gRPC Interceptors

gRPC Interceptors

Interceptors are the gRPC equivalent of HTTP middleware.

Server Interceptor

func authInterceptor(ctx context.Context, req any, info *grpc.UnaryServerInfo,
    handler grpc.UnaryHandler) (any, error) {
    md, _ := metadata.FromIncomingContext(ctx)
    if len(md["token"]) == 0 {
        return nil, status.Error(codes.Unauthenticated, "missing token")
    }
    return handler(ctx, req)
}

server := zrpc.MustNewServer(c.RpcServerConf, func(grpcServer *grpc.Server) {
    greeter.RegisterGreeterServer(grpcServer, srv)
})
server.AddUnaryInterceptors(authInterceptor)
server.Start()

Client Interceptor

conn, _ := zrpc.NewClient(c.GreeterRpc,
    zrpc.WithUnaryClientInterceptor(func(ctx context.Context, method string,
        req, reply any, cc *grpc.ClientConn,
        invoker grpc.UnaryInvoker, opts ...grpc.CallOption) error {
        ctx = metadata.AppendToOutgoingContext(ctx, "token", getToken())
        return invoker(ctx, method, req, reply, cc, opts...)
    }),
)

Built-In Interceptors

Interceptor	What it does
RecoverInterceptor	Converts panics to gRPC errors
PrometheusInterceptor	Records RPC duration metrics
TracingInterceptor	OpenTelemetry span creation
BreakerInterceptor	Circuit-breaker protection
SheddingInterceptor	Load-shedding under heavy traffic
TimeoutInterceptor	Per-RPC deadline enforcement