Fix metrics exporter integration (GoogleCloudPlatform#207)

* Fix metrics exporter example

* Add metrics-exporter example with OpenTelemetrySdk usage

* Update GoogleCloudMetricExporter to return generic types

* Implement deferred initialization of metrics exporter

* Update examples to use the deferred exporters

* Lazy loads default project ID initialization

* Fix failing tests

MetricConfigurationTest had a test that directly invoked a static
method, the state of which is preserved b/w test classes, this lead to
an intermittent failure in one of the tests run in
GoogleCloudMetricConfigurationTest, which made some assumptions about
the state affected by the invocation of the said method.

* Update documentation

* Add readme for metrics exporter example

* Make NoopMetricExport return the same AggregationTemporality as GoogleCloudMetricExporter

* Undo accidental dependency version downgrade

* Fix documentation errors

* Remove the additional example

Author: psx95

examples/metrics/src/main/java/com/google/cloud/opentelemetry/example/metrics/MetricsExporterExample.java

@@ -19,8 +19,8 @@
 import io.opentelemetry.api.metrics.LongCounter;
 import io.opentelemetry.api.metrics.Meter;
 import io.opentelemetry.sdk.metrics.SdkMeterProvider;
+import io.opentelemetry.sdk.metrics.export.MetricExporter;
 import io.opentelemetry.sdk.metrics.export.PeriodicMetricReader;
-import java.io.IOException;
 import java.util.Random;
 
 public class MetricsExporterExample {
@@ -30,25 +30,20 @@ public class MetricsExporterExample {
   private static final Random RANDOM = new Random();
 
   private static void setupMetricExporter() {
-    try {
-      GoogleCloudMetricExporter metricExporter =
-          GoogleCloudMetricExporter.createWithDefaultConfiguration();
-      METER_PROVIDER =
-          SdkMeterProvider.builder()
-              .registerMetricReader(
-                  PeriodicMetricReader.builder(metricExporter)
-                      .setInterval(java.time.Duration.ofSeconds(30))
-                      .build())
-              .build();
+    MetricExporter metricExporter = GoogleCloudMetricExporter.createWithDefaultConfiguration();
+    METER_PROVIDER =
+        SdkMeterProvider.builder()
+            .registerMetricReader(
+                PeriodicMetricReader.builder(metricExporter)
+                    .setInterval(java.time.Duration.ofSeconds(30))
+                    .build())
+            .build();
 
-      METER =
-          METER_PROVIDER
-              .meterBuilder("instrumentation-library-name")
-              .setInstrumentationVersion("semver:1.0.0")
-              .build();
-    } catch (IOException e) {
-      throw new RuntimeException(e);
-    }
+    METER =
+        METER_PROVIDER
+            .meterBuilder("instrumentation-library-name")
+            .setInstrumentationVersion("semver:1.0.0")
+            .build();
   }
 
   private static void myUseCase() {
@@ -72,15 +67,16 @@ private static void doWork(LongCounter counter) {
     }
   }
 
+  // to run this from command line, execute `gradle run`
   public static void main(String[] args) throws InterruptedException {
     System.out.println("Starting the metrics-example application");
     setupMetricExporter();
     try {
       int i = 0;
-      while (true) {
+      while (i < 2) {
         System.out.println("Running example use case: #" + i);
         myUseCase();
-        Thread.sleep(10000);
+        Thread.sleep(5000);
         i++;
       }
     } finally {

exporters/auto/src/main/java/com/google/cloud/opentelemetry/auto/GoogleCloudMetricExporterFactory.java

@@ -19,17 +19,13 @@
 import com.google.cloud.opentelemetry.metric.GoogleCloudMetricExporter;
 import io.opentelemetry.sdk.autoconfigure.spi.ConfigProperties;
 import io.opentelemetry.sdk.autoconfigure.spi.metrics.ConfigurableMetricExporterProvider;
-import java.io.IOException;
+import io.opentelemetry.sdk.metrics.export.MetricExporter;
 
 @AutoService(ConfigurableMetricExporterProvider.class)
 public class GoogleCloudMetricExporterFactory implements ConfigurableMetricExporterProvider {
   @Override
-  public GoogleCloudMetricExporter createExporter(ConfigProperties config) {
-    try {
-      return GoogleCloudMetricExporter.createWithDefaultConfiguration();
-    } catch (IOException ex) {
-      throw new RuntimeException(ex);
-    }
+  public MetricExporter createExporter(ConfigProperties config) {
+    return GoogleCloudMetricExporter.createWithDefaultConfiguration();
   }
 
   @Override

exporters/metrics/build.gradle

@@ -18,15 +18,17 @@ description = 'Cloud Monitoring Exporter for OpenTelemetry'
 dependencies {
 	api(libraries.auto_value_annotations)
 	api(libraries.slf4j)
-	annotationProcessor(libraries.auto_value)
 	api(libraries.opentelemetry_api)
-	api(libraries.opentelemetry_sdk_metrics)
 	api(libraries.google_cloud_core)
 	api(libraries.google_cloud_monitoring)
+	api(libraries.opentelemetry_sdk_metrics)
+	annotationProcessor(libraries.auto_value)
 	implementation(project(':shared-resourcemapping'))
 	testImplementation(libraries.opentelemetry_semconv)
 	testImplementation(testLibraries.junit)
 	testImplementation(testLibraries.mockito)
 	testImplementation(testLibraries.slf4j_simple)
 	testImplementation(testLibraries.test_containers)
+	testImplementation(testLibraries.opentelemetry_sdk_testing)
+	testImplementation(testLibraries.opencensus_shim)
 }

exporters/metrics/src/main/java/com/google/cloud/opentelemetry/metric/AggregateByLabelMetricTimeSeriesBuilder.java

@@ -22,7 +22,6 @@
 import static com.google.cloud.opentelemetry.metric.ResourceTranslator.mapResource;
 
 import com.google.api.MetricDescriptor;
-import com.google.cloud.opentelemetry.metric.GoogleCloudMetricExporter.MetricWithLabels;
 import com.google.monitoring.v3.TimeSeries;
 import com.google.monitoring.v3.TypedValue;
 import io.opentelemetry.api.common.Attributes;