Remove metric registry and fix examples. (#238)

api/src/main/java/io/opentelemetry/metrics/CounterDouble.java

@@ -23,50 +23,33 @@ import javax.annotation.concurrent.ThreadSafe;
  * Counter metric, to report instantaneous measurement of a double value. Cumulative values can go
  * up or stay the same, but can never go down. Cumulative values cannot be negative.
  *
- * <p>Example 1: Create a Cumulative with default labels.
+ * <p>Example:
  *
  * <pre>{@code
  * class YourClass {
  *
  *   private static final Meter meter = Metrics.getMeter();
- *   private static final MetricRegistry metricRegistry = meter.metricRegistryBuilder().build();
- *
- *   List<LabelKey> labelKeys = Arrays.asList(LabelKey.create("Name", "desc"));
- *
- *   CounterDouble cumulative = metricRegistry.addDoubleCumulative("processed_jobs",
- *                       "Processed jobs", "1", labelKeys);
- *
+ *   private static final CounterDouble counter =
+ *       meter.
+ *           .counterDoubleBuilder("processed_jobs")
+ *           .setDescription("Processed jobs")
+ *           .setUnit("1")
+ *           .setLabelKeys(Collections.singletonList(LabelKey.create("Name", "desc")))
+ *           .build();
  *   // It is recommended to keep a reference of a TimeSeries.
- *   CounterDouble.TimeSeries defaultTimeSeries = cumulative.getDefaultTimeSeries();
+ *   private static final CounterDouble.TimeSeries inboundTimeSeries =
+ *       counter.getOrCreateTimeSeries(Collections.singletonList(LabelValue.create("SomeWork")));
+ *   private static final CounterDouble.TimeSeries defaultTimeSeries =
+ *       counter.getDefaultTimeSeries();
  *
- *   void doWork() {
+ *   void doDefaultWork() {
  *      // Your code here.
- *      defaultPoint.add(10);
+ *      defaultTimeSeries.add(10);
  *   }
  *
- * }
- * }</pre>
- *
- * <p>Example 2: You can also use labels (keys and values) to track different types of metric.
- *
- * <pre>{@code
- * class YourClass {
- *
- *   private static final Meter meter = Metrics.getMeter();
- *   private static final MetricRegistry metricRegistry = meter.metricRegistryBuilder().build();
- *
- *   List<LabelKey> labelKeys = Arrays.asList(LabelKey.create("Name", "desc"));
- *   List<LabelValue> labelValues = Arrays.asList(LabelValue.create("Inbound"));
- *
- *   CounterDouble cumulative = metricRegistry.addDoubleCumulative("processed_jobs",
- *                       "Processed jobs", "1", labelKeys);
- *
- *   // It is recommended to keep a reference of a TimeSeries.
- *   CounterDouble.TimeSeries inboundTimeSeries = cumulative.getOrCreateTimeSeries(labelValues);
- *
  *   void doSomeWork() {
  *      // Your code here.
- *      inboundPoint.set(15);
+ *      inboundTimeSeries.set(15);
  *   }
  *
  * }

