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84 lines
3.7 KiB
Markdown
84 lines
3.7 KiB
Markdown
# gRPC Proxy
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[](https://travis-ci.org/mwitkow/grpc-proxy)
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[](https://goreportcard.com/report/github.com/mwitkow/grpc-proxy)
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[](https://pkg.go.dev/github.com/mwitkow/grpc-proxy)
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[](LICENSE)
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[gRPC Go](https://github.com/grpc/grpc-go) Proxy server
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## Project Goal
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Build a transparent reverse proxy for gRPC targets that will make it easy to expose gRPC services
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over the internet. This includes:
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* no needed knowledge of the semantics of requests exchanged in the call (independent rollouts)
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* easy, declarative definition of backends and their mappings to frontends
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* simple round-robin load balancing of inbound requests from a single connection to multiple backends
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The project now exists as a **proof of concept**, with the key piece being the `proxy` package that
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is a generic gRPC reverse proxy handler.
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## Proxy Handler
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The package [`proxy`](proxy/) contains a generic gRPC reverse proxy handler that allows a gRPC server to
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not know about registered handlers or their data types. Please consult the docs, here's an exaple usage.
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You can call `proxy.NewProxy` to create a `*grpc.Server` that proxies requests.
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```go
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proxy := proxy.NewProxy(clientConn)
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```
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More advanced users will want to define a `StreamDirector` that can make more complex decisions on what
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to do with the request.
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```go
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director = func(ctx context.Context, fullMethodName string) (context.Context, *grpc.ClientConn, error) {
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md, _ := metadata.FromIncomingContext(ctx)
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outCtx = metadata.NewOutgoingContext(ctx, md.Copy())
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return outCtx, cc, nil
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// Make sure we never forward internal services.
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if strings.HasPrefix(fullMethodName, "/com.example.internal.") {
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return outCtx, nil, status.Errorf(codes.Unimplemented, "Unknown method")
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}
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if ok {
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// Decide on which backend to dial
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if val, exists := md[":authority"]; exists && val[0] == "staging.api.example.com" {
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// Make sure we use DialContext so the dialing can be cancelled/time out together with the context.
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return outCtx, grpc.DialContext(ctx, "api-service.staging.svc.local", grpc.WithCodec(proxy.Codec())), nil
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} else if val, exists := md[":authority"]; exists && val[0] == "api.example.com" {
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return outCtx, grpc.DialContext(ctx, "api-service.prod.svc.local", grpc.WithCodec(proxy.Codec())), nil
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}
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}
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return outCtx, nil, status.Errorf(codes.Unimplemented, "Unknown method")
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}
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```
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Then you need to register it with a `grpc.Server`. The server may have other handlers that will be served
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locally.
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```go
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server := grpc.NewServer(
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grpc.CustomCodec(proxy.Codec()),
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grpc.UnknownServiceHandler(proxy.TransparentHandler(director)))
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pb_test.RegisterTestServiceServer(server, &testImpl{})
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```
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## Testing
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To make debugging a bit simpler, there are some helpers.
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`testservice` contains a method `TestTestServiceServerImpl` which performs a complete test against
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the reference implementation of the `TestServiceServer`.
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In `proxy_test.go`, the test framework spins up a `TestServiceServer` that it tests the proxy
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against. To make debugging a bit simpler (eg. if the developer needs to step into
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`google.golang.org/grpc` methods), this `TestServiceServer` can be provided by a server by
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passing `-test-backend=addr` to `go test`. A simple, local-only implementation of
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`TestServiceServer` exists in [`testservice/server`](./testservice/server).
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## License
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`grpc-proxy` is released under the Apache 2.0 license. See [LICENSE.txt](LICENSE.txt).
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