When to acknowledge when dispatching using multiple threads?

So on a project I'm working on I read from a queue and I dispatch to a thread pool that has worker threads and the general idea is that I never want to acknowledge a message until I know for sure that I've processed it otherwise it risks becoming lost.
There are two approaches
1. is to acknowledge the message immediately after the details have been written to a working table and then in the event that the client restarts you pickup messages from this table prior to processing any new ones from the queue. upon processing each message you update it's state or delete the row from this table to reflect that it's no longer working.
2. another approach is to queue up acknowledgements in the main message listener thread such that as each worker thread completes it's job it enqueues the message for acknowledge by the main delivery thread (async). ie. the same thread that is picking up the messages. So after pulling a message from the queue and having dispatched it you then at the end of the cycle work thru the queue to acknowledge the messages that has been queued up by the worker threads to be acknowledged. One thing about this is that acknowleding a message implicitly acknowledges all those prior unacknowledged messages it's probably overkill to be acknowledging every message in the "queue." You just want to acknowledge the most recent one.
I believe that option 2 results in less work since there's no round trips to the database necessary to maintain a working table.
Websphere's MQ in JMS requires that you acknowledge in the delivery thread so unless you do it immediately or after processing each message you have to maintain a working table if you want to guarantee that any message pulled off the queue was actually processed and not lost along the way.

steffi wrote:
So on a project I'm working on I read from a queue and I dispatch to a thread pool that has worker threads and the general idea is that I never want to acknowledge a message until I know for sure that I've processed it otherwise it risks becoming lost.
There are two approaches
1. is to acknowledge the message immediately after the details have been written to a working table and then in the event that the client restarts you pickup messages from this table prior to processing any new ones from the queue. upon processing each message you update it's state or delete the row from this table to reflect that it's no longer working.
2. another approach is to queue up acknowledgements in the main message listener thread such that as each worker thread completes it's job it enqueues the message for acknowledge by the main delivery thread (async). ie. the same thread that is picking up the messages. So after pulling a message from the queue and having dispatched it you then at the end of the cycle work thru the queue to acknowledge the messages that has been queued up by the worker threads to be acknowledged. One thing about this is that acknowleding a message implicitly acknowledges all those prior unacknowledged messages it's probably overkill to be acknowledging every message in the "queue." You just want to acknowledge the most recent one.
I believe that option 2 results in less work since there's no round trips to the database necessary to maintain a working table.certainly. but how exactly does it achieve your reliability goals from the first paragraph?
Websphere's MQ in JMS requires that you acknowledge in the delivery thread so unless you do it immediately or after processing each message you have to maintain a working table if you want to guarantee that any message pulled off the queue was actually processed and not lost along the way.sounds about right, yes.

Similar Messages

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.

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/]

Is there any problem to use multiple threads to send email with JavaMail

Dear all,
I am using JavaMail 1.3.2 to send emails with SMTP, it works very well for a long time.
But one day, I found that the email service hanged and I could never send email again until I restart the tomcat. I found that the reason was a deadlock had been created, the required resource for sending email had not been released.
I guess the error is due to multiple threads are sending email at the same time. I made a test to create seperate thread for sending each email. After few days, I found this deadlock happened again. So, my question is: Can I use JavaMail with multiple threads? If not, I may need to sychronized all the thread that using JavaMail. I would like to make sure this is the reason for causing the deadlock problem.
Here is part of my code for using JavaMail:
transport = session.getTransport("smtp");
transport.connect(email_host, smtp_user, smtp_pass);
message.saveChanges();
transport.sendMessage(message,message.getAllRecipients());
which is very standard call, and it worked well for a long time.
Here is part for my thread dump on tomcat:
(Thread-339)
- waiting to lock <0x5447c180> (a sun.nio.cs.StandardCharsets)
(Thread-342)
- locked <0x5447c180> (a sun.nio.cs.StandardCharsets)
It seems that these happened after call the method transport.sendMessage() or message.updateChanges()
, and the underlying implementation may require the JRE StandardCharsets object. But the object had been locked and never be released. So, the sendMessage() or updateChanges() can't be completed.
Please give me some helps if you have any idea about it.
Thanks very much!
Sirius

Note that the Nightly build gets updated daily (and sometimes more than once in case of a respin) and it is always possible that something goes wrong and it doesn't work properly, so be prepared for issues if you decide to stay with the Nightly build and make sure to have the current release with its own profile installed as well in case of problems.
See also:
* http://kb.mozillazine.org/Testing_pre-release_versions
*http://kb.mozillazine.org/Creating_a_new_Firefox_profile_on_Windows
*http://kb.mozillazine.org/Shortcut_to_a_specific_profile
*http://kb.mozillazine.org/Using_multiple_profiles_-_Firefox

Client/Server in one program (using multiple threads)?

Is there some examples out there of how to use a client and server in a single program using separate threads? Also, is it possible to start a third thread to control the packets, such as drop a random or specified number of packets (or match on specific data in a packet)?