api/src/main/java/io/opentelemetry/metrics/CounterLong.java

@@ -24,50 +24,32 @@ import javax.annotation.concurrent.ThreadSafe;
  * Counter metric, to report instantaneous measurement of a long value. Cumulative values can go up
  * or stay the same, but can never go down. Cumulative values cannot be negative.
  *
- * <p>Example 1: Create a Cumulative with default labels.
+ * <p>Example:
  *
  * <pre>{@code
  * class YourClass {
  *
  *   private static final Meter meter = Metrics.getMeter();
- *   private static final MetricRegistry metricRegistry = meter.metricRegistryBuilder().build();
- *
- *   List<LabelKey> labelKeys = Arrays.asList(LabelKey.create("Name", "desc"));
- *
- *   CounterLong cumulative = metricRegistry.addLongCumulative("processed_jobs",
- *                       "Processed jobs", "1", labelKeys);
- *
+ *   private static final CounterLong counter =
+ *       meter.
+ *           .counterLongBuilder("processed_jobs")
+ *           .setDescription("Processed jobs")
+ *           .setUnit("1")
+ *           .setLabelKeys(Collections.singletonList(LabelKey.create("Name", "desc")))
+ *           .build();
  *   // It is recommended to keep a reference of a TimeSeries.
- *   CounterLong.TimeSeries defaultTimeSeries = cumulative.getDefaultTimeSeries();
+ *   private static final CounterLong.TimeSeries inboundTimeSeries =
+ *       counter.getOrCreateTimeSeries(Collections.singletonList(LabelValue.create("SomeWork")));
+ *   private static final CounterLong.TimeSeries defaultTimeSeries = counter.getDefaultTimeSeries();
  *
- *   void doWork() {
+ *   void doDefaultWork() {
  *      // Your code here.
- *      defaultPoint.add(10);
+ *      defaultTimeSeries.add(10);
  *   }
  *
- * }
- * }</pre>
- *
- * <p>Example 2: You can also use labels (keys and values) to track different types of metric.
- *
- * <pre>{@code
- * class YourClass {
- *
- *   private static final Meter meter = Metrics.getMeter();
- *   private static final MetricRegistry metricRegistry = meter.metricRegistryBuilder().build();
- *
- *   List<LabelKey> labelKeys = Arrays.asList(LabelKey.create("Name", "desc"));
- *   List<LabelValue> labelValues = Arrays.asList(LabelValue.create("Inbound"));
- *
- *   CounterLong cumulative = metricRegistry.addLongCumulative("processed_jobs",
- *                       "Processed jobs", "1", labelKeys);
- *
- *   // It is recommended to keep a reference of a TimeSeries.
- *   CounterLong.TimeSeries inboundTimeSeries = cumulative.getOrCreateTimeSeries(labelValues);
- *
  *   void doSomeWork() {
  *      // Your code here.
- *      inboundPoint.set(15);
+ *      inboundTimeSeries.set(15);
  *   }
  *
  * }

api/src/main/java/io/opentelemetry/metrics/GaugeDouble.java

@@ -24,50 +24,32 @@ import javax.annotation.concurrent.ThreadSafe;
  * Gauge metric, to report instantaneous measurement of a double value. Gauges can go both up and
  * down. The gauges values can be negative.
  *
- * <p>Example 1: Create a Gauge with default labels.
+ * <p>Example:
  *
  * <pre>{@code
  * class YourClass {
  *
  *   private static final Meter meter = Metrics.getMeter();
- *   private static final MetricRegistry metricRegistry = meter.metricRegistryBuilder().build();
- *
- *   List<LabelKey> labelKeys = Arrays.asList(LabelKey.create("Name", "desc"));
- *
- *   GaugeDouble gauge = metricRegistry.addDoubleGauge("queue_size",
- *                       "Pending jobs", "1", labelKeys);
- *
+ *   private static final GaugeDouble gauge =
+ *       meter
+ *           .gaugeDoubleBuilder("processed_jobs")
+ *           .setDescription("Processed jobs")
+ *           .setUnit("1")
+ *           .setLabelKeys(Collections.singletonList(LabelKey.create("Name", "desc")))
+ *           .build();
  *   // It is recommended to keep a reference of a TimeSeries.
- *   GaugeDouble.TimeSeries defaultTimeSeries = gauge.getDefaultTimeSeries();
+ *   private static final GaugeDouble.TimeSeries inboundTimeSeries =
+ *       gauge.getOrCreateTimeSeries(Collections.singletonList(LabelValue.create("SomeWork")));
+ *    private static final GaugeDouble.TimeSeries defaultTimeSeries = gauge.getDefaultTimeSeries();
  *
- *   void doWork() {
+ *   void doDefault() {
  *      // Your code here.
- *      defaultPoint.add(10);
+ *      defaultTimeSeries.add(10);
  *   }
  *
- * }
- * }</pre>
- *
- * <p>Example 2: You can also use labels(keys and values) to track different types of metric.
- *
- * <pre>{@code
- * class YourClass {
- *
- *   private static final Meter meter = Metrics.getMeter();
- *   private static final MetricRegistry metricRegistry = meter.metricRegistryBuilder().build();
- *
- *   List<LabelKey> labelKeys = Arrays.asList(LabelKey.create("Name", "desc"));
- *   List<LabelValue> labelValues = Arrays.asList(LabelValue.create("Inbound"));
- *
- *   GaugeDouble gauge = metricRegistry.addDoubleGauge("queue_size",
- *                       "Pending jobs", "1", labelKeys);
- *
- *   // It is recommended to keep a reference of a TimeSeries.
- *   GaugeDouble.TimeSeries inboundTimeSeries = gauge.getOrCreateTimeSeries(labelValues);
- *
  *   void doSomeWork() {
  *      // Your code here.
- *      inboundPoint.set(15);
+ *      inboundTimeSeries.set(15);
  *   }
  *
  * }

