Spawning multiple threads ?

Hi,
          In our application, the content of the main page is being
          retrieved from different databases. All the requests originiate from
          one JSP to different databases to retrieve the info. As the JSP
          processes each of the request sequentailly, there is considerable delay
          before the contents are displayed to the user.
          What I want to acheive is spawn multiple threads and display the content
          to the user in fractions as each thread returns. For eaxmple, if the
          user has subscribed to three news servers.. I want to be able to
          display the news from first server to the user without waiting to
          recieve response from the other two servers.
          What is the best approach to follow for such requirements ?? Any
          thoughts on this would be highly appreciated.
          Thanks,
          Sam

I think you may need to spawn it into HTML frame. Each frame will perform
          and download independently.
          Is it what you need ?
          Siros
          "sam ernie" <[email protected]> wrote in message
          news:[email protected]..
          > Hi,
          >
          > In our application, the content of the main page is being
          > retrieved from different databases. All the requests originiate from
          > one JSP to different databases to retrieve the info. As the JSP
          > processes each of the request sequentailly, there is considerable delay
          > before the contents are displayed to the user.
          >
          > What I want to acheive is spawn multiple threads and display the content
          > to the user in fractions as each thread returns. For eaxmple, if the
          > user has subscribed to three news servers.. I want to be able to
          > display the news from first server to the user without waiting to
          > recieve response from the other two servers.
          >
          > What is the best approach to follow for such requirements ?? Any
          > thoughts on this would be highly appreciated.
          >
          > Thanks,
          >
          > Sam
          >

Similar Messages

Servlet spawning multiple threads causes server to freeze PC

I'm attempting to write a servlet which, upon receipt of a particular GET request, spawns a thread to do various work which can then be queried by a different GET request. A third type of GET request stops a specified thread.
This is working fine, except that I can only seem to have spawned one thread at a time. When I spawn another thread, my entire PC stops responding (even Windows Task Manager becomes so sluggish that I cannot kill the server) , and I have to do a hard reset of my PC. I'm using Sun Java System Application Server. The server logs do not contain any errors. I've tried the NetBeans debugger a bit, and it seems to happen when I call the start() method of the Thread.
This is my first experience with servlets, as well as my first experience with Sun Java System Application Server. I'm also not a Java expert by any means. I'm sure I'm doing something stupid, but I haven't a clue what.
I can post my code if necessary, but does anyone have any idea what could be causing the server to stop responding just because a servlet spawns two threads? Should I post my code?
Sorry if this is a n00b question. Thanks in advance.

I think you may need to spawn it into HTML frame. Each frame will perform
          and download independently.
          Is it what you need ?
          Siros
          "sam ernie" <[email protected]> wrote in message
          news:[email protected]..
          > Hi,
          >
          > In our application, the content of the main page is being
          > retrieved from different databases. All the requests originiate from
          > one JSP to different databases to retrieve the info. As the JSP
          > processes each of the request sequentailly, there is considerable delay
          > before the contents are displayed to the user.
          >
          > What I want to acheive is spawn multiple threads and display the content
          > to the user in fractions as each thread returns. For eaxmple, if the
          > user has subscribed to three news servers.. I want to be able to
          > display the news from first server to the user without waiting to
          > recieve response from the other two servers.
          >
          > What is the best approach to follow for such requirements ?? Any
          > thoughts on this would be highly appreciated.
          >
          > Thanks,
          >
          > Sam
          >

Spawning multiple threads inside a Servlet

Hi All,
We have a situtation where we need to crawl various sites/databases for information to perform a search. As we all know, the most efficient way is to multithread the application. Since J2EE discourages custom Multithreading, we had to search for alternatives to accomplish this task.
We came across few interesting solutions using JMS/MDB. Other than using these is there a simpler way to accomplish this. Any help is appreciated...
Thanks,
Srini

oc4j/orion is the fastest servlet engine on the planet. Those
guys in Sweden don't let you mess around with the number of
servlet instances available. The message here is that you do not
have to resort to any tricks that other servlet engines use to
make sure your servlet will be available to be served up...it
will.
The only thing that slows it down are lack of memory or lack of
resources (the database isn't replying fast enough). You can
solve these problems by clustering your servers on several
machines.
regards,
the elephantwalker
www.elephantwalker.com

