Is load testing a web service with seperate threads from one machinethe same as a single thread from

Discussion in 'Java' started by ses, Mar 25, 2011.

  1. ses

    ses Guest

    Well the title says it all really, I was wondering if testing a web
    service for the load it can take in terms of simultaneous requests by
    using multiple threads from one machine is essentially the same /
    emulates the conditions as testing it from separate machines using one
    thread per machine?

    I think obviously there is some difference, but fundamentally are you
    essentially testing the ability of something to scale by doing
    multiple threads from the same machine?

    Thanks.
    ses, Mar 25, 2011
    #1
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  2. ses

    Lew Guest

    Re: Is load testing a web service with seperate threads from onemachine the same as a single thread from seperate machines?

    On 03/25/2011 06:55 AM, ses wrote:
    > Well the title says it all really, I was wondering if testing a web
    > service for the load it can take in terms of simultaneous requests by
    > using multiple threads from one machine is essentially the same /
    > emulates the conditions as testing it from separate machines using one
    > thread per machine?
    >
    > I think obviously there is some difference, but fundamentally are you
    > essentially testing the ability of something to scale by doing
    > multiple threads from the same machine?


    What does "essentiallY" mean?

    Can one machine generate the load profile you want to use for your test? What
    happens when you try?

    --
    Lew
    Honi soit qui mal y pense.
    http://upload.wikimedia.org/wikipedia/commons/c/cf/Friz.jpg
    Lew, Mar 25, 2011
    #2
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  3. ses

    Esmond Pitt Guest

    Re: Is load testing a web service with seperate threads from onemachine the same as a single thread from seperate machines?

    The first thing you will discover is that multiple logical clients on a
    single physical host will exhaust the port space with outbound
    connections and start incurring BindExceptions. This doesn't happen with
    multiple physical client hosts. So you may not even be able to get to
    the required number of simultaneous connections. Windows limits this
    space to a few thousand.
    Esmond Pitt, Mar 28, 2011
    #3
  4. ses

    ses Guest

    Re: Is load testing a web service with seperate threads from onemachine the same as a single thread from seperate machines?

    On Mar 28, 3:32 am, Esmond Pitt <> wrote:
    > The first thing you will discover is that multiple logical clients on a
    > single physical host will exhaust the port space with outbound
    > connections and start incurring BindExceptions. This doesn't happen with
    > multiple physical client hosts. So you may not even be able to get to
    > the required number of simultaneous connections. Windows limits this
    > space to a few thousand.


    Thanks for the insight, a few thousand connections should do for me,
    in fact if I could test at least 100 simultaneous connections that
    would be suitable for now. I suppose the take home message is to try
    it and see what the load looks like by logging from the web service
    itself.

    Out of interest would it be any different if I used a server with a
    number of virtual machines? (Not that I really have that level of
    resources available to me!)
    ses, Mar 28, 2011
    #4
  5. ses

    Esmond Pitt Guest

    Re: Is load testing a web service with seperate threads from onemachine the same as a single thread from seperate machines?

    On 29/03/2011 6:33 AM, ses wrote:
    > Out of interest would it be any different if I used a server with a
    > number of virtual machines? (Not that I really have that level of
    > resources available to me!)


    *Everything* that represents a difference between the testing
    environment and the deployment environment is significant. In this case
    you would testing the server with 1/N less CPU power than would be
    available if there were N physical rather than virtual servers. Prety
    significant, don't you think?
    Esmond Pitt, Mar 29, 2011
    #5
  6. ses

    Lew Guest

    Re: Is load testing a web service with seperate threads from onemachine the same as a single thread from seperate machines?

    Esmond Pitt wrote:
    > ses wrote:
    >> Out of interest would it be any different if I used a server with a
    >> number of virtual machines? (Not that I really have that level of
    >> resources available to me!)


    > *Everything* that represents a difference between the testing environment and
    > the deployment environment is significant. In this case you would testing the
    > server with 1/N less CPU power than would be available if there were N
    > physical rather than virtual servers. Prety significant, don't you think?


    Real-world anecdote: I was on a big-iron project a few years ago where the
    test environment and production environment servers were two different models,
    with differing core counts, of the same mainframe server brand in the same
    line (the test environment's was the little brother of the production server),
    and that made it impossible for the test environment to replicate certain
    conditions that happened in production.

    There are formal means to project probabilistically from test results in such
    situations, but in practice those who know how to do so rarely get the
    authority to design the test plans.

    Then again, such people are rare.

    --
    Lew
    Honi soit qui mal y pense.
    http://upload.wikimedia.org/wikipedia/commons/c/cf/Friz.jpg
    Lew, Mar 29, 2011
    #6
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