add metric producer manager.

metric/metricexport/producer.go

@@ -19,6 +19,7 @@ import (
 )
 
 // Producer is a source of metrics.
+// Deprecated in lieu of go.opencensus.io.metric.producer.Producer
 type Producer interface {
 	// Read should return the current values of all metrics supported by this
 	// metric provider.

metric/producer/manager.go

@@ -0,0 +1,80 @@
+// Copyright 2019, 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 producer
+
+import (
+	"sync"
+)
+
+type manager struct {
+	mu       sync.RWMutex
+	producers []Producer
+}
+
+var prodMgr *manager
+var once sync.Once
+
+func getManager() *manager {
+	once.Do(func() {
+		prodMgr = &manager{}
+	})
+	return prodMgr
+}
+// Add adds the producer to the manager if it is not already present.
+func Add(producer Producer) {
+	pm := getManager()
+	pm.add(producer)
+}
+
+// Delete deletes the producer from the manager if it is present.
+func Delete(producer Producer) {
+	pm := getManager()
+	pm.delete(producer)
+}
+
+// GetAll returns all producer registered with the manager. It is typically
+// used by exporter to read metrics from producers.
+func GetAll() []Producer{
+	pm := getManager()
+	return pm.producers
+}
+
+func (pm *manager) contains(producer Producer) bool {
+	for _, prod := range pm.producers {
+		if producer == prod {
+			return true
+		}
+	}
+	return false
+}
+
+func (pm *manager) add(producer Producer) {
+	pm.mu.Lock()
+	defer pm.mu.Unlock()
+	if pm.contains(producer) {
+		return
+	}
+	pm.producers = append(pm.producers, producer)
+}
+
+func (pm *manager) delete(producer Producer) {
+	pm.mu.Lock()
+	defer pm.mu.Unlock()
+	for index, prod := range pm.producers {
+		if producer == prod {
+			pm.producers = append(pm.producers[:index], pm.producers[index+1:]...)
+		}
+	}
+}

metric/producer/manager_test.go

@@ -0,0 +1,92 @@
+// Copyright 2019, 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 producer
+
+import (
+	"testing"
+	"go.opencensus.io/metric/metricdata"
+)
+
+type testProducer struct {
+	name string
+}
+
+var (
+	myProd1 = NewTestProducer("foo")
+	myProd2 = NewTestProducer("bar")
+	myProd3 = NewTestProducer("foobar")
+)
+
+func NewTestProducer(name string) *testProducer {
+	return &testProducer{name}
+}
+
+func (mp *testProducer) Read() []*metricdata.Metric {
+	return nil
+}
+
+func TestAdd(t *testing.T) {
+	Add(myProd1)
+	Add(myProd2)
+
+	got := GetAll()
+	want := []*testProducer{myProd1, myProd2}
+	checkSlice("add test", got, want, t)
+}
+
+func TestAddSame(t *testing.T) {
+	Add(myProd1)
+	Add(myProd2)
+	Add(myProd1)
+
+	got := GetAll()
+	want := []*testProducer{myProd1, myProd2}
+	checkSlice("add test", got, want, t)
+}
+
+func TestDelete(t *testing.T) {
+	Add(myProd1)
+	Add(myProd2)
+	Add(myProd3)
+	Delete(myProd2)
+
+	got := GetAll()
+	want := []*testProducer{myProd1, myProd3}
+	checkSlice("add test", got, want, t)
+}
+
+func TestDeleteNonExisting(t *testing.T) {
+	Add(myProd1)
+	Add(myProd3)
+	Delete(myProd2)
+
+	got := GetAll()
+	want := []*testProducer{myProd1, myProd3}
+	checkSlice("add test", got, want, t)
+}
+
+func checkSlice(testName string, got []Producer, want []*testProducer, t *testing.T) {
+	gotLen := len(got)
+	wantLen := len(want)
+	if gotLen != wantLen {
+		t.Errorf("test: %s, got len: %d want: %d\n", testName, gotLen, wantLen)
+	} else {
+		for i := 0 ; i<gotLen; i++ {
+			if got[i] != want[i] {
+				t.Errorf("test: %s, at index %d, got %p, want %p\n", testName, i, got[i], want[i])
+			}
+		}
+	}
+}

metric/producer/producer.go

@@ -0,0 +1,28 @@
+// Copyright 2019, 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 producer
+
+import (
+	"go.opencensus.io/metric/metricdata"
+)
+
+// Producer is a source of metrics.
+type Producer interface {
+	// Read should return the current values of all metrics supported by this
+	// metric provider.
+	// The returned metrics should be unique for each combination of name and
+	// resource.
+	Read() []*metricdata.Metric
+}