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https://issues.apache.org/jira/browse/HDFS-6841?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14123482#comment-14123482
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Colin Patrick McCabe commented on HDFS-6841:
--------------------------------------------
In {{DatanodeInfo#getDatanodeReport}}, we translate {{DatanodeInfo#lastUpdate}}
into a date:
{code}
buffer.append("Last contact: "+new Date(lastUpdate)+"\n");
{code}
This is not going to work if {{lastUpdate}} is a monotonic time. The easiest
way to solve this is to maintain another {{long}} with the wall-clock time,
which we set to the current wall-clock time whenever an update occurs. That
way we get the benefits of calculating staleness and deadness based on
monotonic time, but also reasonable information in {{getDatanodeReport}}.
{{FSNamesystem#reached}}: The same issue occurs here.
{code}
if (reached > 0)
resText += " Threshold was reached " + new Date(reached) + ".";
{code}
{{EditLogTailer#lastLoadTimestamp}}: can we rename this to {{lastLoadTimeMs}}?
It is not a timestamp (those come from the wall clock, generally.) We could
probably get rid of {{EditLogTailer#getLastLoadTimestamp}} since the only use
is in {{FSNamesystem#getMillisSinceLastLoadedEdits}}. All we need is a
function which returns the amount of time since the edits were last loaded.
> Use Time.monotonicNow() wherever applicable instead of Time.now()
> -----------------------------------------------------------------
>
> Key: HDFS-6841
> URL: https://issues.apache.org/jira/browse/HDFS-6841
> Project: Hadoop HDFS
> Issue Type: Bug
> Reporter: Vinayakumar B
> Assignee: Vinayakumar B
> Attachments: HDFS-6841-001.patch, HDFS-6841-002.patch
>
>
> {{Time.now()}} used in many places to calculate elapsed time.
> This should be replaced with {{Time.monotonicNow()}} to avoid effect of
> System time changes on elapsed time calculations.
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