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Date: Wed, 20 May 2009 22:18:45 -0700 (PDT)
From: "Amareshwari Sriramadasu (JIRA)" <jira@apache.org>
To: core-dev@hadoop.apache.org
Subject: [jira] Commented: (HADOOP-5784) The length of the heartbeat cycle
 should be configurable.
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    [ https://issues.apache.org/jira/browse/HADOOP-5784?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12711466#action_12711466 ] 

Amareshwari Sriramadasu commented on HADOOP-5784:
-------------------------------------------------

Current heartbeat interval is set to  {{clusterSize / 100}}, and minimum interval is capped at 3seconds. 
It assumes that JT can process 100 heartbeats in a second. See http://issues.apache.org/jira/browse/HADOOP-1900?focusedCommentId=12542530&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#action_12542530

Now, if we make number of heartbeats that should arrive in a second configurable (with default value as 100) , heartbeat interval can be calculated as 
{code}
 heartbeatInterval = max((clusterSize / #heartbeats in a second),  HEARTBEAT_INTERVAL_MIN) ;
{code}

Thoughts?

> The length of the heartbeat cycle should be configurable.
> ---------------------------------------------------------
>
>                 Key: HADOOP-5784
>                 URL: https://issues.apache.org/jira/browse/HADOOP-5784
>             Project: Hadoop Core
>          Issue Type: Improvement
>          Components: mapred
>            Reporter: Owen O'Malley
>
> Currently, the hearbeat cycle is set to (# nodes / 100) in seconds. This can be too long for clusters that need to run low latency jobs. We should make the number of heartbeats that should arrive a second configurable.

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