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Application Server consuming CPU and freezing

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  • Application Server consuming CPU and freezing

    I have an application that for no apparent reason, the WAS start consuming CPU and freezes.
    I think, I have an error somewhere, but I have no idea how to debug it ?
    I am using the multi-tenant connection string. I tried open the log of the was, but it was like Chinese for me.

    Any help is highly appreciated.


  • #2
    I have an application that for no apparent reason
    means there were no changes to the server admin or changes to the application, just making certain that's what you mean before spending time on this. On the face of it. I would say you are experiencing a denial of service as the server is getting hammered by and external not so well intended source from off-shore (just like your log), it that is the case, i'd contact Steve Wood at the IADN, he's right onto this stuff.
    Insanity: doing the same thing over and over again and expecting different results.
    Albert Einstein, (attributed)
    US (German-born) physicist (1879 - 1955)


    • #3
      Thank you for your answer, I don't think it is a "denial of service", What's happening is the following:
      When I added the multi-tenant connection to the application. couple of my UX started freezing up the WAS, Some times it works perfectly and sometimes the the WAS freezes.
      It is always the same couple of UX that freezes the system, but not every time.


      • #4
        OK so its the 'multi-tenant connection to the application' was the change, then I'd say that is the cause, I'll take a look at that.
        Insanity: doing the same thing over and over again and expecting different results.
        Albert Einstein, (attributed)
        US (German-born) physicist (1879 - 1955)


        • #5
          The problem is that when I run the menu and test the application sometimes it works and others no.
          the same ux might work 1 time and another time it makes the application server freezes...
          I don't know how to debug this :(
          if it wasn't working every time or throwing a message, I could start from there.
          but I run the application, it does work, then another time it doesn't without any change...



          • #6
            can it be the internet speed or latency to reach the server ?
            I live in the middle east and our internet is relatively slow...
            can it be that the server receives a request and the sent answer isn't received on time thus making things unstable?


            • #7
              In xbasic one line of code has to be executed successfully before next one can be executed (actually there are some special xbasic functions that bypass this limitation ). This is why your server hangs. So it seem like there is something wrong with multi-tenant connection and so basically this problem teminates your server. In my undestanding there are problems with multi-tenant connection and it does not actually work as expected and you should avoid using it. But maybe there are success stories using this feature and I am wrong.


              • #8
                If you stop the AWS / WAS in task manager, then restart it, does the excessive processor usage continue, or does it go back to normal.

                If you do nothing, does it recover on it's own, returning to normal processor usage?

                For what it's worth...

                About 2 weeks ago, I started having an issue where all users reported they could not connect to, for example, the web calendar. Everything had been fine for 12 years, then randomly 3 - 5 times a day nothing connected for a few minutes, or more. Once for an hour. Once for 3.5 hours.

                It was suddenly happening several times every day for several days. The AWS went from .1% processor usage to about 14%, often for just 4 minutes.

                Stopping and starting the exe had no positive impact, with the exe jumping right to 14% processor usage.

                It appeared port 80 inbound was blocked, but outbound was fine. I could not remote in through port 80 at those times, but RDP through 3389 was fine.

                After a few minutes, it would just return to normal with no indication anything had ever happened in the AA server logs. The operating system logs showed just Symantec activity, and the AWS was shown as unresponsive.

                Turning off the Symantec AV on the machine may have resolved the issue. The last incident was 3 days ago.

                The only other thing I did was turn off logging, but I am getting more convinced Symantec was sniffing a new attack against some router, and was choking the AWS exe.

                As I say, it's only been 3 days, but the 10 before them were very frustrating.

                Reading your email sounded like you were experiencing what I had just went through...

                At the recommendation of 2 seasoned users, I am looking at CloudFlare to lessen local Anti Virus interception activity.


