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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (CASSANDRA-4533) Multithreaded cache saving can skip caches
Date Tue, 14 Aug 2012 20:17:38 GMT

     [ https://issues.apache.org/jira/browse/CASSANDRA-4533?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Jonathan Ellis updated CASSANDRA-4533:
--------------------------------------

             Reviewer: jbellis
          Description: 
Cassandra flushes the key and row cache to disk periodically. It also uses a atomic flag in
flushInProgress to enforce single cache writer at any time.

However, the cache saving task could be submitted to CompactionManager concurrently, as long
as the number of worker thread in CompactionManager is larger than 1. 

Due to the effect of above atomic flag, only one cache will be written out to disk. Other
writer are cancelled when the flag is true.

I observe the situation in Cassandra 1.0. If nothing is changed, the problem should remain
in Cassandra 1.1, either.

  was:
Cassandra flushes the key and row cache to disk periodically. It also uses a atomic flag in
flushInProgress to enforce single cache writer at any time.

However, the cache saving task could be submitted to CompactionManager concurrently, as long
as the number of worker thread in CompactionManager is larger than 1. 

Due to the effect of above atomic flag, only a cache can be written out to disk. Other writer
are cancelled when the flag is true.

I observe the situation in Cassandra 1.0. If nothing is changed, the problem should remain
in Cassandra 1.1, either.

             Priority: Trivial  (was: Major)
    Affects Version/s:     (was: 1.1.3)
                           (was: 1.0.11)
                       0.8.0
        Fix Version/s: 1.1.5
             Assignee: Yuki Morishita
              Summary: Multithreaded cache saving can skip caches  (was: Cache saving does
not work)

Looks like we should switch to a ConcurrentSet like we did in Memtable.meteringInProgress.
                
> Multithreaded cache saving can skip caches
> ------------------------------------------
>
>                 Key: CASSANDRA-4533
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-4533
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>    Affects Versions: 0.8.0
>            Reporter: Zhu Han
>            Assignee: Yuki Morishita
>            Priority: Trivial
>             Fix For: 1.1.5
>
>
> Cassandra flushes the key and row cache to disk periodically. It also uses a atomic flag
in flushInProgress to enforce single cache writer at any time.
> However, the cache saving task could be submitted to CompactionManager concurrently,
as long as the number of worker thread in CompactionManager is larger than 1. 
> Due to the effect of above atomic flag, only one cache will be written out to disk. Other
writer are cancelled when the flag is true.
> I observe the situation in Cassandra 1.0. If nothing is changed, the problem should remain
in Cassandra 1.1, either.

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