[GitHub] [samza] cameronlee314 commented on a change in pull request #1495: SAMZA-2649: Add MetricsReporter which logs metrics to log file

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cameronlee314 commented on a change in pull request #1495:
URL: https://github.com/apache/samza/pull/1495#discussion_r627009174



##########
File path: samza-core/src/main/java/org/apache/samza/metrics/reporter/LoggingMetricsReporter.java
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@@ -0,0 +1,132 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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 org.apache.samza.metrics.reporter;
+
+import java.util.Map;
+import java.util.Queue;
+import java.util.concurrent.ConcurrentLinkedQueue;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
+import java.util.regex.Pattern;
+import com.google.common.annotations.VisibleForTesting;
+import org.apache.samza.metrics.Counter;
+import org.apache.samza.metrics.Gauge;
+import org.apache.samza.metrics.Metric;
+import org.apache.samza.metrics.MetricsReporter;
+import org.apache.samza.metrics.MetricsVisitor;
+import org.apache.samza.metrics.ReadableMetricsRegistry;
+import org.apache.samza.metrics.Timer;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+
+/**
+ * Implementation of {@link MetricsReporter} which logs metrics which match a regex.
+ * The regex is checked against "[source name]-[group name]-[metric name]".
+ */
+public class LoggingMetricsReporter implements MetricsReporter {
+  private static final Logger LOG = LoggerFactory.getLogger(LoggingMetricsReporter.class);
+  /**
+   * First part is source, second part is group name, third part is metric name
+   */
+  private static final String FULL_METRIC_FORMAT = "%s-%s-%s";
+
+  private final ScheduledExecutorService scheduledExecutorService;

Review comment:
       In general, I like to follow this dependency injection pattern. It gives slightly more flexibility in usage, and it makes mocking easier in tests. Just minor benefits (and they aren't really that helpful in this case) though.




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