Enabling redis cache plugin slowdown the pages

  • Resolved fr3gatte

    (@fr3gatte)


    4 years, 7 months ago

    Hi!
    I’m trying to enable Redis cache plugin on the WP website and receive a strange behavior. Enabling the plugin decreases the number of SQL queries, but doubles the page generation time (we use the “Query Monitor” plugin to check the values). Do you have any ideas why is this happening?
    The Redis Object Cache Dashboard reports the average time ~900ms. But at the same time I’ve checked the latency to the Redis server with “redis-cli –latency” and it’s not above 5ms. This is the fully independent test setup (wp and redis servers) and hasn’t any unrelated workload that can affect the results.

    
Status: Connected
Client: PhpRedis (v5.3.4)
Drop-in: Valid
Disabled: No
Ping: 1
Errors: []
PhpRedis: 5.3.4
Predis: Not loaded
Credis: Not loaded
PHP Version: 7.3.29-1+ubuntu20.04.1+deb.sury.org+1
Plugin Version: 2.0.21
Redis Version: 6.0.5
Multisite: Yes
Metrics: Enabled
Metrics recorded: 69
Filesystem: Working
Global Prefix: ""
Blog Prefix: 32
WP_REDIS_HOST: <our-redis-host-dns-name>
WP_REDIS_PORT: 6379
WP_REDIS_DATABASE: 0
WP_REDIS_TIMEOUT: 1
WP_REDIS_READ_TIMEOUT: 1
Global Groups: [ "blog-details", "blog-id-cache", "blog-lookup", "global-posts", "networks", "rss", "sites", "site-details", "site-lookup", "site-options", "site-transient", "users", "useremail", "userlogins", "usermeta", "user_meta", "userslugs", "redis-cache", "blog_meta" ]
Ignored Groups: [ "counts", "plugins", "themes", "acf" ]
Unflushable Groups: []
Drop-ins: [ "advanced-cache.php v by ", "Query Monitor Database Class v by ", "Redis Object Cache Drop-In v2.0.21 by Till Krüss", "sunrise.php v by " ]
Viewing 3 replies - 1 through 3 (of 3 total)
  • Plugin Author Till Krüss

    (@tillkruess)

    4 years, 7 months ago

    Hey!

    Strange, but I occasionally see this. Do you have New Relic available, or some kind of Redis monitoring?

    Does Redis Server run on the same machine as the web server?

    — Till

    Thread Starter fr3gatte

    (@fr3gatte)

    4 years, 7 months ago

    We use AWS for our environment, EC2 server for WP and ElastiCache service for the Redis setup. So it’s the separate servers. If it help I can provide any stats and monitoring info from the AWS console about the Redis state. Actually it’s the newly created Redis install especially for this test. Does some special configuration require from the Redis side maybe?

    Plugin Author Till Krüss

    (@tillkruess)

    4 years, 7 months ago

    Not that I’m aware of. I’d suggest New Relic or Blackfire to see what’s exactly going on under the hood.

Viewing 3 replies - 1 through 3 (of 3 total)

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