteChannelMember(channelId, userId string) *model.AppError
 	}); ok {
 		returns.A = hook.DeleteChannelMember(args.A, args.B)
+	} else {
+		return fmt.Errorf("API DeleteChannelMember called but not implemented.")
 	}
 	return nil
 }
@@ -938,6 +1004,8 @@ func (s *APIRPCServer) CreatePost(args *CreatePostArgs, returns *CreatePostRetur
 		CreatePost(post *model.Post) (*model.Post, *model.AppError)
 	}); ok {
 		returns.A, returns.B = hook.CreatePost(args.A)
+	} else {
+		return fmt.Errorf("API CreatePost called but not implemented.")
 	}
 	return nil
 }
@@ -964,6 +1032,8 @@ func (s *APIRPCServer) DeletePost(args *DeletePostArgs, returns *DeletePostRetur
 		DeletePost(postId string) *model.AppError
 	}); ok {
 		returns.A = hook.DeletePost(args.A)
+	} else {
+		return fmt.Errorf("API DeletePost called but not implemented.")
 	}
 	return nil
 }
@@ -991,6 +1061,8 @@ func (s *APIRPCServer) GetPost(args *GetPostArgs, returns *GetPostReturns) error
 		GetPost(postId string) (*model.Post, *model.AppError)
 	}); ok {
 		returns.A, returns.B = hook.GetPost(args.A)
+	} else {
+		return fmt.Errorf("API GetPost called but not implemented.")
 	}
 	return nil
 }
@@ -1018,6 +1090,8 @@ func (s *APIRPCServer) UpdatePost(args *UpdatePostArgs, returns *UpdatePostRetur
 		UpdatePost(post *model.Post) (*model.Post, *model.AppError)
 	}); ok {
 		returns.A, returns.B = hook.UpdatePost(args.A)
+	} else {
+		return fmt.Errorf("API UpdatePost called but not implemented.")
 	}
 	return nil
 }
@@ -1045,6 +1119,8 @@ func (s *APIRPCServer) KVSet(args *KVSetArgs, returns *KVSetReturns) error {
 		KVSet(key string, value []byte) *model.AppError
 	}); ok {
 		returns.A = hook.KVSet(args.A, args.B)
+	} else {
+		return fmt.Errorf("API KVSet called but not implemented.")
 	}
 	return nil
 }
@@ -1072,6 +1148,8 @@ func (s *APIRPCServer) KVGet(args *KVGetArgs, returns *KVGetReturns) error {
 		KVGet(key string) ([]byte, *model.AppError)
 	}); ok {
 		returns.A, returns.B = hook.KVGet(args.A)
+	} else {
+		return fmt.Errorf("API KVGet called but not implemented.")
 	}
 	return nil
 }
@@ -1098,6 +1176,8 @@ func (s *APIRPCServer) KVDelete(args *KVDeleteArgs, returns *KVDeleteReturns) er
 		KVDelete(key string) *model.AppError
 	}); ok {
 		returns.A = hook.KVDelete(args.A)
+	} else {
+		return fmt.Errorf("API KVDelete called but not implemented.")
 	}
 	return nil
 }
@@ -1125,6 +1205,120 @@ func (s *APIRPCServer) PublishWebSocketEvent(args *PublishWebSocketEventArgs, re
 		PublishWebSocketEvent(event string, payload map[string]interface{}, broadcast *model.WebsocketBroadcast)
 	}); ok {
 		hook.PublishWebSocketEvent(args.A, args.B, args.C)
+	} else {
+		return fmt.Errorf("API PublishWebSocketEvent called but not implemented.")
+	}
+	return nil
+}
+
+type LogDebugArgs struct {
+	A string
+	B []interface{}
+}
+
+type LogDebugReturns struct {
+}
+
+func (g *APIRPCClient) LogDebug(msg string, keyValuePairs ...interface{}) {
