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Date: Sat, 23 Oct 2010 00:49:22 -0400 (EDT)
From: "Jonathan Ellis (JIRA)" <jira@apache.org>
To: commits@cassandra.apache.org
Subject: [jira] Assigned: (CASSANDRA-876) Support session (read-after-write)
 consistency
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     [ https://issues.apache.org/jira/browse/CASSANDRA-876?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Jonathan Ellis reassigned CASSANDRA-876:
----------------------------------------

    Assignee:     (was: Brian Palmer)

> Support session (read-after-write) consistency
> ----------------------------------------------
>
>                 Key: CASSANDRA-876
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-876
>             Project: Cassandra
>          Issue Type: New Feature
>          Components: Core
>            Reporter: Jonathan Ellis
>            Priority: Minor
>         Attachments: 876-v2.txt, CASSANDRA-876.patch
>
>
> In http://www.allthingsdistributed.com/2007/10/amazons_dynamo.html and http://www.allthingsdistributed.com/2008/12/eventually_consistent.html 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 http://wiki.apache.org/cassandra/MemtableSSTable ) 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  CASSANDRA-569 has some (probably out of date now) code that might be useful here.

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