1 files changed, 96 insertions, 0 deletions
diff --git a/java/com/google/gerrit/server/config/MetricsReservoirConfigImpl.java b/java/com/google/gerrit/server/config/MetricsReservoirConfigImpl.java
new file mode 100644
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+++ b/java/com/google/gerrit/server/config/MetricsReservoirConfigImpl.java
@@ -0,0 +1,96 @@
+// Copyright (C) 2022 The Android Open Source Project
+//
+// 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 com.google.gerrit.server.config;
+
+import com.google.gerrit.metrics.MetricsReservoirConfig;
+import com.google.gerrit.metrics.ReservoirType;
+import com.google.inject.Inject;
+import com.google.inject.Singleton;
+import java.time.Duration;
+import java.util.Optional;
+import java.util.concurrent.TimeUnit;
+import org.eclipse.jgit.lib.Config;
+
+/** Define metrics reservoir settings based on gerrit.config */
+@Singleton
+public class MetricsReservoirConfigImpl implements MetricsReservoirConfig {
+  private static final double RESERVOIR_ALPHA_DEFAULT = 0.015;
+  private static final int METRICS_RESERVOIR_SIZE_DEFAULT = 1028;
+  private static final long METRICS_RESERVOIR_WINDOW_MSEC_DEFAULT = 60000L;
+  private static final String METRICS_SECTION = "metrics";
+  private static final String METRICS_RESERVOIR = "reservoir";
+
+  private final ReservoirType reservoirType;
+
+  private final Duration reservoirWindow;
+  private final int reservoirSize;
+  private final double reservoirAlpha;
+
+  @Inject
+  MetricsReservoirConfigImpl(@GerritServerConfig Config gerritConfig) {
+    this.reservoirType =
+        gerritConfig.getEnum(
+            METRICS_SECTION, null, METRICS_RESERVOIR, ReservoirType.ExponentiallyDecaying);
+
+    reservoirWindow =
+        Duration.ofMillis(
+            ConfigUtil.getTimeUnit(
+                gerritConfig,
+                METRICS_SECTION,
+                reservoirType.name(),
+                "window",
+                METRICS_RESERVOIR_WINDOW_MSEC_DEFAULT,
+                TimeUnit.MILLISECONDS));
+    reservoirSize =
+        gerritConfig.getInt(
+            METRICS_SECTION, reservoirType.name(), "size", METRICS_RESERVOIR_SIZE_DEFAULT);
+    reservoirAlpha =
+        Optional.ofNullable(gerritConfig.getString(METRICS_SECTION, reservoirType.name(), "alpha"))
+            .map(Double::parseDouble)
+            .orElse(RESERVOIR_ALPHA_DEFAULT);
+  }
+
+  /* (non-Javadoc)
+   * @see com.google.gerrit.server.config.MetricsConfig#reservoirType()
+   */
+  @Override
+  public ReservoirType reservoirType() {
+    return reservoirType;
+  }
+
+  /* (non-Javadoc)
+   * @see com.google.gerrit.server.config.MetricsConfig#reservoirWindow()
+   */
+  @Override
+  public Duration reservoirWindow() {
+    return reservoirWindow;
+  }
+
+  /* (non-Javadoc)
+   * @see com.google.gerrit.server.config.MetricsConfig#reservoirSize()
+   */
+  @Override
+  public int reservoirSize() {
+    return reservoirSize;
+  }
+
+  /* (non-Javadoc)
+   * @see com.google.gerrit.server.config.MetricsConfig#reservoirAlpha()
+   */
+  @Override
+  public double reservoirAlpha() {
+    return reservoirAlpha;
+  }
+}