[jira] [Commented] (BOOKKEEPER-347) Provide mechanism to detect r-o bookie by the bookie clients

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

    [ https://issues.apache.org/jira/browse/BOOKKEEPER-347?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13497817#comment-13497817 ] 

Vinay commented on BOOKKEEPER-347:
----------------------------------

Hi Ivan,

{quote}The problem is that, in BookieWatcher, you remove the READONLY znode, which only removes "readonly" from the list, not the znodes under "readonly"{quote}
Here, everytime getChildren() is called, new list of children itself will be used as knownbookies. This list contains only one level of znodes. i.e. It doesn't contains the znodes under 'readonly', but it contains 'readonly'.

Since, during transition to readOnly, we will unregister from 'available' and register under 'readonly' znode, getChildren(..) call will not have this transitioned bookie address. So this bookie will be removed automatically from available bookies on watcher event.

Only thing we need to do is, to avoid closing of the readonly bookie clients, we can add watcher on 'readonly' znode and keep track of readonly bookies, and avoid closing of clients for readonly bookies.

In the above Test, 
I was trying to simulate the transitionToReadOnly. Anyway I corrected the test by directly using the {{Bookie.transitionToReadOnly()}}.

One small change required in {{Bookie.transitionToReadOnly()}} is the order of creating the readonly ephemeral node and deleting the available ephemeral node should be changed to get the updated list of readonly bookies first.

I will post a patch soon regarding these..

                
>  Provide mechanism to detect r-o bookie by the bookie clients
> -------------------------------------------------------------
>
>                 Key: BOOKKEEPER-347
>                 URL: https://issues.apache.org/jira/browse/BOOKKEEPER-347
>             Project: Bookkeeper
>          Issue Type: Sub-task
>          Components: bookkeeper-client
>    Affects Versions: 4.1.0
>            Reporter: Rakesh R
>            Assignee: Vinay
>             Fix For: 4.2.0
>
>         Attachments: BOOKKEEPER-347.patch, BOOKKEEPER-347.patch
>
>
> This jira to discuss, how the bookie client knows about the bookie running in r-o. This would be required by the client to choose writable bookies during add entries. 

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