+	_args := &LogDebugArgs{msg, keyValuePairs}
+	_returns := &LogDebugReturns{}
+	if err := g.client.Call("Plugin.LogDebug", _args, _returns); err != nil {
+		g.log.Error("RPC call to LogDebug API failed.", mlog.Err(err))
+	}
+	return
+}
+
+func (s *APIRPCServer) LogDebug(args *LogDebugArgs, returns *LogDebugReturns) error {
+	if hook, ok := s.impl.(interface {
+		LogDebug(msg string, keyValuePairs ...interface{})
+	}); ok {
+		hook.LogDebug(args.A, args.B...)
+	} else {
+		return fmt.Errorf("API LogDebug called but not implemented.")
+	}
+	return nil
+}
+
+type LogInfoArgs struct {
+	A string
+	B []interface{}
+}
+
+type LogInfoReturns struct {
+}
+
+func (g *APIRPCClient) LogInfo(msg string, keyValuePairs ...interface{}) {
+	_args := &LogInfoArgs{msg, keyValuePairs}
+	_returns := &LogInfoReturns{}
+	if err := g.client.Call("Plugin.LogInfo", _args, _returns); err != nil {
+		g.log.Error("RPC call to LogInfo API failed.", mlog.Err(err))
+	}
+	return
+}
+
+func (s *APIRPCServer) LogInfo(args *LogInfoArgs, returns *LogInfoReturns) error {
+	if hook, ok := s.impl.(interface {
+		LogInfo(msg string, keyValuePairs ...interface{})
+	}); ok {
+		hook.LogInfo(args.A, args.B...)
+	} else {
+		return fmt.Errorf("API LogInfo called but not implemented.")
+	}
+	return nil
+}
+
+type LogErrorArgs struct {
+	A string
+	B []interface{}
+}
+
+type LogErrorReturns struct {
+}
+
+func (g *APIRPCClient) LogError(msg string, keyValuePairs ...interface{}) {
+	_args := &LogErrorArgs{msg, keyValuePairs}
+	_returns := &LogErrorReturns{}
+	if err := g.client.Call("Plugin.LogError", _args, _returns); err != nil {
+		g.log.Error("RPC call to LogError API failed.", mlog.Err(err))
+	}
+	return
+}
+
+func (s *APIRPCServer) LogError(args *LogErrorArgs, returns *LogErrorReturns) error {
+	if hook, ok := s.impl.(interface {
+		LogError(msg string, keyValuePairs ...interface{})
+	}); ok {
+		hook.LogError(args.A, args.B...)
+	} else {
+		return fmt.Errorf("API LogError called but not implemented.")
+	}
+	return nil
+}
+
+type LogWarnArgs struct {
+	A string
+	B []interface{}
+}
+
+type LogWarnReturns struct {
+}
+
+func (g *APIRPCClient) LogWarn(msg string, keyValuePairs ...interface{}) {
+	_args := &LogWarnArgs{msg, keyValuePairs}
+	_returns := &LogWarnReturns{}
+	if err := g.client.Call("Plugin.LogWarn", _args, _returns); err != nil {
+		g.log.Error("RPC call to LogWarn API failed.", mlog.Err(err))
+	}
+	return
+}
+
+func (s *APIRPCServer) LogWarn(args *LogWarnArgs, returns *LogWarnReturns) error {
+	if hook, ok := s.impl.(interface {
+		LogWarn(msg string, keyValuePairs ...interface{})
+	}); ok {
+		hook.LogWarn(args.A, args.B...)
+	} else {
+		return fmt.Errorf("API LogWarn called but not implemented.")
 	}
 	return nil
 }
diff --git a/plugin/hclog_adapter.go b/plugin/hclog_adapter.go
index c8e39877e..55d60f508 100644
--- a/plugin/hclog_adapter.go
+++ b/plugin/hclog_adapter.go
@@ -6,6 +6,7 @@ package plugin
 import (
 	"fmt"
 	"log"
+	"strings"
 
