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https://issues.apache.org/jira/browse/HTRACE-376?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15340478#comment-15340478
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Colin Patrick McCabe commented on HTRACE-376:
---------------------------------------------
Thanks for attaching HTRACE-376.002.patch. I apologize that our review process
still generally involves patch attachments. We've been looking into using
gerrit, but so far we haven't managed to get the ASF infrastructure set up to
use it.
{code}
+ begin(System.currentTimeMillis(),System.nanoTime()).
+ end(0,0).
{code}
As I commented earlier in my review of patch 001, you cannot use
{{System#nanoTime}} here. It's wrong in a few different ways: it results in us
fetching the time twice, and it fetches the monotonic clock rather than the
wall clock. HTrace spans are identified by the wall-clock, not the monotonic
clock. Please understand that the monotonic clock normally gets reset each
time the machine is rebooted, and you cannot meaningfully compare monotonic
clock times across different machines (except by duration).
According to Stack Overflow, there is no way to get the wall-clock time with a
better granularity than milliseconds in JDK8 and earlier. In JDK9, there are
some functions in {{java.time}} which can do it. It seems that you probably
should use reflection to make use of those methods, if they exist in the
current JDK. (We are not ready to drop JDK8 support yet). See
http://stackoverflow.com/questions/1712205/current-time-in-microseconds-in-java
> HTrace should support nanosecond time granularities
> ---------------------------------------------------
>
> Key: HTRACE-376
> URL: https://issues.apache.org/jira/browse/HTRACE-376
> Project: HTrace
> Issue Type: Improvement
> Components: core
> Affects Versions: 3.1.0
> Reporter: Colin Patrick McCabe
> Assignee: Pranavan
> Attachments: HTRACE-376.001.patch, HTRACE-376.002.patch
>
>
> HTrace should support nanosecond time granularities. Currently only a
> granularity of milliseconds is supported.
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