server/prpc: updated server according to protocol

common/prpc/doc.go

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Package prpc (provisional RPC) implements an RPC client over HTTP 1.x.
 //
 // Like gRPC:
 //  - services are defined in .proto files
 //  - service implementation does not depend on pRPC.
 // Unlike gRPC:
@@ skipping 13 matching lines @@
 //  //go:generate cproto
 //
 // Install cproto:
 //  go install github.com/luci/luci-go/tools/cmd/cproto
 //
 // Protocol
 //
 // This section describes the pRPC protocol. It is based on HTTP 1.x and employs
 // gRPC codes.
 //
-// A pRPC server MUST handle HTTP requests at `/prpc/{service}/{method}` path,
+// A pRPC server MUST handle HTTP POST requests at `/prpc/{service}/{method}`,
 // decode an input message from an HTTP request,
 // call the service method implementation and
 // encode the returned output message or error to the HTTP response.
 //
 // pRPC protocol defines three protocol buffer encodings and media types.
 //  - Binary: "application/prpc; encoding=binary"
 //  - JSON:   "application/prpc; encoding=json"   or "application/json"
 //    A response body MUST have `)]}'` prefix to avoid CSRF.
 //  - Text:   "application/prpc; encoding=text"
 // A pRPC server MUST support Binary and SHOULD support JSON and Text.
@@ skipping 35 matching lines @@
 //    A server SHOULD specify it.
 //    If not specified, a client MUST treat it is as Binary.
 //  - Any metadata returned by a service method implementation MUST go into
 //    http headers, unless metadata key starts with "X-Prpc-".
 //
 // A server MUST always specify "X-Prpc-Grpc-Code".
 // The server SHOULD specify HTTP status corresponding to the gRPC code.
 //
 // If a service/method is not found, the server MUST respond with Unimplemented
 // gRPC code and SHOULD specify HTTP 501 status.
-//
-// If HTTP method is not POST, the server MUST respond with Unimplemented
-// gRPC code and SHOULD specify HTTP 405 status.
 package prpc