 	"github.com/hashicorp/go-hclog"
 	"github.com/mattermost/mattermost-server/mlog"
@@ -17,23 +18,48 @@ type HclogAdapter struct {
 }
 
 func (h *HclogAdapter) Trace(msg string, args ...interface{}) {
-	h.wrappedLogger.Debug(msg, mlog.String(h.extrasKey, fmt.Sprintln(args...)))
+	extras := strings.TrimSpace(fmt.Sprint(args...))
+	if extras != "" {
+		h.wrappedLogger.Debug(msg, mlog.String(h.extrasKey, extras))
+	} else {
+		h.wrappedLogger.Debug(msg)
+	}
 }
 
 func (h *HclogAdapter) Debug(msg string, args ...interface{}) {
-	h.wrappedLogger.Debug(msg, mlog.String(h.extrasKey, fmt.Sprintln(args...)))
+	extras := strings.TrimSpace(fmt.Sprint(args...))
+	if extras != "" {
+		h.wrappedLogger.Debug(msg, mlog.String(h.extrasKey, extras))
+	} else {
+		h.wrappedLogger.Debug(msg)
+	}
 }
 
 func (h *HclogAdapter) Info(msg string, args ...interface{}) {
-	h.wrappedLogger.Info(msg, mlog.String(h.extrasKey, fmt.Sprintln(args...)))
+	extras := strings.TrimSpace(fmt.Sprint(args...))
+	if extras != "" {
+		h.wrappedLogger.Info(msg, mlog.String(h.extrasKey, extras))
+	} else {
+		h.wrappedLogger.Info(msg)
+	}
 }
 
 func (h *HclogAdapter) Warn(msg string, args ...interface{}) {
-	h.wrappedLogger.Warn(msg, mlog.String(h.extrasKey, fmt.Sprintln(args...)))
+	extras := strings.TrimSpace(fmt.Sprint(args...))
+	if extras != "" {
+		h.wrappedLogger.Warn(msg, mlog.String(h.extrasKey, extras))
+	} else {
+		h.wrappedLogger.Warn(msg)
+	}
 }
 
 func (h *HclogAdapter) Error(msg string, args ...interface{}) {
-	h.wrappedLogger.Error(msg, mlog.String(h.extrasKey, fmt.Sprintln(args...)))
+	extras := strings.TrimSpace(fmt.Sprint(args...))
+	if extras != "" {
+		h.wrappedLogger.Error(msg, mlog.String(h.extrasKey, extras))
+	} else {
+		h.wrappedLogger.Error(msg)
+	}
 }
 
 func (h *HclogAdapter) IsTrace() bool {
diff --git a/plugin/interface_generator/main.go b/plugin/interface_generator/main.go
index 5f66506d3..8cbaf4249 100644
--- a/plugin/interface_generator/main.go
+++ b/plugin/interface_generator/main.go
@@ -76,12 +76,22 @@ func FieldListDestruct(structPrefix string, fieldList *ast.FieldList, fileset *t
 	}
 	nextLetter := 'A'
 	for _, field := range fieldList.List {
+		typeNameBuffer := &bytes.Buffer{}
+		err := printer.Fprint(typeNameBuffer, fileset, field.Type)
+		if err != nil {
+			panic(err)
+		}
+		typeName := typeNameBuffer.String()
+		suffix := ""
+		if strings.HasPrefix(typeName, "...") {
+			suffix = "..."
+		}
 		if len(field.Names) == 0 {
-			result = append(result, structPrefix+string(nextLetter))
+			result = append(result, structPrefix+string(nextLetter)+suffix)
 			nextLetter += 1
 		} else {
 			for range field.Names {
-				result = append(result, structPrefix+string(nextLetter))
+				result = append(result, structPrefix+string(nextLetter)+suffix)
 				nextLetter += 1
 			}
 		}
@@ -103,6 +113,9 @@ func FieldListToStructList(fieldList *ast.FieldList, fileset *token.FileSet) str
 			panic(err)
 		}
 		typeName := typeNameBuffer.String()
+		if strings.HasPrefix(typeName, "...") {
+			typeName = strings.Replace(typeName, "...", "[]", 1)
+		}
 		if len(field.Names) == 0 {
 			result = append(result, string(nextLetter)+" "+typeName)
 			nextLetter += 1
@@ -224,6 +237,8 @@ func (s *HooksRPCServer) {{.Name}}(args *{{.Name}}Args, returns *{{.Name}}Return
 		{{.Name}}{{funcStyle .Params}} {{funcStyle .Return}}
 	}); ok {
 		{{if .Return}}{{destruct "returns." .Return}} = {{end}}hook.{{.Name}}({{destruct "args." .Params}})
+	} else {
+		return fmt.Errorf("Hook {{.Name}} called but not implemented.")
 	}
 	return nil
 }
@@ -253,6 +268,8 @@ func (s *APIRPCServer) {{.Name}}(args *{{.Name}}Args, returns *{{.Name}}Returns)
 		{{.Name}}{{funcStyle .Params}} {{funcStyle .Return}}
 	}); ok {
 		{{if .Return}}{{destruct "returns." .Return}} = {{end}}hook.{{.Name}}({{destruct "args." .Params}})
+	} else {
+		return fmt.Errorf("API {{.Name}} called but not implemented.")
 	}
 	return nil
 }
diff --git a/plugin/plugintest/api.go b/plugin/plugintest/api.go
index 145fcbf9d..b9d8d7521 100644
--- a/plugin/plugintest/api.go
+++ b/plugin/plugintest/api.go
@@ -1,4 +1,4 @@
-// Code generated by mockery v1.0.0
+// Code generated by mockery v1.0.0. DO NOT EDIT.
 
