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From "Stefania (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-8523) Writes should be sent to a replacement node while it is streaming in data
Date Tue, 05 Apr 2016 01:33:26 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-8523?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15225483#comment-15225483
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Stefania commented on CASSANDRA-8523:
-------------------------------------

bq. Hmm, can you can explain further?

Well, it would be a bit convoluted so a new Gossip state would probably be cleaner if we can
add it. But the idea is to link a host to one or more hosts that act as 'shadows', that is
they receive copies of all writes or hints but are not queried for reads. 

> Writes should be sent to a replacement node while it is streaming in data
> -------------------------------------------------------------------------
>
>                 Key: CASSANDRA-8523
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-8523
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Richard Wagner
>            Assignee: Brandon Williams
>             Fix For: 2.1.x
>
>
> In our operations, we make heavy use of replace_address (or replace_address_first_boot)
in order to replace broken nodes. We now realize that writes are not sent to the replacement
nodes while they are in hibernate state and streaming in data. This runs counter to what our
expectations were, especially since we know that writes ARE sent to nodes when they are bootstrapped
into the ring.
> It seems like cassandra should arrange to send writes to a node that is in the process
of replacing another node, just like it does for a nodes that are bootstraping. I hesitate
to phrase this as "we should send writes to a node in hibernate" because the concept of hibernate
may be useful in other contexts, as per CASSANDRA-8336. Maybe a new state is needed here?
> Among other things, the fact that we don't get writes during this period makes subsequent
repairs more expensive, proportional to the number of writes that we miss (and depending on
the amount of data that needs to be streamed during replacement and the time it may take to
rebuild secondary indexes, we could miss many many hours worth of writes). It also leaves
us more exposed to consistency violations.



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