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Posted to commits@cassandra.apache.org by "Matthew F. Dennis (JIRA)" <ji...@apache.org> on 2010/08/03 20:39:19 UTC
[jira] Updated: (CASSANDRA-876) Support session consistency (i.e.
read after write consistency for clients)
[ https://issues.apache.org/jira/browse/CASSANDRA-876?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Matthew F. Dennis updated CASSANDRA-876:
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Summary: Support session consistency (i.e. read after write consistency for clients) (was: Support session consistency)
> Support session consistency (i.e. read after write consistency for clients)
> ---------------------------------------------------------------------------
>
> Key: CASSANDRA-876
> URL: https://issues.apache.org/jira/browse/CASSANDRA-876
> Project: Cassandra
> Issue Type: New Feature
> Components: Core
> Reporter: Jonathan Ellis
> Fix For: 0.7.0
>
> Attachments: 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 CASSANDRA-569 has some (probably out of date now) code that might be useful here.
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