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https://issues.apache.org/jira/browse/HDFS-4656?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13620833#comment-13620833
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Mohammad Mustaqeem commented on HDFS-4656:
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Hello,
I am totally to open source community.
Can anyone tell me .. How do I start contributing?
How to get the Hadoop source code in eclipse environment?
How to compile it?
How to install the compiled Hadoop?
What is patch and how to generate it?
and How to use this patch with hadoop?
> DN heartbeat loop can be briefly tight
> --------------------------------------
>
> Key: HDFS-4656
> URL: https://issues.apache.org/jira/browse/HDFS-4656
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: datanode
> Affects Versions: 2.0.4-alpha
> Reporter: Aaron T. Myers
> Assignee: Aaron T. Myers
> Priority: Minor
> Attachments: HDFS-4656.patch
>
>
> The DN hearbeat loop looks roughly like this:
> {code}
> if (now - timeOfLastHeartbeat > configuredHeartbeatInterval) {
> // do heartbeat
> }
> timeToWait = configuredHeartbeatInterval - (now - timeOfLastHeartbeat)
> sleep(timeToWait)
> {code}
> The trouble is that since we sleep for exactly the heartbeat interval, and
> then check to see if we have waited _more_ than that heartbeat interval, we
> will very often have waited exactly the heartbeat interval (in millis), and
> not more than it. In this case we will skip actually performing the heartbeat
> and will calculcate timeToWait as being 0ms. The DN heartbeat loop will then
> loop tightly for 1ms. The solution is just to change the "{{>}}" in the code
> above to "{{>=}}".
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