go-zero 的网关服务实际是个 go-zero 的 API 服务，也就是一个 http 服务，或者说 rest 服务。http 转 grpc 使用了开源的 grpcurl 库，当网关需要往 rpc 服务传递额外的数据，比如鉴权数据的时候，通过 http 的 header 进行：
func AuthMiddleware(next http.HandlerFunc, w http.ResponseWriter, r *http.Request) {
authResp, err := authClient.Authenticate(r.Context(), &authReq) // 调用鉴权服务
r.Header.Set("Grpc-Metadata-myuid", authResp.UserId) // 往 rpc 服务传递额外数据
next.ServeHTTP(w, r)
}
rpc 服务端从 metadata 取出数据：
func (l *QueryUserLogic) QueryUser(in *user.UserReq) (*user.UserResp, error) {
vals := metadata.ValueFromIncomingContext(l.ctx, "gateway-myuid")
uid = vals[0]
}
这里有两个需要注意的地方，在网关侧的名必须以“Grpc-Metadata-”打头，而 rpc 服务端必须以“gateway-”打头，这是 go-zero 的 gateway/internal/headerprocessor.go 写死的规则：
const (
metadataHeaderPrefix = "Grpc-Metadata-"
metadataPrefix = "gateway-"
)
// ProcessHeaders builds the headers for the gateway from HTTP headers.
func ProcessHeaders(header http.Header) []string {
var headers []string
for k, v := range header {
if !strings.HasPrefix(k, metadataHeaderPrefix) { // 判断是否以“Grpc-Metadata-”打头（网关侧传递的）
continue // 非以“Grpc-Metadata-”打头的都会被丢弃掉
}
key := fmt.Sprintf("%s%s", metadataPrefix, strings.TrimPrefix(k, metadataHeaderPrefix)) // 替换为新的前缀“gateway-”（rpc 服务端看到的）
for _, vv := range v {
headers = append(headers, key+":"+vv)
}
}
return headers
}
调用栈：
(dlv) bt
0 0x00000000019da092 in github.com/zeromicro/go-zero/gateway/internal.ProcessHeaders
at ./go/pkg/mod/github.com/zeromicro/go-zero@v1.6.0/gateway/internal/headerprocessor.go:15
1 0x00000000019dc40a in github.com/zeromicro/go-zero/gateway.(*Server).prepareMetadata
at ./go/pkg/mod/github.com/zeromicro/go-zero@v1.6.0/gateway/server.go:175
2 0x00000000019dbf69 in github.com/zeromicro/go-zero/gateway.(*Server).buildHandler.func1
at ./go/pkg/mod/github.com/zeromicro/go-zero@v1.6.0/gateway/server.go:132
3 0x000000000089f52f in net/http.HandlerFunc.ServeHTTP
at /usr/local/go/src/net/http/server.go:2122
4 0x00000000008ca162 in net/http.Handler.ServeHTTP-fm
at <autogenerated>:1
5 0x000000000195adc5 in net/http.HandlerFunc.ServeHTTP
at /usr/local/go/src/net/http/server.go:2122
6 0x000000000195adc5 in gateway/middleware.AuthMiddleware // 网关代码
at ./Getting-Started-with-Go-zero/gateway_login/gateway/middleware/login_and_auth.go:98
7 0x000000000195a325 in gateway/middleware.LoginAndAuthMiddleware.func1
at ./Getting-Started-with-Go-zero/gateway_login/gateway/middleware/login_and_auth.go:37
8 0x000000000089f52f in net/http.HandlerFunc.ServeHTTP
at /usr/local/go/src/net/http/server.go:2122
9 0x0000000001969169 in github.com/zeromicro/go-zero/rest/handler.GunzipHandler.func1
at ./go/pkg/mod/github.com/zeromicro/go-zero@v1.6.0/rest/handler/gunziphandler.go:26
10 0x000000000089f52f in net/http.HandlerFunc.ServeHTTP
at /usr/local/go/src/net/http/server.go:2122
11 0x000000000196b3bf in github.com/zeromicro/go-zero/rest/handler.MaxBytesHandler.func2.1
at ./go/pkg/mod/github.com/zeromicro/go-zero@v1.6.0/rest/handler/maxbyteshandler.go:24
