## What changes were proposed in this pull request?
Currently,thread number of broadcast-exchange thread pool is fixed and keepAliveSeconds is also fixed as 60s.
```
object BroadcastExchangeExec {
private[execution] val executionContext = ExecutionContext.fromExecutorService(
ThreadUtils.newDaemonCachedThreadPool("broadcast-exchange", 128))
}
/**
* Create a cached thread pool whose max number of threads is `maxThreadNumber`. Thread names
* are formatted as prefix-ID, where ID is a unique, sequentially assigned integer.
*/
def newDaemonCachedThreadPool(
prefix: String, maxThreadNumber: Int, keepAliveSeconds: Int = 60): ThreadPoolExecutor = {
val threadFactory = namedThreadFactory(prefix)
val threadPool = new ThreadPoolExecutor(
maxThreadNumber, // corePoolSize: the max number of threads to create before queuing the tasks
maxThreadNumber, // maximumPoolSize: because we use LinkedBlockingDeque, this one is not used
keepAliveSeconds,
TimeUnit.SECONDS,
new LinkedBlockingQueue[Runnable],
threadFactory)
threadPool.allowCoreThreadTimeOut(true)
threadPool
}
```
But some times, if the Thead object do not GC quickly it may caused server(driver) OOM. In such case,we need to make this thread pool configurable.
A case has described in https://issues.apache.org/jira/browse/SPARK-26601
## How was this patch tested?
UT
Closes#23670 from caneGuy/zhoukang/make-broadcat-config.
Authored-by: zhoukang <zhoukang199191@gmail.com>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>
126310ca68