Need to spawn multiple Automator app threads

I have an AppleScript that runs on a folder action when files are dropped in.
Each item triggers the same Automator app that FTPs the file.
Problem arises when the files come in faster than the Automator app finishes each FTP job, so some are skipped. If i could have the AppleScript somehow spawn multiple Automator app threads, this would be solved.
How would you go about solving it (sorry, can't slow down the incoming files)?
Mac OS X (10.4.7)

anyone?

Executors.newSingleThreadScheduledExecutor() creating multiple threads?

While examining a stack trace this morning, I found approximately 250 idle threads labelled "pool-4-thread-###", where ### ranged from 1 to 250 or so.
I then traced pool-4-thread to a ScheduledExecutorService and underlying ThreadPoolExecutor object created via a call to Executors.newSingleThreadScheduledExecutor().
There are two types of tasks scheduled on that instance of the Executor. The first is a task which runs twice a day. The second type is something that gets scheduled as the result of a user action, which may occur dozens of times a day.
Under what conditions can a SingleThreadScheduledExecutor create and leave around multiple threads?
Thanks in advance,
Mike Benveniste

If the thread never completes.
It's either hanging, or, more likely, has an exit condition that's never being met. Or it's spawning processes that are not completing.
Simply put a debug statement at the beginning and end of the thread so you can see when (and if) it's starting and stopping.
You may want to use object.killProcess() prior to starting the next instance to force the previous instance to stop if it still exists.
bcf

Can multiple threads use same transaction concurrently?

          Is it possible that same transaction is being used by multiple threads concurrently
          in WLS? If each thread is doing suspend and resume how does it work? Does the
          transaction implementation support it? Is there a way to do it?


Why you don't tell us some more about your application?
          I'm assuming this is a relatively long running transaction if run
          serially. One common solution is to break this type of workflow into
          several separate transactions with queues between them.
          -- Rob
          Karambir Singh wrote:
          > Is there any workaround for this? I mean to something like explicitly associating
          > the txn with user created threads.
          >
          > "krishna" <[email protected]> wrote:
          >
          >>Transaction context cannot be propagated to user created Threads.
          >>-Krishna
          >>"Karambir Singh" <[email protected]> wrote in message
          >>news:[email protected]...
          >>
          >>>I'm starting a transaction in main thread and this thread spawns three
          >>
          >>threads.
          >>
          >>>I want updates done in main transaction and updates done in three child
          >>
          >>threads
          >>
          >>>to be part of the same transaction. The transaction is finally commited
          >>
          >>by
          >>main
          >>
          >>>thread.
          >>>
          >>>
          >>>
          >>>
          >>>
          >>>"Dimitri I. Rakitine" <[email protected]> wrote:
          >>>
          >>>>What are you trying to do ?
          >>>>
          >>>>Karambir Singh <[email protected]> wrote:
          >>>>
          >>>>
          >>>>>Is there any workaround to do this?
          >>>>
          >>>>>"Dimitri I. Rakitine" <[email protected]> wrote:
          >>>>>
          >>>>>>No, it is associated with a thread which started it.
          >>>>>>
          >>>>>>Karambir Singh <[email protected]> wrote:
          >>>>>>
          >>>>>>
          >>>>>>>Is it possible that same transaction is being used by multiple
          >>
          >>threads
          >>
          >>>>>>concurrently
          >>>>>>
          >>>>>>>in WLS? If each thread is doing suspend and resume how does it
          >>
          >>work?
          >>
          >>>>>>Does the
          >>>>>>
          >>>>>>>transaction implementation support it? Is there a way to do it?
          >>>>>>
          >>>>>>--
          >>>>>>Dimitri
          >>>>>>
          >>>>
          >>>>--
          >>>>Dimitri
          >>>>
          >>>
          >>
          >

