Add log output to Windows Event Log

By setting `logging.to_eventlog: true` all log output will be written
to the Application log. The source name will be name of the Beat.

CHANGELOG.asciidoc

@@ -113,6 +113,7 @@ https://github.com/elastic/beats/compare/v6.0.0-beta2...master[Check the HEAD di
 - Add the ability to write structured logs. {pull}5901[5901]
 - Use structured logging for the metrics that are periodically logged via the
   `logging.metrics` feature. {pull}5915[5915]
+- Add the ability to log to the Windows Event Log. {pull}5913[5813]
 
 *Auditbeat*
 

auditbeat/auditbeat.reference.yml

@@ -831,12 +831,11 @@ setup.kibana:
 
 
 #================================ Logging ======================================
-# There are three options for the log output: syslog, file, stderr.
-# Under Windows systems, the log files are per default sent to the file output,
-# under all other system per default to syslog.
+# There are four options for the log output: file, stderr, syslog, eventlog
+# The file output is the default.
 
 # Sets log level. The default log level is info.
-# Available log levels are: critical, error, warning, info, debug
+# Available log levels are: error, warning, info, debug
 #logging.level: info
 
 # Enable debug output for selected components. To enable all selectors use ["*"]
@@ -845,7 +844,10 @@ setup.kibana:
 #logging.selectors: [ ]
 
 # Send all logging output to syslog. The default is false.
-#logging.to_syslog: true
+#logging.to_syslog: false
+
+# Send all logging output to Windows Event Logs. The default is false.
+#logging.to_eventlog: false
 
 # If enabled, auditbeat periodically logs its internal metrics that have changed
 # in the last period. For each metric that changed, the delta from the value at

auditbeat/auditbeat.yml

@@ -138,7 +138,7 @@ output.elasticsearch:
 #================================ Logging =====================================
 
 # Sets log level. The default log level is info.
-# Available log levels are: critical, error, warning, info, debug
+# Available log levels are: error, warning, info, debug
 #logging.level: debug
 
 # At debug level, you can selectively enable logging only for some components.

filebeat/filebeat.reference.yml

@@ -1266,12 +1266,11 @@ setup.kibana:
 
 
 #================================ Logging ======================================
-# There are three options for the log output: syslog, file, stderr.
-# Under Windows systems, the log files are per default sent to the file output,
-# under all other system per default to syslog.
+# There are four options for the log output: file, stderr, syslog, eventlog
+# The file output is the default.
 
 # Sets log level. The default log level is info.
-# Available log levels are: critical, error, warning, info, debug
+# Available log levels are: error, warning, info, debug
 #logging.level: info
 
 # Enable debug output for selected components. To enable all selectors use ["*"]
@@ -1280,7 +1279,10 @@ setup.kibana:
 #logging.selectors: [ ]
 
 # Send all logging output to syslog. The default is false.
-#logging.to_syslog: true
+#logging.to_syslog: false
+
+# Send all logging output to Windows Event Logs. The default is false.
+#logging.to_eventlog: false
 
 # If enabled, filebeat periodically logs its internal metrics that have changed
 # in the last period. For each metric that changed, the delta from the value at

filebeat/filebeat.yml

@@ -167,7 +167,7 @@ output.elasticsearch:
 #================================ Logging =====================================
 
 # Sets log level. The default log level is info.
-# Available log levels are: critical, error, warning, info, debug
+# Available log levels are: error, warning, info, debug
 #logging.level: debug
 
 # At debug level, you can selectively enable logging only for some components.

heartbeat/heartbeat.reference.yml

@@ -941,12 +941,11 @@ setup.kibana:
 
 
 #================================ Logging ======================================
-# There are three options for the log output: syslog, file, stderr.
-# Under Windows systems, the log files are per default sent to the file output,
-# under all other system per default to syslog.
+# There are four options for the log output: file, stderr, syslog, eventlog
+# The file output is the default.
 
