1 files changed, 71 insertions, 0 deletions
diff --git a/api/src/main/java/io/opencensus/metrics/MetricsComponent.java b/api/src/main/java/io/opencensus/metrics/MetricsComponent.java
new file mode 100644
index 00000000..3a992306
--- /dev/null
+++ b/api/src/main/java/io/opencensus/metrics/MetricsComponent.java
@@ -0,0 +1,71 @@
+/*
+ * Copyright 2018, OpenCensus 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.opencensus.metrics;
+
+import io.opencensus.common.ExperimentalApi;
+import io.opencensus.metrics.export.ExportComponent;
+
+/**
+ * Class that holds the implementation instance for {@link ExportComponent}.
+ *
+ * @since 0.17
+ */
+@ExperimentalApi
+public abstract class MetricsComponent {
+
+  /**
+   * Returns the {@link ExportComponent} with the provided implementation. If no implementation is
+   * provided then no-op implementations will be used.
+   *
+   * @return the {@link ExportComponent} implementation.
+   * @since 0.17
+   */
+  public abstract ExportComponent getExportComponent();
+
+  /**
+   * Returns the {@link MetricRegistry} with the provided implementation.
+   *
+   * @return the {@link MetricRegistry} implementation.
+   * @since 0.17
+   */
+  public abstract MetricRegistry getMetricRegistry();
+
+  /**
+   * Returns an instance that contains no-op implementations for all the instances.
+   *
+   * @return an instance that contains no-op implementations for all the instances.
+   */
+  static MetricsComponent newNoopMetricsComponent() {
+    return new NoopMetricsComponent();
+  }
+
+  private static final class NoopMetricsComponent extends MetricsComponent {
+    private static final ExportComponent EXPORT_COMPONENT =
+        ExportComponent.newNoopExportComponent();
+    private static final MetricRegistry METRIC_REGISTRY = MetricRegistry.newNoopMetricRegistry();
+
+    @Override
+    public ExportComponent getExportComponent() {
+      return EXPORT_COMPONENT;
+    }
+
+    @Override
+    public MetricRegistry getMetricRegistry() {
+      return METRIC_REGISTRY;
+    }
+  }
+}