1 files changed, 88 insertions, 0 deletions
diff --git a/api/src/main/java/io/opencensus/metrics/export/MetricProducerManager.java b/api/src/main/java/io/opencensus/metrics/export/MetricProducerManager.java
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@@ -0,0 +1,88 @@
+/*
+ * 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.export;
+
+import io.opencensus.common.ExperimentalApi;
+import io.opencensus.internal.Utils;
+import java.util.Collections;
+import java.util.Set;
+import javax.annotation.concurrent.ThreadSafe;
+
+/**
+ * Keeps a set of {@link MetricProducer} that is used by exporters to determine the metrics that
+ * need to be exported.
+ *
+ * @since 0.17
+ */
+@ExperimentalApi
+@ThreadSafe
+public abstract class MetricProducerManager {
+
+  /**
+   * Adds the {@link MetricProducer} to the manager if it is not already present.
+   *
+   * @param metricProducer the {@code MetricProducer} to be added to the manager.
+   * @since 0.17
+   */
+  public abstract void add(MetricProducer metricProducer);
+
+  /**
+   * Removes the {@link MetricProducer} to the manager if it is present.
+   *
+   * @param metricProducer the {@code MetricProducer} to be removed from the manager.
+   * @since 0.17
+   */
+  public abstract void remove(MetricProducer metricProducer);
+
+  /**
+   * Returns all registered {@link MetricProducer}s that should be exported.
+   *
+   * <p>This method should be used by any metrics exporter that automatically exports data for
+   * {@code MetricProducer} registered with the {@code MetricProducerManager}.
+   *
+   * @return all registered {@code MetricProducer}s that should be exported.
+   * @since 0.17
+   */
+  public abstract Set<MetricProducer> getAllMetricProducer();
+
+  /**
+   * Returns a no-op implementation for {@link MetricProducerManager}.
+   *
+   * @return a no-op implementation for {@code MetricProducerManager}.
+   */
+  static MetricProducerManager newNoopMetricProducerManager() {
+    return new NoopMetricProducerManager();
+  }
+
+  private static final class NoopMetricProducerManager extends MetricProducerManager {
+
+    @Override
+    public void add(MetricProducer metricProducer) {
+      Utils.checkNotNull(metricProducer, "metricProducer");
+    }
+
+    @Override
+    public void remove(MetricProducer metricProducer) {
+      Utils.checkNotNull(metricProducer, "metricProducer");
+    }
+
+    @Override
+    public Set<MetricProducer> getAllMetricProducer() {
+      return Collections.emptySet();
+    }
+  }
+}