NIO readiness selection and thread pool

Hi,
I am new to this stuff, but I�m trying to implement readiness selection (using selectors, channels, keys etc). Generally it is not very difficult, I can do it, there are also some examples on the net. The problem is I need it for heavy duty server and I am obligate to use thread pool. I am facing major problems here, especially when fetching keys form the selectedKeys set create tasks for the pool. Can somebody give me some general hints here? Some examples maybe. In every call to Selector.select() the set is filled with new keys, when I give a key to a thread task to be processed, the next selection generates another key for the same channel, because select() is called earlier than thread processing pointed channel finishes and closes the channel.
Generally, basic help needed to implement readiness selection (NIO) with a thread pool.
Thanks for any help.

I would do the actual I/O in the same thread as you are selecting in, and use the thread pool to dispatch work arising from the I/O.
If you can't do that you will have to cancel the registration of the key when you pass it off to another thread, or set its interestOps to zero, re-registering or restoring when the thread finishes the action.

Similar Messages

Thread Pools

Hi Everyone;
I have a Runnable class called Page.
during the course of my program's execution it might make 300 of these Page threads per hour. Someone suggested that I might have a performance and resource penalty for creating these threads.
They suggested a thread pool. Does anyone know how to make a THread Pool - Or does anyone know if a Thread pool would be useful in this situation?
Stephen

You can make sure that a thread has been removed by using .join() to merge it with an existing thread.
If you are creating one thread per second, then I think a thread pool is still overkill - it really does depend on the OS you are on and the speed of the machine.
The real question is:
1. What is the time required to create and start the thread
2. What is the total processing time of the thread before it dies
If #1 becomes a significant percentage of #2, AND you are having performance problems, then using a pool might be an appropriate strategy for improving performance.
Later Java VMs are pretty efficient when it comes to creating threads, and thread pools have a whole host of nastiness associated with them, so I'd avoid them unless there is a really compelling (i.e. tested and confirmed) reason to do so.
- K

