isle/go/cmd/entrypoint/logger.go

package main

import (
	"fmt"
	"os"
	"path"
	"sync"

	"dev.mediocregopher.com/mediocre-go-lib.git/mctx"
	"dev.mediocregopher.com/mediocre-go-lib.git/mlog"
)

type logMsgHandler struct {
	stderr *os.File
	l      sync.Mutex
}

func newLogMsgHandler() mlog.MessageHandler {
	return &logMsgHandler{
		stderr: os.Stderr,
	}
}

func (h *logMsgHandler) Sync() error {
	return h.stderr.Sync()
}

func (h *logMsgHandler) Handle(msg mlog.FullMessage) error {
	h.l.Lock()
	defer h.l.Unlock()

	var namespaceStr string

	if len(msg.Namespace) > 0 {
		namespaceStr = "[" + path.Join(msg.Namespace...) + "] "
	}

	var annotationsStr string

	if m := mctx.EvaluateAnnotations(msg.Context, nil).StringMap(); len(m) > 0 {

		for k, v := range m {
			annotationsStr += fmt.Sprintf(" %q=%q", k, v)
		}
	}

	fmt.Fprintf(
		h.stderr, "%s %s%s%s\n",
		msg.Level.String(),
		namespaceStr,
		msg.Description,
		annotationsStr,
	)

	return nil
}