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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