Does thread pool really help

Friends,
I wanted your opinion on whether thread pools really help. Some people are of the opinion that thread pools don't really make much difference. On what basis should I make a decision whether to go for a pool or not? Is the reason that I want to limit the number of threads spawned a valid reason for pooling or it depends on the fact that for how much duration each of the threads is going to remain busy?
Can anyone please comment?
Thanks,
praddyB

sztejkat wrote:
I have run into a similar question.
The answer is, as usual, "it depends".
One delegates work to worker thread if things to be done are too long to wait for completion. This is a true sentence.
I have found that it is worth to use pool of worker threads if I need to spawn multiple, but not concurently accessing resources, lengthy tasks which should not wait for each other.
That applies to threads. It provides no basis for pools.
If tasks are to access same resource there is no point in getting a separate thread for each of them. One may get into many deadlocking troubles.
Not sure what you mean by that. If you are actually deadlocking on a single resource then you are doing something weird. Deadlocks result due to multiple resources (and incorrect access).
[http://www.javaworld.com/javaworld/jw-10-2001/jw-1012-deadlock.html]
Blocking on the other hand occurs with a single resource. Obviously if a single resource is used exclusively or primarily in thread processing then either don't use threads or re-arch to split it up.
Worker thread/pool is usually an application wide resource where one does throw "things to be done in background" or "things which can't hold current thread code flow".
Threads, pooled or not, can be the primary focus of the application. I would suppose that when someone considers using a pool that in fact in almost all cases the work tasks to be done are either the primary or a substantial part of the processing.

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What role does thread with name of form pool-n-thread-m play?

Hello
JE version 5.0.97.
Looking at the threads created by a node in the master role, I see only one thread without a descriptive name. It has the executor default of pool-n-thread-m.
What role does this thread take? I ask out of curiosity.
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"Feeder Output for node2" daemon prio=6 tid=0x0000000009a9b800 nid=0x1e20 waiting on condition [0x000000000a82f000]
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ITunes Store for Windows. Everytime I try an access the iTunes Store it takes really long to connect and then it says iTunes store cannot be access. I think I am up to date with iTunes Verizon 11.0.2.26 but no matter what I try it does not connect. HELP P

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With those symptoms, I'd try the following document:
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Sample code:
=====================================
NamedCache dummyCache = CacheFactory.getCache("A");
dummyCache.put("hello", "B");
dummyCache.put("world", "C");
ContinuousQueryCache cqcA = new ContinuousQueryCache(dummyCache, new EqualsFilter("toString", "B"), new MultiplexingMapListener() {
@Override
protected void onMapEvent(MapEvent mapEvent) {
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ContinuousQueryCache cqcB = new ContinuousQueryCache(dummyCache, new EqualsFilter("toString", "C"), new MultiplexingMapListener() {
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=================================
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EventQueue:ContinuousQueryCache{Cache=A, Filter=EqualsFilter(.toString(), C)}
=================================
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"EventQueue:ContinuousQueryCache{Cache=A, Filter=EqualsFilter(.toString(), B)}" daemon prio=6 tid=0x034d7400 nid=0x1370 in Object.wait() [0x03adf000..0x03adfb14]
java.lang.Thread.State: WAITING (on object monitor)
     at java.lang.Object.wait(Native Method)
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==================
http://www.projectseven.com/go
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http://www.dwfaq.com - DW FAQs,
Tutorials & Resources
==================
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message
news:gm3jih$4po$[email protected]..
> ANSWER: Although it is unlikely that your linking your
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unto you.
>
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>
http://www.google.com/support/webmasters/bin/answer.py?answer=34432&cbid=1uggwbr
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JRun Thread Pool Issue

