multithreading - Java ThreadPoolExecutor Hangs while processing -

i having custom thread pool executor

public class customtpexecutor extends threadpoolexecutor {       /* constructor called processor */       public customtpexecutor (int corepoolsize, int maxpoolsize, long keepalivetime,   timeunit timeunit, blockingqueue<runnable> blockingqueue,   threadfactory threadfactory,processor processor)       {         super(corepoolsize, maxpoolsize, keepalivetime, timeunit, blockingqueue,threadfactory);         this.processor = processor;      }      @override      protected void afterexecute(runnable paramrunnable, throwable paramthrowable)      {       super.afterexecute(paramrunnable, paramthrowable);       /* notify processor more records */     } } 

in processor, creating instances customtpexecutor , submit more 1000+ tasks it. maximum pool size 5.

for submitting executor use this.

while(iterating map events containing 1000+records) {  customthread tt = new txntcustomthread(eventmap.get(key), key,maxdate,connpool,connpool.getconnection(),email);   executor.submit(tt);  } 

after processing records calling executor shutdown method.

one thing noticing that, while threads executing hangs sometime in middle of processing. pauses minute or , resumes processing records. not sure reaosn this.

i assuming because of garbage collection not happening. cannot logs debug on this. during process memory consumption java reduced drastically.

any suggestions on how issue resolved helpful.

there's such thing "stop-the-world" gc, speaking means jvm decided needs such "deep clean" temporarily stops of threads prevent references changing. not desired , gc tries avoid in favor of doing gc in background. can happen though, if you're using of cores computation (which may tend prevent background gc) , you're generating lot of objects.

if search online "stop-the-world gc" you'll hits.