From 5150d976b8e7c0ab11a67192a617f81f09f87b50 Mon Sep 17 00:00:00 2001
From: Zach Reyes <zasweq@google.com>
Date: Tue, 10 Jan 2023 13:31:22 -0500
Subject: [PATCH] opencensus instrumentation api

---
 stats/opencensus/opencensus.go | 123 +++++++++++++++++++++++++++++++++
 1 file changed, 123 insertions(+)
 create mode 100644 stats/opencensus/opencensus.go

diff --git a/stats/opencensus/opencensus.go b/stats/opencensus/opencensus.go
new file mode 100644
index 000000000000..f97423726bb2
--- /dev/null
+++ b/stats/opencensus/opencensus.go
@@ -0,0 +1,123 @@
+/*
+ * Copyright 2022 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 opencensus implements opencensus instrumentation code for gRPC-Go
+// clients and servers.
+package opencensus
+
+import (
+	"context"
+	"go.opencensus.io/trace"
+
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/internal"
+	"google.golang.org/grpc/stats"
+)
+
+var (
+	joinDialOptions = internal.JoinDialOptions.(func(...grpc.DialOption) grpc.DialOption)
+)
+
+type traceOptions struct {
+	ts trace.Sampler
+	// disableTrace will overwrite any global dial option setting
+	disableTrace bool
+}
+
+// DialOption returns a dial option which enables OpenCensus instrumentation
+// code for a grpc.ClientConn.
+//
+// Client Applications interested in instrumenting their grpc.ClientConn should
+// pass the dial option returned from this function as the first dial option to
+// grpc.Dial().
+//
+// Using this option will always lead to instrumentation, however in order to
+// use the data an exporter must be registered with the OpenCensus trace package
+// for traces and the OpenCensus view package for metrics. Client Side has
+// retries, so a Unary and Streaming Interceptor are registered to handle per
+// RPC traces/metrics, and a Stats Handler is registered to handle per RPC
+// attempt trace/metrics. These three components registered work together in
+// conjunction, and do not work standalone.
+func DialOption(to traceOptions) grpc.DialOption {
+	return joinDialOptions(grpc.WithChainUnaryInterceptor(unaryInterceptor), grpc.WithChainStreamInterceptor(streamInterceptor), grpc.WithStatsHandler(&clientStatsHandler{to: to}))
+}
+
+// ServerOption returns a server option which enables OpenCensus instrumentation
+// code for a grpc.Server.
+//
+// Server applications interested in instrumenting their grpc.Server should
+// pass the server option returned from this function as the first argument to
+// grpc.NewServer().
+//
+// Using this option will always lead to instrumentation, however in order to
+// use the data an exporter must be registered with the OpenCensus trace package
+// for traces and the OpenCensus view package for metrics. Server Side does not
+// have retries, so a registered Stats Handler is the only component you need
+// for RPC traces/metrics.
+func ServerOption(to traceOptions) grpc.ServerOption {
+	return grpc.StatsHandler(&serverStatsHandler{to: to})
+}
+
+// unaryInterceptor handles per RPC context management. It also handles per RPC
+// tracing and stats.
+func unaryInterceptor(ctx context.Context, method string, req, reply interface{}, cc *grpc.ClientConn, invoker grpc.UnaryInvoker, opts ...grpc.CallOption) error {
+	return invoker(ctx, method, req, reply, cc, opts...)
+}
+
+// streamInterceptor handles per RPC context management. It also handles per RPC
+// tracing and stats.
+func streamInterceptor(ctx context.Context, desc *grpc.StreamDesc, cc *grpc.ClientConn, method string, streamer grpc.Streamer, opts ...grpc.CallOption) (grpc.ClientStream, error) {
+	return streamer(ctx, desc, cc, method, opts...)
+}
+
+type clientStatsHandler struct {
+	to traceOptions
+}
+
+// TagConn exists to satisfy stats.Handler.
+func (csh *clientStatsHandler) TagConn(ctx context.Context, _ *stats.ConnTagInfo) context.Context {
+	return ctx
+}
+
+// HandleConn exists to satisfy stats.Handler.
+func (csh *clientStatsHandler) HandleConn(context.Context, stats.ConnStats) {}
+
+// TagRPC implements per RPC attempt context management.
+func (csh *clientStatsHandler) TagRPC(ctx context.Context, rti *stats.RPCTagInfo) context.Context {
+	return ctx
+}
+
+func (csh *clientStatsHandler) HandleRPC(ctx context.Context, rs stats.RPCStats) {}
+
+type serverStatsHandler struct {
+	to traceOptions
+}
+
+// TagConn exists to satisfy stats.Handler.
+func (ssh *serverStatsHandler) TagConn(ctx context.Context, _ *stats.ConnTagInfo) context.Context {
+	return ctx
+}
+
+// HandleConn exists to satisfy stats.Handler.
+func (ssh *serverStatsHandler) HandleConn(context.Context, stats.ConnStats) {}
+
+// TagRPC implements per RPC context management.
+func (ssh *serverStatsHandler) TagRPC(ctx context.Context, rti *stats.RPCTagInfo) context.Context {
+	return ctx
+}
+
+// HandleRPC implements per RPC tracing and stats implementation.
+func (ssh *serverStatsHandler) HandleRPC(ctx context.Context, rs stats.RPCStats) {}