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From: tillrohrmann <git@git.apache.org>
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Subject: [GitHub] flink pull request #2158: [FLINK-4116] Metrics documentation
Content-Type: text/plain
Message-Id: <20160627113942.0DC9FDFDC3@git1-us-west.apache.org>
Date: Mon, 27 Jun 2016 11:39:42 +0000 (UTC)
archived-at: Mon, 27 Jun 2016 11:39:47 -0000

Github user tillrohrmann commented on a diff in the pull request:

    https://github.com/apache/flink/pull/2158#discussion_r68562093
  
    --- Diff: docs/apis/common/index.md ---
    @@ -1350,3 +1350,211 @@ You may specify program arguments before the job is executed. The plan visualiza
     the execution plan before executing the Flink job.
     
     {% top %}
    +
    +Metrics
    +-------------------
    +
    +Flink exposes a metric system that allows users gather and expose metrics to external systems.
    +
    +### Registering metrics
    +
    +You can access the metric system from any user function that extends [RichFunction]({{ site.baseurl }}/apis/common/index.html#rich-functions) by calling getRuntimeContext().getMetricGroup().
    +This method returns a MetricGroup object on which you can create and register new metrics.
    +
    +If you want to count the number of records your user function has received you could use a Counter like this:
    +
    +{% highlight java %}
    +
    +public class MyMapper extends RichMapFunction<String, Integer> {
    +  private Counter counter;
    +
    +  @Override
    +  public void open(Configuration config) {
    +    // create and register a counter
    +    this.counter = getRuntimeContext().getMetricGroup().counter("myCounter");
    +    ...
    +  }
    +
    +  @public Integer map(String value) throws Exception {
    +    // increment counter
    +    this.counter.inc();
    +    ...
    +  }
    +}
    +
    +{% endhighlight %}
    --- End diff --
    
    Maybe we should also demonstrate how to register a custom metric.


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