mirror of https://github.com/k3s-io/k3s
70 lines
3.0 KiB
Go
70 lines
3.0 KiB
Go
// 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
|