Redis cache filling up causing memory issue

  • Resolved MeOnline

    (@webber2012)


    4 years, 5 months ago

    I use Redis through my host, Redis is optional with the hosting package I have with them.

    After having set up the Redis cache with the plugin, it used to work fine for 1 day. Then the plugin was not connected anymore, tried restarting the Redis server, disabled cache, removed plugin, re-installed it, stopped and started Redis server etc.

    All that I was left with:
    Not Connected

    Then through Query Monitor I discovered the following error: ‘OOM command not allowed when used memory > ‘maxmemory’.
    BTW later on I also found the error in the plugin’s diagnostics.

    An online search disclosed that possibly the Redis cache limit was reached, I checked with my host and they were astounded because they never seen this happen before. In general they set Redis to 512 Mb, so as an exception for me, they increased it to 600 Mb and now the plugin is connected again – but for how long ..?

    So here are my questions:
    Doesn’t Redis cache get flushed automatically after it reaches the apparently set limit?

    Cache is supposed to be temporary storage, I never, ever had any cache fill (hard- and software based) stop something from working because it was filled. Is it correct that with Redis it does?

    Now the limit has been increased a bit but I suspect it will fill up soon again.
    Isn’t there a way to automatically let the cache flush or reset when it reached the limit? Just like normal cache behavior does.

    My host say I need to find out what is filling the cache, but how can I do that then? I read somewhere on your site that you can check logs with a ro subscription? But I am not the direct Redis account holder with access to that.

    Any suggestions and thoughts on what may solve the above issues?

Viewing 4 replies - 1 through 4 (of 4 total)
  • Plugin Author Till Krüss

    (@tillkruess)

    The best approach is setting a max memory policy as part of Redis so it evicts keys automatically instead of crashing.

    Alternatively you can set a MaxTTL in your WP config to something like 12 hours so let’s expire themselves.

    You should also consider using a larger Redis instance if you WordPress site uses that much Redis data.

    Thread Starter MeOnline

    (@webber2012)

    Thanks for your suggestions, I will discuss things with my host first to see what they can do.

    Plugin Author Till Krüss

    (@tillkruess)

    Sure thing. Who is your hosting company?

    Thread Starter MeOnline

    (@webber2012)

    The host is Neostrada, waiting for their reply about things.
    In the meanwhile I have disabled the Redis server and plugin. It was connected again but I don’t see any improvement in speed and get strange things happening, like backoffice redirect errors when the Redis plugin is enabled.

Viewing 4 replies - 1 through 4 (of 4 total)
  • The topic ‘Redis cache filling up causing memory issue’ is closed to new replies.