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https://issues.apache.org/jira/browse/FLINK-18808?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17175639#comment-17175639
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ming li commented on FLINK-18808:
---------------------------------
I also agree to modify {{OperatorIOMetricGroup#reuseOutputMetricsForTask}}. We
can add a {{numRecordsOutForTask}} metric in {{OperatorIOMetricGroup}} to
describe the total number of records sent to other tasks.
{{OperatorIOMetricGroup#reuseOutputMetricsForTask}} will use this new metric to
count the total task output.
But there is still a problem here: the structure of output is similar to:
{code:java}
CountingOutput -> BroadcastingOutputCollector -> [RecordWriterOutput,
ChainingOutput...].
{code}
At the operator level, how do we determine that a record will be written by
{{RecordWriterOutput}} instead of just calling the {{collect(OutputTag<X>
outputTag, StreamRecord<X> record)}} method. Do I need to add a
{{isOutputToTask(OutputTag<X> outputTag)}} method to determine whether it will
be sent to another task?
If needed, this method will be implemented like this:
* In nested {{Output}}, this method of each output will be called recursively.
* {{False}} will be returned directly in {{ChainingOutput}}.
* In {{RecordWriterOutput}}, it will determine whether the {{OutputTags}} are
equal.
{code:java}
@Override
public <X> boolean isOutputToTask(OutputTag<X> outputTag) {
return (this.outputTag == null && outputTag == null ) || (this.outputTag !=
null && this.outputTag.equals(outputTag));
}{code}
> Task-level numRecordsOut metric may be underestimated
> -----------------------------------------------------
>
> Key: FLINK-18808
> URL: https://issues.apache.org/jira/browse/FLINK-18808
> Project: Flink
> Issue Type: Improvement
> Components: Runtime / Metrics, Runtime / Task
> Affects Versions: 1.11.1
> Reporter: ming li
> Assignee: ming li
> Priority: Major
> Labels: pull-request-available, usability
> Attachments: image-2020-08-04-11-28-13-800.png,
> image-2020-08-04-11-32-20-678.png
>
>
> At present, we only register task-level numRecordsOut metric by reusing
> operator output record counter at the end of OperatorChain.
> {code:java}
> if (config.isChainEnd()) {
> operatorMetricGroup.getIOMetricGroup().reuseOutputMetricsForTask();
> }
> {code}
> If we only send data out through the last operator of OperatorChain, there is
> no problem with this statistics. But consider the following scenario:
> !image-2020-08-04-11-28-13-800.png|width=507,height=174!
> In this JobGraph, we not only send data in the last operator, but also send
> data in the middle operator of OperatorChain (the map operator just returns
> the original value directly). Below is one of our test topology, we can see
> that the statistics actually only have half of the total data received by the
> downstream.
> !image-2020-08-04-11-32-20-678.png|width=648,height=251!
> I think the data sent out by the intermediate operator should also be counted
> into the numRecordsOut of the Task. But currently we are not reusing
> operators output record counters in the intermediate operators, which leads
> to our task-level numRecordsOut metric is underestimated (although this has
> no effect on the actual operation of the job, it may affect our monitoring).
> A simple idea of mine is to modify the condition of reusing operators
> output record counter:
> {code:java}
> if (!config.getNonChainedOutputs(getUserCodeClassloader()).isEmpty()) {
> operatorMetricGroup.getIOMetricGroup().reuseOutputMetricsForTask();
> }{code}
> In addition, I have another question: If a record is broadcast to all
> downstream, should the numRecordsOut counter increase by one or the
> downstream number? It seems that currently we are adding one to calculate the
> numRecordsOut metric.
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