NIO Socket implementation - delay between select and get data from socket

Hi all,
I have implemented a internal CallAPI for RPC over a socket connection. It works fine but if there are more than five clients and some load I have the phenomena that the READ selector returns a SelectorKey but I did not get any data from the socket.
My implementation is based on NIO has following components:
+ Accept-Thread
Thread handles new clients.
+ Read-Thread
Thread handles the data from the socket for the registered client. Each request is handled in an own Process-Thread. A Thread-Pool implementation is used for processing.
+ Process-Thread
The Process-Thread reads the data from the socket and starts the processing of the logical request.
In my tests I get the notification of data at the socket. The Process-Thread want to read the data for the socket, but no data are available. In some situations if have to read about 20 times and more to get the data. Between each read attempt I have inserted a sleep in the Process-Thread if no data was available. This have improved the problem, but it already exists. I tested the problem with several systems and jvm's but it seams that it is independent from the system.
What can I to do improve the situation?
I already include the read implementation from the grizzly-Framework. But it doesn't improve the situation.
Socket - Init
 protected void openSocket( String host, int port ) throws IOException
 serverChannel = ServerSocketChannel.open();
 serverChannel.configureBlocking( false );
 serverSocket = serverChannel.socket();
 serverSocket.setReuseAddress( true );
 this.serverhost = host;
 this.serverport = port;
 this.srvAcceptSelector = Selector.open();
 this.srvReadSelector = Selector.open();
 InetSocketAddress isa = null;
 if ( serverhost != null )
 isa = new InetSocketAddress( this.serverhost, this.serverport );
 else
 isa = new InetSocketAddress( this.serverport );
 serverSocket.bind( isa, 50 );
 serverChannel.register( this.srvAcceptSelector, SelectionKey.OP_ACCEPT );
 }New Client � Init
 // New Client
 if ( key.isAcceptable())
 keyCountConnect++;
 ServerSocketChannel actChannel =
 (ServerSocketChannel) key.channel();
 // Socket akteptieren
 SocketChannel actSocket = actChannel.accept();
 if ( actSocket != null )
 actSocket.finishConnect();
 actSocket.configureBlocking( false );
 actSocket.socket().setTcpNoDelay( true );
 this.registerSocketList.add( actSocket );
 this.srvReadSelector.wakeup();
 }Read Data from Socket
 protected int readDatafromSocket( ByteArrayOutputStream socketdata )
 throws IOException
 int readedChars = 0;
 int count = -1;
 Selector readSelector = null;
 SelectionKey tmpKey = null;
 if ( sc.isOpen())
 ByteBuffer inputbuffer = null;
 try
 inputbuffer = bufferpool.getBuffer();
 while (( count = sc.read( inputbuffer )) > 0 )
 readedChars += count;
 inputbuffer.flip();
 byte[] tmparray=new byte[inputbuffer.remaining()];
 inputbuffer.get( tmparray );
 socketdata.write( tmparray );
 inputbuffer.clear();
 if ( count < 0 )
 this.closeSocket();
 if( readedChars == 0 )
 readedChars = -1;
 if ( log.isDebug())
 log.debug( "Socket is closed! " );
 else if ( readedChars == 0 )
 if ( log.isDebug())
 log.debug( "Reread with TmpSelector" );
 // Glassfish/Grizzly-Implementation
 readSelector = SelectorFactory.getSelector();
 if ( readSelector == null )
 return 0;
 count = 1;
 tmpKey = this.sc.register( readSelector, SelectionKey.OP_READ );
 tmpKey.interestOps(
 tmpKey.interestOps() | SelectionKey.OP_READ );
 int code = readSelector.select( 500 );
 tmpKey.interestOps(
 tmpKey.interestOps() & ( ~SelectionKey.OP_READ ));
 if ( code == 0 )
 return 0;
 // Return on the main Selector and try again.
 while (( count = sc.read( inputbuffer )) > 0 )
 readedChars += count;
 inputbuffer.flip();
 byte[] tmparray=new byte[inputbuffer.remaining()];
 inputbuffer.get( tmparray );
 socketdata.write( tmparray );
 inputbuffer.clear();
 if ( count < 0 )
 this.closeSocket();
 if( readedChars == 0 )
 readedChars =-1;
 else if ( count == 0 )
 // No data
 finally
 if ( inputbuffer != null )
 bufferpool.releaseBuffer( inputbuffer );
 inputbuffer = null;
 // Glassfish-Implementierung
 if ( tmpKey != null )
 tmpKey.cancel();
 if ( readSelector != null)
 // Bug 6403933
 try
 readSelector.selectNow();
 catch (IOException ex)
 SelectorFactory.returnSelector( readSelector );
 return readedChars;
 }Thanks for your time.

I've commented on that blog before. It is rubbish:
- what does 'overloading the main Selector' actually mean? if anything?
- 'Although this not clearly stated inside the NIO API documentation': The API documentation doesn't say anything about which Selector you should register channels with. Why would it? Register it with any Selector you like ...
- 'the cost of maintaining multiple Selectors can reduce scalability instead of improving it' Exactly. So what is the point again?
- 'wrapping a ByteBuffer inside a ByteBufferInputStream:' Code is rubbish and redundant. java.nio.channels.Channels has methods for this.
There is no a priori advantage to using multiple Selectors and threads unless you have multiple CPUs. And even then not much, as non-blocking reads and writes don't consume significant amounts of CPU. It's the processing of the data once you've got it that takes the CPU, and that should be done in a separate thread.
So I would re-evaluate your strategy. I suspect you're getting the channel registered with more than one Selector at a time. Implement it the simple way first then see if you really have a problem with 'overloading the main Selector' ...

Threads: Pooling and groups

Hello there! I need to implement a solution that will use threads, I write down my problem, to be more precisely on the questions.
The scenario:
An extrator, reads from a flat file, and insert into a table.
Another process runs threads to read this table, perform an ETL and then insert in antoher table. I'm considering that the file read process's time is <<< (much smaller) than the ETL, due the transformations involved.
So my first solution was to use thread pooling (Im reading about, and already have some implementations), since I dont want to have more than a few threads running at same time (let's say 5-6).
Ok my first Ideia was to do something like this:
a main class that will run a thread (the text file extractor), this will be done from the pool of threads, so I have n-1 threads left.
This thread would read the lines and at each 10k read, commit the result, and now its the tricky part, warn its parent process (main class) that it already processed 10k registers. The main class would know that and then start a new thread (the ETL thread, reading from 0-10k) now I have n-2 threads left. The process would go on, since the text thread is faster, It would continue warning the main class, that it had processed 10k registers and main class would continue dispatching new threads, untill it reaches a maximum number (controled by the pool). The pool would be responsible to create its own list of waiting threads to run.
My main problem is to make sure that the text thread can warn the main thread. Can someone point me so directions to it? a tutorial, a hint, anything would help

