I just rebuilt a site with 8GB ram. Apparently sidekiq had died a few days ago and is now trying to catch up on 500K queued processes. It runs for a while and then redis stops responding. Logs have errors like these: Error connecting to Redis on localhost:6379 (Redis::TimeoutError) subscribe failed, reconnecting in 1 s econd. Call stack ["/var/www/discourse/vendor/bundle/ruby/2.4.0/gems/redis-3.3.5/lib/redis/client.rb:34 5:in `rescue in establish_connection'", "/var/www/discourse/vendor/bundle/ruby/2.4.0/gems/redis-3.3.5/l ib/redis/client.rb:331:in `establish_connection'", "/var/www/discourse/vendor/bundle/ruby/2.4.0/gems/re dis-3.3.5/lib/redis/client.rb:101:in `block in connect'", "/var/www/discourse/vendor/bundle/ruby/2.4.0/ gems/redis-3.3.5/lib/redis/client.rb:293:in `with_reconnect'", "/var/www/discourse/vendor/bundle/ruby/2 .4.0/gems/redis-3.3.5/lib/redis/client.rb:100:in `connect'", "/var/www/discourse/vendor/bundle/ruby/2.4 .0/gems/redis-3.3.5/lib/redis/client.rb:276:in `with_socket_timeout'", "/var/www/discourse/vendor/bundl e/ruby/2.4.0/gems/redis-3.3.5/lib/redis/client.rb:133:in `call_loop'", "/var/www/discourse/vendor/bundl e/ruby/2.4.0/gems/redis-3.3.5/lib/redis/subscribe.rb:43:in `subscription'", "/var/www/discourse/vendor/ bundle/ruby/2.4.0/gems/redis-3.3.5/lib/redis/subscribe.rb:12:in `subscribe'", "/var/www/discourse/vendo r/bundle/ruby/2.4.0/gems/redis-3.3.5/lib/redis.rb:2775:in `_subscription'", "/var/www/discourse/vendor/ bundle/ruby/2.4.0/gems/redis-3.3.5/lib/redis.rb:2143:in `block in subscribe'", "/var/www/discourse/vend or/bundle/ruby/2.4.0/gems/redis-3.3.5/lib/redis.rb:58:in `block in synchronize'", "/usr/local/lib/ruby/ 2.4.0/monitor.rb:214:in `mon_synchronize'", "/var/www/discourse/vendor/bundle/ruby/2.4.0/gems/redis-3.3 .5/lib/redis.rb:58:in `synchronize'", "/var/www/discourse/vendor/bundle/ruby/2.4.0/gems/redis-3.3.5/lib /redis.rb:2142:in `subscribe'", "/var/www/discourse/vendor/bundle/ruby/2.4.0/gems/message_bus-2.1.1/lib /message_bus/backends/redis.rb:336:in `global_subscribe'", "/var/www/discourse/vendor/bundle/ruby/2.4.0 /gems/message_bus-2.1.1/lib/message_bus.rb:525:in `global_subscribe_thread'", "/var/www/discourse/vendo r/bundle/ruby/2.4.0/gems/message_bus-2.1.1/lib/message_bus.rb:473:in `block in new_subscriber_thread'"] Job exception: Connection timed out Job exception: Connection timed out Job exception: Error connecting to Redis on localhost:6379 (Redis::TimeoutError) Job exception: Connection timed out Job exception: Connection timed out I’ve got this set now: db_shared_buffers: "2048MB" db_work_mem: "50MB" I’m going to try doubling db_shared_buffers next. Edit: but that didn’t help either. My multisite instance has also been having the database die several times a day. I thought it was coincident with backups, but I’m not convinced that’s true. Has something changed about redis in the past couple weeks that could affect this?

After further investigation, I’ve confirmed a bug in Docker, and it would be entirely capable of causing all of the seemingly unrelated symptoms you described. The linked post has more details and a rundown of how to downgrade Docker, which I’m pretty confident will solve all these problems.

