1 files changed, 224 insertions, 0 deletions
diff --git a/utils/logger/logger.go b/utils/logger/logger.go
new file mode 100644
index 000000000..dc4aec19f
--- /dev/null
+++ b/utils/logger/logger.go
@@ -0,0 +1,224 @@
+// this is a new logger interface for mattermost
+
+package logger
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"path/filepath"
+	"runtime"
+
+	l4g "github.com/alecthomas/log4go"
+
+	"github.com/mattermost/platform/model"
+	"github.com/mattermost/platform/utils"
+	"github.com/pkg/errors"
+	"strings"
+)
+
+// this pattern allows us to "mock" the underlying l4g code when unit testing
+var debugLog = l4g.Debug
+var infoLog = l4g.Info
+var errorLog = l4g.Error
+
+func init() {
+	initL4g(utils.Cfg.LogSettings)
+}
+
+// listens for configuration changes that we might need to respond to
+var configListenerID = utils.AddConfigListener(func(oldConfig *model.Config, newConfig *model.Config) {
+	infoLog("Configuration change detected, reloading log settings")
+	initL4g(newConfig.LogSettings)
+})
+
+// assumes that ../config.go::configureLog has already been called, and has in turn called l4g.close() to clean up
+// any old filters that we might have previously created
+func initL4g(logSettings model.LogSettings) {
+	// TODO: add support for newConfig.LogSettings.EnableConsole. Right now, ../config.go sets it up in its configureLog
+	// method. If we also set it up here, messages will be written to the console twice. Eventually, when all instances
+	// of l4g have been replaced by this logger, we can move that code to here
+	if logSettings.EnableFile {
+		level := l4g.DEBUG
+		if logSettings.FileLevel == "INFO" {
+			level = l4g.INFO
+		} else if logSettings.FileLevel == "WARN" {
+			level = l4g.WARNING
+		} else if logSettings.FileLevel == "ERROR" {
+			level = l4g.ERROR
+		}
+
+		// create a logger that writes JSON objects to a file, and override our log methods to use it
+		flw := NewJSONFileLogger(level, utils.GetLogFileLocation(logSettings.FileLocation)+".jsonl")
+		debugLog = flw.Debug
+		infoLog = flw.Info
+		errorLog = flw.Error
+	}
+}
+
+// contextKey lets us add contextual information to log messages
+type contextKey string
+
+func (c contextKey) String() string {
+	return string(c)
+}
+
+const contextKeyUserID contextKey = contextKey("user_id")
+const contextKeyRequestID contextKey = contextKey("request_id")
+
+// any contextKeys added to this array will be serialized in every log message
+var contextKeys = [2]contextKey{contextKeyUserID, contextKeyRequestID}
+
+// WithUserId adds a user id to the specified context. If the returned Context is subsequently passed to a logging
+// method, the user id will automatically be included in the logged message
+func WithUserId(ctx context.Context, userID string) context.Context {
+	return context.WithValue(ctx, contextKeyUserID, userID)
+}
+
+// WithRequestId adds a request id to the specified context. If the returned Context is subsequently passed to a logging
+// method, the request id will automatically be included in the logged message
+func WithRequestId(ctx context.Context, requestID string) context.Context {
+	return context.WithValue(ctx, contextKeyRequestID, requestID)
+}
+
+// extracts known contextKey values from the specified Context and assembles them into the returned map
+func serializeContext(ctx context.Context) map[string]string {
+	serialized := make(map[string]string)
+	for _, key := range contextKeys {
+		value, ok := ctx.Value(key).(string)
+		if ok {
+			serialized[string(key)] = value
+		}
+	}
+	return serialized
+}
+
+// Returns the path to the next file up the callstack that has a different name than this file
+// in other words, finds the path to the file that is doing the logging.
+// Removes machine-specific prefix, so returned path starts with /platform.
+// Looks a maximum of 10 frames up the call stack to find a file that has a different name than this one.