Thread.sleep()
Thread.interrupt()
Well, I'm sorry but I dont think ? I made my self
clear. I need to know how to warn my parent thread not
put the one I'm running in sleep or terminate it.Well. A call to interrupt() does not terminate another thread,
rather, like the name indicates, it interrupts it, but only if
the thread to be interrupted is blocking on a sleep(), join(), or wait() call or is blocking on interruptible I/O (java.nio.channels stuff).
If the thread is not currently blocking, a flag is set.
If there is no need for the parent to sleep() you can just call interrupted() to check the flag at regular intervals.

Cold Fusion in a generic thread pool and enabling JAVA don't mix

I've got Cold Fusion MX installed on a server running Sun One 6.1. I ran into a problem trying to enable JAVA (for servlet support) which I had previous disabled because I didn't use it.
Well, when I went to enable JAVA on the server last week, the service wouldn't restart and the error logs gave me no indication of the problem.
Through a tedious trial-and-error process I've found that having Cold Fusion running under a generic thread pool while trying to have JAVA (the j2ee plugin) running under Sun One simply doesn't work (for whatever reason).
Once I killed the pool, everything runs fine.
Does anyone happen to know why this is? I keep CFMX under its own thread pool because there are certain elements to CFMX that aren't wholly stable and can result in CFMX crashing. If it crashes, the process keeps accepting requests, but never processes them. I'd like to keep the native thread pool free to keep accepting non-CFMX requests even when CFMX crashes.
Thus the separate thread pool for CFMX.
But now I can't run CFMX in a separate thread pool with JAVA enabled.
Anyone have any insights into why this is?
Thanks

Two things. Firstly, it's better to use private static final Object classLock = new Object();because that saves you worrying about whether any other code synchronises on it. Secondly, if you do decide to go for the delegation route then java.lang.reflect.Proxy may be a good way forward.

On Threads, Pools and other beasts

I'm seeing some unexpected behaviours in our production system relating to
(AFAICS) threads and connection pools, and hope you could bring some info
about them.
Our system is built over 4 PIII Xeon processors under Linux.
We do currently have this configuration:
15 threads for the "default" queue and 10 for an special servlet one, we
decided to separate threads in two queues in order to assure our users get
always a thread besides what the rest of the system is "doing".
Even we do not have a lot of users (about 20 or so) they do generate a lot
of load as for the bussiness logic inherent to the application.
For sample, so you can understand what goes with practically any user
"action", think on this.
After a user "confirms" some data via a servlet and after executing the data
validation and bussines rules some messages are sent via JMS to the
"asynchronous" part of the system (that is running in the same weblogic
instance). After commiting the user transaction an thus releasing the
servlet thread, so it can be used by the same or other user, JMS messages
are delivered to MDBs that must transform information from on-line (servlet)
processes in different ways so they can be stored onto other systems, i.e.
into a mainframe, into an XML DB and possibly into another RDBMS. Our
configuration is that there can be as much as 10 MDB of each type (I mean
for each kind of "action" of a servlet) running concurrently and as you can
suppose those processes do take some time to communicate with destination
systems and perform their work.
We end at last with a lot of concurrent processes in our system that ends
some time with the users complaining about system responsiveness.
After all this explanation I would like to know if 25 threads for
"background" and on-line processes is too low (as I'm afraid they are). The
problem is we can't seem to increase the number of threads without being
very careful with JDBC connection pools.
Currently we have two connection pools. We do demarcate transactions in the
clients (servlets, batch processes) we have a "transacted" pool and a "non
transacted" one.
We are delegating persistence to the contanier (formally in our case we are
using TopLink persistence and it uses in it's deployment descriptor both
types of pools)
Our configuration is as follows:
Oracle pool NON Tx 60 connections
Oracle pool Tx 30 connections
initially we create 5 connections for each pool with an increment of 5 for
each one too.
From the tests I have made I have discovered that setting more threads than
the minimum amount of pools yields to this exception:
weblogic.common.ResourceException: No available connections in pool
myNonTxPool
at
weblogic.common.internal.ResourceAllocator.reserve(ResourceAllocator.java:57
8)
at
weblogic.common.internal.ResourceAllocator.reserve(ResourceAllocator.java:40
5)
at
weblogic.common.internal.ResourceAllocator.reserveNoWait(ResourceAllocator.j
ava:373)
at
weblogic.jdbc.common.internal.ConnectionPool.reserve(ConnectionPool.java:165
at
weblogic.jdbc.common.internal.ConnectionPool.reserveNoWait(ConnectionPool.ja
va:126)
at
weblogic.jdbc.common.internal.RmiDataSource.getPoolConnection(RmiDataSource.
java:194)
at
weblogic.jdbc.common.internal.RmiDataSource.getConnection(RmiDataSource.java
:219)
the behaviour I would expect is that in case a thread needs a connection and
there isn't any one available the thread may be blocked and it would receive
the connecion once one is released, of course as I can see in the stack the
ConnectionPool.reserveNoWait() method is behaving just the other way.
The main problem with this is that as you can see we are "forced" to spend
90 (60+30) connections to the DB (even we will never use more than 25
(15+10) simultaneously just because we must assure that at least there is
one "reserved" connection to each thread.
Our DBA thinks that it can't be possible that we spend such number of
connections that could be taken by another application(s) (as the DB is
shared with other apps)
Currently our DB system is not set as "multithreaded" so each connection
created against the DB is a process on the system and of course they are a
really scarce resource.
My question is. What would be a "fine" number of threads for an application
like this that is mainly "background-batch processing" but assuring on-line
users have their threads always available?
I have just another doubt (maybe this is not the right thread to ask for it
but...) how does the UserTransaction actually works? I mean, is the
connection given to the thread (and thus extracted from pool) as soon as the
thread begin it's work? or is it given in the instant of "commiting" to the
DB. I know maybe using TopLink changes default Weblogic CMP behaviour but I
would like to know what the "default" Weblogic behaviour is; and, what
happens when you don't start a transaction in the client and total execution
time exceeds 30 seconds? I have seen a rollback due to "exceeding" those 30
seconds althought I'm sure we do not open any transaction, what kind of
"transaction" is that? Is just a way of Weblogic to assure a thread is not
"locked" more than a certain period of time so the system never "stalls"?
Thanks in advance.
Regards.
Ignacio.

