Server overload when clear cache

  • Resolved longnha

    (@longnha)


    4 years, 7 months ago

    Hi,

    Each time a post is published, whether publish instantly or via cron job, it make the site inaccessible for around 3 minutes due to high server load, it rocks 10 times the normal server load.

    The cache purge setting as showed: https://imgur.com/F565LZA

    Checking SQL Process I saw a lot of “Creating sort index” queries:

    SELECT SQL_CALC_FOUND_ROWS wp_posts.ID FROM wp_posts WHERE 1=1 AND wp_posts.post_type = 'post' AN

    Report number: HHPFMWHO

    I don’t know since which version the issue happens, I just notice it recently.

    Thank you.

    • This topic was modified 4 years, 7 months ago by longnha.
Viewing 10 replies - 1 through 10 (of 10 total)
  • Plugin Support qtwrk

    (@qtwrk)

    Hi,

    If your site has a lot of traffic , then after cache is purged when you publish something , then it could result as all the request are directly hitting PHP process.

    Best regards,
    Ruikai.

    Thread Starter longnha

    (@longnha)

    Hi,

    Isn’t there a better way to handle the cache purge such as batch purge instead of purge everything at once?

    Thank you.

    Plugin Support qtwrk

    (@qtwrk)

    Hi,

    In Cache setting —> Purge —> there is an option called Purge Stale , please try enable it and see if it helps.

    Best regards,

    Thread Starter longnha

    (@longnha)

    I do see the Purge Stale option but it make no different, so no idea whether or not it works! Is there a way to confirm that?

    I still think limit numbers of cache purge at one time is a better idea, W3 cache has such options.

    Thank you.

    Plugin Support qtwrk

    (@qtwrk)

    Hi,

    If you still see “cache: hit” after purge , then it means the stale cache is working.

    Based on your setting , it should only purge the relevant pages, instead of all the caches , therefore should not create an overload like this.

    Please try , if you uncheck all of them , how does it go ?

    Best regards,

    Thread Starter longnha

    (@longnha)

    When uncheck all of them, no cache is purged.

    Thank you.

    Thread Starter longnha

    (@longnha)

    Checking the Web Admin, I also see unusual behavior.

    Normally, when the cache is cleared I should see a drop in Public Cache Hits/Sec and increase Req/Sec to the server. But the recent event show that the rate increase for both!

    I also unchecked Purge Stale as it makes no different at my end.

    Thank you.

    • This reply was modified 4 years, 6 months ago by longnha.
    Plugin Support qtwrk

    (@qtwrk)

    Hi,

    May I know if your site has a lot of pages ? and incoming traffic are always into different pages ?

    When uncheck all of them, no cache is purged.

    when no cache is purged , you still see request number raise up a lot ?

    Best regards,

    Thread Starter longnha

    (@longnha)

    May I know if your site has a lot of pages ? and incoming traffic are always into different pages ?

    The site has around 40k post, 400 cats and around 4k tags.

    when no cache is purged , you still see request number raise up a lot ?

    It’s normal load, nothing changes when no cache is purged.

    As I have no idea on how to troubleshoot this issue, I downgraded to version 2.9.8.7 and it backs to normal so it should be some changes in new version that caused the issue, not my side.

    Thanks.

    Plugin Support qtwrk

    (@qtwrk)

    Hi,

    Could you please compare if both v2.9 setting and v3.0 setting are same ? I did see in some rare case some setting got lost during upgrade.

    Perhaps some setting caused additional load.

    And also if you could try on v3 with default setting ?

    Checking SQL Process I saw a lot of “Creating sort index” queries:

    SELECT SQL_CALC_FOUND_ROWS wp_posts.ID FROM wp_posts WHERE 1=1 AND wp_posts.post_type = ‘post’ AN

    Do you also see this on v2.9 ?

    Best regards,

Viewing 10 replies - 1 through 10 (of 10 total)
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