                • #9
                  This really is unacceptable report it.
                  Insanity: doing the same thing over and over again and expecting different results.
                  Albert Einstein, (attributed)
                  US (German-born) physicist (1879 - 1955)


                  • #10
                    1) So, if you are using the Alpha traditional web server and not the IIS version then are you using a software load-balancer to run multiple instances of WAS and monitor their responses? If not then I believe it is still recommended, by other developers, that you put in a software load-balancer. It should have the ability to monitor the health of WAS instances and the ability to kill errant instances and start up new instances to take their place. The alternative to 3rd party software load balancer is to use the IIS version of Alpha server and let IIS manage “worker processes”. For a Load Balancer, I would first look at the one offered here:

                    2) To reproduce random problems with the system, you might try using an automated testing tool. I tried many different tools, the one I liked the most was the one from MicroFocus called LoadRunner that used “TruClient” as the client-side script recorder.


                    • #11
                      Thanks for the answers.
                      When the app server is not responding and consuming CPU leaving it alone for any period of time doesn't change anything. even if I try to open another page from another browser it stops responding.
                      When I restart it the issue is fixed. nevertheless it will popup again at a random page and or time.

                      I am worried about switching to IIS, I am afraid it will be too much work ..
                      I never used a load balancer, this at least might be a quick fix until I figure it out. If someone can point me to the right direction.
                      Currently I am using alwaysup and using the sanity check features, so when alpha is not responding alwaysup will restart it, but first of all it takes 2-3 minutes for alwaysup to kill the task and restart it. the other downside is that the session will expires and the user gets redirected to the login screen.
                      will a load balancer redirect the requests to another instance and the session stays alive ? if so that's great

                      Meanwhile I will try to do some extensive test directly from the server using localhost, soI can overrule the firewall, internet speed/latency etc..

                      Sometimes ago, I tried some automated testing tools, it was too complex for me. I will give LoadRunner a try. Thanks for the hint.

                      I will post here what I find.


                      • #12
                        tell me how do you know it's not Denial of service to to attack?, I've seen this before several times and it was the issue, each time its an invisible site killer.
                        Insanity: doing the same thing over and over again and expecting different results.
                        Albert Einstein, (attributed)
                        US (German-born) physicist (1879 - 1955)


                        • #13
                          I am not an expert on security but as far as I know, DDOS will attack the server regardless if I have an open page or no.
                          it's been around 2 weeks I am troubleshooting this issue and these are my findings:

                          1-I created another application, very simple application a grid than insert data into one table. I published it to the same server. Regardless on how many time I open and close this small app it will always work.
                          2-the main application (the one that freezes) will always start at first (if it was a DDOS you might try to run the app and you find the webserver down), so if the webserver is up it will stay working until I open this app that has a multi tenant connection, and play around with it.
                          sometimes I can keep on doing test data entry for 15 minutes without any issues and some time it will freeze after 2 minutes.
                          3-Whenever I log to the server the CPU,network,memory usage of the server is always minimal (unless I run the app that freezes it). if it was a kind of DDOS or some malware then the server will consume resources even if I am not using it.

                          as I said, I am no expert in security but all this is making me believe either I am using a feature that has a bug (something that isn't used a lot) as an example, i am using a ux with a lookup grid with a multi-tenant connection while the grid has combo box ...
                          or it might be something buggy in my code, probably linked to the multi-tenant connection string (as an example a table that doesn't have the tenant_id field or maybe using a reserved word somewhere etc...
                          I am also suspecting my internet speed and latency. I will test this tomorrow, I will try it from another network. maybe since my internet is bad all the call back are not getting to the server fast enough with a proper reply when the browser makes many retry the WAS freezes...

                          I have no idea what's the issue, I am trying to eliminate one issue at a time. After I try testing on another network tomorrow, I will remove the multi-tenant connection and test again.

                          what I was hoping from this thread is some guru will guide me where to look / enable some log that will show the last action that server made before freezing..

                          sooner or later I will get to the bottom of it, but I am loosing too much time in trial and error :)

                          Thanks again for all the replies and help