Hi Ignacio,
See my answer inline.
"Ignacio G. Dupont" <[email protected]> wrote in message
news:[email protected]...
I'm seeing some unexpected behaviors in our production system relating to
(AFAICS) threads and connection pools, and hope you could bring some info
about them.
Our system is built over 4 PIII Xeon processors under Linux.
We do currently have this configuration:
15 threads for the "default" queue and 10 for an special servlet one, weThat numbers defines number of concurrent requests services
associated with that queues can handle. If monitoring CPU utilization
shows that CPU load is not high, let say less than 90%, - you can increase
that numbers.
decided to separate threads in two queues in order to assure our users get
always a thread besides what the rest of the system is "doing".
Even we do not have a lot of users (about 20 or so) they do generate a lot
of load as for the bussiness logic inherent to the application.>
For sample, so you can understand what goes with practically any user
"action", think on this.[eaten]
We end at last with a lot of concurrent processes in our system that ends
some time with the users complaining about system responsiveness.You will have to run a load test in your QA environment and play with queue
sizes. In addition, you may want to run a profiler (like JProbe or
OptimizeIt)
for maximum load to find if there are bottlenecks in the application.
After all this explanation I would like to know if 25 threads for
"background" and on-line processes is too low (as I'm afraid they are).The
It all depends of the usage pattern. I'd say that for a production
environment
with any noticeable load, it's low.
problem is we can't seem to increase the number of threads without being
very careful with JDBC connection pools.Yes, you will have to increase size of the pools to match maximum
number of ongoing transactions. Minimum would be a number of execution
threads. Actual number should be determined either by load testing or
by setting it to a guaranteed high level.
Currently we have two connection pools. We do demarcate transactions inthe
clients (servlets, batch processes) we have a "transacted" pool and a "non
transacted" one.
We are delegating persistence to the contanier (formally in our case weare
using TopLink persistence and it uses in it's deployment descriptor both
types of pools)
Our configuration is as follows:
Oracle pool NON Tx 60 connections
Oracle pool Tx 30 connections
initially we create 5 connections for each pool with an increment of 5 for
each one too.
From the tests I have made I have discovered that setting more threadsthan
the minimum amount of pools yields to this exception:That's quite natural.
weblogic.common.ResourceException: No available connections in pool
myNonTxPool[eaten]
the behaviour I would expect is that in case a thread needs a connectionand
there isn't any one available the thread may be blocked and it wouldreceive
That would lock exec threads very quickly. A connection pool is a vital
resource that is to be available constantly. So weblogic uses fail-fast
approach so that you can adjust setting to match highest load.
the connecion once one is released, of course as I can see in the stackthe
ConnectionPool.reserveNoWait() method is behaving just the other way.>
The main problem with this is that as you can see we are "forced" to spend
90 (60+30) connections to the DB (even we will never use more than 25
(15+10) simultaneously just because we must assure that at least there is
one "reserved" connection to each thread.That's right.
Our DBA thinks that it can't be possible that we spend such number of
connections that could be taken by another application(s) (as the DB is
shared with other apps)I don't think it's a correct observation. Oracle can be configured to handle
more connections. I saw weblogic pools configured to handle 200
connections.
Currently our DB system is not set as "multithreaded" so each connection
created against the DB is a process on the system and of course they are a
scarce resource.Application demand for resources should be satisfied.
My question is. What would be a "fine" number of threads for anapplication
like this that is mainly "background-batch processing" but assuringon-line
users have their threads always available?It should be high enough to satisfy requirement to handle given number
of concurrent requests processed on given hardware. Normally this
is determined by load testing and gradual increase of this number
to the point where you see that hardware (seen as CPU load)
cannot handle it. Buy the way this point sometimes is unreachable
as application becomes DB-bound, i.e. bottleneck is shifted to
the database.
I have just another doubt (maybe this is not the right thread to ask forit
but...) how does the UserTransaction actually works? I mean, is the
connection given to the thread (and thus extracted from pool) as soon asthe
thread begin it's work? or is it given in the instant of "committing" tothe
It's given when a connection, assuming it's obtained from TxDatasource,
is requested.
DB. I know maybe using TopLink changes default Weblogic CMP behavior but I
would like to know what the "default" Weblogic behavior is; and, what
happens when you don't start a transaction in the client and totalexecution
time exceeds 30 seconds? I have seen a rollback due to "exceeding" those30
seconds although I'm sure we do not open any transaction, what kind of
"transaction" is that? Is just a way of Weblogic to assure a thread is notFor instance, stateful session beans are transactional.
"locked" more than a certain period of time so the system never "stalls"?Basically, no, it's not. There is no way to "unlock" thread after certain
period.
So when a queue has finished processing, TX monitor checks the timeout,
and if there is one, issues a corresponding rollback. So, it's possible
for thread to run for 10 hours if the timeout is 30 seconds.
Since 7.0 weblogic is capable of detecting such situations so that
administrator can be informed about it and required actions can be
taken [on application side].
Hope this helps.
Regards,
Slava Imeshev