 # Sets log level. The default log level is info.
-# Available log levels are: critical, error, warning, info, debug
+# Available log levels are: error, warning, info, debug
 #logging.level: info
 
 # Enable debug output for selected components. To enable all selectors use ["*"]
@@ -955,7 +954,10 @@ setup.kibana:
 #logging.selectors: [ ]
 
 # Send all logging output to syslog. The default is false.
-#logging.to_syslog: true
+#logging.to_syslog: false
+
+# Send all logging output to Windows Event Logs. The default is false.
+#logging.to_eventlog: false
 
 # If enabled, heartbeat periodically logs its internal metrics that have changed
 # in the last period. For each metric that changed, the delta from the value at

heartbeat/heartbeat.yml

@@ -114,7 +114,7 @@ output.elasticsearch:
 #================================ Logging =====================================
 
 # Sets log level. The default log level is info.
-# Available log levels are: critical, error, warning, info, debug
+# Available log levels are: error, warning, info, debug
 #logging.level: debug
 
 # At debug level, you can selectively enable logging only for some components.

libbeat/_meta/config.reference.yml

@@ -727,12 +727,11 @@ setup.kibana:
 
 
 #================================ Logging ======================================
-# There are three options for the log output: syslog, file, stderr.
-# Under Windows systems, the log files are per default sent to the file output,
-# under all other system per default to syslog.
+# There are four options for the log output: file, stderr, syslog, eventlog
+# The file output is the default.
 
 # Sets log level. The default log level is info.
-# Available log levels are: critical, error, warning, info, debug
+# Available log levels are: error, warning, info, debug
 #logging.level: info
 
 # Enable debug output for selected components. To enable all selectors use ["*"]
@@ -741,7 +740,10 @@ setup.kibana:
 #logging.selectors: [ ]
 
 # Send all logging output to syslog. The default is false.
-#logging.to_syslog: true
+#logging.to_syslog: false
+
+# Send all logging output to Windows Event Logs. The default is false.
+#logging.to_eventlog: false
 
 # If enabled, beatname periodically logs its internal metrics that have changed
 # in the last period. For each metric that changed, the delta from the value at

libbeat/_meta/config.yml

@@ -84,7 +84,7 @@ output.elasticsearch:
 #================================ Logging =====================================
 
 # Sets log level. The default log level is info.
-# Available log levels are: critical, error, warning, info, debug
+# Available log levels are: error, warning, info, debug
 #logging.level: debug
 
 # At debug level, you can selectively enable logging only for some components.

libbeat/docs/loggingconfig.asciidoc

@@ -44,6 +44,11 @@ You can specify the following options in the `logging` section of the
 
 When true, writes all logging output to the syslog.
 
+[float]
+==== `logging.to_eventlog`
+
+When true, writes all logging output to the Windows Event Log.
+
 [float]
 ==== `logging.to_files`
 

libbeat/logp/config.go

@@ -13,6 +13,7 @@ type Config struct {
 	ToStderr    bool `config:"to_stderr"`
 	ToSyslog    bool `config:"to_syslog"`
 	ToFiles     bool `config:"to_files"`
+	ToEventLog  bool `config:"to_eventlog"`
 
 	Files FileConfig `config:"files"`
 

libbeat/logp/core.go

@@ -55,6 +55,8 @@ func Configure(cfg Config) error {
 		sink, err = makeStderrOutput(cfg)
 	case cfg.ToSyslog:
 		sink, err = makeSyslogOutput(cfg)
+	case cfg.ToEventLog:
+		sink, err = makeEventLogOutput(cfg)
 	case cfg.ToFiles:
 		fallthrough
 	default:
@@ -158,6 +160,10 @@ func makeSyslogOutput(cfg Config) (zapcore.Core, error) {
 	return newSyslog(buildEncoder(cfg), cfg.Level.zapLevel())
 }
 
