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From "Sandeep Tata (JIRA)" <j...@apache.org>
Subject [jira] Commented: (CASSANDRA-195) Improve bootstrap algorithm
Date Wed, 12 Aug 2009 21:32:14 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-195?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12742587#action_12742587
] 

Sandeep Tata commented on CASSANDRA-195:
----------------------------------------


>> This should throw some kind of error -- either the other nodes are buggy, sending
reads to a bootstrapping node, or your ops team has screwed up and is allowing client-level
traffic to the node. neither should fail silently.

Good call. I'll throw a runtime exception here.

>> Similarly, we should add a verifyNotBootstrapping (better name?) call to CassandraServer
instead of adding && !bootstrapping to all the StorageProxy calls. (There may be a
place we can do this centrally by overriding the right method from the thrift-generated Cassandra
interface.)

There's only one place in StorageProxy.readProtocol that we're testing for bootstrap mode.
 I don't see why/how to move this to CassandraServer.


> + cf.addColumn(new Column(BOOTSTRAP, BasicUtilities.shortToByteArray(isBootstrap?(short)1:(short)0)));
> + return new StorageMetadata(token, generation,isBootstrap);

> not to be anal, but watch the spacing on the ?: operator and method arguments (this comment
applies to other patch lines too)

Okay -- I'll do the right thing and move this into boolean methods in BasicUtilities.

>> I don't think storing the mode in ST and trying to second-guess the op is a good
idea. If the op says -b, then we bootstrap. Otherwise we don't.

Yeah, I thought about this a bit ... I did this so that the op doesn't have to worry about
re-starting correctly in bootstrap mode if the node died during bootstrap and got restarted.
When it comes back up, you want it to resume bootstrap.
It makes it trickier to abort the bootstrap and startup in an unsafe mode. If that is really
what the op wants to do, he should delete the entry in the ST from an admin app. I figured
the normal thing would be to resume bootstrap and wanted to make that simpler/easier. I'd
lean towards keeping this behaviour.

> + protected boolean localOnly;

>I think this means "send messages out to other nodes to bootstrap me" if true, otherwise,
bootstrap some other node. Is that right? It seems like those two operations should be in
difference classes, not a single class doing two different things based on an if statement.

Yes -- that was the plan, but I ended up not using it. I'll clean this part out -- we're really
using the same code to do either thing.

> + public static synchronized SSTableReader renameAndOpen(String dataFileName) throws
IOException

> fits better in SSTW -- Reader shouldn't be renaming things just as a conceptual purity
thing. :)

:-) Okay. Done.


> Improve bootstrap algorithm
> ---------------------------
>
>                 Key: CASSANDRA-195
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-195
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>         Environment: all
>            Reporter: Sandeep Tata
>            Assignee: Sandeep Tata
>             Fix For: 0.5
>
>         Attachments: 195-v1.patch, 195-v2.patch
>
>
> When you add a node to an existing cluster and the map gets updated, the new node may
respond to read requests by saying it doesn't have any of the data until it gets the data
from the node(s) the previously owned this range (the load-balancing code, when working properly
can take care of this). While this behaviour is compatible with eventual consistency, it would
be much friendlier for the new node not to "surface" in the EndPoint maps for reads until
it has transferred the data over from the old nodes.

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