Combining the fixed and cached thread pools

Is there a way to 'combine' the behavior of cached and fixed thread pools ? I have a requirement where
- at startup, I need to execute a fixed number of short-lived tasks at the background
- after startup, on demand, I need to run one short-lived task at a time
If I use a fixed thread pool for my startup processing, it creates the fixed number of threads to process the tasks. But subsequently, those many threads are not required since my task submission is going to be one at a time. The remaining (n-1) threads therefore are really sitting idle & useless.
If I use a cached thread pool, then I cannot constrain the number of threads to run at startup (since it creates one for each task). Though it ends up taking those threads out after they are idle for a fixed period. But I'm worried that it might create many threads and possibly slowing down the startup ?
Is there a way to create a pool with a fixed number of threads but 'remove' a set of threads when they are idle ?
TIA

v_bala wrote:
Thanks. The SynchronousQueue worked as expected. But I tried a LinkedBlockingQueue with size 1 hoping that would cause the second task submission to cause a new thread creation. It didn't. Instead it queues up the request (maybe the doc in ThreadPoolExecutor says that when it mentions "If corePoolSize or more threads are running, the Executor always prefers queuing a request rather than adding a new thread"). I suppose if I were to try another it would create another thread ? (I was testing with only two tasks - the first one ended up creating a thread for the task and the next got queued since the queue capacity is 1)yes, the TPE will not start adding threads until the queue starts rejecting them. kind of odd in my opinion, but that's how it works.
Btw, that was an interesting idea to add a task that scale the core pool number down ! Currently it comes back down to just the one thread (my core pool size is one) after the idle timeout but your idea may give me a slightly better response since it will scale down the core pool size quicker....I suppose if there was a task submission before that idle time there maybe a performance hit (but I don't anticipate that in my case )?actually, that won't scale things down any faster. changing the core pool size will not ditch the other threads immediately, they will still stick around until they idle timeout. changing the core pool size allows you to not worry about the queue implementation (the first solution). you can set the initial core pool size to your "max" size on startup, then drop it down for the normal processing, all the while using a linkedblockingqueue of unlimited size.