api/src/main/java/io/opentelemetry/metrics/GaugeLong.java

@@ -23,48 +23,32 @@ import javax.annotation.concurrent.ThreadSafe;
  * Gauge metric, to report instantaneous measurement of an long value. Gauges can go both up and
  * down. The gauges values can be negative.
  *
- * <p>Example 1: Create a Gauge with default labels.
+ * <p>Example:
  *
  * <pre>{@code
  * class YourClass {
  *
  *   private static final Meter meter = Metrics.getMeter();
- *   private static final MetricRegistry metricRegistry = meter.metricRegistryBuilder().build();
- *
- *   List<LabelKey> labelKeys = Arrays.asList(LabelKey.create("Name", "desc"));
- *
- *   GaugeLong gauge = metricRegistry.addLongGauge("queue_size", "Pending jobs", "1", labelKeys);
- *
+ *   private static final GaugeLong gauge =
+ *       meter
+ *           .gaugeLongBuilder("processed_jobs")
+ *           .setDescription("Processed jobs")
+ *           .setUnit("1")
+ *           .setLabelKeys(Collections.singletonList(LabelKey.create("Name", "desc")))
+ *           .build();
  *   // It is recommended to keep a reference of a TimeSeries.
- *   GaugeLong.TimeSeries defaultTimeSeries = gauge.getDefaultTimeSeries();
+ *   private static final GaugeLong.TimeSeries inboundTimeSeries =
+ *       gauge.getOrCreateTimeSeries(Collections.singletonList(LabelValue.create("SomeWork")));
+ *    private static final GaugeLong.TimeSeries defaultTimeSeries = gauge.getDefaultTimeSeries();
  *
- *   void doWork() {
+ *   void doDefault() {
  *      // Your code here.
- *      defaultPoint.add(10);
+ *      defaultTimeSeries.add(10);
  *   }
  *
- * }
- * }</pre>
- *
- * <p>Example 2: You can also use labels(keys and values) to track different types of metric.
- *
- * <pre>{@code
- * class YourClass {
- *
- *   private static final Meter meter = Metrics.getMeter();
- *   private static final MetricRegistry metricRegistry = meter.metricRegistryBuilder().build();
- *
- *   List<LabelKey> labelKeys = Arrays.asList(LabelKey.create("Name", "desc"));
- *   List<LabelValue> labelValues = Arrays.asList(LabelValue.create("Inbound"));
- *
- *   GaugeLong gauge = metricRegistry.addLongGauge("queue_size", "Pending jobs", "1", labelKeys);
- *
- *   // It is recommended to keep a reference of a TimeSeries.
- *   GaugeLong.TimeSeries inboundTimeSeries = gauge.getOrCreateTimeSeries(labelValues);
- *
  *   void doSomeWork() {
  *      // Your code here.
- *      inboundPoint.set(15);
+ *      inboundTimeSeries.set(15);
  *   }
  *
  * }

api/src/main/java/io/opentelemetry/metrics/Meter.java

@@ -16,13 +16,50 @@
 
 package io.opentelemetry.metrics;
 
-/** Entry point fot metrics API, this object allows to create new {@link MetricRegistry}. */
+/** Entry point fot metrics API, this object allows to record measurements and {@link Metric}s. */
 public interface Meter {
 
   /**
-   * Returns a new builder for a {@code MetricRegistry}.
+   * Returns a builder for a {@link GaugeLong} to be added to the registry.
    *
-   * @return a new builder for a {@code MetricRegistry}.
+   * @param name the name of the metric.
+   * @return a {@code GaugeLong.Builder}.
+   * @throws NullPointerException if {@code name} is null.
+   * @throws IllegalArgumentException if different metric with the same name already registered.
+   * @since 0.1.0
    */
-  MetricRegistry.Builder metricRegistryBuilder();
+  GaugeLong.Builder gaugeLongBuilder(String name);
+
+  /**
+   * Returns a builder for a {@link GaugeDouble} to be added to the registry.
+   *
+   * @param name the name of the metric.
+   * @return a {@code GaugeDouble.Builder}.
+   * @throws NullPointerException if {@code name} is null.
+   * @throws IllegalArgumentException if different metric with the same name already registered.
+   * @since 0.1.0
+   */
+  GaugeDouble.Builder gaugeDoubleBuilder(String name);
+
+  /**
+   * Returns a builder for a {@link CounterDouble} to be added to the registry.
+   *
+   * @param name the name of the metric.
+   * @return a {@code CounterDouble.Builder}.
+   * @throws NullPointerException if {@code name} is null.
+   * @throws IllegalArgumentException if different metric with the same name already registered.
+   * @since 0.1.0
+   */
+  CounterDouble.Builder counterDoubleBuilder(String name);
+
+  /**
+   * Returns a builder for a {@link CounterLong} to be added to the registry.
+   *
+   * @param name the name of the metric.
+   * @return a {@code CounterLong.Builder}.
+   * @throws NullPointerException if {@code name} is null.
+   * @throws IllegalArgumentException if different metric with the same name already registered.
+   * @since 0.1.0
+   */
+  CounterLong.Builder counterLongBuilder(String name);
 }

api/src/main/java/io/opentelemetry/metrics/Metric.java

@@ -16,6 +16,7 @@
 
 package io.opentelemetry.metrics;
 
