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From Michaël Figuière (JIRA) <j...@apache.org>
Subject [jira] [Created] (CASSANDRA-5714) Allow coordinator failover for cursors
Date Sat, 29 Jun 2013 01:32:19 GMT
Michaël Figuière created CASSANDRA-5714:
-------------------------------------------

             Summary: Allow coordinator failover for cursors
                 Key: CASSANDRA-5714
                 URL: https://issues.apache.org/jira/browse/CASSANDRA-5714
             Project: Cassandra
          Issue Type: Improvement
    Affects Versions: 1.2.0 beta 1
            Reporter: Michaël Figuière
            Priority: Minor


With CASSANDRA-4415 if a coordinator fails or gets slow, causing the {{NEXT}} request to timeout,
the client application won't be able to complete its browsing of the result. That implies
that most of the time when the developer will rely on cursors he will have to write some logic
to handle a retry request for results starting where the iteration failed. This will quickly
become painful.

Ideally the driver should handle this failover by itself by transparently issuing this retry
query when {{NEXT}} fail, but as the driver doesn't understand CQL queries, the only thing
it's aware of is the number of rows already read. Therefore we should allow an optional parameter
{{<initial_row_number>}} in {{QUERY}} and {{EXECUTE}} messages that would allow a kind
of stateless failover of cursors.

With such an option, developers wouldn't have to write any failover/retry logic on failure
as they would know that everything has already been tried by the driver.

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