Error establishing a Redis connection

Resolved mcdeth
(@mcdeth)

1 week, 5 days ago

Hi,
I recently migrated two of our shops to Hetzner servers. Previously they were hosted on a platform using LiteSpeed and Redis. One of the shops is running smoothly, but the other – despite having only around 100 visitors per hour (and being heavily cached through Cloudflare) frequently throws error.
To temporarily fix the issue, I have to remove the object-cache.php file.

I doubt it’s a server configuration problem, since it’s a managed Hetzner server and the other shop works fine. The databases are also isolated (different paths, and I’ve set different Redis DB numbers).

From what I can see, occasional spikes occur in the number of calls or data usage. I suspect a plugin might be causing this. How can I debug it effectively?

Previously, I had a plugin that fetched all products into an external database, and Redis usage spikes were so large that they caused the database to hang. After adding pagination, the issue was resolved. However, it seems that another plugin is still generating usage spikes and I’m not sure how to debug this further.
How can I identify which plugin is responsible? Thank you

Viewing 6 replies - 1 through 6 (of 6 total)

Plugin Author

Till Krüss

(@tillkruess)

1 week, 5 days ago

Hey!

You’d first need to identify what throws error entails. What do your logs show?

Thread Starter

mcdeth

(@mcdeth)

1 week, 5 days ago

Thanks for prompt reply, these are PHP errors:

[01-Dec-2025 20:44:03 UTC] RedisException: read error on connection to /run/redis_s01/redis.sock in /usr/www/users/s01/wp-content/object-cache.php:1934
#0 /usr/www/users/s01/wp-content/object-cache.php(1934): Redis->get()
[01-Dec-2025 20:44:03 UTC] RedisException: read error on connection to /run/redis_s01/redis.sock in /usr/www/users/s01/wp-content/object-cache.php:1934
#0 /usr/www/users/s01/wp-content/object-cache.php(1934): Redis->get()
[01-Dec-2025 20:44:03 UTC] RedisException: read error on connection to /run/redis_s01/redis.sock in /usr/www/users/s01/wp-content/object-cache.php:1934
#0 /usr/www/users/s01/wp-content/object-cache.php(1934): Redis->get()

I changed these settings from 1 to 3 for now:

define( 'WP_REDIS_TIMEOUT', 3 );
define( 'WP_REDIS_READ_TIMEOUT', 3 );

Plugin Author

Till Krüss

(@tillkruess)

1 week, 5 days ago

Did that resolve it?

Thread Starter

mcdeth

(@mcdeth)

1 week, 4 days ago

No, sometimes I get an ‘error establishing connection’, but only in this specific shop. The other shops using Redis on the same server work perfectly fine. I’ll be checking for possible memory leaks… In the meantime, would increasing or decreasing the RAM be beneficial?

Here are logs, I dont see such spikes in other shops

View post on imgur.com

Plugin Author

Till Krüss

(@tillkruess)

1 week, 4 days ago

How many keys are in the db of the site with timeouts?

Thread Starter

mcdeth

(@mcdeth)

1 week, 4 days ago


db1:keys=683597,expires=4252,avg_ttl=2128419180

evicted_keys:580307
keyspace_hits:15333759
keyspace_misses:2508765

total_connections_received:17820
instantaneous_ops_per_sec:0
rejected_connections:0

used_memory:534246600
used_memory_human:509.50M
used_memory_rss:586928128
used_memory_rss_human:559.74M
used_memory_peak:641976912
used_memory_peak_human:612.24M
used_memory_peak_perc:83.22%
used_memory_overhead:36761840
used_memory_startup:876304
used_memory_dataset:497484760
used_memory_dataset_perc:93.27%
used_memory_lua:39936
used_memory_vm_eval:39936
used_memory_lua_human:39.00K
used_memory_scripts_eval:760
used_memory_vm_functions:33792
used_memory_vm_total:73728
used_memory_vm_total_human:72.00K
used_memory_functions:200
used_memory_scripts:960
used_memory_scripts_human:960B
maxmemory:536870912
maxmemory_human:512.00M
maxmemory_policy:allkeys-lru
mem_fragmentation_ratio:1.10

Viewing 6 replies - 1 through 6 (of 6 total)

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