Chesnay Schepler created FLINK-5150:
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             Summary: WebUI metric-related resource leak
                 Key: FLINK-5150
                 URL: https://issues.apache.org/jira/browse/FLINK-5150
             Project: Flink
          Issue Type: Bug
          Components: Webfrontend
    Affects Versions: 1.1.3
            Reporter: Chesnay Schepler
            Priority: Critical
             Fix For: 1.2.0


The WebUI maintains a list of selected metrics for all jobs and vertices. When 
a metric is selected in the metric screen it is added to this list, and removed 
if it is unselected.

The contents of this list are stored in the browser's localStorage. This allows 
a user to setup a metric screen, move to another page, and return to the 
original screen completely intact.

However, if the metrics are never *unselected* by the user they will remain in 
this list. They will also still be in this list if the WebUI can't even display 
the corresponding job page anymore, if for example the history size limit was 
exceeded. They will even survive a browser restart, since they are not stored 
in a session-based storage.

Furthermore, these metrics are still getting updated, adding additional 
overhead to the WebBackend and potentially network.

In other words, if you _ever_ checked out metrics tab for some job, chances are 
that the next time you start the WebInterface it will still try to update the 
metrics for it.



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