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Diffstat (limited to 'vendor/go.opencensus.io/exemplar')
-rw-r--r-- | vendor/go.opencensus.io/exemplar/exemplar.go | 78 |
1 files changed, 78 insertions, 0 deletions
diff --git a/vendor/go.opencensus.io/exemplar/exemplar.go b/vendor/go.opencensus.io/exemplar/exemplar.go new file mode 100644 index 000000000..e676df837 --- /dev/null +++ b/vendor/go.opencensus.io/exemplar/exemplar.go @@ -0,0 +1,78 @@ +// Copyright 2018, OpenCensus 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 exemplar implements support for exemplars. Exemplars are additional +// data associated with each measurement. +// +// Their purpose it to provide an example of the kind of thing +// (request, RPC, trace span, etc.) that resulted in that measurement. +package exemplar + +import ( + "context" + "time" +) + +const ( + KeyTraceID = "trace_id" + KeySpanID = "span_id" + KeyPrefixTag = "tag:" +) + +// Exemplar is an example data point associated with each bucket of a +// distribution type aggregation. +type Exemplar struct { + Value float64 // the value that was recorded + Timestamp time.Time // the time the value was recorded + Attachments Attachments // attachments (if any) +} + +// Attachments is a map of extra values associated with a recorded data point. +// The map should only be mutated from AttachmentExtractor functions. +type Attachments map[string]string + +// AttachmentExtractor is a function capable of extracting exemplar attachments +// from the context used to record measurements. +// The map passed to the function should be mutated and returned. It will +// initially be nil: the first AttachmentExtractor that would like to add keys to the +// map is responsible for initializing it. +type AttachmentExtractor func(ctx context.Context, a Attachments) Attachments + +var extractors []AttachmentExtractor + +// RegisterAttachmentExtractor registers the given extractor associated with the exemplar +// type name. +// +// Extractors will be used to attempt to extract exemplars from the context +// associated with each recorded measurement. +// +// Packages that support exemplars should register their extractor functions on +// initialization. +// +// RegisterAttachmentExtractor should not be called after any measurements have +// been recorded. +func RegisterAttachmentExtractor(e AttachmentExtractor) { + extractors = append(extractors, e) +} + +// NewFromContext extracts exemplars from the given context. +// Each registered AttachmentExtractor (see RegisterAttachmentExtractor) is called in an +// unspecified order to add attachments to the exemplar. +func AttachmentsFromContext(ctx context.Context) Attachments { + var a Attachments + for _, extractor := range extractors { + a = extractor(ctx, a) + } + return a +} |