Scheduled thread pools and blocking

Hello,
I am using a scheduled thread pool created in the following way:
ScheduledExecutorService scheduler = Executors.newScheduledThreadPool();I want to schedule a task on the scheduler, but this task uses a MulticastSocket and can block on:
byte[] b = new byte[BUFFER_LENGTH];
DatagramPacket dgram = new DatagramPacket(b, b.length);
socket.receive(dgram);Say I schedule this code to run at 500 ms. The first run blocks on the receive method. If the block lasts for more that 500ms, what happens when the scheduler allocates another thread at the next 500ms mark? Can I "lose" a thread from the pool permanently? Can I cause a backup of multiple threads blocking every time the scheduler runs the task?
Thanks!
-pm

Well it used to be a plain old Runnable with the receive() inside the run() method, and the runnable was launched inside a Thread. However, I have an infrastructure that adds tasks to a ScheduledExecutorService so that I can run tasks that require a timing mechanism. I also have an ExecutorService for executing tasks at one time. I want to use these concurrency facilities to get this task to always run, not just once, and I thought scheduling would allow that. Would the ExecutorService's submit() method do that? Would it make more sense to have the run() method loop:
run(){
byte[] b = new byte[BUFFER_LENGTH];
DatagramPacket dgram = new DatagramPacket(b, b.length);
while(true){
socket.receive(dgram);
// do something ...
}and then have ExecutorService simply run execute()?
Thanks!

Pool # and thread #

hello all:
My understanding about APIs such as Executors#newCachedThreadPool and Executors#newFixedThreadPool is that they have a thread pool and various or fixed number of threads. The source code shows that they internally call ThreadPoolExecutor, whose parameters, corePoolSize or maxPoolSize, IMO, also refer to the number of threads.
However, when I log the default thread name when using these APIs, I see some format like pool-1-thread-202, pool-3-thread-1, which apprear to me there are multiple pools.
Any clarifications?
Thanks,
John

Johnny_hunter wrote:
thanks Jahlborn. I didn't create multile executor instances explicitly - under what circurmstances that the JVM feel needs to create multiple executor instances?for whatever it needs a thread-pool (likely candidates are more significant frameworks like webservers, etc). if you create stack dump of your application, you should be able to see what all the threads are doing. additionally, if you attach a memory profile to your application, you should probably be able to figure out what classes own what thread pools. this should enable you to determine where the other thread pools are getting instantiated.
Edited by: jtahlborn on Jan 9, 2012 11:23 AM

Basics of Thread Pool and MDB

Hi,
I am not able to connects the dots between Self-Tuning Thread Pool Threads ,number of MDB's and Open connection to Queue Manager (Listeners).
Following is my setting
1 Self-Tuning Thread Pool : Default i.e 5
2) Initial Beans in Free Pool: 100
3) Max Beans in Free Pool : 200
What i see
Pool Current Count :- 100 (this is as expected)
On start up of server 105 MDB's are created (No problem with this ) (Have put static variable incrementing in constructor)
When Messages are sent to MQ (50-100) the "Beans In Use Count" under Monitoring never shows more then 16
and finally the "open MQ Count" on MQ Explorer is always 16.
Questions.
1) What do i need to change, for increasing the count of "Beans In Use Count" and "open MQ Count" on MQ Explorer to be more than 16?
2)If the Self-Tuning thread pool is 5, how come 16 beans are executed at once? or its just that 16 are picked from pool and only 5 are executed at given time?
NOTE:- I am using weblogic app server to connecto IBM MQ with JMS Module, so creating the customer WorkManager and attaching it to my listener (MDB) is not supported by weblogic, it says the mdb is not under webloic thread pool so this settingt will have no effect
-thnaks

