[jira] [Commented] (CASSANDRA-3494) Streaming is mono-threaded (the bulk loader too by extension)

["Jonathan Ellis (Commented) (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-3494?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13150599#comment-13150599 ] 

Jonathan Ellis commented on CASSANDRA-3494:
-------------------------------------------

This was intentional to start with (it pre-dates the stream throttling).  And if we can hit the throttle cap w/ a single thread (we can) then I'm not sure that part needs to be multithreaded.

The sstable building pre-stream seems like a more profitable area to multithread for the bulkloader scenario.
                
> Streaming is mono-threaded (the bulk loader too by extension)
> -------------------------------------------------------------
>
>                 Key: CASSANDRA-3494
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-3494
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>    Affects Versions: 0.8.0
>            Reporter: Sylvain Lebresne
>            Priority: Minor
>
> The streamExecutor is define as:
> {noformat}
> streamExecutor_ = new DebuggableThreadPoolExecutor("Streaming", Thread.MIN_PRIORITY);
> {noformat}
> In the meantime, in DebuggableThreadPoolExecutor.java:
> {noformat}
> public DebuggableThreadPoolExecutor(String threadPoolName, int priority)
> {
>    this(1, Integer.MAX_VALUE, TimeUnit.SECONDS, new LinkedBlockingQueue<Runnable>(), new NamedThreadFactory(threadPoolName, priority));
> }
> {noformat}
> In other word, since the core pool size is 1 and the queue unbounded, tasks will always queued and the executor is essentially mono-threaded.
> This is clearly not necessary since we already have stream throttling nowadays. And it could be a limiting factor in the case of the bulk loader.
> Besides, I would venture that this maybe was not the intention, because putting the max core size to MAX_VALUE would suggest that the intention was to spawn threads on demand. 

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