Improve test coverage, and don't send empty batches in OC bridge (#3263)

* improve test coverage, and don't send empty batches in OC bridge

* Update bridge/opencensus/metric_test.go

Co-authored-by: Tyler Yahn <MrAlias@users.noreply.github.com>

* remove 1.18 rule

Co-authored-by: Tyler Yahn <MrAlias@users.noreply.github.com>

CHANGELOG.md

@@ -24,6 +24,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 ### Fixed
 
 - Use default view if instrument does not match any registered view of a reader. (#3224, #3237)
+- The OpenCensus bridge no longer sends empty batches of metrics. (#3263)
 
 ## [0.32.1] Metric SDK (Alpha) - 2022-09-22
 

bridge/opencensus/go.mod

@@ -3,6 +3,7 @@ module go.opentelemetry.io/otel/bridge/opencensus
 go 1.18
 
 require (
+	github.com/stretchr/testify v1.7.1
 	go.opencensus.io v0.23.0
 	go.opentelemetry.io/otel v1.10.0
 	go.opentelemetry.io/otel/metric v0.32.1
@@ -12,10 +13,15 @@ require (
 )
 
 require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/go-logr/logr v1.2.3 // indirect
 	github.com/go-logr/stdr v1.2.2 // indirect
 	github.com/golang/groupcache v0.0.0-20200121045136-8c9f03a8e57e // indirect
+	github.com/kr/pretty v0.1.0 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
 	golang.org/x/sys v0.0.0-20220919091848-fb04ddd9f9c8 // indirect
+	gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15 // indirect
+	gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c // indirect
 )
 
 replace go.opentelemetry.io/otel => ../..

bridge/opencensus/go.sum

@@ -3,8 +3,9 @@ github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03
 github.com/census-instrumentation/opencensus-proto v0.2.1/go.mod h1:f6KPmirojxKA12rnyqOA5BBL4O983OfeGPqjHWSTneU=
 github.com/client9/misspell v0.3.4/go.mod h1:qj6jICC3Q7zFZvVWo7KLAzC3yx5G7kyvSDkc90ppPyw=
 github.com/cncf/udpa/go v0.0.0-20191209042840-269d4d468f6f/go.mod h1:M8M6+tZqaGXZJjfX53e64911xZQV5JYwmTeXPW+k8Sc=
-github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/envoyproxy/go-control-plane v0.9.0/go.mod h1:YTl/9mNaCwkRvm6d1a2C3ymFceY/DCBVvsKhRF0iEA4=
 github.com/envoyproxy/go-control-plane v0.9.1-0.20191026205805-5f8ba28d4473/go.mod h1:YTl/9mNaCwkRvm6d1a2C3ymFceY/DCBVvsKhRF0iEA4=
 github.com/envoyproxy/go-control-plane v0.9.4/go.mod h1:6rpuAdCZL397s3pYoYcLgu1mIlRU8Am5FuJP05cCM98=
@@ -35,12 +36,18 @@ github.com/google/go-cmp v0.5.0/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/
 github.com/google/go-cmp v0.5.3/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
 github.com/google/go-cmp v0.5.8 h1:e6P7q2lk1O+qJJb4BtCQXlK8vWEO8V1ZeuEdJNOqZyg=
 github.com/google/uuid v1.1.2/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
+github.com/kr/pretty v0.1.0 h1:L/CwN0zerZDmRFUapSPitk6f+Q3+0za1rQkzVuMiMFI=
+github.com/kr/pretty v0.1.0/go.mod h1:dAy3ld7l9f0ibDNOQOHHMYYIIbhfbHSm3C4ZsoJORNo=
+github.com/kr/pty v1.1.1/go.mod h1:pFQYn66WHrOpPYNljwOMqo10TkYh1fy3cYio2l3bCsQ=
+github.com/kr/text v0.1.0 h1:45sCR5RtlFHMR4UwH9sdQ5TC8v0qDQCHnXt+kaKSTVE=
+github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/prometheus/client_model v0.0.0-20190812154241-14fe0d1b01d4/go.mod h1:xMI15A0UPsDsEKsMN9yxemIoYk6Tm2C1GtYGdfGttqA=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/testify v1.6.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
 github.com/stretchr/testify v1.7.1 h1:5TQK59W5E3v0r2duFAb7P95B6hEeOyEnHRa8MjYSMTY=
+github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
 go.opencensus.io v0.23.0 h1:gqCw0LfLxScz8irSi8exQc7fyQ0fKQU/qnC/X8+V/1M=
 go.opencensus.io v0.23.0/go.mod h1:XItmlyltB5F7CS4xOC1DcqMoFqwtC6OG2xF7mCv7P7E=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
@@ -93,6 +100,8 @@ google.golang.org/protobuf v1.23.0/go.mod h1:EGpADcykh3NcUnDUJcl1+ZksZNG86OlYog2
 google.golang.org/protobuf v1.23.1-0.20200526195155-81db48ad09cc/go.mod h1:EGpADcykh3NcUnDUJcl1+ZksZNG86OlYog2l/sGQquU=
 google.golang.org/protobuf v1.25.0/go.mod h1:9JNX74DMeImyA3h4bdi1ymwjUzf21/xIlbajtzgsN7c=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15 h1:YR8cESwS4TdDjEe65xsg0ogRM/Nc3DYOhEAlW+xobZo=
+gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c h1:dUUwHk2QECo/6vqA44rthZ8ie2QXMNeKRTHCNY2nXvo=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 honnef.co/go/tools v0.0.0-20190102054323-c2f93a96b099/go.mod h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4=

