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Diffstat (limited to 'vendor/github.com/grpc-ecosystem/go-grpc-middleware/doc.go')
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diff --git a/vendor/github.com/grpc-ecosystem/go-grpc-middleware/doc.go b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/doc.go new file mode 100644 index 00000000..71689503 --- /dev/null +++ b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/doc.go @@ -0,0 +1,69 @@ +// Copyright 2016 Michal Witkowski. All Rights Reserved. +// See LICENSE for licensing terms. + +/* +`grpc_middleware` is a collection of gRPC middleware packages: interceptors, helpers and tools. + +Middleware + +gRPC is a fantastic RPC middleware, which sees a lot of adoption in the Golang world. However, the +upstream gRPC codebase is relatively bare bones. + +This package, and most of its child packages provides commonly needed middleware for gRPC: +client-side interceptors for retires, server-side interceptors for input validation and auth, +functions for chaining said interceptors, metadata convenience methods and more. + +Chaining + +By default, gRPC doesn't allow one to have more than one interceptor either on the client nor on +the server side. `grpc_middleware` provides convenient chaining methods + +Simple way of turning a multiple interceptors into a single interceptor. Here's an example for +server chaining: + + myServer := grpc.NewServer( + grpc.StreamInterceptor(grpc_middleware.ChainStreamServer(loggingStream, monitoringStream, authStream)), + grpc.UnaryInterceptor(grpc_middleware.ChainUnaryServer(loggingUnary, monitoringUnary, authUnary), + ) + +These interceptors will be executed from left to right: logging, monitoring and auth. + +Here's an example for client side chaining: + + clientConn, err = grpc.Dial( + address, + grpc.WithUnaryInterceptor(grpc_middleware.ChainUnaryClient(monitoringClientUnary, retryUnary)), + grpc.WithStreamInterceptor(grpc_middleware.ChainStreamClient(monitoringClientStream, retryStream)), + ) + client = pb_testproto.NewTestServiceClient(clientConn) + resp, err := client.PingEmpty(s.ctx, &myservice.Request{Msg: "hello"}) + +These interceptors will be executed from left to right: monitoring and then retry logic. + +The retry interceptor will call every interceptor that follows it whenever when a retry happens. + +Writing Your Own + +Implementing your own interceptor is pretty trivial: there are interfaces for that. But the interesting +bit exposing common data to handlers (and other middleware), similarly to HTTP Middleware design. +For example, you may want to pass the identity of the caller from the auth interceptor all the way +to the handling function. + +For example, a client side interceptor example for auth looks like: + + func FakeAuthUnaryInterceptor(ctx context.Context, req interface{}, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (interface{}, error) { + newCtx := context.WithValue(ctx, "user_id", "john@example.com") + return handler(newCtx, req) + } + +Unfortunately, it's not as easy for streaming RPCs. These have the `context.Context` embedded within +the `grpc.ServerStream` object. To pass values through context, a wrapper (`WrappedServerStream`) is +needed. For example: + + func FakeAuthStreamingInterceptor(srv interface{}, stream grpc.ServerStream, info *grpc.StreamServerInfo, handler grpc.StreamHandler) error { + newStream := grpc_middleware.WrapServerStream(stream) + newStream.WrappedContext = context.WithValue(ctx, "user_id", "john@example.com") + return handler(srv, stream) + } +*/ +package grpc_middleware |