Multiple Threads and Loggers

I have a program that spawns off multiple threads. I want each thread to have its own logger and file name. The catch is that the file names must be dynamic.
Basically, each thread should have its own log file.
I'm using commons-logging.
I know one suggestion is to let it all log into one file, and then parse afterwards. I figured that if the only way the log file is readable is in its parsed form, why not try to create these parsed files from the program itself.

dewalt wrote:
I have a program that spawns off multiple threads. I want each thread to have its own logger and file name. The catch is that the file names must be dynamic.
Basically, each thread should have its own log file. Sounds like a bad idea to me.
I know one suggestion is to let it all log into one file, and then parse afterwards. I figured that if the only way the log file is readable is in its parsed form, why not try to create these parsed files from the program itself.Because if you are spending all your time reading a log file then either there is something seriously wrong with your code or something seriously wrong with your requirements.
You read a log file because there is a problem in production.
So now you have 20 or 300 log files to look at just to find the problem. And operations has to collect those 20 or 300 files so you can look at them in the first place. (Or maybe 40 to 600 because the problem happen sometime between yesterday and today.)
Then you have to assume that there is absolutely no intentional interaction between the threads at all. Because if there is then obviously you are going to be looking at more than one file (and finding it) anyways.
And what if there is an unintentional interaction? How are you going to even figure that out, since you won't have a semi-accurrate timeline of all the threads running at that time.....without puting all of the log files back together.

Can Java Spawn multiple processes?

I see that Directory proxy server is spawning multiple processes. Is this really possible? How should one shut down this process? kill -15 did not kill child process
Operation System is Solaris 10.
-bash-3.00$ ptree 27450
27450 /usr/jdk/instances/jdk1.6.0/bin/java -Xss128k -Xmx1400M -Xms1400M -XX:NewSize=1
27789 /usr/jdk/instances/jdk1.6.0/bin/java -Xss128k -Xmx1400M -Xms1400M -XX:NewSize=1
27790 /usr/jdk/instances/jdk1.6.0/bin/java -Xss128k -Xmx1400M -Xms1400M -XX:NewSize=1
Thanks!

Because on linux threads are implemented as standard processes but on other
platform like windows and solaris they are not processes.

How to protect the creation of a db across multiple threads/processes?

Given a multi-process, multi-threaded application, and one database file to be created, how can I guarantee that only one of the threads in one of the processes successfully creates the database, when ALL of the threads are going to either attempt to create it, or open it (if it already exists) upon startup?
My current logic for all threads is:
set open flags to DB_THREAD
start transaction
attempt to open the db
if ENOENT
abort transaction
change open flags to DB_CREATE | DB_EXCL | DB_THREAD
retry
else if EEXIST
abort transaction
change open flags to DB_THREAD
retry
else if !ok
# some other error
end
commit transaction
I'm testing on Linux right now, with plans to move to Windows, AIX, and Solaris. What I'm experiencing on Linux is several of the threads (out of 10 threads I'm testing) will succeed in creating the database. The others will receive either either succeed in opening the first time through, or will receive the EEXIST when they do the open w/ create flags - ultimately, they open the same created db (I'm presuming the last one that's created by one of the other threads). Effectively, the open with DB_CREATE | DB_EXCL is not ensuring that only one DB is created. I was under the impression that opening in a transaction would guarantee this, but it does not, or maybe I'm doing something incorrectly?
Should DB_CREATE | DB_EXCL and opening in a transaction guarantee that only one thread can create the database? Do I need to use another synchronization method?
Note: I am running off of a local disk, not over NFS or anything like that.
I tried taking out my transaction and using DB_AUTO_COMMIT instead, still no go - multiple threads still report they successfully created the DB. Using BDB 4.5.
Thanks,
Kevin Burge