+import io.opentelemetry.resource.Resource;
 import java.util.Collections;
 import java.util.List;
 import java.util.Map;
@@ -79,7 +80,7 @@ public interface Metric<T> {
 
   interface Builder<B extends Builder<B, V>, V> {
     /**
-     * Sets the description of the Metric.
+     * Sets the description of the {@code Metric}.
      *
      * <p>Default value is {@code ""}.
      *
@@ -89,7 +90,7 @@ public interface Metric<T> {
     B setDescription(String description);
 
     /**
-     * Sets the unit of the Metric.
+     * Sets the unit of the {@code Metric}.
      *
      * <p>Default value is {@code "1"}.
      *
@@ -118,6 +119,32 @@ public interface Metric<T> {
      */
     B setConstantLabels(Map<LabelKey, LabelValue> constantLabels);
 
+    /**
+     * Sets the name of the component that reports this {@code Metric}.
+     *
+     * <p>The final name of the reported metric will be <code>component + "_" + name</code> if the
+     * component is not empty.
+     *
+     * <p>It is recommended to always set a component name for all the metrics, because some
+     * implementations may filter based on the component.
+     *
+     * @param component the name of the component that reports these metrics.
+     * @return this.
+     */
+    B setComponent(String component);
+
+    /**
+     * Sets the {@code Resource} associated with this {@code Metric}.
+     *
+     * <p>This should be set only when reporting out-of-band metrics, otherwise the implementation
+     * will set the {@code Resource} for in-process metrics (or user can do that when initialize the
+     * {@code Meter}).
+     *
+     * @param resource the {@code Resource} associated with this {@code Metric}.
+     * @return this.
+     */
+    B setResource(Resource resource);
+
     /**
      * Builds and returns a metric with the desired options.
      *

api/src/main/java/io/opentelemetry/metrics/MetricRegistry.java

@@ -1,104 +0,0 @@
-/*
- * Copyright 2019, 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 io.opentelemetry.metrics;
-
-import io.opentelemetry.resource.Resource;
-
-/**
- * Creates and manages a set of metrics for a library/application.
- *
- * @since 0.1.0
- */
-public interface MetricRegistry {
-
-  /**
-   * Returns a builder for a {@link GaugeLong} to be added to the registry.
-   *
-   * @param name the name of the metric.
-   * @return a {@code GaugeLong.Builder}.
-   * @throws NullPointerException if {@code name} is null.
-   * @throws IllegalArgumentException if different metric with the same name already registered.
-   * @since 0.1.0
-   */
-  GaugeLong.Builder gaugeLongBuilder(String name);
-
-  /**
-   * Returns a builder for a {@link GaugeDouble} to be added to the registry.
-   *
-   * @param name the name of the metric.
-   * @return a {@code GaugeDouble.Builder}.
-   * @throws NullPointerException if {@code name} is null.
-   * @throws IllegalArgumentException if different metric with the same name already registered.
-   * @since 0.1.0
-   */
-  GaugeDouble.Builder gaugeDoubleBuilder(String name);
-
-  /**
-   * Returns a builder for a {@link CounterDouble} to be added to the registry.
-   *
-   * @param name the name of the metric.
-   * @return a {@code CounterDouble.Builder}.
-   * @throws NullPointerException if {@code name} is null.
-   * @throws IllegalArgumentException if different metric with the same name already registered.
-   * @since 0.1.0
-   */
-  CounterDouble.Builder counterDoubleBuilder(String name);
-
-  /**
-   * Returns a builder for a {@link CounterLong} to be added to the registry.
-   *
-   * @param name the name of the metric.
-   * @return a {@code CounterLong.Builder}.
-   * @throws NullPointerException if {@code name} is null.
-   * @throws IllegalArgumentException if different metric with the same name already registered.
-   * @since 0.1.0
-   */
-  CounterLong.Builder counterLongBuilder(String name);
-
-  /** Builder class for the {@link MetricRegistry}. */
-  interface Builder {
-
-    /**
-     * Sets the name of the component that reports these metrics.
-     *
-     * <p>The final name of the reported metric will be <code>component + "_" + name</code> if the
-     * component is not empty.
-     *
-     * @param component the name of the component that reports these metrics.
-     * @return this.
-     */
-    Builder setComponent(String component);
-
-    /**
-     * Sets the {@code Resource} associated with the new {@code MetricRegistry}.
-     *
-     * <p>This should be set only when reporting out-of-band metrics, otherwise the implementation
-     * will set the {@code Resource} for in-process metrics.
-     *
-     * @param resource the {@code Resource} associated with the new {@code MetricRegistry}.
-     * @return this.
-     */
-    Builder setResource(Resource resource);
-
-    /**
-     * Builds and returns a {@link MetricRegistry} with the desired options.
-     *
-     * @return a {@link MetricRegistry} with the desired options.
-     */
-    MetricRegistry build();
-  }
-}