I'm running CF 9.0.1 on Ubuntu on an "Medium" Amazon EC2 instance. CF has been crashing intermittently (several times per day). At such times, running top gets me this (or something similar):
PID
USER
PR
NI
VIRT
RES
SHR
S
%CPU
%MEM
TIME+COMMAND
15855
wwwrun
20
0
1762m
730m
20m
S
99.3
19.4
13:22.96 coldfusion9
So, it's obviously consuming most of the server resources. The following error has been showing up in my cfserver.log in the leadup to each crash:
java.lang.RuntimeException: Request timed out waiting for an available thread to run. You may want to consider increasing the number of active threads in the thread pool.
If I run /opt/coldfusion9/bin/coldfusion status, I get:
Pg/Sec DB/Sec CP/Sec Reqs Reqs Reqs AvgQ   AvgReq AvgDB Bytes Bytes
Now Hi Now Hi Now Hi Q'ed Run'g TO'ed Time   Time   Time   In/Sec Out/Sec
0   0   0   0   -1 -1 150   25    0     0      -1352560      0      0
In the administrator, under Server Settings > Request Tuning, the setting for Maximum number of simultaneous Template requests is 25. So this makes sense so far. I could just increase the thread pool to cover these sort of load spikes. I could make it 200. (Which I did just now as a test.)
However, there's also this file /opt/coldfusion9/runtime/servers/coldfusion/SERVER-INF/jrun.xml. And some of the settings in there appear to conflict. For example, it reads:
<service class="jrunx.scheduler.SchedulerService" name="SchedulerService">
<attribute name="bindToJNDI">true</attribute>
<attribute name="activeHandlerThreads">25</attribute>
<attribute name="maxHandlerThreads">1000</attribute>
<attribute name="minHandlerThreads">20</attribute>
<attribute name="threadWaitTimeout">180</attribute>
<attribute name="timeout">600</attribute>
</service>
Which a) has fewer active threads (what does this mean?), and b) has a max threads that exceed the simultaneous request limit set in the admin. So, I'm not sure. Are these independent configs that need to be made to match manually? Or is the jrun.xml file supposed to be written by the CF Admin when changes are made there? Hmm. But maybe this is different because presumably the CF Scheduler should only use a subset of all available threads, right...so we'd always have some threads for real live users. We also have this in there:
<service class="jrun.servlet.http.WebService" name="WebService">
<attribute name="port">8500</attribute>
<attribute name="interface">*</attribute>
<attribute name="deactivated">true</attribute>
<attribute name="activeHandlerThreads">200</attribute>
<attribute name="minHandlerThreads">1</attribute>
<attribute name="maxHandlerThreads">1000</attribute>
<attribute name="mapCheck">0</attribute>
<attribute name="threadWaitTimeout">300</attribute>
<attribute name="backlog">500</attribute>
<attribute name="timeout">300</attribute>
</service>
This appears to have changed when I changed the CF Admin setting...maybe...but it's the activeHandlerThreads that matches my new maximum simulataneous requests setting...rather than the maxHandlerThreads, which again exceeds it. Finally, we have this:
<service class="jrun.servlet.jrpp.JRunProxyService" name="ProxyService">
<attribute name="activeHandlerThreads">200</attribute>
<attribute name="minHandlerThreads">1</attribute>
<attribute name="maxHandlerThreads">1000</attribute>
<attribute name="mapCheck">0</attribute>
<attribute name="threadWaitTimeout">300</attribute>
<attribute name="backlog">500</attribute>
<attribute name="deactivated">false</attribute>
<attribute name="interface">*</attribute>
<attribute name="port">51800</attribute>
<attribute name="timeout">300</attribute>
<attribute name="cacheRealPath">true</attribute>
</service>
So, I'm not certain which (if any) of these I should change and what exactly the relationship is between maximum requests and maximum threads. Also, since several of these list the maxHandlerThreads as 1000, I'm wondering if I should just set the maximum simultaneous requests to 1000. There must be some upper limit that depends on available server resources...but I'm not sure what it is and I don't really want to play around with it since it's a production environment.
I'm not sure if it pertains to this issue at all, but when I run a ps aux | grep coldfusion I get the following:
wwwrun   15853 0.0 0.0   8704   760 pts/1
S
20:22   0:00 /opt/coldfusion9/runtime/bin/coldfusion9 -jar jrun.jar -autorestart -start coldfusion
wwwrun   15855 5.4 18.2 1678552 701932 pts/1
Sl
20:22   1:38 /opt/coldfusion9/runtime/bin/coldfusion9 -jar jrun.jar -start coldfusion
There are always these two and never more than these two processes. So there does not appear to be a one-to-one relationship between processes and threads. I recall from an MX 6.1 install I maintained for many years that additional CF processes were visible in the process list. It seemed to me at the time like I had a process for each thread...so either I was wrong or something is quite different in version 9 since it's reporting 25 running requests and only showing these two processes. If a single process can have multiple threads in the background, then I'm given to wonder why I have two processes instead of one...just curious.
So, anyway, I've been experimenting while composing this post. As noted above I adjusted the maximum simulataneous requests up to 200. I was hoping this would solve my problem, but CF just crashed again (rather it slogged down and requests started timing out...so effectively "crashed"). This time, top looked similar (still consuming more than 99% of the CPU), but CF status looked different:
Pg/Sec DB/Sec CP/Sec Reqs Reqs Reqs AvgQ   AvgReq AvgDB Bytes Bytes
Now Hi Now Hi Now Hi Q'ed Run'g TO'ed Time   Time   Time   In/Sec Out/Sec
0   0   0   0   -1 -1 0     150   0     0      0      0      0      0
Obviously, since I'd increased the maximum simultaneous requests, it was allowing more requests to run simultaneously...but it was still maxing out the server resources.
Further experiments (after restarting CF) showed me that the server became unusably slogged after about 30-35 "Reqs Run'g", with all additional requests headed for an inevitible timeout:
Pg/Sec DB/Sec CP/Sec Reqs Reqs Reqs AvgQ   AvgReq AvgDB Bytes Bytes
Now Hi Now Hi Now Hi Q'ed Run'g TO'ed Time   Time   Time   In/Sec Out/Sec
0   0   0   0   -1 -1 0     33    0     0      -492   0      0      0
So, it's clear that increasing the maximum simultaneous requests has not helped. I guess what it comes down to is this: What is it having such a hard time with? Where are these spikes coming from? Bursts of traffic? On what pages? What requests are running at any given time? I guess I simply need more information to continue troubleshooting. If there are long-running requests, or other issues, I'm not seeing it in the logs (although I do have that option checked in the admin). I need to know which requests exactly are those responsible for these spikes. Any help would be much appreciated. Thanks.
~Day