Brian,
Thanks for the reply. I think I'm doing what you said, unless I'm misunderstanding. I do have all threads try to do the DB_CREATE | DB_EXCL. Are you saying I shouldn't use the DB_EXCL flag?
The problem I was seeing with 10 threads calling open w/ DB_CREATE | DB_EXCL on the same db:
* Between 1 and 9 threads would return success from db->open with the creation flags.... but the last one to create "wins".
* All the other threads would get EEXIST, as expected.
The threads that "lost", do get a successful return code from "open" with the create flags, but all data written to them is lost. They act normally except for the fact that the have a deleted file-handle that they are writing to. There's no indicator that records written to them are going into the void.
My test:
I had 10 threads each trying to create or open a recno db, then append 10 records, for a total of 100 records expected. Ultimately, I would end up with between 20 to 100 records in the db, depending on how many of the threads said they successfully created the db. So, if 5 threads said they created the db successfully, then 40 records would be missing, because 4 of those threads were writing to deleted file handles. If 2 threads said they created the db, then 10 records would be missing....If 8 threads, then 70 records missing, etc.
In other words, multiple threads creating the db appears to work correctly, because there are no errors. It was the missing records that caught my attention, and prompted my question on this forum.
For what it's worth, I've worked around the problem by opening a similarly named file via the open() system call, with O_CREAT|O_EXCL, which is guaranteed to be atomic. The first thread that can create this temp file is the only thread that can actually create the db - all others sleep upon open with ENOENT until it's created.
Thanks,
Kevin

Multiple Thread of a xml publisher report - messed up fonts in the PDF out

We are running 60000 invoices at a given time. In order to get the job done faster, the xml publisher report is set up to run mulitple threads. Each thread running unique set of invoices.
I am seeing this issue, randomly.
The pdf output of the invoice is having the fonts messed up. font 10 shows up as 14 and the invoice looks very bad.
When i rerun the same set of invoices it looks absolutely normal.
Also if I retrieve the xml output of the bad pdf and view it through the xmlpub desktop, it looks perfectly fine.
Two times we saw this issue
PRODUCTION
- when i run 8 threads, i saw this issue in one of the thread and affected one invoice. (Production- 1 concurrent processing node+ 5 OPP processes and 5 threads + MEMORY is J:oracle.apps.fnd.cp.gsf.GSMServiceController:-mx3072m )
TEST INSTANCE
- when i ran with 16 threads, one of the thread running xml pub report affected all the invoices (UAT environment-1 concurrent processing node+ 7 OPP processes and 1 threads + MEMORY is J:oracle.apps.fnd.cp.gsf.GSMServiceController:-mx3072m )
Looks like it is happening when running multiple threads.
The formatting command or information is getting lost somewhere and the report is all messed up.
Please advise.
Thanks
SJ

Really appreciate your response. Can you pls give little more details.
1] Are there any standard API's which I can use to submit XML publisher report from the JSP pages
2]Is there any sample code snippet for any of the options that I can refer to..or pls let me know the API's, I will check on them
Appreciate any help

PrinterException when multiple threads try to print report using JRC

Iam using Crystal Report's JRC for printing reports, it works fine.
But the problem araises when i use multiple threads.
I used the following:
reportClientDocument.getPrinterOutputController().printReport(.....); to print.
I get the following exception
Caused by: java.awt.print.PrinterException: No printer named "\\ch03\printer05" could be found.
Without multiple thread it works fine.
I have been scratching my head for days on this problem, any help is very much appreciated..

If an API doesn't specifically say that it is thread safe then it isn't likely to be thread safe and the only way to approach it is to assume that it isn't.

How do i use multiple threads( very much real time), using JavaFX?

I'm creating an application, using JavaFX because one can create awesome GUI using JavaFX. I need to know how to create real time multiple threads using javafx.
JavaFX doesn't support creation of multiple threads, but i think there is another way of doing it. I need it work in real time as my application works with an hardware (wacom intous 3 tablet), and i need mutiple threads to get all the parameters from the stylus of the tablet simultaneously...
any code which will help me out or explaination on how to go about this is appreciated...
Help required quickly...