bridge/opencensus/metric.go

@@ -23,6 +23,7 @@ import (
 	ocmetricdata "go.opencensus.io/metric/metricdata"
 	"go.opencensus.io/metric/metricexport"
 
+	"go.opentelemetry.io/otel"
 	internal "go.opentelemetry.io/otel/bridge/opencensus/internal/ocmetric"
 	"go.opentelemetry.io/otel/sdk/instrumentation"
 	"go.opentelemetry.io/otel/sdk/metric"
@@ -30,6 +31,8 @@ import (
 	"go.opentelemetry.io/otel/sdk/resource"
 )
 
+const scopeName = "go.opentelemetry.io/otel/bridge/opencensus"
+
 // exporter implements the OpenCensus metric Exporter interface using an
 // OpenTelemetry base exporter.
 type exporter struct {
@@ -38,7 +41,7 @@ type exporter struct {
 }
 
 // NewMetricExporter returns an OpenCensus exporter that exports to an
-// OpenTelemetry exporter.
+// OpenTelemetry (push) exporter.
 func NewMetricExporter(base metric.Exporter, res *resource.Resource) metricexport.Exporter {
 	return &exporter{base: base, res: res}
 }
@@ -48,14 +51,17 @@ func NewMetricExporter(base metric.Exporter, res *resource.Resource) metricexpor
 func (e *exporter) ExportMetrics(ctx context.Context, ocmetrics []*ocmetricdata.Metric) error {
 	otelmetrics, err := internal.ConvertMetrics(ocmetrics)
 	if err != nil {
-		return err
+		otel.Handle(err)
+	}
+	if len(otelmetrics) == 0 {
+		return nil
 	}
 	return e.base.Export(ctx, metricdata.ResourceMetrics{
 		Resource: e.res,
 		ScopeMetrics: []metricdata.ScopeMetrics{
 			{
 				Scope: instrumentation.Scope{
-					Name: "go.opentelemetry.io/otel/bridge/opencensus",
+					Name: scopeName,
 				},
 				Metrics: otelmetrics,
 			},