I really appreciate your help. However, I haven't been able to find the JRun Thread settings you describe above.
Under Request Tuning, I see:
Server Settings > Request Tuning
Request Limits
Maximum number of simultaneous Template requests
Restricts the number of simultaneously processed requests. Use this setting to increase overall system performance for heavy load applications. Requests beyond the specified limit are queued. On Standard Edition, you must restart ColdFusion to enable this setting.
Maximum number of simultaneous Flash Remoting requests
The number of Flash Remoting requests that can be processed concurrently.
Maximum number of simultaneous Web Service requests
The number of Web Service requests that can be processed concurrently.
Maximum number of simultaneous CFC function requests
The number of ColdFusion Component methods that can be processed concurrently via HTTP. This does not affect invocation of CFC methods from within CFML, only methods requested via an HTTP request.
Tag Limit Settings
Maximum number of simultaneous Report threads
The maximum number of ColdFusion reports that can be processed concurrently.
Maximum number of threads available for CFTHREAD
The maximum number of threads created by CFTHREAD that will be run concurrently. Threads created by CFTHREAD in excess of this are queued. On Standard Edition, the maximum limit is 10.
And under Java and JVM, I see:
Server Settings > Java and JVM
    Java and JVM settings control the way ColdFusion starts the Java Virtual Machine when it starts. You can control settings like what classpaths are used and how memory is allocated as well as add custom command line arguments. Changing these settings requires restarting ColdFusion. If you enter an incorrect setting, ColdFusion may not restart properly.
   Backups of the jvm.config file are created when you hit the submit button. You can use this backup to restore from a critical change.
   Java Virtual Machine Path
Specifies the location of the Java Virtual Machine.
   Minimum JVM Heap Size (MB)         Maximum JVM Heap Size (MB)
   The Memory Size settings determine the amount of memory that the JVM can use for programs and data.
   ColdFusion Class Path
Specifies any additional class paths for the JVM, with multiple directories separated by commas.
   JVM Arguments
-server -Dsun.io.useCanonCaches=false -XX:MaxPermSize=192m -XX:+UseParallelGC -Xbatch -Dcoldfusion.rootDir={application.home}/../ -Dcoldfusion.libPath={application.home}/../lib
Specifies any specific JVM initialization options, separated by spaces.
I did go take a look at FusionReactor and found it's not free (which would be fine, of course, if it would actually help). It looks like there's a fully functional demo, which is cool...but I've haven't been able to get it to install yet, so we'll see.
Thanks again!
~Day
(By the way, I've cross-posted this inquiry on StackOverflow. So if you're able to help me arrive at a solution you might want to answer there as well.)

