2018-09-18 19:50:17 +00:00
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// Copyright 2017, OpenCensus Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//
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package tag
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2018-12-20 21:43:52 +00:00
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import (
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"context"
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"go.opencensus.io/exemplar"
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)
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2018-09-18 19:50:17 +00:00
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// FromContext returns the tag map stored in the context.
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func FromContext(ctx context.Context) *Map {
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// The returned tag map shouldn't be mutated.
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ts := ctx.Value(mapCtxKey)
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if ts == nil {
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return nil
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}
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return ts.(*Map)
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}
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// NewContext creates a new context with the given tag map.
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// To propagate a tag map to downstream methods and downstream RPCs, add a tag map
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// to the current context. NewContext will return a copy of the current context,
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// and put the tag map into the returned one.
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// If there is already a tag map in the current context, it will be replaced with m.
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func NewContext(ctx context.Context, m *Map) context.Context {
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return context.WithValue(ctx, mapCtxKey, m)
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}
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type ctxKey struct{}
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var mapCtxKey = ctxKey{}
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2018-12-20 21:43:52 +00:00
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func init() {
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exemplar.RegisterAttachmentExtractor(extractTagsAttachments)
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}
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func extractTagsAttachments(ctx context.Context, a exemplar.Attachments) exemplar.Attachments {
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m := FromContext(ctx)
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if m == nil {
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return a
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}
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if len(m.m) == 0 {
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return a
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}
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if a == nil {
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a = make(map[string]string)
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}
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for k, v := range m.m {
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a[exemplar.KeyPrefixTag+k.Name()] = v
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}
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return a
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}
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