api/src/main/java/io/opentelemetry/metrics/NoopMetrics.java

@@ -40,14 +40,6 @@ public final class NoopMetrics {
   }
 
   private static final class NoopMeter implements Meter {
-
-    @Override
-    public MetricRegistry.Builder metricRegistryBuilder() {
-      return new NoopMetricCollection.Builder();
-    }
-  }
-
-  private static final class NoopMetricCollection implements MetricRegistry {
     @Override
     public GaugeLong.Builder gaugeLongBuilder(String name) {
       Utils.checkNotNull(name, "name");
@@ -71,27 +63,6 @@ public final class NoopMetrics {
       Utils.checkNotNull(name, "name");
       return new NoopCounterLong.NoopBuilder();
     }
-
-    private static final class Builder implements MetricRegistry.Builder {
-      private static final MetricRegistry METRIC_COLLECTION = new NoopMetricCollection();
-
-      @Override
-      public MetricRegistry.Builder setComponent(String component) {
-        Utils.checkNotNull(component, "component");
-        return this;
-      }
-
-      @Override
-      public MetricRegistry.Builder setResource(Resource resource) {
-        Utils.checkNotNull(resource, "resource");
-        return this;
-      }
-
-      @Override
-      public MetricRegistry build() {
-        return METRIC_COLLECTION;
-      }
-    }
   }
 
   /** No-op implementations of GaugeLong class. */
@@ -169,6 +140,18 @@ public final class NoopMetrics {
         return this;
       }
 
+      @Override
+      public Builder setComponent(String component) {
+        Utils.checkNotNull(component, "component");
+        return this;
+      }
+
+      @Override
+      public Builder setResource(Resource resource) {
+        Utils.checkNotNull(resource, "resource");
+        return this;
+      }
+
       @Override
       public GaugeLong build() {
         return new NoopGaugeLong(labelKeysSize);
@@ -251,6 +234,18 @@ public final class NoopMetrics {
         return this;
       }
 
+      @Override
+      public Builder setComponent(String component) {
+        Utils.checkNotNull(component, "component");
+        return this;
+      }
+
+      @Override
+      public Builder setResource(Resource resource) {
+        Utils.checkNotNull(resource, "resource");
+        return this;
+      }
+
       @Override
       public GaugeDouble build() {
         return new NoopGaugeDouble(labelKeysSize);
@@ -335,6 +330,18 @@ public final class NoopMetrics {
         return this;
       }
 
+      @Override
+      public Builder setComponent(String component) {
+        Utils.checkNotNull(component, "component");
+        return this;
+      }
+
+      @Override
+      public Builder setResource(Resource resource) {
+        Utils.checkNotNull(resource, "resource");
+        return this;
+      }
+
       @Override
       public CounterDouble build() {
         return new NoopCounterDouble(labelKeysSize);
@@ -419,6 +426,18 @@ public final class NoopMetrics {
         return this;
       }
 
+      @Override
+      public Builder setComponent(String component) {
+        Utils.checkNotNull(component, "component");
+        return this;
+      }
+
+      @Override
+      public Builder setResource(Resource resource) {
+        Utils.checkNotNull(resource, "resource");
+        return this;
+      }
+
       @Override
       public CounterLong build() {
         return new NoopCounterLong(labelKeysSize);

api/src/test/java/io/opentelemetry/metrics/CounterDoubleTest.java

@@ -37,13 +37,12 @@ public class CounterDoubleTest {
       Collections.singletonList(LabelKey.create("key", "key description"));
   private static final List<LabelValue> EMPTY_LABEL_VALUES = new ArrayList<>();
 
