[jira] [Commented] (LENS-993) Estimate thread pool does not grow beyond minimum pool size.

["Amareshwari Sriramadasu (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/LENS-993?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15209763#comment-15209763 ] 

Amareshwari Sriramadasu commented on LENS-993:
----------------------------------------------

As per https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/ThreadPoolExecutor.html :

----
Any BlockingQueue may be used to transfer and hold submitted tasks. The use of this queue interacts with pool sizing:
# If fewer than corePoolSize threads are running, the Executor always prefers adding a new thread rather than queuing.
# If corePoolSize or more threads are running, the Executor always prefers queuing a request rather than adding a new thread.
# If a request cannot be queued, a new thread is created unless this would exceed maximumPoolSize, in which case, the task will be rejected.
----

With following code in QueryExecutionServiceImpl:
{code}
    ThreadPoolExecutor estimatePool = new ThreadPoolExecutor(minPoolSize, maxPoolSize, keepAlive, TimeUnit.MILLISECONDS,
      new LinkedBlockingQueue<Runnable>(), threadFactory);
{code}

It would never create thread more than minPoolSize. Some discussion - http://stackoverflow.com/questions/19528304/how-to-get-the-threadpoolexecutor-to-increase-threads-to-max-before-queueing

I'm proposing we use Executoes.newCachedThreadPool instead of creating ThreadPoolExecutor by the server, as suggested in javadoc.

> Estimate thread pool does not grow beyond minimum pool size.
> ------------------------------------------------------------
>
>                 Key: LENS-993
>                 URL: https://issues.apache.org/jira/browse/LENS-993
>             Project: Apache Lens
>          Issue Type: Bug
>          Components: server
>            Reporter: Amareshwari Sriramadasu
>            Assignee: Amareshwari Sriramadasu
>             Fix For: 2.6
>
>
> We noticed that there are only 3 threads (the min pool size) on the server and not growing. And 3 threads are blocked on JDBC connection and all subsequent estimate calls timeout as there are no threads.



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