Hi ,
You have to create a custom work manager and then you have to associate this customer work manager to the dispatch policy of the MDB to increase the threads.
Following links would surely help you as TomB has explained the same issue very well, do have a look at them.
Re: WorkManager Max thread constraints not applied to MDB
Also you can also go through this links which would help you get more information:
Topic: Configuring Enterprise Beans in WebLogic Search for "To map an EJB to a workmanager"
http://middlewaremagic.com/weblogic/?p=5665
Topic: WebLogic WorkManager with EJB3 And MaxThread Constraint
http://middlewaremagic.com/weblogic/?p=5507
Regards,
Ravish Mody
http://middlewaremagic.com/weblogic/
Come, Join Us and Experience The Magic…

Thread Pool with Min,Max. and other thread parameters

hello,
I found an Implementation of ThreadPool in the java.sun.com,but it didn't have the minimum,maximum no. of threads implemented in the code.
Could you help me find out an implementation of Thread Pool,that keeps track of minimum no. of threads,max. no. of threads in the pool,the increment size of threads,number of idle threads,idle time allowable for a thread,etc...
I also need to know if it is possible to have >5000 threads in a ThreadPool,beacuse I get OutofMemoryError,when I used a ThreadPool( which didn't have any of the above-mentioned parameters!)
Thanks!!!

Having greater then 5000 threads is a sign of a problem with your design. Threads are relativly costly
beasties. The idea of using a pool for your threads is that you won't need to use 5000 threads
simultaniously. Most OS's will have problems trying to create this many threads per process (unless you
tune the OS itself (which is normally not too difficult))
matfud

Reg. cursor-selection in module pool....have ur points.

Hi all,
Pleas. help me with a simple example of at cursor-selection in module pool programming.
with simple code & steps
Have ur points.
Regards,
[email protected]

Hi Pradeep,
The Best explanation with example comes from our help.sap.com....
http://help.sap.com/saphelp_nw04/helpdata/en/9f/dbabbd35c111d1829f0000e829fbfe/content.htm
Also this might help...
MODULE mod [ AT {EXIT-COMMAND|CURSOR-SELECTION} ]
[ ON {CHAIN-INPUT|CHAIN-REQUEST} ]
[ SWITCH switch ].
... AT CURSOR-SELECTION
The AT CURSOR-SELECTION addition at the event PAI causes the module mod to be called only if
The function used to trigger event PAI has function code "CS" and function type "S"
The cursor is placed on a single input or output field of the screen at the moment of the user action
The call occurs within the usual PAI processing, meaning that the automatic input checks defined in the system or in the ABAP Dictionary are executed and the MODULE statement is called according to its position in the event block. You can use the addition in connection with the FIELD statement.
If the PAI event is triggered under the above circumstances, the function code is not passed to sy-ucomm and the OK field. They keep their previous values.
Note
The function type and function code of a function are determined in the Screen Painter or in the Menu Painter. We recommend to assign function code "CS" in the Menu Painter to function key F2 in order to simultaneously assign the double-click function of the mouse to it. This allows you to assign dialog modules to the selection of input or output fields.
Refer thread: Re: MODULE REQUEST
Hope that helps!!
*Reward useful answers*
Regards,
Naveenan.

NIO Selector.select() enters a 100% CPU infinite loop on interruption

This issue is only reproducible in Windows.
When a thread is calling Selector.select() and the other thread interrupts the selector thread, Selector.select() enters an infinite loop taking up CPU time. All other JDKs I've tried including IBM 1.5 / 1.6, SUN 1.5 / 1.6 simply returned 0 when its interrupted. I think JRockit needs to behave similarly, without 100% CPU consumption. Here's the test code:
import java.nio.channels.Selector;
public class Main {
public static void main(String[] args) throws Exception {
final Thread mainThread = Thread.currentThread();
final Selector s = Selector.open();
new Thread() {
@Override
public void run() {
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
// Ignore.
System.out.println("interrupt()");
mainThread.interrupt();
}.start();
System.out.println("select()");
s.select(5000);
System.out.println("success");
s.close();
Expected result:
select()
interrupt()
success
Actual result:
select()
interrupt()
<stuck with 100% CPU consumption>
Version:
JRMC-3.0.3-1.5.0 - build R27.6.0-50_o-100423-1.5.0_15-20080626-2105-windows-ia32, compiled mode
JRMC-3.0.3-1.6.0 - build R27.6.0-50_o-100423-1.6.0_05-20080626-2105-windows-ia32, compiled mode

