Merge pull request #1 from cabify/colega/rc-v1.3.0-configure-service-logger

RC v1.3.0 configure service logger

Author: colega

CHANGELOG.md

@@ -0,0 +1,30 @@
+# Changelog
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [Unreleased]
+### Added
+- Nothing
+
+### Changed
+- Nothing
+
+### Deprecated
+- Nothing
+
+### Removed
+- Nothing
+
+### Fixed
+- Nothing
+
+### Security
+- Nothing
+
+## [1.3.0] - 2019-02-27
+### Added
+- `ConfigureDefaultLogger` boilerplate for logger configuration
+- `measuredLoggingHandler` to wrap loggers with metrics
+- `CHANGELOG.md`: this file

configure.go

@@ -0,0 +1,55 @@
+package log
+
+import (
+	"os"
+)
+
+// Config defines the logging configuration
+type Config struct {
+	Level  string `default:"info"`
+	Output string `default:"stdout"`
+}
+
+// ConfigureDefaultLogger configures loggers for your service, optionally adding log message counters with your favorite
+// metrics system
+func ConfigureDefaultLogger(name string, cfg Config, logCounters ...CountLogMessage) {
+	if logLevel, ok := logLevelMap[cfg.Level]; ok {
+		SetLevel(logLevel) // This sets the default level for all future
+		DefaultLevel = logLevel
+	} else {
+		Warningf("Unknown log level configured: %s", cfg.Level)
+	}
+
+	var handler Handler = NewFileHandler(getLoggerOutput(cfg.Output))
+
+	if len(logCounters) > 0 {
+		handler = &metricsAgentLoggingHandler{
+			Handler:     handler,
+			logCounters: logCounters,
+		}
+	}
+	handler.SetFormatter(DefaultFormatter)
+
+	logger := NewLogger(name)
+	if cfg.Level != logLevelDebug {
+		logger = NoDebugLogger{
+			Logger: logger,
+		}
+	}
+	logger.SetHandler(handler)
+
+	DefaultLogger = logger
+	Infof("Configured default logger %s with log level %s", name, cfg.Level)
+}
+
+func getLoggerOutput(outputName string) *os.File {
+	switch outputName {
+	case "stdout":
+		return os.Stdout
+	case "stderr":
+		return os.Stderr
+	default:
+		Warningf("Unknown logger output defined in the config: '%s'", outputName)
+		return os.Stderr
+	}
+}

log.go

@@ -58,3 +58,29 @@ func Infoln(args ...interface{})                   { DefaultLogger.Infoln(args..
 func Debug(args ...interface{})                    { DefaultLogger.Debug(args...) }
 func Debugf(format string, args ...interface{})    { DefaultLogger.Debugf(format, args...) }
 func Debugln(args ...interface{})                  { DefaultLogger.Debugln(args...) }
+
+const (
+	logLevelCritical = "critical"
+	logLevelError    = "error"
+	logLevelWarning  = "warning"
+	logLevelNotice   = "notice"
+	logLevelInfo     = "info"
+	logLevelDebug    = "debug"
+)
+
+var logLevelMap = map[string]Level{
+	logLevelCritical: CRITICAL,
+	logLevelError:    ERROR,
+	logLevelWarning:  WARNING,
+	logLevelNotice:   NOTICE,
+	logLevelInfo:     INFO,
+	logLevelDebug:    DEBUG,
+}
+
+var logLevelNameMap = make(map[Level]string)
+
+func init() {
+	for name, value := range logLevelMap {
+		logLevelNameMap[value] = name
+	}
+}

metrics_logging_handler.go

@@ -0,0 +1,21 @@
+package log
+
+// CountLogMessage offers a method to count log messages logged by the logger
+type CountLogMessage func(level string)
+
+type metricsAgentLoggingHandler struct {
+	Handler
+	logCounters []CountLogMessage
+}
+
+// Handle decorates Handler's Handle method counting the log messages
+func (h *metricsAgentLoggingHandler) Handle(record *Record) {
+	level := "unknown"
+	if levelName, ok := logLevelNameMap[record.Level]; ok {
+		level = levelName
+	}
+	for _, countLogMessage := range h.logCounters {
+		countLogMessage(level)
+	}
+	h.Handler.Handle(record)
+}