Introduce SetCustomReceiver in the logger

ecs-agent/logger/custom_receiver.go

@@ -0,0 +1,61 @@
+package logger
+
+import (
+	"fmt"
+
+	"github.com/cihub/seelog"
+)
+
+// CustomReceiver defines the interface for custom logging implementations
+type CustomReceiver interface {
+	GetOutputFormat() string
+	Trace(message string)
+	Debug(message string)
+	Info(message string)
+	Warn(message string)
+	Error(message string)
+	Critical(message string)
+	Flush() error
+	Close() error
+}
+
+// internal wrapper that implements seelog.CustomReceiver
+type customReceiverWrapper struct {
+	receiver CustomReceiver
+}
+
+func (w *customReceiverWrapper) ReceiveMessage(message string, level seelog.LogLevel, context seelog.LogContextInterface) error {
+
+	switch level {
+	case seelog.TraceLvl:
+		w.receiver.Trace(message)
+	case seelog.DebugLvl:
+		w.receiver.Debug(message)
+	case seelog.InfoLvl:
+		w.receiver.Info(message)
+	case seelog.WarnLvl:
+		w.receiver.Warn(message)
+	case seelog.ErrorLvl:
+		w.receiver.Error(message)
+	case seelog.CriticalLvl:
+		w.receiver.Critical(message)
+	default:
+		fmt.Printf("Unhandled level: %v", level)
+	}
+	return nil
+}
+
+func (w *customReceiverWrapper) AfterParse(initArgs seelog.CustomReceiverInitArgs) error {
+	return nil
+}
+
+func (w *customReceiverWrapper) Flush() {
+	err := w.receiver.Flush()
+	if err != nil {
+		fmt.Printf("Couldn't flush the logger due to: %v", err)
+	}
+}
+
+func (w *customReceiverWrapper) Close() error {
+	return w.receiver.Close()
+}

ecs-agent/logger/log.go

@@ -339,6 +339,49 @@ func SetLogToStdout(duplicate bool) {
 	reloadConfig()
 }
 
+// SetCustomReceiver configures the ECS Agent logger to use a custom logger implementation.
+// This allows external applications to intercept and handle ECS Agent logs in their own way,
+// such as sending logs to a custom destination or formatting them differently.
+// More details can be found here: https://github.com/cihub/seelog/wiki/Custom-receivers
+// The custom receiver must implement the CustomReceiver interface, which requires:
+// - GetTimestampFormat(): returns the desired timestamp format (e.g., "2006-01-02T15:04:05Z07:00")
+// - GetOutputFormat(): returns the desired output format ("logfmt", "json", or "windows")
+// - Log handling methods (Debug, Info, Warn, etc.)
+func SetCustomReceiver(receiver CustomReceiver) {
+	registerCustomFormatters()
+	wrapper := &customReceiverWrapper{receiver: receiver}
+	outputFormat := receiver.GetOutputFormat()
+
+	// Internal seelog configuration
+	customConfig := `
+    <seelog type="asyncloop">
+        <outputs>
+            <custom name="customReceiver" formatid="` + outputFormat + `"/>
+        </outputs>
+        <formats>
+			<format id="` + logFmt + `" format="%EcsAgentLogfmt" />
+			<format id="` + jsonFmt + `" format="%EcsAgentJson" />
+			<format id="windows" format="%EcsMsg" />
+        </formats>
+    </seelog>
+    `
+
+	parserParams := &seelog.CfgParseParams{
+		CustomReceiverProducers: map[string]seelog.CustomReceiverProducer{
+			"customReceiver": func(seelog.CustomReceiverInitArgs) (seelog.CustomReceiver, error) {
+				return wrapper, nil
+			},
+		},
+	}
+
+	replacementLogger, err := seelog.LoggerFromParamConfigAsString(customConfig, parserParams)
+	if err != nil {
+		fmt.Println("Failed to create a replacement logger", err)
+	}
+
+	setGlobalLogger(replacementLogger, outputFormat)
+}
+
 func init() {
 	Config = &logConfig{
 		logfile:       os.Getenv(LOGFILE_ENV_VAR),
@@ -352,10 +395,7 @@ func init() {
 	}
 }
 
-// InitSeelog registers custom logging formats, updates the internal Config struct
-// and reloads the global logger. This should only be called once, as external
-// callers should use the Config struct over environment variables directly.
-func InitSeelog() {
+func registerCustomFormatters() {
 	if err := seelog.RegisterCustomFormatter("EcsAgentLogfmt", logfmtFormatter); err != nil {
 		seelog.Error(err)
 	}
@@ -365,6 +405,13 @@ func InitSeelog() {
 	if err := seelog.RegisterCustomFormatter("EcsMsg", ecsMsgFormatter); err != nil {
 		seelog.Error(err)
 	}
+}
+
+// InitSeelog registers custom logging formats, updates the internal Config struct
+// and reloads the global logger. This should only be called once, as external
+// callers should use the Config struct over environment variables directly.
+func InitSeelog() {
+	registerCustomFormatters()
 
 	if DriverLogLevel := os.Getenv(LOGLEVEL_ENV_VAR); DriverLogLevel != "" {
 		SetDriverLogLevel(DriverLogLevel)