See example at
[http://jfxstudio.wordpress.com/2009/06/09/asynchronous-operations-in-javafx/|http://jfxstudio.wordpress.com/2009/06/09/asynchronous-operations-in-javafx/]

Problem with multiple threads accessing the same Image

I'm trying to draw into one Image from multiple threads. It works fine for a while, but then suddenly, the image stops updating. Threads are still running but the image won't update. I'm using doublebuffering and threads are simply drawing counters into Image with different speed.
It seems like the Image gets deadlocked or something. Anyone have any idea what's behind this behavior or perhaps better solution to do such thing.
Any help will be appreciated.

Sorry Kglad, I didn't mean to be rude. With "No coding
errors" I meant the animation itself runs with no errors. I'm sure
you could run the 20 instances with no freezing (that's why I put
the post :) ) But I'm affraid it is an animation for a client, so I
cannot distribute the code.
Perhaps I didnt explain the situation clearly enough (in part
because of my poor english...).-
- By 20 instances I mean 20 separated embedded objects in the
html
- The animation is relatively simple. A turned on candle, in
each cycle I calculate the next position of the flame (that
oscilates from left to right). The flame is composed by 4
concentric gradients. There is NO loops, only an 'onEnterFrame'
function refreshing the flame each time.
- It's true that I got plenty variables at the _root level.
If that could be the problem, how can I workaround it?
- It is my first time trying to embed so many objects at the
same time too. No idea if the problem could be the way I embed the
object from the html :(
- The only thing I can guess is that when a cycle of one of
the object is running, the other 19 objects must wait their turn.
That would explain why the more instances I run, the worst results
I get. In that case, I wonder if there's a way to run them in a
kind of asynchronous mode, just guessing...
Any other comment would be appreciated. Anyway, thanks a lot
everybody for your colaboration.

How to use multiple threads and swing for displaying status/interaction

I have a Swing-app which have to show progress and allow userinteraction for these tasks:
* First:
retrieve a list of IDs(String) from the database (single thread running)
* Second:
some work on the id-list and list written to hd (same thread as above)
* Third:
retrieve Objects (based on the id-list) from different sources (Multiple Threads are running)
To show the status I have a JProgressBar (indeterminate while task1&2 running) and
a JTextArea showing the current status (connect,retrieve list, sort, ...)
When task3 is starting the JTextArea have to disappear and be replaced by a ScrollPane
with an array of Labels/TextAreas showing the status of each thread.
While theses threads are working, the ID-list will be consumed and the JProgressBar
shows the remaining precentage of the hole progress.
Everything is working so far (excepts UI :) , the problem(s) I have:
I need the threads to interacts with the user through the ui. e.g: "Connection to db-xyz lost! reconnect?"
But I don´t know how to do this correctly.
I think one way would be to send an event to the ui... but how?
(the ui must know which thread is calling to unpause it after user answered)
I know that threads should NOT change the swing(-container) - How do I notify the ui that a thread has a question?
Since these threads are really time-consuming the UI is not updated frequently,
how can I increase this? (perhaps using another thread-priority?)
thanks for help!

if/when your threads need to interact with the UI, they can create a Runnable & send it to SwingUtilities.invokeLater or invokeAndWait. This Runnable can popup a message to the user, and act on the choice of the user (reconnect, cancel, ...). This action could be something which "unpauses" the task thread.
You may need to do synchronisation between the code in the Runnable & the Thread to which it is related - so the latter Thread knows when the user has made the choice.

Suddenly, I've been put on multiple threads over multiple firefox problems, which is filling up my inbox. How do I get out of these?

Details? I posted a question about one problem (for which no answers have been offered, but that's okay) and somehow, I've become part of multiple threads about various firefox problems. I have no interest in any of these questions/problems.
How do I get out of these threads? I get about 15-20 emails a day! Firefox is by far the worst community I've even been dragged into....

Sorry you are having problems.
Have a look at your settings in the dropdown from the username or https://support.mozilla.org/en-US/users/settings
Not too sure what you could subscribe to accidentally that causes that behaviour though.
It would be interesting to know what option caused all the email. If something has gone wrong and you are getting e-mails that you should not be getting we can refer this to the admins to look into. The Firefox sumo community certainly does not intentionally spam, and if you are having a problem lets find out more, because others may have a problem and not have reported it.

Spawning multiple threads ?

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