tap.go

/*
 *
 * Copyright 2016 gRPC authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */

// Package tap defines the function handles which are executed on the transport
// layer of gRPC-Go and related information. Everything here is EXPERIMENTAL.
package tap

import (
	"context"
)

// Info defines the relevant information needed by the handles.
type Info struct {
	// FullMethodName is the string of grpc method (in the format of
	// /package.service/method).
	FullMethodName string
	// TODO: More to be added.
}

// ServerInHandle defines the function which runs before a new stream is created
// on the server side. If it returns a non-nil error, the stream will not be
// created and a RST_STREAM will be sent back to the client with REFUSED_STREAM.
// The client will receive an RPC error "code = Unavailable, desc = stream
// terminated by RST_STREAM with error code: REFUSED_STREAM".
//
// It's intended to be used in situations where you don't want to waste the
// resources to accept the new stream (e.g. rate-limiting). And the content of
// the error will be ignored and won't be sent back to the client. For other
// general usages, please use interceptors.
//
// Note that it is executed in the per-connection I/O goroutine(s) instead of
// per-RPC goroutine. Therefore, users should NOT have any
// blocking/time-consuming work in this handle. Otherwise all the RPCs would
// slow down. Also, for the same reason, this handle won't be called
// concurrently by gRPC.
type ServerInHandle func(ctx context.Context, info *Info) (context.Context, error)