+func getCallerFilename() (string, error) {
+	_, currentFilename, _, ok := runtime.Caller(0)
+	if !ok {
+		return "", errors.New("Failed to traverse stack frame")
+	}
+
+	platformDirectory := currentFilename
+	for filepath.Base(platformDirectory) != "platform" {
+		platformDirectory = filepath.Dir(platformDirectory)
+		if platformDirectory == "." || platformDirectory == string(filepath.Separator) {
+			break
+		}
+	}
+
+	for i := 1; i < 10; i++ {
+		_, parentFilename, _, ok := runtime.Caller(i)
+		if !ok {
+			return "", errors.New("Failed to traverse stack frame")
+		} else if parentFilename != currentFilename && strings.Contains(parentFilename, platformDirectory) {
+			// trim parentFilename such that we return the path to parentFilename, relative to platformDirectory
+			return parentFilename[strings.LastIndex(parentFilename, platformDirectory)+len(platformDirectory)+1:], nil
+		}
+	}
+	return "", errors.New("Failed to traverse stack frame")
+}
+
+// creates a JSON representation of a log message
+func serializeLogMessage(ctx context.Context, message string) string {
+	callerFilename, err := getCallerFilename()
+	if err != nil {
+		callerFilename = "Unknown"
+	}
+
+	bytes, err := json.Marshal(&struct {
+		Context map[string]string `json:"context"`
+		File    string            `json:"file"`
+		Message string            `json:"message"`
+	}{
+		serializeContext(ctx),
+		callerFilename,
+		message,
+	})
+	if err != nil {
+		errorLog("Failed to serialize log message %v", message)
+	}
+	return string(bytes)
+}
+
+func formatMessage(args ...interface{}) string {
+	msg, ok := args[0].(string)
+	if !ok {
+		panic("Second argument is not of type string")
+	}
+	if len(args) > 1 {
+		variables := args[1:]
+		msg = fmt.Sprintf(msg, variables...)
+	}
+	return msg
+}
+
+// Debugc logs a debugLog level message, including context information that is stored in the first parameter.
+// If two parameters are supplied, the second must be a message string, and will be logged directly.
+// If more than two parameters are supplied, the second parameter must be a format string, and the remaining parameters
+// must be the variables to substitute into the format string, following the convention of the fmt.Sprintf(...) function.
+func Debugc(ctx context.Context, args ...interface{}) {
+	debugLog(func() string {
+		msg := formatMessage(args...)
+		return serializeLogMessage(ctx, msg)
+	})
+}
+
+// Debugf logs a debugLog level message.
+// If one parameter is supplied, it must be a message string, and will be logged directly.
+// If two or more parameters are specified, the first parameter must be a format string, and the remaining parameters
+// must be the variables to substitute into the format string, following the convention of the fmt.Sprintf(...) function.
+func Debugf(args ...interface{}) {
+	debugLog(func() string {
+		msg := formatMessage(args...)
+		return serializeLogMessage(context.Background(), msg)
+	})
+}
+
+// Infoc logs an infoLog level message, including context information that is stored in the first parameter.
+// If two parameters are supplied, the second must be a message string, and will be logged directly.
+// If more than two parameters are supplied, the second parameter must be a format string, and the remaining parameters
+// must be the variables to substitute into the format string, following the convention of the fmt.Sprintf(...) function.
+func Infoc(ctx context.Context, args ...interface{}) {
+	infoLog(func() string {
+		msg := formatMessage(args...)
+		return serializeLogMessage(ctx, msg)
+	})
+}
+
+// Infof logs an infoLog level message.
+// If one parameter is supplied, it must be a message string, and will be logged directly.
+// If two or more parameters are specified, the first parameter must be a format string, and the remaining parameters
+// must be the variables to substitute into the format string, following the convention of the fmt.Sprintf(...) function.
+func Infof(args ...interface{}) {
+	infoLog(func() string {
+		msg := formatMessage(args...)
+		return serializeLogMessage(context.Background(), msg)
+	})
+}
+
+// Errorc logs an error level message, including context information that is stored in the first parameter.
+// If two parameters are supplied, the second must be a message string, and will be logged directly.
+// If more than two parameters are supplied, the second parameter must be a format string, and the remaining parameters
+// must be the variables to substitute into the format string, following the convention of the fmt.Sprintf(...) function.
+func Errorc(ctx context.Context, args ...interface{}) {
+	errorLog(func() string {
+		msg := formatMessage(args...)
+		return serializeLogMessage(ctx, msg)
+	})
+}
+
+// Errorf logs an error level message.
+// If one parameter is supplied, it must be a message string, and will be logged directly.
+// If two or more parameters are specified, the first parameter must be a format string, and the remaining parameters
+// must be the variables to substitute into the format string, following the convention of the fmt.Sprintf(...) function.
+func Errorf(args ...interface{}) {
+	errorLog(func() string {
+		msg := formatMessage(args...)
+		return serializeLogMessage(context.Background(), msg)
+	})
+}