receiver/prometheus/internal: add createNodeAndResourcePdata for Prom…

…etheus->OTLP Pdata (#3139)

* receiver/prometheus/internal: add createNodeAndResourcePdata for Prometheus->OTLP Pdata

Starts the progressive effort to convert directly from
    Prometheus->OTLPPdata

directly instead of

    Prometheus->OpenCensusProto->OTLPPdata

by adding a converter for node+resource -> pdata.Resource.

Updates #3137

* Use .Attributes to skip unsafe extraction plus use require.Equal

Addresses feedback pointed out by Bogdan, Tigran, Jaana
by using Resource.Attributes().Sort() instead and also avoid
using go-cmp/cmp and instead opt to using require.Equal.

* Add comment and rename parity test check

* Add createNodeAndResource unit test

receiver/prometheusreceiver/internal/prom_to_otlp.go

@@ -0,0 +1,39 @@
+// 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 internal
+
+import (
+	"net"
+
+	"go.opentelemetry.io/collector/consumer/pdata"
+	"go.opentelemetry.io/collector/translator/conventions"
+)
+
+func createNodeAndResourcePdata(job, instance, scheme string) pdata.Resource {
+	host, port, err := net.SplitHostPort(instance)
+	if err != nil {
+		host = instance
+	}
+	resource := pdata.NewResource()
+	attrs := resource.Attributes()
+	attrs.UpsertString(conventions.AttributeServiceName, job)
+	attrs.UpsertString(conventions.AttributeHostName, host)
+	attrs.UpsertString(jobAttr, job)
+	attrs.UpsertString(instanceAttr, instance)
+	attrs.UpsertString(portAttr, port)
+	attrs.UpsertString(schemeAttr, scheme)
+
+	return resource
+}

receiver/prometheusreceiver/internal/prom_to_otlp_test.go

@@ -0,0 +1,120 @@
+// 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 internal
+
+import (
+	"testing"
+
+	metricspb "github.com/census-instrumentation/opencensus-proto/gen-go/metrics/v1"
+	"github.com/stretchr/testify/require"
+
+	"go.opentelemetry.io/collector/consumer/pdata"
+	"go.opentelemetry.io/collector/translator/internaldata"
+)
+
+// Parity test to ensure that createNodeAndResource produces identical results to createNodeAndResourcePdata.
+func TestCreateNodeAndResourceEquivalence(t *testing.T) {
+	job, instance, scheme := "converter", "ocmetrics", "http"
+	ocNode, ocResource := createNodeAndResource(job, instance, scheme)
+	mdFromOC := internaldata.OCToMetrics(ocNode, ocResource,
+		// We need to pass in a dummy set of metrics
+		// just to populate and allow for full conversion.
+		[]*metricspb.Metric{
+			{
+				MetricDescriptor: &metricspb.MetricDescriptor{
+					Name:        "m1",
+					Description: "d1",
+					Unit:        "By",
+				},
+			},
+		},
+	)
+
+	fromOCResource := mdFromOC.ResourceMetrics().At(0).Resource().Attributes().Sort()
+	byDirectOTLPResource := createNodeAndResourcePdata(job, instance, scheme).Attributes().Sort()
+
+	require.Equal(t, byDirectOTLPResource, fromOCResource)
+}
+
+type jobInstanceDefinition struct {
+	job, instance, host, scheme, port string
+}
+
+func makeResourceWithJobInstanceScheme(def *jobInstanceDefinition) pdata.Resource {
+	resource := pdata.NewResource()
+	attrs := resource.Attributes()
+	// Using hardcoded values to assert on outward expectations so that
+	// when variables change, these tests will fail and we'll have reports.
+	attrs.UpsertString("service.name", def.job)
+	attrs.UpsertString("host.name", def.host)
+	attrs.UpsertString("job", def.job)
+	attrs.UpsertString("instance", def.instance)
+	attrs.UpsertString("port", def.port)
+	attrs.UpsertString("scheme", def.scheme)
+	return resource
+}
+
+func TestCreateNodeAndResourcePromToOTLP(t *testing.T) {
+	tests := []struct {
+		name, job string
+		instance  string
+		scheme    string
+		want      pdata.Resource
+	}{
+		{
+			name: "all attributes proper",
+			job:  "job", instance: "localhost:8888", scheme: "http",
+			want: makeResourceWithJobInstanceScheme(&jobInstanceDefinition{
+				"job", "localhost:8888", "localhost", "http", "8888",
+			}),
+		},
+		{
+			name: "missing port",
+			job:  "job", instance: "myinstance", scheme: "https",
+			want: makeResourceWithJobInstanceScheme(&jobInstanceDefinition{
+				"job", "myinstance", "myinstance", "https", "",
+			}),
+		},
+		{
+			name: "blank scheme",
+			job:  "job", instance: "myinstance:443", scheme: "",
+			want: makeResourceWithJobInstanceScheme(&jobInstanceDefinition{
+				"job", "myinstance:443", "myinstance", "", "443",
+			}),
+		},
+		{
+			name: "blank instance, blank scheme",
+			job:  "job", instance: "", scheme: "",
+			want: makeResourceWithJobInstanceScheme(&jobInstanceDefinition{
+				"job", "", "", "", "",
+			}),
+		},
+		{
+			name: "blank instance, non-blank scheme",
+			job:  "job", instance: "", scheme: "http",
+			want: makeResourceWithJobInstanceScheme(&jobInstanceDefinition{
+				"job", "", "", "http", "",
+			}),
+		},
+	}
+
+	for _, tt := range tests {
+		tt := tt
+		t.Run(tt.name, func(t *testing.T) {
+			got := createNodeAndResourcePdata(tt.job, tt.instance, tt.scheme)
+			require.Equal(t, got, tt.want)
+		})
+	}
+}