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
15package view
16
17import "sync"
18
19var (
20	exportersMu sync.RWMutex // guards exporters
21	exporters   = make(map[Exporter]struct{})
22)
23
24// Exporter exports the collected records as view data.
25//
26// The ExportView method should return quickly; if an
27// Exporter takes a significant amount of time to
28// process a Data, that work should be done on another goroutine.
29//
30// It is safe to assume that ExportView will not be called concurrently from
31// multiple goroutines.
32//
33// The Data should not be modified.
34type Exporter interface {
35	ExportView(viewData *Data)
36}
37
38// RegisterExporter registers an exporter.
39// Collected data will be reported via all the
40// registered exporters. Once you no longer
41// want data to be exported, invoke UnregisterExporter
42// with the previously registered exporter.
43//
44// Binaries can register exporters, libraries shouldn't register exporters.
45func RegisterExporter(e Exporter) {
46	exportersMu.Lock()
47	defer exportersMu.Unlock()
48
49	exporters[e] = struct{}{}
50}
51
52// UnregisterExporter unregisters an exporter.
53func UnregisterExporter(e Exporter) {
54	exportersMu.Lock()
55	defer exportersMu.Unlock()
56
57	delete(exporters, e)
58}
59