-  private final MetricRegistry metricRegistry =
-      NoopMetrics.newNoopMeter().metricRegistryBuilder().build();
+  private final Meter meter = Metrics.getMeter();
 
   @Test
   public void noopGetOrCreateTimeSeries_WithNullLabelValues() {
     CounterDouble counterDouble =
-        metricRegistry
+        meter
             .counterDoubleBuilder(NAME)
             .setDescription(DESCRIPTION)
             .setLabelKeys(LABEL_KEY)
@@ -58,7 +57,7 @@ public class CounterDoubleTest {
   public void noopGetOrCreateTimeSeries_WithNullElement() {
     List<LabelValue> labelValues = Collections.singletonList(null);
     CounterDouble counterDouble =
-        metricRegistry
+        meter
             .counterDoubleBuilder(NAME)
             .setDescription(DESCRIPTION)
             .setLabelKeys(LABEL_KEY)
@@ -72,7 +71,7 @@ public class CounterDoubleTest {
   @Test
   public void noopGetOrCreateTimeSeries_WithInvalidLabelSize() {
     CounterDouble counterDouble =
-        metricRegistry
+        meter
             .counterDoubleBuilder(NAME)
             .setDescription(DESCRIPTION)
             .setLabelKeys(LABEL_KEY)
@@ -86,7 +85,7 @@ public class CounterDoubleTest {
   @Test
   public void noopRemoveTimeSeries_WithNullLabelValues() {
     CounterDouble counterDouble =
-        metricRegistry
+        meter
             .counterDoubleBuilder(NAME)
             .setDescription(DESCRIPTION)
             .setLabelKeys(LABEL_KEY)

api/src/test/java/io/opentelemetry/metrics/CounterLongTest.java

@@ -37,13 +37,12 @@ public class CounterLongTest {
       Collections.singletonList(LabelKey.create("key", "key description"));
   private static final List<LabelValue> EMPTY_LABEL_VALUES = new ArrayList<>();
 
-  private final MetricRegistry metricRegistry =
-      NoopMetrics.newNoopMeter().metricRegistryBuilder().build();
+  private final Meter meter = Metrics.getMeter();
 
   @Test
   public void noopGetOrCreateTimeSeries_WithNullLabelValues() {
     CounterLong counterLong =
-        metricRegistry
+        meter
             .counterLongBuilder(NAME)
             .setDescription(DESCRIPTION)
             .setLabelKeys(LABEL_KEY)
@@ -58,7 +57,7 @@ public class CounterLongTest {
   public void noopGetOrCreateTimeSeries_WithNullElement() {
     List<LabelValue> labelValues = Collections.singletonList(null);
     CounterLong counterLong =
-        metricRegistry
+        meter
             .counterLongBuilder(NAME)
             .setDescription(DESCRIPTION)
             .setLabelKeys(LABEL_KEY)
@@ -72,7 +71,7 @@ public class CounterLongTest {
   @Test
   public void noopGetOrCreateTimeSeries_WithInvalidLabelSize() {
     CounterLong counterLong =
-        metricRegistry
+        meter
             .counterLongBuilder(NAME)
             .setDescription(DESCRIPTION)
             .setLabelKeys(LABEL_KEY)
@@ -86,7 +85,7 @@ public class CounterLongTest {
   @Test
   public void noopRemoveTimeSeries_WithNullLabelValues() {
     CounterLong counterLong =
-        metricRegistry
+        meter
             .counterLongBuilder(NAME)
             .setDescription(DESCRIPTION)
             .setLabelKeys(LABEL_KEY)

api/src/test/java/io/opentelemetry/metrics/GaugeDoubleTest.java

@@ -37,13 +37,12 @@ public class GaugeDoubleTest {
       Collections.singletonList(LabelKey.create("key", "key description"));
   private static final List<LabelValue> EMPTY_LABEL_VALUES = new ArrayList<>();
 
-  private final MetricRegistry metricRegistry =
-      NoopMetrics.newNoopMeter().metricRegistryBuilder().build();
+  private final Meter meter = Metrics.getMeter();
 
