gRPC HTTP/1.1 bridge

• gRPC architecture overview
• v1 API reference
• v2 API reference

This is a simple filter which enables the bridging of an HTTP/1.1 client which does not support response trailers to a compliant gRPC server. It works by doing the following:

• When a request is sent, the filter sees if the connection is HTTP/1.1 and the request content type is application/grpc.
• If so, when the response is received, the filter buffers it and waits for trailers and then checks the grpc-status code. If it is not zero, the filter switches the HTTP response code to 503. It also copies the grpc-status and grpc-message trailers into the response headers so that the client can look at them if it wishes.
• The client should send HTTP/1.1 requests that translate to the following psuedo headers:
  • :method: POST
  • :path: <gRPC-METHOD-NAME>
  • content-type: application/grpc
• The body should be the serialized grpc body which is:
  • 1 byte of zero (not compressed).
  • network order 4 bytes of proto message length.
  • serialized proto message.
• Because this scheme must buffer the response to look for the grpc-status trailer it will only work with unary gRPC APIs.

More info: http://www.grpc.io/docs/guides/wire.html

This filter also collects stats for all gRPC requests that transit, even if those requests are normal gRPC requests over HTTP/2.

Statistics

The filter emits statistics in the cluster.<route target cluster>.grpc. namespace.

Name	Type	Description
<grpc service>.<grpc method>.success	Counter	Total successful service/method calls
<grpc service>.<grpc method>.failure	Counter	Total failed service/method calls
<grpc service>.<grpc method>.total	Counter	Total service/method calls