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From "Siddharth Wagle (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (AMBARI-12453) Ambari server deadlock causing cluster create to be stuck
Date Fri, 17 Jul 2015 23:33:06 GMT

    [ https://issues.apache.org/jira/browse/AMBARI-12453?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14632101#comment-14632101
] 

Siddharth Wagle commented on AMBARI-12453:
------------------------------------------

The high level picture seems to be: Requests made from the UI for host metrics trying to figure
out the actual metrics service and the code that updates in-memory maps which hold information
of where that service is and what ports to use to connect to it etc. These property maps are
update by Observers on important events like Cluster/Service/Host CRUD by resetting a volatile
variable.

The contention occurs due the thread that actually enters the monitor protecting the volatile
var and asks for another lock on the cluster which is held by some other thread which also
needs a value from the in-memory maps and waits on the object monitor that it cannot enter.

Note: Web based deployments get away because not a lot of CRUD ops happen in parallel to Reads
like the use case of monitoring the Blueprint deploy as the cluster is being provisioned.

> Ambari server deadlock causing cluster create to be stuck
> ---------------------------------------------------------
>
>                 Key: AMBARI-12453
>                 URL: https://issues.apache.org/jira/browse/AMBARI-12453
>             Project: Ambari
>          Issue Type: Bug
>          Components: ambari-server
>    Affects Versions: 2.1.0
>            Reporter: Siddharth Wagle
>            Assignee: Siddharth Wagle
>            Priority: Critical
>             Fix For: 2.1.1
>
>
> Deadlock appears due to conflicting locking mechanisms used by the Property Provider
module.
> Attaching jstack for the deadlock.



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