Go 微服务可观测性：日志、指标、追踪实战

import "github.com/rs/zerolog"

func main() {
    log := zerolog.New(os.Stdout).
        With().
        Timestamp().
        Caller().
        Logger()

    log.Info().
        Str("service", "user-service").
        Int("request_id", 12345).
        Msg("User login successful")
}

{"level":"info","service":"user-service","request_id":12345,"time":"2026-04-11T10:00:00Z","caller":"main.go:25","message":"User login successful"}

import "github.com/prometheus/client_golang/prometheus"
import "github.com/prometheus/client_golang/prometheus/promhttp"

var (
    httpRequests = prometheus.NewCounterVec(
        prometheus.CounterOpts{
            Name: "http_requests_total",
            Help: "Total HTTP requests",
        },
        []string{"method", "path", "status"},
    )

    httpDuration = prometheus.NewHistogramVec(
        prometheus.HistogramOpts{
            Name:    "http_request_duration_seconds",
            Buckets: prometheus.DefBuckets,
        },
        []string{"method", "path"},
    )
)

func init() {
    prometheus.MustRegister(httpRequests, httpDuration)
}

// 中间件示例
func promMiddleware(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        start := time.Now()
        
        rw := &responseWriter{ResponseWriter: w, statusCode: 200}
        next.ServeHTTP(rw, r)
        
        duration := time.Since(start).Seconds()
        httpRequests.WithLabelValues(r.Method, r.URL.Path, strconv.Itoa(rw.statusCode)).Inc()
        httpDuration.WithLabelValues(r.Method, r.URL.Path).Observe(duration)
    })
}

import "go.opentelemetry.io/otel"
import "go.opentelemetry.io/otel/exporters/jaeger"
import "go.opentelemetry.io/otel/sdk/trace"

func initTracer() (func(), error) {
    exp, err := jaeger.New(jaeger.WithAgentEndpoint())
    if err != nil {
        return nil, err
    }

    tp := trace.NewTracerProvider(
        trace.WithBatcher(exp),
        trace.WithSampler(trace.AlwaysSample()),
    )

    otel.SetTracerProvider(tp)

    return func() {
        ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
        defer cancel()
        tp.Shutdown(ctx)
    }, nil
}

// 在 HTTP handler 中使用
func handleGetUser(w http.ResponseWriter, r *http.Request) {
    ctx, span := otel.Tracer("user-service").Start(r.Context(), "GetUser")
    defer span.End()

    span.SetAttributes(
        attribute.String("user.id", r.URL.Query().Get("id")),
    )

    user, err := getUserFromDB(ctx, r.URL.Query().Get("id"))
    if err != nil {
        span.RecordError(err)
        // ...
    }

    // 传递给后续调用
    go someAsyncOperation(ctx, user)
}

type UserService struct {
    logger       zerolog.Logger
    tracer      trace.Tracer
    metrics     *UserMetrics
    userRepo    *UserRepository
}

func (s *UserService) GetUser(ctx context.Context, id string) (*User, error) {
    // 1. 开始追踪
    ctx, span := s.tracer.Start(ctx, "UserService.GetUser")
    defer span.End()
    span.SetAttributes(attribute.String("user.id", id))

    // 2. 记录指标
    s.metrics.requests.Inc()
    timer := s.metrics.duration.NewTimer()

    // 3. 结构化日志
    s.logger.Info().
        Str("user_id", id).
        Str("trace_id", span.SpanContext().TraceID().String()).
        Msg("Fetching user")

    // 4. 业务逻辑
    user, err := s.userRepo.FindByID(ctx, id)
    if err != nil {
        // 记录错误，包含追踪上下文
        s.logger.Error().
            Err(err).
            Str("user_id", id).
            Str("trace_id", span.SpanContext().TraceID().String()).
            Msg("Failed to fetch user")
        span.RecordError(err)
        s.metrics.errors.Inc()
        return nil, err
    }

    timer.ObserveDuration()
    return user, nil
}