1 files changed, 117 insertions, 0 deletions
diff --git a/api/src/main/java/io/opencensus/metrics/MetricRegistry.java b/api/src/main/java/io/opencensus/metrics/MetricRegistry.java
new file mode 100644
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+++ b/api/src/main/java/io/opencensus/metrics/MetricRegistry.java
@@ -0,0 +1,117 @@
+/*
+ * 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.common.ToDoubleFunction;
+import io.opencensus.common.ToLongFunction;
+import io.opencensus.internal.Utils;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.LinkedHashMap;
+
+/**
+ * Creates and manages your application's set of metrics. Exporters use the metric registry to
+ * iterate over the set of metrics instrumenting your application, and then further export each
+ * metric to the backend of choice.
+ *
+ * @since 0.16
+ */
+@ExperimentalApi
+public abstract class MetricRegistry extends MetricProducer {
+  /**
+   * Build a new long gauge to be added to the registry.
+   *
+   * <p>Must be called only once.
+   *
+   * @param name the name of the metric.
+   * @param description the description of the metric.
+   * @param unit the unit of the metric.
+   * @param obj the function argument.
+   * @param function the function to be called.
+   * @since 0.16 @ExperimentalApi
+   */
+  public abstract <T> void addLongGauge(
+      String name,
+      String description,
+      String unit,
+      LinkedHashMap<LabelKey, LabelValue> labels,
+      T obj,
+      ToLongFunction<T> function);
+
+  /**
+   * Build a new double gauge to be added to the registry.
+   *
+   * <p>Must be called only once.
+   *
+   * @param name the name of the metric.
+   * @param description the description of the metric.
+   * @param unit the unit of the metric.
+   * @param obj the function argument.
+   * @param function the function to be called.
+   * @since 0.16 @ExperimentalApi
+   */
+  public abstract <T> void addDoubleGauge(
+      String name,
+      String description,
+      String unit,
+      LinkedHashMap<LabelKey, LabelValue> labels,
+      T obj,
+      ToDoubleFunction<T> function);
+
+  static MetricRegistry newNoopMetricRegistry() {
+    return new NoopMetricRegistry();
+  }
+
+  private static final class NoopMetricRegistry extends MetricRegistry {
+
+    @Override
+    public <T> void addLongGauge(
+        String name,
+        String description,
+        String unit,
+        LinkedHashMap<LabelKey, LabelValue> labels,
+        T obj,
+        ToLongFunction<T> function) {
+      Utils.checkNotNull(name, "name");
+      Utils.checkNotNull(description, "description");
+      Utils.checkNotNull(unit, "unit");
+      Utils.checkNotNull(labels, "labels");
+      Utils.checkNotNull(function, "function");
+    }
+
+    @Override
+    public <T> void addDoubleGauge(
+        String name,
+        String description,
+        String unit,
+        LinkedHashMap<LabelKey, LabelValue> labels,
+        T obj,
+        ToDoubleFunction<T> function) {
+      Utils.checkNotNull(name, "name");
+      Utils.checkNotNull(description, "description");
+      Utils.checkNotNull(unit, "unit");
+      Utils.checkNotNull(labels, "labels");
+      Utils.checkNotNull(function, "function");
+    }
+
+    @Override
+    public Collection<Metric> getMetrics() {
+      return Collections.emptyList();
+    }
+  }
+}