Go-Logs an UptimeEye senden (slog, zap)

logger := slog.New(slog.NewJSONHandler(os.Stdout, nil)).With(
    "service", "checkout",
    "env", os.Getenv("ENV"),
)
slog.SetDefault(logger)

slog.Info("payment authorized", "order_id", "4711", "duration_ms", 812)
// {"time":"2026-09-04T11:42:08.877Z","level":"INFO","msg":"payment authorized","service":"checkout","env":"prod","order_id":"4711","duration_ms":812}

package uptimeeye

import (
	"bytes"
	"net/http"
	"os"
	"sync"
	"time"
)

const endpoint = "https://logs.uptimeeye.com/v1/ingest/jsonline?_msg_field=msg&_time_field=time&_stream_fields=service,env"

// Writer buffers JSON lines and posts them every 2s or at 256 KiB.
type Writer struct {
	mu  sync.Mutex
	buf bytes.Buffer
	key string
}

func New() *Writer {
	w := &Writer{key: os.Getenv("UPTIMEEYE_INGEST_KEY")}
	go func() {
		for range time.Tick(2 * time.Second) {
			w.Flush()
		}
	}()
	return w
}

func (w *Writer) Write(p []byte) (int, error) {
	w.mu.Lock()
	w.buf.Write(p)
	full := w.buf.Len() >= 256<<10
	w.mu.Unlock()
	if full {
		w.Flush()
	}
	return len(p), nil
}

func (w *Writer) Flush() {
	w.mu.Lock()
	if w.buf.Len() == 0 {
		w.mu.Unlock()
		return
	}
	body := make([]byte, w.buf.Len())
	copy(body, w.buf.Bytes())
	w.buf.Reset()
	w.mu.Unlock()

	req, _ := http.NewRequest(http.MethodPost, endpoint, bytes.NewReader(body))
	req.Header.Set("Authorization", "Bearer "+w.key)
	req.Header.Set("Content-Type", "application/x-ndjson")
	if res, err := http.DefaultClient.Do(req); err == nil {
		res.Body.Close()
	}
}

// usage:
//   w := uptimeeye.New(); defer w.Flush()
//   slog.SetDefault(slog.New(slog.NewJSONHandler(io.MultiWriter(os.Stdout, w), nil)).With("service", "checkout", "env", "prod"))
//   zap: zapcore.NewCore(zapcore.NewJSONEncoder(cfg), zapcore.AddSync(w), zap.InfoLevel)