[jira] [Comment Edited] (CLOUDSTACK-1522) File lock mechanism cannot get correct order when two process want to get the lock in the same second

["Sheng Yang (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CLOUDSTACK-1522?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13594126#comment-13594126 ] 

Sheng Yang edited comment on CLOUDSTACK-1522 at 3/6/13 12:03 AM:
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This fix has potentially big impact, so put it to 4.2.0 rather than 4.1.0.
                
      was (Author: yasker):
    This fix has potentially big impact, so put it to 4.2.0 rather than 4.1.0. For 4.1.0, 
                  
> File lock mechanism cannot get correct order when two process want to get the lock in the same second
> -----------------------------------------------------------------------------------------------------
>
>                 Key: CLOUDSTACK-1522
>                 URL: https://issues.apache.org/jira/browse/CLOUDSTACK-1522
>             Project: CloudStack
>          Issue Type: Bug
>      Security Level: Public(Anyone can view this level - this is the default.) 
>    Affects Versions: 4.0.0, 4.1.0
>            Reporter: Sheng Yang
>            Assignee: Sheng Yang
>            Priority: Critical
>             Fix For: 4.2.0
>
>
> The file lock mechanism is trying to provide a function that the lock requester would get the lock in the order they requested. This is implemented by using lock file's timestamp. 
> But in ext3, timestamp's precision is only in seconds, so when two requester want to get the same lock in the same second, the order cannot be guaranteed. 
> This caused issue in redundant router, when keepalived detected MASTER disappear then soon MASTER back again, keepalived would call switch to MASTER script first, then immediately call switch to BACKUP script, which may result in BACKUP script is called before MASTER script, since they're executed in the same second.
> File lock need to get high precision for determining the order of requester.

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