12 0x000000000089f52f in net/http.HandlerFunc.ServeHTTP
at /usr/local/go/src/net/http/server.go:2122
13 0x000000000196ba15 in github.com/zeromicro/go-zero/rest/handler.MetricHandler.func1.1
at ./go/pkg/mod/github.com/zeromicro/go-zero@v1.6.0/rest/handler/metrichandler.go:21
14 0x000000000089f52f in net/http.HandlerFunc.ServeHTTP
at /usr/local/go/src/net/http/server.go:2122
15 0x000000000196c243 in github.com/zeromicro/go-zero/rest/handler.RecoverHandler.func1
at ./go/pkg/mod/github.com/zeromicro/go-zero@v1.6.0/rest/handler/recoverhandler.go:21
16 0x000000000089f52f in net/http.HandlerFunc.ServeHTTP
at /usr/local/go/src/net/http/server.go:2122
17 0x000000000196d45c in github.com/zeromicro/go-zero/rest/handler.(*timeoutHandler).ServeHTTP.func1
at ./go/pkg/mod/github.com/zeromicro/go-zero@v1.6.0/rest/handler/timeouthandler.go:82
18 0x0000000000471921 in runtime.goexit
at /usr/local/go/src/runtime/asm_amd64.s:1598
(dlv) bt
0 0x00000000019d636a in google.golang.org/grpc/metadata.NewOutgoingContext
at ./go/pkg/mod/google.golang.org/grpc@v1.59.0/metadata/metadata.go:165
1 0x00000000019d636a in github.com/fullstorydev/grpcurl.InvokeRPC
at ./go/pkg/mod/github.com/fullstorydev/grpcurl@v1.8.9/invoke.go:136
2 0x00000000019dc058 in github.com/zeromicro/go-zero/gateway.(*Server).buildHandler.func1
at ./go/pkg/mod/github.com/zeromicro/go-zero@v1.6.0/gateway/server.go:132
3 0x000000000089f52f in net/http.HandlerFunc.ServeHTTP
at /usr/local/go/src/net/http/server.go:2122
4 0x00000000008ca162 in net/http.Handler.ServeHTTP-fm
at <autogenerated>:1
5 0x000000000195adc5 in net/http.HandlerFunc.ServeHTTP
at /usr/local/go/src/net/http/server.go:2122
6 0x000000000195adc5 in gateway/middleware.AuthMiddleware // 网关代码
at ./Getting-Started-with-Go-zero/gateway_login/gateway/middleware/login_and_auth.go:98
7 0x000000000195a325 in gateway/middleware.LoginAndAuthMiddleware.func1
at ./Getting-Started-with-Go-zero/gateway_login/gateway/middleware/login_and_auth.go:37
8 0x000000000089f52f in net/http.HandlerFunc.ServeHTTP
at /usr/local/go/src/net/http/server.go:2122
9 0x0000000001969169 in github.com/zeromicro/go-zero/rest/handler.GunzipHandler.func1
at ./go/pkg/mod/github.com/zeromicro/go-zero@v1.6.0/rest/handler/gunziphandler.go:26
10 0x000000000089f52f in net/http.HandlerFunc.ServeHTTP
at /usr/local/go/src/net/http/server.go:2122
11 0x000000000196b3bf in github.com/zeromicro/go-zero/rest/handler.MaxBytesHandler.func2.1
at ./go/pkg/mod/github.com/zeromicro/go-zero@v1.6.0/rest/handler/maxbyteshandler.go:24
12 0x000000000089f52f in net/http.HandlerFunc.ServeHTTP
at /usr/local/go/src/net/http/server.go:2122
13 0x000000000196ba15 in github.com/zeromicro/go-zero/rest/handler.MetricHandler.func1.1
at ./go/pkg/mod/github.com/zeromicro/go-zero@v1.6.0/rest/handler/metrichandler.go:21
14 0x000000000089f52f in net/http.HandlerFunc.ServeHTTP
