ExecutorService creating tasks to send HTTP requests - time out

Question

In my java application, I have introduced ExecutorService to create tasks. The tasks consist of sending HTTP requests to an application server, to process transactions. The ExecutorService will process about 1000 requests.
The executor process the transactions and terminates OK, but some of the transactions timed out (before introducing ExecutorService, I was just sending one transaction at time, all the transactions were processed OK; but, it was taking a long time to process).
See the code below.
private ExecutorService threadExecutor;
threadExecutor = Executors.newFixedThreadPool(30);
threadExecutor.execute(transaction);
try
     //Shutting down the ThreadExecutor
threadExecutor.shutdown();
threadExecutor.awaitTermination(30, TimeUnit.SECONDS);
threadExecutor.shutdownNow();
catch (InterruptedException e)
     System.out.println("ERROR - cannot shutdown the ThreadExecutor - exception is: " + e);
Is this the best way to implement this use case?
Thank you.

Answer 1

From the above code, it seems like you are starting only a single transaction in a thread pool. Or does the transaction object you pass to the threadExecutor spawn more tasks for the executor?
If you are indeed still making all HTTP requests from the single transaction object, then yes, it will 'time-out' after 30 seconds, since the ExecutorService was instructed to stop its threads after that period of time.
Your description of the use case is actually a good example of the usage of an ExecutorService, since it is faster to do 1000 HTTP requests in parallel than it is to do them sequentially.
Consider this:
ExecutorService threadExecutor = Executors.newFixedThreadPool(30);
for (int i = 0; i < 1000; i++)
  threadExecutor.execute(new Transaction());
try
  threadExecutor.shutdown();
  threadExecutor.awaitTermination(30, TimeUnit.SECONDS);
  threadExecutor.shutdownNow();
catch (InterruptedException e)
  // Ignore
}This will spawn 1000 transactions that will execute in parallel, with max. 30 running at any single point in time. Any transactions still not executed after 30 seconds will be terminated.
Hope this helps.
--JH
Edited by: Kramor_dude on Nov 5, 2009 6:55 AM