   @Test
   public void noopGetOrCreateTimeSeries_WithNullLabelValues() {
     GaugeDouble gaugeDouble =
-        metricRegistry
+        meter
             .gaugeDoubleBuilder(NAME)
             .setDescription(DESCRIPTION)
             .setLabelKeys(LABEL_KEY)
@@ -58,7 +57,7 @@ public class GaugeDoubleTest {
   public void noopGetOrCreateTimeSeries_WithNullElement() {
     List<LabelValue> labelValues = Collections.singletonList(null);
     GaugeDouble gaugeDouble =
-        metricRegistry
+        meter
             .gaugeDoubleBuilder(NAME)
             .setDescription(DESCRIPTION)
             .setLabelKeys(LABEL_KEY)
@@ -72,7 +71,7 @@ public class GaugeDoubleTest {
   @Test
   public void noopGetOrCreateTimeSeries_WithInvalidLabelSize() {
     GaugeDouble gaugeDouble =
-        metricRegistry
+        meter
             .gaugeDoubleBuilder(NAME)
             .setDescription(DESCRIPTION)
             .setLabelKeys(LABEL_KEY)
@@ -86,7 +85,7 @@ public class GaugeDoubleTest {
   @Test
   public void noopRemoveTimeSeries_WithNullLabelValues() {
     GaugeDouble gaugeDouble =
-        metricRegistry
+        meter
             .gaugeDoubleBuilder(NAME)
             .setDescription(DESCRIPTION)
             .setLabelKeys(LABEL_KEY)

api/src/test/java/io/opentelemetry/metrics/GaugeLongTest.java

@@ -37,13 +37,12 @@ public class GaugeLongTest {
       Collections.singletonList(LabelKey.create("key", "key description"));
   private static final List<LabelValue> EMPTY_LABEL_VALUES = new ArrayList<>();
 
-  private final MetricRegistry metricRegistry =
-      NoopMetrics.newNoopMeter().metricRegistryBuilder().build();
+  private final Meter meter = Metrics.getMeter();
 
   @Test
   public void noopGetOrCreateTimeSeries_WithNullLabelValues() {
     GaugeLong gaugeLong =
-        metricRegistry
+        meter
             .gaugeLongBuilder(NAME)
             .setDescription(DESCRIPTION)
             .setLabelKeys(LABEL_KEY)
@@ -58,7 +57,7 @@ public class GaugeLongTest {
   public void noopGetOrCreateTimeSeries_WithNullElement() {
     List<LabelValue> labelValues = Collections.singletonList(null);
     GaugeLong gaugeLong =
-        metricRegistry
+        meter
             .gaugeLongBuilder(NAME)
             .setDescription(DESCRIPTION)
             .setLabelKeys(LABEL_KEY)
@@ -72,7 +71,7 @@ public class GaugeLongTest {
   @Test
   public void noopGetOrCreateTimeSeries_WithInvalidLabelSize() {
     GaugeLong gaugeLong =
-        metricRegistry
+        meter
             .gaugeLongBuilder(NAME)
             .setDescription(DESCRIPTION)
             .setLabelKeys(LABEL_KEY)
@@ -86,7 +85,7 @@ public class GaugeLongTest {
   @Test
   public void noopRemoveTimeSeries_WithNullLabelValues() {
     GaugeLong gaugeLong =
-        metricRegistry
+        meter
             .gaugeLongBuilder(NAME)
             .setDescription(DESCRIPTION)
             .setLabelKeys(LABEL_KEY)

api/src/test/java/io/opentelemetry/metrics/MeterTest.java

@@ -22,39 +22,37 @@ import org.junit.rules.ExpectedException;
 import org.junit.runner.RunWith;
 import org.junit.runners.JUnit4;
 
-/** Unit tests for {@link MetricRegistry}. */
+/** Unit tests for {@link Meter}. */
 @RunWith(JUnit4.class)
-public class MetricRegistryTest {
+public class MeterTest {
   @Rule public ExpectedException thrown = ExpectedException.none();
-
-  private final MetricRegistry metricRegistry =
-      NoopMetrics.newNoopMeter().metricRegistryBuilder().build();
+  private final Meter meter = Metrics.getMeter();
 
   @Test
   public void noopAddLongGauge_NullName() {
     thrown.expect(NullPointerException.class);
     thrown.expectMessage("name");
-    metricRegistry.gaugeLongBuilder(null);
+    meter.gaugeLongBuilder(null);
   }
 
   @Test
   public void noopAddDoubleGauge_NullName() {
     thrown.expect(NullPointerException.class);
     thrown.expectMessage("name");
-    metricRegistry.gaugeDoubleBuilder(null);
+    meter.gaugeDoubleBuilder(null);
   }
 
   @Test
   public void noopAddDoubleCumulative_NullName() {
     thrown.expect(NullPointerException.class);
     thrown.expectMessage("name");
-    metricRegistry.counterDoubleBuilder(null);
+    meter.counterDoubleBuilder(null);
   }
 