Creating our own Thread Pool

We have an application running on WLS6.1 with WLI2.1. We're using WLI2.1 to define
workflows; we interface to the workflow definitions with custom EJB/JSP code.
Without getting too detailed, we would like to spawn a thread when a user submits
some of our forms. From the point of submittal onwards, there is nothing in the
execution of the workflow that requires user intervention.
We initially tackled this problem with the use of internal JMS messages in the
workflow. However, the way our workflow is structured we would really like to
manually spawn threads instead of embedding JMS messages in the flow. (For instance,
we may want to obtain multiple workflow instances and execute them all at once
with the same action).
Is there any downside to us developing our own ThreadPool? Is there a pre-canned
Thread Pool service that is available as part of the WLS package?
I've already got a ThreadPool implementation working and it seems to be doing
the right thing. There's just some concern in our company that we should be using
a WLS service instead of rolling our own.
Details of our threadpool:
- it's a long-lived Singleton that is instantated at application startup.
- A predefined number of Worker threads are created, and they can be set with
a Runnable object to execute.
- I have synchronized LinkedList containers for idleThreads, busyThreads, and
tasksToRun (Runnables that have not yet been assigned to a thread).
Thanks!
Ron

Hi,
You have to configure these things.
Goto System Admin>System Configuration>Universal Worklist & Workflow-->WorkFlow, it shows subareas like
Engine
Mail
Scheduler
User Interface
Workflow Notification Settings
To follow this link
http://help.sap.com/saphelp_nw04/helpdata/en/57/5b781705184211a4ba344387a992e5/frameset.htm
Regards,
Senthil K.

Thread pool executor problem

When using a thread pool executor (java.util.concurrent.ThreadPoolExecutor) to limit the number of threads executing at a time, the number of threads running still exceeds the limit number.
This is the code:
private ThreadPoolExecutor threadPoolExecutor = new ThreadPoolExecutor(2, 3, 20, TimeUnit.SECONDS, new LinkedBlockingQueue());
The number of tasks in my program are 4, so i always have 4 threads running, although i limited it to 3.
Can anyone help me with this problem? Or can u propose another solution to limit the number of running threads? By the way, i also tried using a newFixedThreadPool() and got the same problem.
Thx.

The number of tasks in my program are 4, so i always
have 4 threads running, although i limited it to 3.How do you know that there are 4 threads running? If you're generating a JVM thread dump, you're going to see threads that are used internally by the JVM.
Here's a simple program that creates a fixed-size threadpool and runs jobs. It limits the number of concurrent threads to 3. Compare it to what you're doing, I'm sure that you'll find something different. Also, verify that you're not creating threads somewhere else in your program; all of the ThreadPoolExecutor threads will have names of the form "pool-X-thread-Y"
import java.util.concurrent.Executors;
import java.util.concurrent.ExecutorService;
public class ThreadPoolTest {
    public static void main(String[] args) {
        ExecutorService pool = Executors.newFixedThreadPool(3);
        for (int ii = 0 ; ii < 10 ; ii++) {
            pool.execute(new MyRunnable());
        pool.shutdown();
    private static class MyRunnable implements Runnable {
        public void run() {
            log("running");
            try {
                Thread.sleep(1000L);
            catch (InterruptedException e) {
                log("interrupted");
        private void log(String msg) {
            System.err.println(
                    msg + " on " + Thread.currentThread().getName()
                    + " at " + System.currentTimeMillis());
}

BEA-002900 Initializing self-tuning thread pool HANGS

Hi All,
Trying to start a WLS 10.3.5 instance using jrockit and it is hanging on:
Apr 6, 2013 2:08:39 AM CDT> <Info> <WorkManager> <BEA-002900> <Initializing self-tuning thread pool>
end of trace
I took a thread dump and see this:
"[ACTIVE] ExecuteThread: '0' for queue: 'weblogic.kernel.Default (self-tuning)'" id=15 idx=0x3c tid=3810 prio=5 alive, waiting, native_blocked, daemon
-- Waiting for notification on: weblogic/work/ExecuteThread@0xa0c21480[fat lock]
at jrockit/vm/Threads.waitForNotifySignal(JLjava/lang/Object;)Z(Native Method)
at java/lang/Object.wait(J)V(Native Method)
at java/lang/Object.wait(Object.java:485)
at weblogic/work/ExecuteThread.waitForRequest(ExecuteThread.java:162)
^-- Lock released while waiting: weblogic/work/ExecuteThread@0xa0c21480[fat lock]
at weblogic/work/ExecuteThread.run(ExecuteThread.java:183)
at jrockit/vm/RNI.c2java(JJJJJ)V(Native Method)
-- end of trace
"JFR request timer" id=16 idx=0x40 tid=3811 prio=5 alive, waiting, native_blocked, daemon
-- Waiting for notification on: java/util/TaskQueue@0xa0c20b28[fat lock]
at jrockit/vm/Threads.waitForNotifySignal(JLjava/lang/Object;)Z(Native Method)
at java/lang/Object.wait(J)V(Native Method)
at java/lang/Object.wait(Object.java:485)
at java/util/TimerThread.mainLoop(Timer.java:483)
^-- Lock released while waiting: java/util/TaskQueue@0xa0c20b28[fat lock]
at java/util/TimerThread.run(Timer.java:462)
at jrockit/vm/RNI.c2java(JJJJJ)V(Native Method)
-- end of trace
===== END OF THREAD DUMP ===============
Done:
1). Cleared TMP and CACHE directories and still does not solve the issue.
Any ideas are appreciated.
thanks

