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https://issues.apache.org/jira/browse/YARN-4526?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15075322#comment-15075322
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Arun Suresh commented on YARN-4526:
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Agreed, it does seem wasteful... Thanks for the patch [~kasha]..
I was the just wondering though.. instead of passing the clock instance in the
constructor and setting it to a field, why not do away with the {{this.clock}}
field itself and just use {{SystemClock.getInstance()}} whenever you need it. I
understand the constructor injection was probably put there for improved
testability (I havnt seen it used though.. but i might be missing something).
But wouldn't a {{SystemClock.setInstance(clock)}} with an *\@visibleForTesting*
tag, which you set per testcase serve the same purpose ?
> Make SystemClock singleton so AppSchedulingInfo could use it
> ------------------------------------------------------------
>
> Key: YARN-4526
> URL: https://issues.apache.org/jira/browse/YARN-4526
> Project: Hadoop YARN
> Issue Type: Sub-task
> Components: scheduler
> Affects Versions: 2.8.0
> Reporter: Karthik Kambatla
> Assignee: Karthik Kambatla
> Attachments: yarn-4526-1.patch
>
>
> To track the time a request is received, we need to get current system time.
> For better testability of this, we are likely better off using a Clock
> instance that uses SystemClock by default. Instead of creating umpteen
> instances of SystemClock, we should just reuse the same instance.
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