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https://issues.apache.org/jira/browse/FLINK-13496?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16897146#comment-16897146
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Yun Tang commented on FLINK-13496:
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[~Zentol], you're correct. I just found our customer used a wrapper class
{{Double}} instead of primitive and he just followed the guide to configure
that value as {{transient}}, that's why he got {{null}} when reporting metrics.
> Correct the documentation of Gauge metric initialization
> --------------------------------------------------------
>
> Key: FLINK-13496
> URL: https://issues.apache.org/jira/browse/FLINK-13496
> Project: Flink
> Issue Type: Bug
> Components: Documentation
> Reporter: Yun Tang
> Priority: Major
>
> Current documentation of
> [Gauge|https://ci.apache.org/projects/flink/flink-docs-stable/monitoring/metrics.html#gauge]
> set the value to expose as {{transient}}.
> {code:java}
> public class MyMapper extends RichMapFunction<String, String> {
> private transient int valueToExpose = 0;
> @Override
> public void open(Configuration config) {
> getRuntimeContext()
> .getMetricGroup()
> .gauge("MyGauge", new Gauge<Integer>() {
> @Override
> public Integer getValue() {
> return valueToExpose;
> }
> });
> }
> @Override
> public String map(String value) throws Exception {
> valueToExpose++;
> return value;
> }
> }
> {code}
> However, this would let the initialization value {{valueToExpose}} within
> {{MyGauge}} as null on task manager side. This would actually mislead users
> who want to add customized gauge.
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