Threading in web Application

Discussion in 'Java' started by Ershad, Apr 24, 2007.

  1. Ershad

    Ershad Guest

    I have a Question about Threading In webApplication,
    J2ee Support threading! Is it Usefull for web appliction?
    if you know php does not support Threading without any problem in web
    application
     
    Ershad, Apr 24, 2007
    #1
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  2. Ershad

    Lew Guest

    Ershad wrote:
    > I have a Question about Threading In webApplication,
    > J2ee Support threading! Is it Usefull for web appliction?
    > if you know php does not support Threading without any problem in web
    > application


    JEE containers are multi-threaded, so generally web apps do "support"
    threading, however it is extremely bad practice and a source of multiple bugs
    for the web-app developer to explicitly manipulate threads.

    It is better to write thread-safe code but not to spawn any threads of your
    own, in web-app development.

    --
    Lew
     
    Lew, Apr 24, 2007
    #2
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  3. Ershad

    Daniel Pitts Guest

    On Apr 24, 4:59 am, Lew <> wrote:
    > Ershad wrote:
    > > I have a Question about Threading In webApplication,
    > > J2ee Support threading! Is it Usefull for web appliction?
    > > if you know php does not support Threading without any problem in web
    > > application

    >
    > JEE containers are multi-threaded, so generally web apps do "support"
    > threading, however it is extremely bad practice and a source of multiple bugs
    > for the web-app developer to explicitly manipulate threads.
    >
    > It is better to write thread-safe code but not to spawn any threads of your
    > own, in web-app development.
    >
    > --
    > Lew


    Why is that Lew? Concurrency programming is trickier than serial
    programming, but since your webapp is possibly concurrent anyway, you
    should learn how that effects your design...

    Knowing this, you should also know what is safe to do as far as
    spawning your own threads. In general, this means using proper
    synchronization constructs, and limiting the number of threads created
    so that they don't cause a problem.

    There are cases where spawning multiple threads for a single request
    make sense. If you have a request that needs to access two separate
    high-latency data sources, it makes sense to do them concurrently.
     
    Daniel Pitts, Apr 25, 2007
    #3
  4. Ershad

    Lew Guest

    Lew <> wrote:
    >> JEE containers are multi-threaded, so generally web apps do "support"
    >> threading, however it is extremely bad practice and a source of multiple bugs
    >> for the web-app developer to explicitly manipulate threads.
    >>
    >> It is better to write thread-safe code but not to spawn any threads of your
    >> own, in web-app development.


    Daniel Pitts wrote:
    > Why is that Lew? Concurrency programming is trickier than serial
    > programming, but since your webapp is possibly concurrent anyway, you
    > should learn how that effects your design...


    > Knowing this, you should also know what is safe to do as far as
    > spawning your own threads. In general, this means using proper
    > synchronization constructs, and limiting the number of threads created
    > so that they don't cause a problem.


    > There are cases where spawning multiple threads for a single request
    > make sense. If you have a request that needs to access two separate
    > high-latency data sources, it makes sense to do them concurrently.


    I am concerned with the additional difficulties of thread management when the
    Web container itself is trying to manage threads. Concurrent programming is
    fraught with peril even when the programmer has a measure of control over the
    whole process. In a Web container with multiple applications existent
    ignorant of each other, and its own thread policies, small mistakes can have
    devastating consequences.

    I'm sure it's possible and even occasionally useful to explicitly spawn
    threads in a web container environment, but there is much more care needed not
    to interfere with what the web container does. A badly managed thread could
    damage not only the application that spawned it but every application running
    on the server.

    Your example seems to imply a limited context where threads are born and die
    within the handling of a single request. There the risks are much more
    contained, and an error-free implementation seems easier. For such a thing I
    can see a smart programmer making good use of the idiom, but it isn't
    something to abuse or take lightly.

    I would never make a blanket statement about never doing something.

    --
    Lew
     
    Lew, Apr 25, 2007
    #4
  5. Ershad

    Wojtek Guest

    Lew wrote :
    > Lew <> wrote:
    >>> JEE containers are multi-threaded, so generally web apps do "support"
    >>> threading, however it is extremely bad practice and a source of multiple
    >>> bugs
    >>> for the web-app developer to explicitly manipulate threads.
    >>>
    >>> It is better to write thread-safe code but not to spawn any threads of
    >>> your
    >>> own, in web-app development.

    >
    > Daniel Pitts wrote:
    >> Why is that Lew? Concurrency programming is trickier than serial
    >> programming, but since your webapp is possibly concurrent anyway, you
    >> should learn how that effects your design...

    >
    >> Knowing this, you should also know what is safe to do as far as
    >> spawning your own threads. In general, this means using proper
    >> synchronization constructs, and limiting the number of threads created
    >> so that they don't cause a problem.

    >
    >> There are cases where spawning multiple threads for a single request
    >> make sense. If you have a request that needs to access two separate
    >> high-latency data sources, it makes sense to do them concurrently.

    >
    > I am concerned with the additional difficulties of thread management when the
    > Web container itself is trying to manage threads. Concurrent programming is
    > fraught with peril even when the programmer has a measure of control over the
    > whole process. In a Web container with multiple applications existent
    > ignorant of each other, and its own thread policies, small mistakes can have
    > devastating consequences.


    Only if my thread in some way interacts with the web container threads.
    If the threads I kick off are "self contained" within my code context,
    then having threads does not impact the web container.

    I have several housekeeping threads which live in the application
    object.

    > I'm sure it's possible and even occasionally useful to explicitly spawn
    > threads in a web container environment, but there is much more care needed
    > not to interfere with what the web container does. A badly managed thread
    > could damage not only the application that spawned it but every application
    > running on the server.
    >
    > Your example seems to imply a limited context where threads are born and die
    > within the handling of a single request. There the risks are much more
    > contained, and an error-free implementation seems easier. For such a thing I
    > can see a smart programmer making good use of the idiom, but it isn't
    > something to abuse or take lightly.


    Consider a request which takes a long time to process, say over 2
    minutes. Within that time period, most browsers will time out. The user
    sees the time out, and re-tries the request. Now TWO processes are
    running this long request.

    OTOH, the first request could spawn a thread to do the work, place it
    in the session, then return to the user. Each request after that checks
    to see if the thread has finished, and if so re-directs the user to the
    result.

    --
    Wojtek :)
     
    Wojtek, Apr 25, 2007
    #5
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