bridge/opencensus/metric_test.go

@@ -0,0 +1,157 @@
+// Copyright The OpenTelemetry 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 opencensus // import "go.opentelemetry.io/otel/bridge/opencensus"
+
+import (
+	"context"
+	"fmt"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+	ocmetricdata "go.opencensus.io/metric/metricdata"
+	ocresource "go.opencensus.io/resource"
+
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/sdk/instrumentation"
+	"go.opentelemetry.io/otel/sdk/metric"
+	"go.opentelemetry.io/otel/sdk/metric/metricdata"
+	"go.opentelemetry.io/otel/sdk/metric/metricdata/metricdatatest"
+	"go.opentelemetry.io/otel/sdk/resource"
+)
+
+func TestPushMetricsExporter(t *testing.T) {
+	now := time.Now()
+	for _, tc := range []struct {
+		desc          string
+		input         []*ocmetricdata.Metric
+		inputResource *resource.Resource
+		exportErr     error
+		expected      *metricdata.ResourceMetrics
+		expectErr     bool
+	}{
+		{
+			desc: "empty batch isn't sent",
+		},
+		{
+			desc:      "export error",
+			exportErr: fmt.Errorf("failed to export"),
+			input: []*ocmetricdata.Metric{
+				{
+					Resource: &ocresource.Resource{
+						Labels: map[string]string{
+							"R1": "V1",
+							"R2": "V2",
+						},
+					},
+					TimeSeries: []*ocmetricdata.TimeSeries{
+						{
+							StartTime: now,
+							Points: []ocmetricdata.Point{
+								{Value: int64(123), Time: now},
+							},
+						},
+					},
+				},
+			},
+			expectErr: true,
+		},
+		{
+			desc: "success",
+			input: []*ocmetricdata.Metric{
+				{
+					Resource: &ocresource.Resource{
+						Labels: map[string]string{
+							"R1": "V1",
+							"R2": "V2",
+						},
+					},
+					TimeSeries: []*ocmetricdata.TimeSeries{
+						{
+							StartTime: now,
+							Points: []ocmetricdata.Point{
+								{Value: int64(123), Time: now},
+							},
+						},
+					},
+				},
+			},
+			inputResource: resource.NewSchemaless(
+				attribute.String("R1", "V1"),
+				attribute.String("R2", "V2"),
+			),
+			expected: &metricdata.ResourceMetrics{
+				Resource: resource.NewSchemaless(
+					attribute.String("R1", "V1"),
+					attribute.String("R2", "V2"),
+				),
+				ScopeMetrics: []metricdata.ScopeMetrics{
+					{
+						Scope: instrumentation.Scope{
+							Name: scopeName,
+						},
+						Metrics: []metricdata.Metrics{
+							{
+								Name:        "",
+								Description: "",
+								Unit:        "",
+								Data: metricdata.Gauge[int64]{
+									DataPoints: []metricdata.DataPoint[int64]{
+										{
+											Attributes: attribute.NewSet(),
+											StartTime:  now,
+											Time:       now,
+											Value:      123,
+										},
+									},
+								},
+							},
+						},
+					},
+				},
+			},
+		},
+	} {
+		t.Run(tc.desc, func(t *testing.T) {
+			fake := &fakeExporter{err: tc.exportErr}
+			exporter := NewMetricExporter(fake, tc.inputResource)
+			err := exporter.ExportMetrics(context.Background(), tc.input)
+			if tc.expectErr {
+				require.Error(t, err)
+			} else {
+				require.NoError(t, err)
+			}
+			if tc.expected != nil {
+				require.NotNil(t, fake.data)
+				metricdatatest.AssertEqual(t, *tc.expected, *fake.data)
+			} else {
+				require.Nil(t, fake.data)
+			}
+		})
+	}
+}
+
+type fakeExporter struct {
+	metric.Exporter
+	data *metricdata.ResourceMetrics
+	err  error
+}
+
+func (f *fakeExporter) Export(ctx context.Context, data metricdata.ResourceMetrics) error {
+	if f.err == nil {
+		f.data = &data
+	}
+	return f.err
+}

bridge/opencensus/test/go.sum

@@ -3,8 +3,8 @@ github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03
 github.com/census-instrumentation/opencensus-proto v0.2.1/go.mod h1:f6KPmirojxKA12rnyqOA5BBL4O983OfeGPqjHWSTneU=
 github.com/client9/misspell v0.3.4/go.mod h1:qj6jICC3Q7zFZvVWo7KLAzC3yx5G7kyvSDkc90ppPyw=
 github.com/cncf/udpa/go v0.0.0-20191209042840-269d4d468f6f/go.mod h1:M8M6+tZqaGXZJjfX53e64911xZQV5JYwmTeXPW+k8Sc=
-github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/envoyproxy/go-control-plane v0.9.0/go.mod h1:YTl/9mNaCwkRvm6d1a2C3ymFceY/DCBVvsKhRF0iEA4=
 github.com/envoyproxy/go-control-plane v0.9.1-0.20191026205805-5f8ba28d4473/go.mod h1:YTl/9mNaCwkRvm6d1a2C3ymFceY/DCBVvsKhRF0iEA4=
 github.com/envoyproxy/go-control-plane v0.9.4/go.mod h1:6rpuAdCZL397s3pYoYcLgu1mIlRU8Am5FuJP05cCM98=

example/opencensus/go.sum

@@ -3,8 +3,8 @@ github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03
 github.com/census-instrumentation/opencensus-proto v0.2.1/go.mod h1:f6KPmirojxKA12rnyqOA5BBL4O983OfeGPqjHWSTneU=
 github.com/client9/misspell v0.3.4/go.mod h1:qj6jICC3Q7zFZvVWo7KLAzC3yx5G7kyvSDkc90ppPyw=
 github.com/cncf/udpa/go v0.0.0-20191209042840-269d4d468f6f/go.mod h1:M8M6+tZqaGXZJjfX53e64911xZQV5JYwmTeXPW+k8Sc=
-github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/envoyproxy/go-control-plane v0.9.0/go.mod h1:YTl/9mNaCwkRvm6d1a2C3ymFceY/DCBVvsKhRF0iEA4=
 github.com/envoyproxy/go-control-plane v0.9.1-0.20191026205805-5f8ba28d4473/go.mod h1:YTl/9mNaCwkRvm6d1a2C3ymFceY/DCBVvsKhRF0iEA4=
 github.com/envoyproxy/go-control-plane v0.9.4/go.mod h1:6rpuAdCZL397s3pYoYcLgu1mIlRU8Am5FuJP05cCM98=