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From "Tibor Kiss (JIRA)" <j...@apache.org>
Subject [jira] Commented: (WHIRR-221) Optionally control the order of starting services
Date Wed, 02 Feb 2011 09:55:28 GMT

    [ https://issues.apache.org/jira/browse/WHIRR-221?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12989576#comment-12989576

Tibor Kiss commented on WHIRR-221:

What exactly means that? We have a BootstrapClusterAction and a ConfigureClusterAction. It
is enough to serialize according the the specified order only inside BootstrapCluterAction
or BootstrapCluterAction and ConfigureClusterAction has to be serialized in one, role by role?
There are two places where the change has to take place. The BootstrapCluterAction#doAction
and eventually the parent ScriptBasedClusterAction#execute. The latter one raises a new question.
It is important to serialize in the same way (ordered) the handler.beforeAction and handler.afterAction
event handlers? The latter question is harder to answer, at least for me and now.

If it is enough to serialize according to order only at the level of BootstrapCluterAction#doAction,
then I would say that when I was fixing WHIRR-167 I was taking in consideration such a change
and I tried to reduce the complexity of BootstrapCluterAction#doAction. The WHIRR-167 is near
to be commited in trunk (read the latest comments there), this change is much easier to schedule
after WHIRR-167 has been merged into trunk.

Anyway, lets answer the questions raised by the desired feature. 

> Optionally control the order of starting services
> -------------------------------------------------
>                 Key: WHIRR-221
>                 URL: https://issues.apache.org/jira/browse/WHIRR-221
>             Project: Whirr
>          Issue Type: New Feature
>          Components: core, documentation
>            Reporter: Andrei Savu
>            Priority: Critical
>             Fix For: 0.4.0
> As Lars sugested in WHIRR-170:
> The user should "be able to optionally control the order (services start). This could
be role based and specified like so
> {code}
> whirr.role-order=zk,nn+jt,dn+tt,hbase-master,hbase-regionserver
> {code}
> If not specified the system should make any effort to start the services as quickly as
possible, for example in multiple threads. In other words, when the role-order is not given
no guarantee about order can be given."

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