Hi,
This looks like a bug. Please open a support ticket and request a patch if you need a fix asap. If you can wait we will fix this in an upcoming release. Thank you for your help

Creating Thread Pool with Executors.newFixedThreadPool(poolSize)

I am creating a server socket and want a Thread pool to limit the number of threads created for serving each clients. I have written a code:
private ExecutorService threadPool;
//Creating a Thread Pool for handling new sessions
threadPool=ThreadPool.createSessionThreadPool(poolSize);
and in my main listen logic:
serverSocket = new ServerSocket(listenPort);
clientSocket = serverSocket.accept();
                    threadPool.execute(new Runnable(){
                         public void run(){
                              handleConnection();
and in handleConnection I am trying to read the inputstream in a while loop:
public void handleConnection(){
BufferedReader in=null;
in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
while (true) {
if((fullCommandString = in.readLine()) ==null){
wait(); // I assume that this wait will block the thread and keep the thread back in to the pool.
                    System.out.println(Thread.currentThread().getName() + " received the message");
                    System.out.println("echo: " + fullCommandString);
                    out.println("230 reply back \r\n");
why don't it keep the thread back in the pool when I call the wait() ? Is it since the thread is still active in reading the input stream? If so can any one hepl me with a snippet which will keep the thread back in the pool when there is noting on the input stream to read.

Hi,
The call to wait does not return the thread pool back to the pool. The thread will be associated with your runnable as long as your run method hasn't returned.
It looks like you instead want to use NIO if you want to use a few threads to handle many clients.
Kaj

C# compiling error: 'System.Array' does not contain a definition for 'Select' and no extension method 'Select' accepting a first argument of type 'System.Array' could be found (are you missing a using directive or an assembly reference?)

Hello experts,
I'm totally new to C#. I'm trying to modify existing code to automatically rename a file if exists. I found a solution online as follows:
string[] allFiles = Directory.GetFiles(folderPath).Select(filename => Path.GetFileNameWithoutExtension(filename)).ToArray();
string tempFileName = fileName;
int count = 1;
while (allFiles.Contains(tempFileName ))
tempFileName = String.Format("{0} ({1})", fileName, count++);
output = Path.Combine(folderPath, tempFileName );
string fullPath=output + ".xml";
However, it gives the following compilation errors
for the Select and Contain methods respectively.:
'System.Array' does not contain a definition for 'Select' and no extension method 'Select' accepting a first argument of type 'System.Array' could be found
(are you missing a using directive or an assembly reference?)
'System.Array' does not contain a definition for 'Contains' and no extension method 'Contains' accepting a first argument of type 'System.Array' could be
found (are you missing a using directive or an assembly reference?)
I googled on these errors, and people suggested to add using System.Linq;
I did, but the errors persist.
Any help and information is greatly appreciated.
P. S. Here are the using clauses I have:
using System;
using System.Data;
using System.Windows.Forms;
using System.IO;
using System.Collections.Generic;
using System.Text;
using System.Linq;

Besides your issue with System.Core, you also have a problem with the logic of our code, particularly your variables. It is confusing what your variables represent. You have an infinite loop, so the last section of code is never reached. Take a look
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.IO;
namespace consAppFileManipulation
class Program
static void Main(string[] args)
string fullPath = @"c:\temp\trace.log";
string folderPath = @"c:\temp\";
string fileName = "trace.log";
string output = "";
string fileNameOnly = Path.GetFileNameWithoutExtension(fullPath);
string extension = Path.GetExtension(fullPath);
string path = Path.GetDirectoryName(fullPath);
string newFullPath = fullPath;
string[] allFiles = Directory.GetFiles(folderPath).Select(filename => Path.GetFileNameWithoutExtension(filename)).ToArray();
string tempFileName = fileName;
int count = 1;
//THIS IS AN INFINITE LOOP
while (allFiles.Contains(fileNameOnly))
tempFileName = String.Format("{0} ({1})", fileName, count++);
//THIS CODE IS NEVER REACHED
output = Path.Combine(folderPath, tempFileName);
fullPath = output + ".xml";
//string fullPath = output + ".xml";
UML, then code

NIO readiness selection and thread pool

Similar Messages

Maybe you are looking for