Stephan Ewen created FLINK-6453:
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Summary: Web UI metrics charts should update only when a new data
point is available
Key: FLINK-6453
URL: https://issues.apache.org/jira/browse/FLINK-6453
Project: Flink
Issue Type: Sub-task
Components: Webfrontend
Reporter: Stephan Ewen
Metrics are pulled by the web server every 10 seconds by default.
The metric charts update more frequently and pull new events.
The charts assume that these are new data points, when in fact, they are mostly
not. Drawing the same datapoint again to a different time makes all charts look
stepwise, which is misleading:
There are some cases where metrics in fact increase stepwise (for example num
events in bursty event channels) and currently there is no way to tell the
difference.
A way around that would be to plot data points only if there are new data
points. Identifying new data points can be done via attaching sequence numbers
in the metrics handlers (incremented whenever the metrics are re-requested from
TMs). The chart can ignore data points with the same sequence number.
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