at /usr/local/go/src/net/http/server.go:2122
15 0x000000000196c243 in github.com/zeromicro/go-zero/rest/handler.RecoverHandler.func1
at ./go/pkg/mod/github.com/zeromicro/go-zero@v1.6.0/rest/handler/recoverhandler.go:21
16 0x000000000089f52f in net/http.HandlerFunc.ServeHTTP
at /usr/local/go/src/net/http/server.go:2122
17 0x000000000196d45c in github.com/zeromicro/go-zero/rest/handler.(*timeoutHandler).ServeHTTP.func1
at ./go/pkg/mod/github.com/zeromicro/go-zero@v1.6.0/rest/handler/timeouthandler.go:82
18 0x0000000000471921 in runtime.goexit
at /usr/local/go/src/runtime/asm_amd64.s:1598
在文件 zrpc/internal/clientinterceptors/tracinginterceptor.go 中调用了 metadata.NewOutgoingContext：
func startSpan(ctx context.Context, method, target string) (context.Context, trace.Span) {
md, ok := metadata.FromOutgoingContext(ctx)
if !ok {
md = metadata.MD{}
}
tr := otel.Tracer(ztrace.TraceName)
name, attr := ztrace.SpanInfo(method, target)
ctx, span := tr.Start(ctx, name, trace.WithSpanKind(trace.SpanKindClient),
trace.WithAttributes(attr...))
ztrace.Inject(ctx, otel.GetTextMapPropagator(), &md)
ctx = metadata.NewOutgoingContext(ctx, md)
return ctx, span
}
// UnaryTracingInterceptor returns a grpc.UnaryClientInterceptor for opentelemetry.
func UnaryTracingInterceptor(ctx context.Context, method string, req, reply any,
cc *grpc.ClientConn, invoker grpc.UnaryInvoker, opts ...grpc.CallOption) error {
ctx, span := startSpan(ctx, method, cc.Target())
defer span.End()
ztrace.MessageSent.Event(ctx, 1, req)
err := invoker(ctx, method, req, reply, cc, opts...)
ztrace.MessageReceived.Event(ctx, 1, reply)
if err != nil {
s, ok := status.FromError(err)
if ok {
span.SetStatus(codes.Error, s.Message())
span.SetAttributes(ztrace.StatusCodeAttr(s.Code()))
} else {
span.SetStatus(codes.Error, err.Error())
}
return err
}
span.SetAttributes(ztrace.StatusCodeAttr(gcodes.OK))
return nil
}
拦截器：
./zrpc/internal/rpcserver.go: interceptors = append(interceptors, serverinterceptors.UnaryTracingInterceptor)
./zrpc/internal/client.go: interceptors = append(interceptors, clientinterceptors.UnaryTracingInterceptor)
服务端代码：
//zrpc/internal/rpcserver.go
func (s *rpcServer) buildUnaryInterceptors() []grpc.UnaryServerInterceptor {
var interceptors []grpc.UnaryServerInterceptor
if s.middlewares.Trace {
interceptors = append(interceptors, serverinterceptors.UnaryTracingInterceptor)
}
if s.middlewares.Recover {
interceptors = append(interceptors, serverinterceptors.UnaryRecoverInterceptor)
}
if s.middlewares.Stat {
interceptors = append(interceptors,
serverinterceptors.UnaryStatInterceptor(s.metrics, s.middlewares.StatConf))
}
if s.middlewares.Prometheus {
interceptors = append(interceptors, serverinterceptors.UnaryPrometheusInterceptor)
}
if s.middlewares.Breaker {
interceptors = append(interceptors, serverinterceptors.UnaryBreakerInterceptor)
}
return append(interceptors, s.unaryInterceptors...)
