Are WordPress objects stored in Redis considered as “discardable”?

  • Resolved trendycloud

    (@trendycloud)


    1 year, 11 months ago

    Hello from France!

    First, many, many thanks for this awesome plugin. ??

    I am (very) new to Redis: reading the docs, googling and so on… ^^

    About WordPress, I would like to know if data/objects are “persistent” (backups required in Redis crash) or if these data/objects are “non-persistent”.

    The plugin supports “flushing (Redis) cache” and max TTL, so I suppose that every object saved by WordPress object cache is “discardable” at any time (like WP transients).

    In this case, Redis would act as another (very good) layer of “caching only”, just like Varnish.

     Long story short:

    – can redis-server (configured with no persistence => save “”) be restarted at any time without data loss from WordPress perspective?

    – are there some gotchas about plugins/themes/other using WordPress object cache as a “permanent” storage?

    Have a great night. ??

    The page I need help with: [log in to see the link]

Viewing 8 replies - 1 through 8 (of 8 total)
  • Plugin Author Till Krüss

    (@tillkruess)

    Yes, Redis can be configured to be persistent ??https://redis.io/docs/management/persistence/

    You can safely use that, the only gotcha is as your cache size grows large it may take Redis several seconds to boot.

    Thread Starter trendycloud

    (@trendycloud)

    Thank you for your answer!

    However, my question was more:

    • “can Redis be configurered with “No Persistence””?
    • “Are all WordPress objects discardable at any time”?
    • “Is there any data loss when flushing Redis cache”?

    I know you are really busy so if you have some RTFM, it would be great! ??

    Plugin Author Till Krüss

    (@tillkruess)

    Yes, yes, no.

    Thread Starter trendycloud

    (@trendycloud)

    Many thanks for your precious answer!

    Have a great day. ??

    Plugin Author Till Krüss

    (@tillkruess)

    I think “Redis with no persistence is the default”.

    WordPress considers anything you throw into wp_cache_*() functions as ephemeral.

    Data loss is complicated. When flushing Redis all object cache data is wiped. There is no data loss because MySQL is your source of truth. However if you toggle the cache drop-in or object-cache.php file manually without flushing the cache, it may go out of sync and could lead to data loss.

    Object Cache Pro does a lot of extra work around this specific issue to avoid your cache ever going out of sync with MySQL.

    Thread Starter trendycloud

    (@trendycloud)

    Hello!

    Again, many, many thanks for your precious answer and the hint. ??

    Long story short:

    • “Redis Server” works great and is quite easy to configure
    • “Redis Object Cache” works flawlessly and is very easy to install
    • Source code of the Plugin is “insanely” clean and readable!
    • We saw improvements even with the WP administation… ^^

    Concerning “Object Cache Pro”, I have no doubt that it is worth the money but, currently, this is way too “advanded” (and pricy) for our needs.

    However, if the website would have to handle massive visitors spike after being showed on TV, I know whom to contact… ^^

    Have a great day! ??

    Plugin Author Till Krüss

    (@tillkruess)

    @trendycloud: I love hearing that. Would you mind posting that as a 5-star review? ??

    Thread Starter trendycloud

    (@trendycloud)

    Done! ^^

Viewing 8 replies - 1 through 8 (of 8 total)
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