+func makeEventLogOutput(cfg Config) (zapcore.Core, error) {
+	return newEventLog(cfg.Beat, buildEncoder(cfg), cfg.Level.zapLevel())
+}
+
 func makeFileOutput(cfg Config) (zapcore.Core, error) {
 	name := cfg.Beat
 	if cfg.Files.Name != "" {

libbeat/logp/encoding.go

@@ -6,6 +6,21 @@ import (
 	"go.uber.org/zap/zapcore"
 )
 
+var baseEncodingConfig = zapcore.EncoderConfig{
+	TimeKey:        "timestamp",
+	LevelKey:       "level",
+	NameKey:        "logger",
+	CallerKey:      "caller",
+	MessageKey:     "message",
+	StacktraceKey:  "stacktrace",
+	LineEnding:     zapcore.DefaultLineEnding,
+	EncodeLevel:    zapcore.LowercaseLevelEncoder,
+	EncodeTime:     zapcore.ISO8601TimeEncoder,
+	EncodeDuration: millisecondsDurationEncoder,
+	EncodeCaller:   zapcore.ShortCallerEncoder,
+	EncodeName:     zapcore.FullNameEncoder,
+}
+
 func buildEncoder(cfg Config) zapcore.Encoder {
 	if cfg.JSON {
 		return zapcore.NewJSONEncoder(jsonEncoderConfig())
@@ -17,37 +32,14 @@ func buildEncoder(cfg Config) zapcore.Encoder {
 }
 
 func jsonEncoderConfig() zapcore.EncoderConfig {
-	return zapcore.EncoderConfig{
-		TimeKey:        "timestamp",
-		LevelKey:       "level",
-		NameKey:        "logger",
-		CallerKey:      "caller",
-		MessageKey:     "message",
-		StacktraceKey:  "stacktrace",
-		LineEnding:     zapcore.DefaultLineEnding,
-		EncodeLevel:    zapcore.LowercaseLevelEncoder,
-		EncodeTime:     zapcore.ISO8601TimeEncoder,
-		EncodeDuration: millisecondsDurationEncoder,
-		EncodeCaller:   zapcore.ShortCallerEncoder,
-		EncodeName:     zapcore.FullNameEncoder,
-	}
+	return baseEncodingConfig
 }
 
 func consoleEncoderConfig() zapcore.EncoderConfig {
-	return zapcore.EncoderConfig{
-		TimeKey:        "timestamp",
-		LevelKey:       "level",
-		NameKey:        "logger",
-		CallerKey:      "caller",
-		MessageKey:     "message",
-		StacktraceKey:  "stacktrace",
-		LineEnding:     zapcore.DefaultLineEnding,
-		EncodeLevel:    zapcore.CapitalLevelEncoder,
-		EncodeTime:     zapcore.ISO8601TimeEncoder,
-		EncodeDuration: millisecondsDurationEncoder,
-		EncodeCaller:   zapcore.ShortCallerEncoder,
-		EncodeName:     bracketedNameEncoder,
-	}
+	c := baseEncodingConfig
+	c.EncodeLevel = zapcore.CapitalLevelEncoder
+	c.EncodeName = bracketedNameEncoder
+	return c
 }
 
 func syslogEncoderConfig() zapcore.EncoderConfig {

libbeat/logp/eventlog_unsupported.go

@@ -0,0 +1,12 @@
+// +build !windows
+
+package logp
+
+import (
+	"github.com/pkg/errors"
+	"go.uber.org/zap/zapcore"
+)
+
+func newEventLog(beatname string, encoder zapcore.Encoder, enab zapcore.LevelEnabler) (zapcore.Core, error) {
+	return nil, errors.New("eventlog is only supported on Windows")
+}

