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https://issues.apache.org/jira/browse/WHIRR-221?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13199652#comment-13199652
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Andrei Savu commented on WHIRR-221:
-----------------------------------
bq. I get that we need timeouts has some services's scripts will return success
before the service is actually running. How do you suggest we implement this?
my idea would be that each handler could return (optionally) a waitTime for the
service to be available, at each state, after all scripts were executed whirr
would wait for the longest of these times. I mean if services have no need for
a wait time then why wait.
Sounds reasonable as long as we make this optional and we have a global default
value. If it's easier for you the global value should be good enough for now.
bq. Something else came to mind while implementing dependencies: default
service configuration and implicit roles. Let me clarify: if we start a hbase
cluster we need a zookeeper cluster, it would be nice if whirr could figure
that out and install zookeeper without the user explicitely telling it to. In
this case the zookeeper handler could return a typical layout for zookeeper
depending on cluster size (<3 nodes clusters 1 zk node, 3<=cluster<5 3 zk nodes
cluster>=5 5 zk nodes. And this is a complex case, more often that not services
can simply be installed in all nodes.
I don't think we should go that far for the first implementation. Let's try to
keep things simple & explicit (at least for now) so that we can focus on
releasing this as part of 0.7.1. BTW HBase can also use an embedded ZooKeeper
server so I think if the dependent service is missing it should be ignored by
the dependency analyser. What do you think?
And finally I think we should also have the following option as a way to
override the implicit graph:
whirr.role-order=role1+role2,role3,role4,role5
Let me know what do you think? BTW I can help testing this (manual or by
writing tests).
> 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
> Assignee: David Alves
> Priority: Critical
> Fix For: 0.8.0
>
> Attachments: WHIRR-221-v1.patch, WHIRR-221-v3.patch, WHIRR-221.patch
>
>
> 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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