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https://issues.apache.org/jira/browse/FLINK-6053?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16391224#comment-16391224
]
ASF GitHub Bot commented on FLINK-6053:
---------------------------------------
Github user StephanEwen commented on a diff in the pull request:
https://github.com/apache/flink/pull/5501#discussion_r173149289
--- Diff:
flink-metrics/flink-metrics-core/src/main/java/org/apache/flink/metrics/reporter/AbstractReporterV2.java
---
@@ -0,0 +1,89 @@
+/*
+ * 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.flink.metrics.reporter;
+
+import org.apache.flink.metrics.CharacterFilter;
+import org.apache.flink.metrics.Counter;
+import org.apache.flink.metrics.Histogram;
+import org.apache.flink.metrics.Meter;
+import org.apache.flink.metrics.Metric;
+import org.apache.flink.metrics.MetricGroup;
+import org.apache.flink.metrics.NumberGauge;
+import org.apache.flink.metrics.StringGauge;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * Base interface for custom metric reporters.
+ */
+public abstract class AbstractReporterV2 implements MetricReporter,
CharacterFilter {
+ protected final Logger log = LoggerFactory.getLogger(getClass());
+
+ protected final Map<StringGauge, String> stringGauges = new HashMap<>();
+ protected final Map<NumberGauge, String> numberGauges = new HashMap<>();
+ protected final Map<Counter, String> counters = new HashMap<>();
+ protected final Map<Histogram, String> histograms = new HashMap<>();
+ protected final Map<Meter, String> meters = new HashMap<>();
+
+ @Override
+ public void notifyOfAddedMetric(Metric metric, String metricName,
MetricGroup group) {
+ final String name = group.getMetricIdentifier(metricName, this);
+
+ synchronized (this) {
--- End diff --
Minor: It is good practice to not lock on `this` for strictly internal
mutual exclusion, because someone from the outside can lock on the same object
- it is outside the class's control. Having a dedicated lock object instead is
the recommendation.
> Gauge<T> should only take subclasses of Number, rather than everything
> ----------------------------------------------------------------------
>
> Key: FLINK-6053
> URL: https://issues.apache.org/jira/browse/FLINK-6053
> Project: Flink
> Issue Type: Improvement
> Components: Metrics
> Affects Versions: 1.2.0
> Reporter: Bowen Li
> Assignee: Chesnay Schepler
> Priority: Major
> Fix For: 1.6.0
>
>
> Currently, Flink's Gauge is defined as
> ```java
> public interface Gauge<T> extends Metric {
> T getValue();
> }
> ```
> But it doesn't make sense to have Gauge take generic types other than Number.
> And it blocks I from finishing FLINK-6013, because I cannot assume Gauge is
> only about Number. So the class should be like
> ```java
> public interface Gauge<T extends Number> extends Metric {
> T getValue();
> }
> ```
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