A massive server load caused by admin-ajax.php

  • Nephalem

    (@nephalem)


    10 years, 7 months ago

    Well, here it goes again. Another issue. And this time, a big one. WpDiscuz 3.x generates an extreme server load caused by lots of instances of admin-ajax.php in our Apache/Nginx environment. The older version of wpDiscuz doesn’t have this issue, these instances are not generated by wpDiscuz 2.x at all.

    Each instance generates a massive load of ~35% of CPU resources and when we have more visitors on our site (like hundreds and more), the entire server gets frozen, not even Nginx is able to handle that load.

    Live updates are turned off. But it doesn’t help. As soon as a visitor comes to our site, an admin-ajax.php instance is generated on our server and it starts drawing resources like never before.

    People are angry and hitting our support desk because the server load slows down our site so bad people can’t use it. We had to downgrade wpDiscuz back to 2.2.10 and immediately after this downgrade, the server load was gone, everything was back to normal.

    You must have changed something in wpDiscuz 3.x that creates these persistent admin-ajax.php instances and until this issue is resolved, we have to use the previous production line of wpDiscuz (v2.2.10).

    https://ww.wp.xz.cn/plugins/wpdiscuz/

Viewing 7 replies - 1 through 7 (of 7 total)
  • Plugin Author gVectors Team

    (@gvectors-team)

    10 years, 7 months ago

    Nephalem,
    It seems you’ve set 10 sec live update. That’s very fast.
    Also when you disabling it, you should remove all caches. Please do that and all will be good. Also could you please leave the ajax request url here. It seems something is wrong on your end, it can’t load 35% of CPU, even with 10 sec update.

    Plugin Author gVectors Team

    (@gvectors-team)

    10 years, 7 months ago

    wpDiscuz 3 doesn’t setup live update requests if the post has no comments or comments are closed. Also there is an additional option which allows site administrators to disable live updating functions for guests, you should use it as well.

    Plugin Author gVectors Team

    (@gvectors-team)

    10 years, 7 months ago

    Here is the correct configuration of live update: http://screencast.com/t/QB0fpsAJmgm And this will not cause any issue.
    Also please let us know what hosting plan you use.

    Thread Starter Nephalem

    (@nephalem)

    10 years, 7 months ago

    We had the live updates configured exactly like that. It didn’t help. For instance, captcha generation took almost 7 seconds under the heavy load.

    The issue is caused by similar instances like this one:

    http://example.com/xxx/wp-admin/admin-ajax.php?action=generateCaptcha&wpdiscuz_captcha_id=wpdiscuzuniqueid&_wpnonce=6af9b597fc&wpdiscuz-rand=e7f9ed42adb5c8e29677612ef7ec1baf

    According to GTmetrix, an instance like this takes 7 seconds while drawing an immense load on our server. In wpDiscuz 2.2.10, admin-ajax.php instances are handled flawlessly with no impact on our server.

    We have a standalone dedicated server (Intel Xeon 3.0 GHz x 3 CPUs), 16GB RAM, CentOS, Apache + Nginx (working as a proxy-cache).

    Plugin Author gVectors Team

    (@gvectors-team)

    10 years, 7 months ago

    Ok, thank you very much for this data, we’re going to test all live update processes with this info and update wpDiscuz asap.

    Plugin Author gVectors Team

    (@gvectors-team)

    10 years, 7 months ago

    And as far as I see this is a CAPTCHA issue, which is being updated by ajax. In wpDiscuz 2 the CAPTCHA was not loading by ajax.
    So I think this is not a live update issue. The core live update functions are very light in wpDiscuz 3, even many time those are lighter and faster. We see the reason of your problem, that’s CAPTCHA. We’re going to fix it asap.

    Thread Starter Nephalem

    (@nephalem)

    10 years, 6 months ago

    I have sent an email to your support with more details. The issue is clearly caused by admin-ajax.php instances when wpDiscuz 3.x is installed.

Viewing 7 replies - 1 through 7 (of 7 total)

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