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From "Hudson (JIRA)" <>
Subject [jira] Commented: (CASSANDRA-876) Support session (read-after-write) consistency
Date Sat, 21 Aug 2010 11:16:25 GMT


Hudson commented on CASSANDRA-876:

Integrated in Cassandra #518 (See [])
    per-connection read-your-writes "session" consistency.  patch by Brian Palmer; reviewed
by jbellis for CASSANDRA-876

> Support session (read-after-write) consistency
> ----------------------------------------------
>                 Key: CASSANDRA-876
>                 URL:
>             Project: Cassandra
>          Issue Type: New Feature
>          Components: Core
>            Reporter: Jonathan Ellis
>            Assignee: Brian Palmer
>            Priority: Minor
>             Fix For: 0.7.0
>         Attachments: 876-v2.txt, CASSANDRA-876.patch
> In and
Amazon discusses the concept of "eventual consistency."  Cassandra uses eventual consistency
in a design similar to Dynamo.
> Supporting session consistency would be useful and relatively easy to add: we already
have the concept of a Memtable (see ) to
"stage" updates in before flushing to disk; if we applied mutations to a session-level memtable
on the coordinator machine (that is, the machine the client is connected to), and then did
a final merge from that table against query results before handing them to the client, we'd
get it almost for free.
> Of course, the devil is in the details; thrift doesn't provide any hooks for session-level
data out of the box, but we could do this with a threadlocal approach fairly easily.  CASSANDRA-569
has some (probably out of date now) code that might be useful here.

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