Hi,
we had same hang issue. Unfortunately we run behind VM.
It was an issue with securerandom generation.
We solved the issue as described here http://stackoverflow.com/a/2564406/2098832
Also deleted the <server>/tmp directory before.
Hope this helps.
Casey

Pattern for Thread Pool?

Hi
i want to build a kind of download manager. The application should be able to handle some concurrent threads, each representing a download in progress.
I thought i might be more efficient to reuse a download thread after the download has ended as to create a new thread each time (like the connection object for db queries). Is this right? If yes, i thought to build a thread pool that serves a limited number of threaded download objects as requested (am I on the right way?).
Now, I have to basic problems: (a) is it right, that, if the run() method of a thread has ended, the whole thread gets destroved? if yes, how should i prevent the thread from being destroyed, so i can reuse it later on? Second (b) how would that pool mechnism look like, means, there must be some kind of vector where i put in and take out the threads.
As you see, these are basic "pool" technique questions. So, I thought, maybe there is a design pattern that would give me the basic mechanism, Does anyone know such a pattern?
Thanks for your help
josh

I thought i might be more efficient to reuse a
download thread after the download has ended as to
create a new thread each time (like the connection
object for db queries). Is this right? If yes, iIt may be right, if creating new threads is wasting enough CPU cycles to justify the complication of a thread pool. Maybe for a high-load server it would be more efficient. You'll have to figure that out for your own specific application.
Another good use for thread pools is to avoid putting time-consuming operations in ActionListeners, etc. Instead you can have them pass the task off to a thread pool, keeping the GUI responsive.
Now, I have to basic problems: (a) is it right, that,
if the run() method of a thread has ended, the whole
thread gets destroved? if yes, how should i prevent
the thread from being destroyed, so i can reuse it
later on? Second (b) how would that pool mechnism look
like, means, there must be some kind of vector where i
put in and take out the threads. (a) You are right. Therefore, the worker threads should not exit their run() methods until interrupted. (b) Worker threads could check a job queue (containing Runnables, perhaps) and if there are none, they should wait() on some object. When another thread adds a new job to the queue, it should call notify() on the same object, thus waking up one of the worker threads to perform the task.
I wrote a thread pool once, just as an exercise. You will run into a number of problems and design issues (such as, what should the worker threads do when interrupted, exit immediately or clear the job queue and then exit?) If you have any more questions, ask in this thead.
Krum

Thread pool configuration for write-behind cache store operation?

Hi,
Does Coherence have a thread pool configuration for the Coherence CacheStore operation?
Or the CacheStore implementation needs to do that?
We're using write-behind and want to use multiple threads to speed up the store operation (storeAll()...)
Thanks in advance for your help.

user621063 wrote:
Hi,
Does Coherence have a thread pool configuration for the Coherence CacheStore operation?
Or the CacheStore implementation needs to do that?
We're using write-behind and want to use multiple threads to speed up the store operation (storeAll()...)
Thanks in advance for your help.Hi,
read/write-through operations are carried out on the worker thread (so if you configured a thread-pool for the service the same thread-pool will be used for the cache-store operation).
for write-behind/read-ahead operations, there is a single dedicated thread per cache above whatever thread-pool is configured, except for remove operations which are synchronous and still carried out on the worker thread (see above).
All above is of course per storage node.
Best regards,
Robert

Thread Pool Size

What can be the maximum thread pool size used in java.
What happens if i put up a thread pool size in range of 10k or 20k.
how does affect system performance ???
Its quite urgent for me to know. Can someone help out ???
Regards
Hrushi

I'd say it depends on the machine you are running on, amount of memory and number of CPUs and such, not on Java itself. And with that many threads your implementation better be darn good in order not to be the bottleneck...

Does thread pool really help

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