Feature Request: Prevent Cache Expiration on high Server Load

[raamdev]

Requested on WordPress.org:

If the Server Load is greater than a number, DO NOT expire the cached page but serve it from the cache.

Such a feature, utilizing the PHP sys_getloadavg() function, would only work in non-Windows hosting platforms, but nevertheless we could detect if sys_getloadavg() works on the current platform and then provide options for letting a site owner configure a specific server-load at which Quick Cache should not allow cache expiration.

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Support threads referencing this issue

• https://wordpress.org/support/topic/some-suggestions-29?replies=1#post-6081899

[jaswrks]

Just wanted to comment that implementing this will be super simple once the work in #288 is complete. We can simply connect this to the new purge_ methods in the \quick_cache\share class.

[jaswrks]

This is ready for work IMO.

• Add a new option in ZenCache Pro that enables this.
• Add a new option that controls what should be considered too high of a load average; i.e., at what load should purging not occur.
• Add a conditional check here that stops before purging occurs whenever the load average is high.
• Also prevent ZenCache from checking the age of existing cache files; i.e., update the AdvancedCache class.

[jaswrks]

A new utility was implemented in wpsharks/comet-cache-pro#127

/*
 * System load averages.
 *
 * @since 15xxxx Adding cache directory statistics.
 *
 * @return array System load averages.
 */
$self->sysLoadAverages = function () use ($self) {
    if (!is_null($averages = &$self->cacheKey('sysLoadAverages'))) {
        return $averages; // Already cached these.
    }
    if (!$self->functionIsPossible('sys_getloadavg')) {
        return ($averages = array());
    }
    if (!is_array($averages = sys_getloadavg()) || !$averages) {
        return ($averages = array());
    }
    $averages = array_map('floatval', $averages);
    $averages = array_slice($averages, 0, 3);
    // i.e., 1m, 5m, 15m; see: <http://jas.xyz/1gWyJLt>
    return $averages;
};

Example Usage

$load_averages = $self->sysLoadAverages();
if ($load_averages) {
    // 1 minute ago = (float) $load_averages[0];
    // 5 minutes ago = (float) $load_averages[1];
    // 15 minutes ago = (float) $load_averages[2];
}

[raamdev]

Next Pro Release Changelog:

• New Feature: It's now possible to "Disable Cache Expiration If Server Load Average is High" (see Dashboard → ZenCache → Plugin Options → Cache Expiration Time). This allows you to provide a specific load average that should cause ZenCache to disable cache expiration and help reduce stress on the server; i.e., to avoid generating a new version of the cache while the server is very busy. Props @jaswsinc. See Issue #347.

[raamdev]

ZenCache Pro v151002 has been released and includes changes from this GitHub Issue.

See the v151002 release announcement for further details.

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This issue will now be locked to further updates. If you have something to add related to this GitHub Issue, please open a new GitHub Issue and reference this one (#347).