accumulo-notifications mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Josh Elser (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ACCUMULO-1833) MultiTableBatchWriterImpl.getBatchWriter() is not performant for multiple threads
Date Fri, 01 Nov 2013 04:00:17 GMT

    [ https://issues.apache.org/jira/browse/ACCUMULO-1833?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13811014#comment-13811014
] 

Josh Elser commented on ACCUMULO-1833:
--------------------------------------

[~cmccubbin] I've been playing around with this. Can you give any insight into the type of
workload you were running when you saw this?

Even distribution of mutations across many tables? Many to one table and few to many tables?
How many threads is "multiple"?

> MultiTableBatchWriterImpl.getBatchWriter() is not performant for multiple threads
> ---------------------------------------------------------------------------------
>
>                 Key: ACCUMULO-1833
>                 URL: https://issues.apache.org/jira/browse/ACCUMULO-1833
>             Project: Accumulo
>          Issue Type: Improvement
>    Affects Versions: 1.5.0, 1.6.0
>            Reporter: Chris McCubbin
>
> This issue comes from profiling our application. We have a MultiTableBatchWriter created
by normal means. I am attempting to write to it with multiple threads by doing things like
the following:
> {code}
> batchWriter.getBatchWriter(table).addMutations(mutations);
> {code}
> In my test with 4 threads writing to one table, this call is quite inefficient and results
in a large performance degradation over a single BatchWriter.
> I believe the culprit is the fact that the call is synchronized. Also there is the possibility
that the zookeeper call to Tables.getTableState on every call is negatively affecting performance:
> {code}
>   @Override
>   public synchronized BatchWriter getBatchWriter(String tableName) throws AccumuloException,
AccumuloSecurityException, TableNotFoundException {
>     ArgumentChecker.notNull(tableName);
>     String tableId = Tables.getNameToIdMap(instance).get(tableName);
>     if (tableId == null)
>       throw new TableNotFoundException(tableId, tableName, null);
>     
>     if (Tables.getTableState(instance, tableId) == TableState.OFFLINE)
>       throw new TableOfflineException(instance, tableId);
>     
>     BatchWriter tbw = tableWriters.get(tableId);
>     if (tbw == null) {
>       tbw = new TableBatchWriter(tableId);
>       tableWriters.put(tableId, tbw);
>     }
>     return tbw;
>   }
> {code}
> I recommend moving the synchronized block to happen only if the batchwriter is not present,
and also only checking if the table is online at that time:
> {code}
>   @Override
>   public BatchWriter getBatchWriter(String tableName) throws AccumuloException, AccumuloSecurityException,
TableNotFoundException {
>     ArgumentChecker.notNull(tableName);
>     String tableId = Tables.getNameToIdMap(instance).get(tableName);
>     if (tableId == null)
>       throw new TableNotFoundException(tableId, tableName, null);
>     BatchWriter tbw = tableWriters.get(tableId);
>     if (tbw == null) {
>       if (Tables.getTableState(instance, tableId) == TableState.OFFLINE)
>           throw new TableOfflineException(instance, tableId);
>       tbw = new TableBatchWriter(tableId);
>       synchronized(tableWriters){
>           //only create a new table writer if we haven't been beaten to it.
>           if (tableWriters.get(tableId) == null)      
>               tableWriters.put(tableId, tbw);
>       }
>     }
>     return tbw;
>   }
> {code}



--
This message was sent by Atlassian JIRA
(v6.1#6144)

Mime
View raw message