1// Copyright 2017, OpenCensus Authors
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7//     http://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14//
15
16package ocgrpc
17
18import (
19	"time"
20
21	"golang.org/x/net/context"
22
23	"go.opencensus.io/tag"
24	"google.golang.org/grpc/grpclog"
25	"google.golang.org/grpc/stats"
26)
27
28// statsTagRPC gets the metadata from gRPC context, extracts the encoded tags from
29// it and creates a new tag.Map and puts them into the returned context.
30func (h *ServerHandler) statsTagRPC(ctx context.Context, info *stats.RPCTagInfo) context.Context {
31	startTime := time.Now()
32	if info == nil {
33		if grpclog.V(2) {
34			grpclog.Infof("opencensus: TagRPC called with nil info.")
35		}
36		return ctx
37	}
38	d := &rpcData{
39		startTime: startTime,
40		method:    info.FullMethodName,
41	}
42	propagated := h.extractPropagatedTags(ctx)
43	ctx = tag.NewContext(ctx, propagated)
44	ctx, _ = tag.New(ctx, tag.Upsert(KeyServerMethod, methodName(info.FullMethodName)))
45	return context.WithValue(ctx, rpcDataKey, d)
46}
47
48// extractPropagatedTags creates a new tag map containing the tags extracted from the
49// gRPC metadata.
50func (h *ServerHandler) extractPropagatedTags(ctx context.Context) *tag.Map {
51	buf := stats.Tags(ctx)
52	if buf == nil {
53		return nil
54	}
55	propagated, err := tag.Decode(buf)
56	if err != nil {
57		if grpclog.V(2) {
58			grpclog.Warningf("opencensus: Failed to decode tags from gRPC metadata failed to decode: %v", err)
59		}
60		return nil
61	}
62	return propagated
63}
64