 // Regenerate this file using `make plugin-mocks`.
 
@@ -563,6 +563,38 @@ func (_m *API) LoadPluginConfiguration(dest interface{}) error {
 	return r0
 }
 
+// LogDebug provides a mock function with given fields: msg, keyValuePairs
+func (_m *API) LogDebug(msg string, keyValuePairs ...interface{}) {
+	var _ca []interface{}
+	_ca = append(_ca, msg)
+	_ca = append(_ca, keyValuePairs...)
+	_m.Called(_ca...)
+}
+
+// LogError provides a mock function with given fields: msg, keyValuePairs
+func (_m *API) LogError(msg string, keyValuePairs ...interface{}) {
+	var _ca []interface{}
+	_ca = append(_ca, msg)
+	_ca = append(_ca, keyValuePairs...)
+	_m.Called(_ca...)
+}
+
+// LogInfo provides a mock function with given fields: msg, keyValuePairs
+func (_m *API) LogInfo(msg string, keyValuePairs ...interface{}) {
+	var _ca []interface{}
+	_ca = append(_ca, msg)
+	_ca = append(_ca, keyValuePairs...)
+	_m.Called(_ca...)
+}
+
+// LogWarn provides a mock function with given fields: msg, keyValuePairs
+func (_m *API) LogWarn(msg string, keyValuePairs ...interface{}) {
+	var _ca []interface{}
+	_ca = append(_ca, msg)
+	_ca = append(_ca, keyValuePairs...)
+	_m.Called(_ca...)
+}
+
 // PublishWebSocketEvent provides a mock function with given fields: event, payload, broadcast
 func (_m *API) PublishWebSocketEvent(event string, payload map[string]interface{}, broadcast *model.WebsocketBroadcast) {
 	_m.Called(event, payload, broadcast)
diff --git a/plugin/plugintest/hooks.go b/plugin/plugintest/hooks.go
index 0d335a626..790a5a993 100644
--- a/plugin/plugintest/hooks.go
+++ b/plugin/plugintest/hooks.go
@@ -1,4 +1,4 @@
-// Code generated by mockery v1.0.0
+// Code generated by mockery v1.0.0. DO NOT EDIT.
 
 // Regenerate this file using `make plugin-mocks`.
 
diff --git a/plugin/supervisor.go b/plugin/supervisor.go
index 0471f7861..58a7aa783 100644
--- a/plugin/supervisor.go
+++ b/plugin/supervisor.go
@@ -5,7 +5,6 @@ package plugin
 
 import (
 	"fmt"
-	"os"
 	"os/exec"
 	"path/filepath"
 	"strings"
@@ -29,7 +28,7 @@ func NewSupervisor(pluginInfo *model.BundleInfo, parentLogger *mlog.Logger, apiI
 	wrappedLogger := pluginInfo.WrapLogger(parentLogger)
 
 	hclogAdaptedLogger := &HclogAdapter{
-		wrappedLogger: wrappedLogger,
+		wrappedLogger: wrappedLogger.WithCallerSkip(1),
 		extrasKey:     "wrapped_extras",
 	}
 
@@ -50,8 +49,8 @@ func NewSupervisor(pluginInfo *model.BundleInfo, parentLogger *mlog.Logger, apiI
 		HandshakeConfig: Handshake,
 		Plugins:         pluginMap,
 		Cmd:             exec.Command(executable),
-		SyncStdout:      os.Stdout,
-		SyncStderr:      os.Stdout,
+		SyncStdout:      wrappedLogger.With(mlog.String("source", "plugin_stdout")).StdLogWriter(),
+		SyncStderr:      wrappedLogger.With(mlog.String("source", "plugin_stderr")).StdLogWriter(),
 		Logger:          hclogAdaptedLogger,
 		StartTimeout:    time.Second * 3,
 	})