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https://issues.apache.org/jira/browse/ACCUMULO-1833?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13810635#comment-13810635
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Billie Rinaldi edited comment on ACCUMULO-1833 at 10/31/13 8:02 PM:
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It would be better if it didn't have to do the table name to id lookup each
time, and that would be avoided if the app had its own cache based on name. We
could consider adding a new method that gets based on the id rather than the
name, but I don't think we should change the existing method to use the id.
In any case it seems like there might be a problem with the ZooCache that we
should fix.
was (Author: billie.rinaldi):
It would be better if it didn't have to do the table name to id lookup each
time, and that would be avoided if the app had its own cache based on name. We
could consider adding a new method that gets based on the id rather than the
name, but I don't think we should change the existing method to use the id.
In any case it seems like might be a problem with the ZooCache that we should
fix.
> 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}
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