libbeat/logp/eventlog_windows.go

@@ -0,0 +1,92 @@
+package logp
+
+import (
+	"strings"
+
+	"github.com/pkg/errors"
+	"go.uber.org/zap/zapcore"
+	"golang.org/x/sys/windows/svc/eventlog"
+)
+
+const (
+	// eventID is arbitrary but must be between [1-1000].
+	eventID  = 100
+	supports = eventlog.Error | eventlog.Warning | eventlog.Info
+)
+
+const alreadyExistsMsg = "registry key already exists"
+
+type eventLogCore struct {
+	zapcore.LevelEnabler
+	encoder zapcore.Encoder
+	fields  []zapcore.Field
+	log     *eventlog.Log
+}
+
+func newEventLog(appName string, encoder zapcore.Encoder, enab zapcore.LevelEnabler) (zapcore.Core, error) {
+	if appName == "" {
+		return nil, errors.New("appName cannot be empty")
+	}
+	appName = strings.Title(strings.ToLower(appName))
+
+	if err := eventlog.InstallAsEventCreate(appName, supports); err != nil {
+		if !strings.Contains(err.Error(), alreadyExistsMsg) {
+			return nil, errors.Wrap(err, "failed to setup eventlog")
+		}
+	}
+
+	log, err := eventlog.Open(appName)
+	if err != nil {
+		return nil, errors.Wrap(err, "failed to open eventlog")
+	}
+
+	return &eventLogCore{
+		LevelEnabler: enab,
+		encoder:      encoder,
+		log:          log,
+	}, nil
+}
+
+func (c *eventLogCore) With(fields []zapcore.Field) zapcore.Core {
+	clone := c.Clone()
+	clone.fields = append(clone.fields, fields...)
+	return clone
+}
+
+func (c *eventLogCore) Check(entry zapcore.Entry, checked *zapcore.CheckedEntry) *zapcore.CheckedEntry {
+	if c.Enabled(entry.Level) {
+		return checked.AddCore(entry, c)
+	}
+	return checked
+}
+
+func (c *eventLogCore) Write(entry zapcore.Entry, fields []zapcore.Field) error {
+	buffer, err := c.encoder.EncodeEntry(entry, fields)
+	if err != nil {
+		return errors.Wrap(err, "failed to encode entry")
+	}
+
+	msg := buffer.String()
+	switch entry.Level {
+	case zapcore.DebugLevel, zapcore.InfoLevel:
+		return c.log.Info(eventID, msg)
+	case zapcore.WarnLevel:
+		return c.log.Warning(eventID, msg)
+	case zapcore.ErrorLevel, zapcore.DPanicLevel, zapcore.PanicLevel, zapcore.FatalLevel:
+		return c.log.Error(eventID, msg)
+	default:
+		return errors.Errorf("unhandled log level: %v", entry.Level)
+	}
+}
+
+func (c *eventLogCore) Sync() error {
+	return nil
+}
+
+func (c *eventLogCore) Clone() *eventLogCore {
+	clone := *c
+	clone.encoder = c.encoder.Clone()
+	clone.fields = make([]zapcore.Field, len(c.fields), len(c.fields)+10)
+	copy(clone.fields, c.fields)
+	return &clone
+}

libbeat/logp/fields.go

@@ -38,7 +38,7 @@ var (
 	Int64s      = zap.Int64s
 	Namespace   = zap.Namespace
 	Reflect     = zap.Reflect
-	Stack       = zap.Reflect
+	Stack       = zap.Stack
 	String      = zap.String
 	Stringer    = zap.Stringer
 	Strings     = zap.Strings

libbeat/logp/syslog_unix.go

@@ -53,7 +53,7 @@ func (c *syslogCore) Write(entry zapcore.Entry, fields []zapcore.Field) error {
 	}
 
 	// Console encoder writes tabs which don't render nicely with syslog.
-	replaceTabsWithSpaces(buffer.Bytes(), 2)
+	replaceTabsWithSpaces(buffer.Bytes(), 4)
 
 	msg := buffer.String()
 	switch entry.Level {

libbeat/logp/syslog_unsupported.go

@@ -3,9 +3,10 @@
 package logp
 
 import (
+	"github.com/pkg/errors"
 	"go.uber.org/zap/zapcore"
 )
 
 func newSyslog(_ zapcore.Encoder, _ zapcore.LevelEnabler) (zapcore.Core, error) {
-	return zapcore.NewNopCore(), nil
+	return nil, errors.New("syslog is not supported on this OS")
 }