   @Test
   public void noopAddLongCumulative_NullName() {
     thrown.expect(NullPointerException.class);
     thrown.expectMessage("name");
-    metricRegistry.counterLongBuilder(null);
+    meter.counterLongBuilder(null);
   }
 }

contrib/src/main/java/io/opentelemetry/contrib/metrics/runtime/GarbageCollector.java

@@ -19,7 +19,7 @@ package io.opentelemetry.contrib.metrics.runtime;
 import io.opentelemetry.metrics.CounterLong;
 import io.opentelemetry.metrics.LabelKey;
 import io.opentelemetry.metrics.LabelValue;
-import io.opentelemetry.metrics.MetricRegistry;
+import io.opentelemetry.metrics.Meter;
 import io.opentelemetry.metrics.Metrics;
 import java.lang.management.GarbageCollectorMXBean;
 import java.lang.management.ManagementFactory;
@@ -45,12 +45,12 @@ public final class GarbageCollector {
   private static final LabelKey GC = LabelKey.create("gc", "");
 
   private final List<GarbageCollectorMXBean> garbageCollectors;
-  private final MetricRegistry metricRegistry;
+  private final Meter meter;
 
   /** Constructs a new module that is capable to export metrics about "jvm_gc". */
   public GarbageCollector() {
     this.garbageCollectors = ManagementFactory.getGarbageCollectorMXBeans();
-    this.metricRegistry = Metrics.getMeter().metricRegistryBuilder().setComponent("jvm_gc").build();
+    this.meter = Metrics.getMeter();
   }
 
   /** Export all metrics generated by this module. */
@@ -58,11 +58,12 @@ public final class GarbageCollector {
     // TODO: This should probably be a cumulative Histogram without buckets (or Summary without
     //  percentiles) to allow count/sum.
     final CounterLong collectionMetric =
-        metricRegistry
+        meter
             .counterLongBuilder("collection")
             .setDescription("Time spent in a given JVM garbage collector in milliseconds.")
             .setUnit("ms")
             .setLabelKeys(Collections.singletonList(GC))
+            .setComponent("jvm_gc")
             .build();
     collectionMetric.setCallback(
         new Runnable() {

contrib/src/main/java/io/opentelemetry/contrib/metrics/runtime/MemoryPools.java

@@ -19,7 +19,7 @@ package io.opentelemetry.contrib.metrics.runtime;
 import io.opentelemetry.metrics.GaugeLong;
 import io.opentelemetry.metrics.LabelKey;
 import io.opentelemetry.metrics.LabelValue;
-import io.opentelemetry.metrics.MetricRegistry;
+import io.opentelemetry.metrics.Meter;
 import io.opentelemetry.metrics.Metrics;
 import java.lang.management.ManagementFactory;
 import java.lang.management.MemoryMXBean;
@@ -57,14 +57,13 @@ public final class MemoryPools {
 
   private final MemoryMXBean memoryBean;
   private final List<MemoryPoolMXBean> poolBeans;
-  private final MetricRegistry metricRegistry;
+  private final Meter meter;
 
   /** Constructs a new module that is capable to export metrics about "jvm_memory". */
   public MemoryPools() {
     this.memoryBean = ManagementFactory.getMemoryMXBean();
     this.poolBeans = ManagementFactory.getMemoryPoolMXBeans();
-    this.metricRegistry =
-        Metrics.getMeter().metricRegistryBuilder().setComponent("jvm_memory").build();
+    this.meter = Metrics.getMeter();
   }
 
   /** Export only the "area" metric. */
@@ -74,11 +73,12 @@ public final class MemoryPools {
     //  memory is committed (this can also be achieved by displaying the two metrics in the same
     //  chart).
     final GaugeLong areaMetric =
-        this.metricRegistry
+        this.meter
             .gaugeLongBuilder("area")
             .setDescription("Bytes of a given JVM memory area.")
             .setUnit("By")
             .setLabelKeys(Arrays.asList(TYPE, AREA))
+            .setComponent("jvm_memory")
             .build();
     final GaugeLong.TimeSeries usedHeap =
         areaMetric.getOrCreateTimeSeries(Arrays.asList(USED, HEAP));
@@ -111,11 +111,12 @@ public final class MemoryPools {
   /** Export only the "pool" metric. */
   public void exportMemoryPoolMetric() {
     final GaugeLong poolMetric =
-        this.metricRegistry
+        this.meter
             .gaugeLongBuilder("pool")
             .setDescription("Bytes of a given JVM memory pool.")
             .setUnit("By")
             .setLabelKeys(Arrays.asList(TYPE, POOL))
+            .setComponent("jvm_memory")
             .build();
     poolMetric.setCallback(
         new Runnable() {