PHP FPM Segfault with Object Cache Enabled

  • Resolved Kevin Shenk

    (@batonac)


    1 year, 11 months ago

    Hi, and thanks for this amazing plugin.

    I’m having a really hard time trying to get Docket Cache working with my own VPS-based hosting setup. I’m running PHP 8.1 FPM + NGINX on Ubuntu 22.04. Opcache is enabled. NGINX serves to a Cloudflare tunnel via a Unix socket.

    When accessing the WordPress backend (/wp-admin), the PHP FPM service constantly crashes with Docket Cache enabled, to the point of making it unusable. The corresponding error in the php log looks like:

    fpm_children_bury(), line 258: child 29975 exited on signal 11 (SIGSEGV) after 8.270777 seconds from start

    And from dmesg:

    php-fpm8.1[824022]: segfault at 7ffcf5140fe8 ip 00005569f5036814 sp 00007ffcf5140ff0 error 6 in php-fpm8.1[5569f4e5b000+2fd000] likely on CPU 0 (core 0, socket 0)

    From a coredump of the PHP FPM process:

    from gdb bt:

    0x0000561fcb1073a2 in zend_eval_const_expr (ast_ptr=0x7fd40f8a6108) at ./Zend/zend_compile.c:10299

    and gdb info locals: 

    result = <error reading variable result (Cannot access memory at address 0x7ffe62b25fb0)>

    Sorry if that’s not all that helpful, I’m still very new at using/understanding coredumps.

    This is all very obscure to me, and the site is nice and stable without Docket Cache Object Cache enabled. I’m afraid I’ll probably just need to let Docket Cache go for now, but I figured I’ll give this a shot.

    Any idea of what might be going on based on the above?

    Thanks!

Viewing 5 replies - 1 through 5 (of 5 total)
  • Thread Starter Kevin Shenk

    (@batonac)

    I should have mentioned, here’s my Docket Cache configuration:

    define('DOCKET_CACHE_ADVCPOST', true);
define('DOCKET_CACHE_ADVPOST_POSTTYPE_ALL', true);
define('DOCKET_CACHE_AUTOUPDATE', false);
define('DOCKET_CACHE_CHECKVERSION', false);
define('DOCKET_CACHE_CRONBOT', false);
define('DOCKET_CACHE_CRONOPTMZDB', 'weekly');
define('DOCKET_CACHE_FLUSHACTION', true);
define('DOCKET_CACHE_GCACTION', true);
define('DOCKET_CACHE_HEADERJUNK', true);
define('DOCKET_CACHE_LIMITHTTPREQUEST', true);
define('DOCKET_CACHE_LOG', false);
define('DOCKET_CACHE_LOG_ALL', false);
define('DOCKET_CACHE_MENUCACHE', true);
define('DOCKET_CACHE_MISC_TWEAKS', true);
define('DOCKET_CACHE_MOCACHE', true);
define('DOCKET_CACHE_OPCSHUTDOWN', true);
define('DOCKET_CACHE_OPTERMCOUNT', true);
define('DOCKET_CACHE_OPTWPQUERY', true);
define('DOCKET_CACHE_PAGELOADER', false);
define('DOCKET_CACHE_PINGBACK', true);
define('DOCKET_CACHE_POSTMISSEDSCHEDULE', true);
define('DOCKET_CACHE_PRECACHE', false);
define('DOCKET_CACHE_PRELOAD', true);
define('DOCKET_CACHE_RTIMAGEOVERWRITE', true);
define('DOCKET_CACHE_SIGNATURE', true);
define('DOCKET_CACHE_STATS', false);
define('DOCKET_CACHE_WOOTWEAKS', true);
define('DOCKET_CACHE_WPAPPPASSWORD', true);
define('DOCKET_CACHE_WPBROWSEHAPPY', true);
define('DOCKET_CACHE_WPDASHBOARDNEWS', true);
define('DOCKET_CACHE_WPEMOJI', true);
define('DOCKET_CACHE_WPFEED', true);
define('DOCKET_CACHE_WPLAZYLOAD', false);
define('DOCKET_CACHE_WPOPTALOAD', false);
define('DOCKET_CACHE_WPSERVEHAPPY', true);
define('DOCKET_CACHE_WPSITEMAP', true);
    Thread Starter Kevin Shenk

    (@batonac)

    Upon further diagnosis, this seems to be related to my backup/restore/migrate mechanism. Apparently stale and misplaced cache can be lethal. I’ll keep you posted.

    Plugin Author Nawawi Jamili

    (@nawawijamili)

    Hi there,

    Normally it is caused by not enough memory, you may try to disable the advanced post cache:

    define('DOCKET_CACHE_ADVCPOST', false);
define('DOCKET_CACHE_ADVPOST_POSTTYPE_ALL', false);

    Thanks.

    Thread Starter Kevin Shenk

    (@batonac)

    In this scenario, I was installing docket cache on a “placeholder” site before migrating other sites into/ontop it. Once I removed all the docket cache data before migrate, it worked.

    Plugin Author Nawawi Jamili

    (@nawawijamili)

    glad to hear that, thanks.

Viewing 5 replies - 1 through 5 (of 5 total)
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