}
func (s *rpcServer) Start(register RegisterFn) error {
lis, err := net.Listen("tcp", s.address)
if err != nil {
return err
}
unaryInterceptorOption := grpc.ChainUnaryInterceptor(s.buildUnaryInterceptors()...)
streamInterceptorOption := grpc.ChainStreamInterceptor(s.buildStreamInterceptors()...)
options := append(s.options, unaryInterceptorOption, streamInterceptorOption)
server := grpc.NewServer(options...)
register(server)
// register the health check service
if s.health != nil {
grpc_health_v1.RegisterHealthServer(server, s.health)
s.health.Resume()
}
s.healthManager.MarkReady()
health.AddProbe(s.healthManager)
// we need to make sure all others are wrapped up,
// so we do graceful stop at shutdown phase instead of wrap up phase
waitForCalled := proc.AddShutdownListener(func() {
if s.health != nil {
s.health.Shutdown()
}
server.GracefulStop()
})
defer waitForCalled()
return server.Serve(lis)
}
客户端代码：
//zrpc/internal/client.go
func (c *client) buildUnaryInterceptors(timeout time.Duration) []grpc.UnaryClientInterceptor {
var interceptors []grpc.UnaryClientInterceptor
if c.middlewares.Trace {
interceptors = append(interceptors, clientinterceptors.UnaryTracingInterceptor)
}
if c.middlewares.Duration {
interceptors = append(interceptors, clientinterceptors.DurationInterceptor)
}
if c.middlewares.Prometheus {
interceptors = append(interceptors, clientinterceptors.PrometheusInterceptor)
}
if c.middlewares.Breaker {
interceptors = append(interceptors, clientinterceptors.BreakerInterceptor)
}
if c.middlewares.Timeout {
interceptors = append(interceptors, clientinterceptors.TimeoutInterceptor(timeout))
}
return interceptors
}
func (c *client) buildDialOptions(opts ...ClientOption) []grpc.DialOption {
var cliOpts ClientOptions
for _, opt := range opts {
opt(&cliOpts)
}
var options []grpc.DialOption
if !cliOpts.Secure {
options = append([]grpc.DialOption(nil),
grpc.WithTransportCredentials(insecure.NewCredentials()))
}
if !cliOpts.NonBlock {
options = append(options, grpc.WithBlock())
}
options = append(options,
grpc.WithChainUnaryInterceptor(c.buildUnaryInterceptors(cliOpts.Timeout)...),
grpc.WithChainStreamInterceptor(c.buildStreamInterceptors()...),
)
return append(options, cliOpts.DialOptions...)
}
func (c *client) dial(server string, opts ...ClientOption) error {
options := c.buildDialOptions(opts...)
timeCtx, cancel := context.WithTimeout(context.Background(), dialTimeout)
defer cancel()
conn, err := grpc.DialContext(timeCtx, server, options...)
if err != nil {
service := server
if errors.Is(err, context.DeadlineExceeded) {
pos := strings.LastIndexByte(server, separator)
// len(server) - 1 is the index of last char
if 0 < pos && pos < len(server)-1 {
service = server[pos+1:]
}
}
return fmt.Errorf("rpc dial: %s, error: %s, make sure rpc service %q is already started",
server, err.Error(), service)
}
c.conn = conn
return nil
}
// NewClient returns a Client.
func NewClient(target string, middlewares ClientMiddlewaresConf, opts ...ClientOption) (Client, error) {
cli := client{
middlewares: middlewares,
}
svcCfg := fmt.Sprintf(`{"loadBalancingPolicy":"%s"}`, p2c.Name)
balancerOpt := WithDialOption(grpc.WithDefaultServiceConfig(svcCfg))
opts = append([]ClientOption{balancerOpt}, opts...)
if err := cli.dial(target, opts...); err != nil {
return nil, err
}
return &cli, nil
}
