address feedback and add readme

Author: dashpole

exporter/collector/googlemanagedprometheus/README.md

@@ -0,0 +1,52 @@
+# Google Managed Service for Prometheus Collector Exporter
+
+## Building a container image with the googlemanagedprometheus exporter
+
+In your own fork of [open-telemetry/opentelemetry-collector-releases](https://github.com/open-telemetry/opentelemetry-collector-releases), add your own "distribution" directory within the distributions directory, based on either the otelcol or otelcol-contrib distributions. In the `exporters` list in `manifest.yaml`, add:
+```yaml
+exporters:
+  - gomod: "github.com/GoogleCloudPlatform/exporter/collector/googlemanagedprometheus v0.29.0"
+```
+
+The syntax of `manifest.yaml` is described in the [Collector Builder documentation](https://github.com/open-telemetry/opentelemetry-collector/blob/54f271b7d473f36b4ecbc21994d59359dbd263f6/cmd/builder/README.md#opentelemetry-collector-builder).
+
+In the `configs` directory, add your collector configuration yaml file, which should look something like:
+
+```yaml
+receivers:
+    prometheus:
+        config:
+          scrape_configs:
+            # TODO: Add your prometheus scrape configuration here.
+            # Using kubernetes_sd_configs with namespaced resources
+            # ensures the namespace is set on your metrics.
+processors:
+    batch:
+        # batch metrics before sending to reduce API usage
+        send_batch_max_size: 200
+        send_batch_size: 200
+        timeout: 5s
+    memory_limiter:
+        # drop metrics if memory usage gets too high
+        check_interval: 1s
+        limit_percentage: 65
+        spike_limit_percentage: 20
+    resourcedetection:
+        # detect cluster name and location
+        detectors: [gce, gke]
+        timeout: 10s
+exporters:
+    googlemanagedprometheus:
+```
+
+Change the Dockerfile in your directory within `distributions` to point to your collector config [here](https://github.com/open-telemetry/opentelemetry-collector-releases/blob/main/distributions/otelcol-contrib/Dockerfile#L17).
+
+Finally, build the image: 
+
+```sh
+DISTRIBUTIONS=my-distribution make build
+```
+
+## Additional Options
+
+The [filterprocessor](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/processor/filterprocessor) can filter out metrics. The [metricstransformprocessor](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/processor/metricstransformprocessor) can manipulate metrics in a variety of ways, including synthesizing new metrics from other metrics, adding or removing labels, renaming metrics, and scaling metrics. `metric_relabl_configs` within the prometheus receiver configuration can also be used to manipulate metrics.

exporter/collector/googlemanagedprometheus/factory.go

@@ -48,7 +48,7 @@ func createDefaultConfig() config.Exporter {
 		RetrySettings:    exporterhelper.NewDefaultRetrySettings(),
 		QueueSettings:    exporterhelper.NewDefaultQueueSettings(),
 		GMPConfig: GMPConfig{
-			UserAgent: "opentelemetry-collector-contrib {{version}}",
+			UserAgent: "opentelemetry-collector-contrib/{{version}}",
 		},
 	}
 }
@@ -83,7 +83,9 @@ func (c *GMPConfig) toCollectorConfig() collector.Config {
 	cfg.MetricConfig.SkipCreateMetricDescriptor = true
 	cfg.MetricConfig.InstrumentationLibraryLabels = false
 	cfg.MetricConfig.ServiceResourceLabels = false
+	// Update metric naming to match GMP conventions
 	cfg.MetricConfig.GetMetricName = GetMetricName
+	// Map to the prometheus_target monitored resource
 	cfg.MetricConfig.MapMonitoredResource = MapToPrometheusTarget
 	cfg.MetricConfig.EnableSumOfSquaredDeviation = true
 	// TODO: Change to GMP's method of reset handling.

exporter/collector/googlemanagedprometheus/naming.go

@@ -15,25 +15,34 @@
 package googlemanagedprometheus
 
 import (
+	"strings"
+
 	"go.opentelemetry.io/collector/model/pdata"
 	"go.opentelemetry.io/collector/pdata/pmetric"
 )
 
 func GetMetricName(baseName string, metric pdata.Metric) string {
-	return baseName + gmpMetricSuffix(metric)
-}
-
-func gmpMetricSuffix(metric pdata.Metric) string {
 	switch metric.DataType() {
 	case pmetric.MetricDataTypeSum:
-		return "/counter"
+		return baseName + "/counter"
 	case pmetric.MetricDataTypeGauge:
-		return "/gauge"
+		return baseName + "/gauge"
 	case pmetric.MetricDataTypeSummary:
-		return "/summary"
+		// summaries are sent as the following series:
+		// * Sum: prometheus.googleapis.com/<baseName>_sum/summary:counter
+		// * Count: prometheus.googleapis.com/<baseName>_count/summary
+		// * Quantiles: prometheus.googleapis.com/<baseName>/summary
+		if strings.HasSuffix(baseName, "_sum") {
+			return baseName + "/summary:counter"
+		}
+		return baseName + "/summary"
 	case pmetric.MetricDataTypeHistogram:
-		return "/histogram"
+		return baseName + "/histogram"
+	case pmetric.MetricDataTypeExponentialHistogram:
+		return baseName + "/exponentialhistogram"
 	default:
+		// This should never happen, as we have already dropped other data
+		// types at this point.
 		return ""
 	}
 }

exporter/collector/googlemanagedprometheus/naming_test.go

@@ -51,7 +51,7 @@ func TestGetMetricName(t *testing.T) {
 		{
 			desc:     "other",
 			datatype: pmetric.MetricDataTypeExponentialHistogram,
-			expected: baseName,
+			expected: baseName + "/exponentialhistogram",
 		},
 	} {
 		t.Run(tc.desc, func(t *testing.T) {

exporter/collector/integrationtest/testdata/config.yaml

@@ -24,4 +24,8 @@ service:
         receivers: [nop]
         processors: [nop]
         exporters: [googlecloud]
+    metrics:
+        receivers: [nop]
+        processors: [nop]
+        exporters: [googlecloud]
 

exporter/collector/integrationtest/testdata/gmp_config.yaml

@@ -14,7 +14,7 @@ exporters:
 
 service:
   pipelines:
-    traces:
+    metrics:
         receivers: [nop]
         processors: [nop]
         exporters: [googlemanagedprometheus]