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From "Vijay (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-957) convenience workflow for replacing dead node
Date Thu, 25 Aug 2011 22:32:31 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-957?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13091376#comment-13091376
] 

Vijay commented on CASSANDRA-957:
---------------------------------

* In Gossiper.doStatusCheck() you made it ignore any state that is for the local endpoint
and is not a dead state. Shouldn't it just always ignore any state about the local endpoint
though? Basically what it was doing previously?
* Basically the same question about Gossiper.applyStateLocally() the loop continues if the
state is for the local node and the state is dead. Why would we want to apply a live local
state?
-> Fixed, initial intention was to find the old state of the node, Seems like it is not
possible now…

* Does the hibernate state need the true/false value? Seems like all we care about is that
it is set at all. Looks like we we are starting up right now we automatically go into a hibernate
state, then we go into a bootstrap state afterwards if the specified a replace token. Seems
like we shouldn't set a state at all until we know we are doing one of replace/bootstrap/just
joining.
-> it will be either true or false (If not a replace, or overwrite with the state normal)…
if you don't then Gossiper.applyStateLocally will mark it alive on all the other nodes.

* It looks like right now you could specify a replace token that isn't part of the cluster.
If that happens we should throw an exception and tell the user to do the normal bootstrap
process.
-> As we are ignoring the local states… this information is hard to gather when we are
trying to replace the same node…. The check is to see no other live node owns this token….
-> We can document in the wiki about the effects if they replace a token which is not part
of the ring…. (repair/decommission)

* Why use the last gossip time to determine if the node we are replacing is alive? Why not
just check gossip to see if the ring thinks it is alive?
-> because by default when we hear about someone we consider them to be alive…. the idea
is to check and see if we heard from them back or not (After the ring delay) if not then there
is more probability that the dead node is dead (Thats why we have to wait for 90 + delay 

* We should update the the message for the exception that is thrown when you try to bootstrap
to an existing token. It should indicate either remove the dead node or follow this replacement
process.
-> I am not sure if i parse that, i have added more to it plz check.

* I'm not sure why we are calling updateNormalToken() in the StorageService.bootstrap() method
when it's a token replacement.
-> Thats because you don't want the range request sent to the node which is not existing.

* A little bit of doc on this would be good, maybe in cassandra.yaml? Just on how to pass
the argument to the startup process.
-> Yaml is bad because this is a one time thing…. Wiki page? like the don't join ring
property

> convenience workflow for replacing dead node
> --------------------------------------------
>
>                 Key: CASSANDRA-957
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-957
>             Project: Cassandra
>          Issue Type: Wish
>          Components: Core, Tools
>    Affects Versions: 0.8.2
>            Reporter: Jonathan Ellis
>            Assignee: Vijay
>             Fix For: 1.0
>
>         Attachments: 0001-Support-Token-Replace.patch, 0001-Support-bringing-back-a-node-to-the-cluster-that-exi.patch,
0001-Support-token-replace.patch, 0001-support-for-replace-token-v3.patch, 0002-Do-not-include-local-node-when-computing-workMap.patch,
0002-Rework-Hints-to-be-on-token.patch, 0002-Rework-Hints-to-be-on-token.patch, 0002-upport-for-hints-on-token-v3.patch,
0003-Make-HintedHandoff-More-reliable.patch, 0003-Make-hints-More-reliable.patch, 0003-making-bootstrap-sleep-longer.patch
>
>   Original Estimate: 24h
>  Remaining Estimate: 24h
>
> Replacing a dead node with a new one is a common operation, but "nodetool removetoken"
followed by bootstrap is inefficient (re-replicating data first to the remaining nodes, then
to the new one) and manually bootstrapping to a token "just less than" the old one's, followed
by "nodetool removetoken" is slightly painful and prone to manual errors.
> First question: how would you expose this in our tool ecosystem?  It needs to be a startup-time
option to the new node, so it can't be nodetool, and messing with the config xml definitely
takes the "convenience" out.  A one-off -DreplaceToken=XXY argument?

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