Just trying to have a client send udp packets to a server (all on the same machine running from the same program) and want to be able to drop packets coming from the client side to the server side.
E.g.,
Here's an example that I found here: http://compnet.epfl.ch/tps/tp5.html
import java.io.<strong>;
import java.net.</strong>;
import java.util.<strong>;
/</strong>
* Server to process ping requests over UDP.
public class PingServer {
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          Random random = new Random();
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}I'm looking to do the "processing loop" in a separate thread, but I'd also like to do the client in a separate thread
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Modifying the stack class to use multiple threads

Im trying to re write the stack class but with using 2 threads. One of the thread calls the pop method and the other calls the push method.
I don't know where im going wrong...
Any tips would be great thnx
Haven't bothered putting in any try / catch clauses yet, will make it look pretty later :)
http://nopaste.php-q.net/19555

java.util.Stack is thread safe so all you need to do are create two threads
one which pushes data onto the stack and one which pops it off.
class PushThread implements Runnable {
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would force an ordering onto the stack. The code instead goes into a
loop that should waste time.
your PopThread class will be identical but will call stack.pop() instead.
matfud

How to decrease CPU usage when using multiple threads?

I am using vb.net , .NetFramework 2.0 .
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I observed that all threads works at the same time. how to make each thread wait until the second ends?
This is my code. The problem is in function updateThreaded2().
Please I need quick help. Thanks
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For j As Integer = 0 To threadcount - 1
If threads(j) Is Nothing Then
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threads(j) = New SUTC(Me.Stocks(i), Me.DefaultService, AdjustSplits, Use20Minutes, l)
threads(j).Thread.Priority = Threading.ThreadPriority.BelowNormal
threads(j).Thread.IsBackground = True
threads(j).Thread.Start()
i += 1
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If i < Me.Stocks.Count Then
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threads(j).Thread.Start()
i += 1
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End If
Next
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For j As Integer = 0 To threadcount - 1
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pending = threadcount
tempcount = 0
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When the market is opened, stock prices changed every 500 ms . You can see this change on google finance.
I figured as much, but my thoughts are that if you can somehow find a way to make your program more event driven, then it may be possible to reduce unnecessary looping...
“If you want something you've never had, you need to do something you've never done.”
Don't forget to mark
helpful posts and answers
! Answer an interesting question? Write a
new article
about it! My Articles
*This post does not reflect the opinion of Microsoft, or its employees.

Connection problems when I use multiple Airport Expresses

I have one Mac that I use to stream music to multiple Airport Express's. Its seems that when I connect to 3 expresses things work fine. If I connect to 4 the sound cuts out on all speakers.
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Yes you can but....
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Sonus are good but $$$. by then rewire!

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It's recommended to download and install
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Using Multiple Threads

I'm pretty new to Java and am currently working on this assignment for one of my classes:
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Below is the portion of code on the client side that works for transfer and play, but not for streaming.
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<<<CODE>>>
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Well nix that I managed to have a breakthrough and got things working. =)
Cheers!

Will using multiple threads get me my curry in a hurry?

Mr. Singh says no, but I say otherwise. What say you all?
http://blogs.phillynews.com/inquirer/foodanddrinq/2007/12/you_cant_hurry_curry.html
Just a minor diversion from ongoing production issues...
:-(

Well nix that I managed to have a breakthrough and got things working. =)
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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 to proces the record in Table with multiple threads using Pl/Sql & Java

I have a table containing millions of records in it; and numbers of records also keep on increasing because of a high speed process populating this table.
I want to process this table using multiple threads of java. But the condition is that each records should process only once by any of the thread. And after processing I need to delete that record from the table.
Here is what I am thinking. I will put the code to process the records in PL/SQL procedure and call it by multiple threads of Java to make the processing concurrent.
Java Thread.1 }
Java Thread.2 }
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Java Thread.n }
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I am very much familiar with PL/SQL code. Only issue I am facing is How to fetch/process/delete the record only once.
I can change the structure of table to add any new column if needed.
Thanks in advance.
Edited by: abhisheak123 on Aug 2, 2009 11:29 PM

Check if you can use the bucket logic in your PLSQL code..
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Regards
Arun

A hint if you use multiple mail clients to check one IMAP account

FYI:
Mail.app in leopard turns on an advanced "push" mail feature automatically, called IDLE. This can cause strange problems when you use multiple IMAP clients to access you IMAP server.
For instance, I have a computer in my office and one in my lab. Normally Mail.app is running on them both constantly. After installing Leopard I would sit in my office delete and move messages from my INBOX, and when I went down to the lab I would find those emails still in my INBOX and also in the mailboxes I had moved them to on my office machine. In very short order I ended up with multiple copies of emails in many places and no ability to actually delete mail.
Originally I thought this was a bug with Leopard Mail.app, or a problem with compatibility between Mail.app and the UW IMAP server that I use. I wasted significant time searching on the web for possible solutions.
It turns out that the IDLE feature (that is automatically turned on for you in Leopard) was the cause of my problems. Turning this feature off (in the Advanced pane of the accounts setting) on EACH machine caused me email to return to its previous functional state.
If you only use one IMAP mail client the IDLE feature is nice, it pushes new mail to you as soon as the IMAP server receives the new mail.
(note -- IDLE is also automatically turned on in Thunderbird)

Assuming you're on a NAT'd network, DNS services can cause all sorts of weird errors with the mail server, including spontaneous name changes.
To verify local DNS services, launch Terminal.app from Applications > Utilities and issue the following harmless diagnostic message:
sudo changeip -checkhostname
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When to acknowledge when dispatching using multiple threads?

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