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Thread: About how many concurrent users can one instance of Alpha Application Server handle ?

  1. #1
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    Default About how many concurrent users can one instance of Alpha Application Server handle ?

    I have a web app running in production at a client. Server has alot of memory about 8GB.

    Few times for the day the application gets really slow.
    I have 2 instances of the app running on the same server.
    I saw today where one instance had 32 users on it and the other had 9 users.
    Is that too many users for one instance ?

    If so, what kind of user load can one instance handle ?

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    Moderator Steve Workings's Avatar
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    Default Re: About how many concurrent users can one instance of Alpha Application Server handle ?

    There's no fixed answer for your core question. Search this board and you'll find many discussions that all point to all kinds of variables about your application.

    The amount of RAM you use isn't an indicator of the number of users - there's some correlation there but it's not a way to really measure much of anything.

    Alpha recommends 4 GB of RAM per instance. You should be fine with 2 instances on that 8 GB.

    The question of whether 32 users is "too much" depends on what they were doing. There's quite a difference between all users being simply logged in, doing something minor, vs. all of them running complex queries, huge reports and hundreds of PDF pages for instance. You get the idea.

    It can be hard to track down those slow points and their cause. It can take a good analysis of logs, some observations and figuring out / learning what's going on during those times. If your load balance can distribute the users more evenly then that may be worth pursuing.

    And restart the A5 instances each night if you can. This is made easy with a utility such as Always Up.
    -Steve


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    "Certified" Alphaholic kkfin's Avatar
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    Default Re: About how many concurrent users can one instance of Alpha Application Server handle ?

    Quote Originally Posted by gilbertro View Post
    I have a web app running in production at a client. Server has alot of memory about 8GB.

    Few times for the day the application gets really slow.
    I have 2 instances of the app running on the same server.
    I saw today where one instance had 32 users on it and the other had 9 users.
    Is that too many users for one instance ?

    If so, what kind of user load can one instance handle ?
    Obviously you have found the limits in your application.

    In theory AA server can handle 4 GB memory but can it in practise is an other question.
    You can check for example from servers task manager the actual use of memory.

    The need to restart AA server frequently points to a very serious memory leak in the AA server.

    Because the need to restart still exists means that Alpha has not solved this problem.

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    Default Re: About how many concurrent users can one instance of Alpha Application Server handle ?

    Also watch how much memory each instance of applicationserver.exe takes. If it is more than 500.000 kb start monitoring it closely.
    If it go's over 1 million expect an crash soon.

    This is not only alpha. We had customers that had troubles on there own (really big) servers and that growing of instances in memory dissappeared immediately when they took our offer to host them at Zebrahost. (Same software, same usage!)

    Important is also the number of free cores, to give room for the reportservers (if your application facilitate pdf printing). Pdf printing really can ask a lot of resources....

    We have some very busy clients. And currently we don't want more than 15 of them on 1 instance.
    But we also see that prerendering component cuts in half the power needed, so do that for often used forms if you can.

    Memory isn't the only thing: we have 8 instances on 16 cores and 10 gb memory. With version v4.01 running flawless at Zebra.
    Last edited by cptutrecht; 04-28-2016 at 04:15 AM.
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    Moderator Steve Wood's Avatar
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    Default Re: About how many concurrent users can one instance of Alpha Application Server handle ?

    From my experience, AA will start to delay response (be slow) after about 25 truly concurrent users per core and it does not make any difference how much memory you have on your server.
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    Default Re: About how many concurrent users can one instance of Alpha Application Server handle ?

    Thank you all for your response so far.
    The concurrent users are all updating records.

    BTW, are the following settings okay to be using in my scenario ?

    Threads.MaxSpareThreads = "8"
    Threads.MaxThreads = "48"
    Threads.MinSpareThreads = "4"
    Threads.StartThreads = "8"

    I always wondered if these settings ever need to be tweaked ?
    (I am still using default settings)

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    Default Re: About how many concurrent users can one instance of Alpha Application Server handle ?

    Running Quad core with 8GB, hosted internally.. Have 3 instances running with no real noticeable delays.

    App 1: 4-6 concurrent users
    App 2: 2-3 concurrent users
    App 3: 100+ concurrent users

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    Moderator Steve Wood's Avatar
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    Default Re: About how many concurrent users can one instance of Alpha Application Server handle ?

    Every time we go through this, the definition of "concurrent user" is always the varying factor. We really should be using terms like "concurrent requests" or "hits all at once" or measure it more accurately like "X hits to this resource over a period of Y minutes". I mean, ONE user hitting an A5W page that happens to generate massive load will bog down or kill the application for everyone else.
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    Default Re: About how many concurrent users can one instance of Alpha Application Server handle ?

    Steve,

    Do you know of any free server load testing application(s) that simulate X number of users loading? https://loadimpact.com/ is a pretty decent tool for testing smaller applications, free version simulates 25 virtual users.

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    Moderator Steve Wood's Avatar
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    Default Re: About how many concurrent users can one instance of Alpha Application Server handle ?

    That is the only one I have used before; it used to be less expensive. If I thought it would get used, I would purchase a subscription under IADN and rent out the service. But I don't think there is enough demand for that.
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    Default Re: About how many concurrent users can one instance of Alpha Application Server handle ?

    http://tsung.erlang-projects.org/ Might be worth checking out - praised in multiple places including Stackoverflow. Love open source ;)

    I would think stress testing would continue to grow in demand as the Alpha platform gets more and more popular. Going to experiment with a few of the ones I've found that are open sourced/licensed freeware and will revert back.

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    Default Re: About how many concurrent users can one instance of Alpha Application Server handle ?

    Okay, so..

    On my app server, I ran a stress test with Webserver Stress Tool 8, which you can find for free online..

    Ran the test with 30 clicks per user, at 100 users with a click delay of 20 seconds. Ran the test hitting both my login.a5w and index.a5w.

    Took the app offline in approximately 6 minutes. What is odd though, I was monitoring on the server as well and didn't see any significant spiking..

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