监控扩展

Kitex 提供了 Tracer 接口，可以更灵活地自定义数据监控和链路追踪拓展能力，并通过 WithTracer Option 来注入。

// Tracer is executed at the start and finish of an RPC.
type Tracer interface {
    Start(ctx context.Context) context.Context
    Finish(ctx context.Context)
}

监控信息拓展

用户如果需要更详细的打点，例如包大小，或者想要更换其他数据源，例如 influxDB，用户可以根据自己的需求实现 Tracer 接口。

从 ctx 中可以获得 RPCInfo，进一步的从 RPCInfo 中获取请求耗时、包大小和请求返回的错误信息等，举例：

type clientTracer struct {
    // contain entities which recording metric
}

// Start record the beginning of an RPC invocation.
func (c *clientTracer) Start(ctx context.Context) context.Context {
    // do nothing
	return ctx
}

// Finish record after receiving the response of server.
func (c *clientTracer) Finish(ctx context.Context) {
	ri := rpcinfo.GetRPCInfo(ctx)
	rpcStart := ri.Stats().GetEvent(stats.RPCStart)
	rpcFinish := ri.Stats().GetEvent(stats.RPCFinish)
	cost := rpcFinish.Time().Sub(rpcStart.Time())
	// TODO: record the cost of request
}

链路追踪拓展

除此之外，Tracer 接口也可用于自定义链路追踪，比如以简单的方式集成 OpenTracing，举例：

Client 端

import "github.com/cloudwego/kitex/client"
...
type myTracer struct {}

func (m *myTracer) Start(ctx context.Context) context.Context {
	_, ctx = opentracing.StartSpanFromContextWithTracer(ctx, o.tracer, "RPC call")
	return ctx
}

func (m *myTracer) Finish(ctx context.Context) {
	span := opentracing.SpanFromContext(ctx)
	span.Finish()
}
...
client, err := echo.NewClient("echo", client.WithTracer(&myTracer{}))
if err != nil {
	log.Fatal(err)
}

Server 端

import "github.com/cloudwego/kitex/server"
...
type myTracer struct {}

func (m *myTracer) Start(ctx context.Context) context.Context {
	_, ctx = opentracing.StartSpanFromContextWithTracer(ctx, o.tracer, "RPC handle")
	return ctx
}

func (m *myTracer) Finish(ctx context.Context) {
	span := opentracing.SpanFromContext(ctx)
	span.Finish()
}
...
svr, err := echo.NewServer(server.WithTracer(&myTracer{}))
if err := svr.Run(); err != nil {
	log.Println("server stopped with error:", err)
} else {
	log.Println("server stopped")
}

最后修改 September 20, 2024 : doc: remove basic_usage.md internal words (#1151) (77b6e1f)