[image] mpalmer: Are you collecting all this data while the system is misbehaving, or during correct operation? Stats while the system is running properly aren’t as likely to show problems. Yes, this is while it’s working. I’ve got 1-second stats running now, so hopefully I can catch it misbehaving. My multisite instance fairly reliably has the database die when I do a bootstrap of the web container when it’s rebuilding the CSS. It’s running in the tens of ops/sec & once it dies hangs redis-cli won’t give me any stats. I’ll try to see what’s up with that next. What and where can one tweak on the redis config?

[image] pfaffman: once it dies hangs redis-cli won’t give me any stats. I’ll try to see what’s up with that next. Hmm, yeah, I guess once Redis stops talking to the world, you’re going to have a hard time connecting to it to get stats… although if you run redis-cli while everything is hunky-dory, then stay connected, you should be able to keep running info stats (assuming Redis hasn’t completely lost its tiny mind). Another thing to check is the Redis logs; from memory, I think we’ve got Redis logging to Docker, so ./launcher logs app is what you want there. If Redis is really playing up hard, that should tell you what’s what. I’d also like to definitively rule out swapping as a contributing factor; can you collect the output of free -m from just before and just after the problem occurs, and run sar -W 1 (on the host) before and after :fire:.

Well, I got the multisite instance to crash the database again during a rebuild when compiling css. sar showed a couple seconds of 30 swaps, but free still said only about 150M of the 2027M of swap available. ops/sec was less than 100 up until it died. I’m pretty stumped on this one. I keep thinking that it’s my imagination, but it always dies on a rebuild and most nights it crashes a couple times. It didn’t crash the one night I had all of the backups turned off. Meanwhile, the big sidekiq backlog site keeps functioning.

Hi Jay, The Redis::TimeoutError problems appear to be caused by a bug in Docker. I’ve just done a writeup on my findings from another misbehaving machine, which might be useful to you.

Do you know if the Docker bug is still around in 18.03.1~ce-0~ubuntu? I am seeing the following and am wondering if this is the same issue again: production.log Unexpected error in Message Bus : Connection timed out Job exception: Connection timed out Failed to process job: Connection timed out ["/var/www/discourse/vendor/bundle/ruby/2.5.0/gems/redis-4.0.1/lib/redis/connection/hiredis.rb:58:in `rescue in read'", "/var/www/discourse/vendor/bundle/ruby/2.5.0/gems/redis-4.0.1/lib/redis/connection/hiredis.rb:53:in `read'", "/var/www/discourse/vendor/bundle/ruby/2.5.0/gems/redis-4.0.1/lib/redis/client.rb:260:in `block in read'", "/var/www/discourse/vendor/bundle/ruby/2.5.0/gems/redis-4.0.1/lib/redis/client.rb:248:in `io'", "/var/www/discourse/vendor/bundle/ruby/2.5.0/gems/redis-4.0.1/lib/redis/client.rb:259:in `read'", "/var/www/discourse/vendor/bundle/ruby/2.5.0/gems/redis-4.0.1/lib/redis/client.rb:118:in `block in call'", "/var/www/discourse/vendor/bundle/ruby/2.5.0/gems/redis-4.0.1/lib/redis/client.rb:229:in `block (2 levels) in process'", "/var/www/discourse/vendor/bundle/ruby/2.5.0/gems/redis-4.0.1/lib/redis/client.rb:366:in `ensure_connected'", "/var/www/discourse/vendor/bundle/ruby/2.5.0/gems/redis-4.0.1/lib/redis/client.rb:219:in `block in process'", "/var/www/discourse/vendor/bundle/ruby/2.5.0/gems/redis-4.0.1/lib/redis/client.rb:304:in `logging'", "/var/www/discourse/vendor/bundle/ruby/2.5.0/gems/redis-4.0.1/lib/redis/client.rb:218:in `process'", "/var/www/discourse/vendor/bundle/ruby/2.5.0/gems/redis-4.0.1/lib/redis/client.rb:118:in `call'", "/var/www/discourse/vendor/bundle/ruby/2.5.0/gems/redis-4.0.1/lib/redis.rb:2448:in `block in _eval'", "/var/www/discourse/vendor/bundle/ruby/2.5.0/gems/redis-4.0.1/lib/redis.rb:45:in `block in synchronize'", "/usr/local/lib/ruby/2.5.0/monitor.rb:226:in `mon_synchronize'", "/var/www/discourse/vendor/bundle/ruby/2.5.0/gems/redis-4.0.1/lib/redis.rb:45:in `synchronize'", "/var/www/discourse/vendor/bundle/ruby/2.5.0/gems/redis-4.0.1/lib/redis.rb:2447:in `_eval'", "/var/www/discourse/vendor/bundle/ruby/2.5.0/gems/redis-4.0.1/lib/redis.rb:2499:in `evalsha'", "/var/www/discourse/vendor/bundle/ruby/2.5.0/gems/message_bus-2.1.5/lib/message_bus/backends/redis.rb:381:in `cached_eval'", "/var/www/discourse/vendor/bundle/ruby/2.5.0/gems/message_bus-2.1.5/lib/message_bus/backends/redis.rb:141:in `publish'", "/var/www/discourse/vendor/bundle/ruby/2.5.0/gems/message_bus-2.1.5/lib/message_bus.rb:253:in `publish'", "/var/www/discourse/vendor/bundle/ruby/2.5.0/gems/message_bus-2.1.5/lib/message_bus.rb:490:in `block in new_subscriber_thread'", "/var/www/discourse/vendor/bundle/ruby/2.5.0/gems/message_bus-2.1.5/lib/message_bus/timer_thread.rb:102:in `do_work'", "/var/www/discourse/vendor/bundle/ruby/2.5.0/gems/message_bus-2.1.5/lib/message_bus/timer_thread.rb:30:in `block in initialize'"] Unexpected error in Message Bus : Connection timed out Job exception: Connection timed out unicorn.stderr.log E, [2018-06-27T11:55:52.507207 #31436] ERROR -- : master loop error: Connection timed out (Redis::TimeoutError) E, [2018-06-27T11:55:52.507357 #31436] ERROR -- : /var/www/discourse/vendor/bundle/ruby/2.4.0/gems/redis-4.0.1/lib/redis/connection/hiredis.rb:58:in `rescue in read' E, [2018-06-27T11:55:52.507423 #31436] ERROR -- : /var/www/discourse/vendor/bundle/ruby/2.4.0/gems/redis-4.0.1/lib/redis/connection/hiredis.rb:53:in `read' E, [2018-06-27T11:55:52.507464 #31436] ERROR -- : /var/www/discourse/vendor/bundle/ruby/2.4.0/gems/redis-4.0.1/lib/redis/client.rb:260:in `block in read' E, [2018-06-27T11:55:52.507503 #31436] ERROR -- : /var/www/discourse/vendor/bundle/ruby/2.4.0/gems/redis-4.0.1/lib/redis/client.rb:248:in `io' E, [2018-06-27T11:55:52.507536 #31436] ERROR -- : /var/www/discourse/vendor/bundle/ruby/2.4.0/gems/redis-4.0.1/lib/redis/client.rb:259:in `read' E, [2018-06-27T11:55:52.507560 #31436] ERROR -- : /var/www/discourse/vendor/bundle/ruby/2.4.0/gems/redis-4.0.1/lib/redis/client.rb:118:in `block in call' E, [2018-06-27T11:55:52.507583 #31436] ERROR -- : /var/www/discourse/vendor/bundle/ruby/2.4.0/gems/redis-4.0.1/lib/redis/client.rb:229:in `block (2 levels) in process' E, [2018-06-27T11:55:52.507609 #31436] ERROR -- : /var/www/discourse/vendor/bundle/ruby/2.4.0/gems/redis-4.0.1/lib/redis/client.rb:366:in `ensure_connected' E, [2018-06-27T11:55:52.507630 #31436] ERROR -- : /var/www/discourse/vendor/bundle/ruby/2.4.0/gems/redis-4.0.1/lib/redis/client.rb:219:in `block in process' E, [2018-06-27T11:55:52.507655 #31436] ERROR -- : /var/www/discourse/vendor/bundle/ruby/2.4.0/gems/redis-4.0.1/lib/redis/client.rb:304:in `logging' E, [2018-06-27T11:55:52.507674 #31436] ERROR -- : /var/www/discourse/vendor/bundle/ruby/2.4.0/gems/redis-4.0.1/lib/redis/client.rb:218:in `process' E, [2018-06-27T11:55:52.507698 #31436] ERROR -- : /var/www/discourse/vendor/bundle/ruby/2.4.0/gems/redis-4.0.1/lib/redis/client.rb:118:in `call' E, [2018-06-27T11:55:52.507716 #31436] ERROR -- : /var/www/discourse/vendor/bundle/ruby/2.4.0/gems/redis-4.0.1/lib/redis.rb:889:in `block in get' E, [2018-06-27T11:55:52.507736 #31436] ERROR -- : /var/www/discourse/vendor/bundle/ruby/2.4.0/gems/redis-4.0.1/lib/redis.rb:45:in `block in synchronize' E, [2018-06-27T11:55:52.507753 #31436] ERROR -- : /usr/local/lib/ruby/2.4.0/monitor.rb:214:in `mon_synchronize' E, [2018-06-27T11:55:52.507781 #31436] ERROR -- : /var/www/discourse/vendor/bundle/ruby/2.4.0/gems/redis-4.0.1/lib/redis.rb:45:in `synchronize' E, [2018-06-27T11:55:52.507804 #31436] ERROR -- : /var/www/discourse/vendor/bundle/ruby/2.4.0/gems/redis-4.0.1/lib/redis.rb:888:in `get' E, [2018-06-27T11:55:52.507822 #31436] ERROR -- : /var/www/discourse/lib/discourse_redis.rb:188:in `block (3 levels) in ' E, [2018-06-27T11:55:52.507838 #31436] ERROR -- : /var/www/discourse/lib/discourse_redis.rb:153:in `ignore_readonly' E, [2018-06-27T11:55:52.507855 #31436] ERROR -- : /var/www/discourse/lib/discourse_redis.rb:188:in `block (2 levels) in ' E, [2018-06-27T11:55:52.507876 #31436] ERROR -- : /var/www/discourse/app/jobs/regular/run_heartbeat.rb:15:in `last_heartbeat' E, [2018-06-27T11:55:52.507896 #31436] ERROR -- : config/unicorn.conf.rb:172:in `check_sidekiq_heartbeat' E, [2018-06-27T11:55:52.507915 #31436] ERROR -- : config/unicorn.conf.rb:199:in `master_sleep' E, [2018-06-27T11:55:52.507933 #31436] ERROR -- : /var/www/discourse/vendor/bundle/ruby/2.4.0/gems/unicorn-5.4.0/lib/unicorn/http_server.rb:294:in `join' E, [2018-06-27T11:55:52.507954 #31436] ERROR -- : /var/www/discourse/vendor/bundle/ruby/2.4.0/gems/unicorn-5.4.0/bin/unicorn:126:in ` ' E, [2018-06-27T11:55:52.507971 #31436] ERROR -- : /var/www/discourse/vendor/bundle/ruby/2.4.0/bin/unicorn:23:in `load' E, [2018-06-27T11:55:52.507987 #31436] ERROR -- : /var/www/discourse/vendor/bundle/ruby/2.4.0/bin/unicorn:23:in ` ' Failed to report error: Connection timed out 3 Job exception: Connection timed out apt-cache showpkg docker-ce shows me versions 17.09 and 17.12, but 17.10 is not available in my repo. Are you aware of any other version besides 17.10 which does not have problems with Discourse? (assuming mine is the same problem) Edit: Some more info: Discourse was running rock-solid since a month, no problems. Yesterday evening I rebuilt the app and did a upgrade / dist-upgrade during a short maint window. 18 hours later the forum died. Host ressources are fine. Now I restored a snapshot from before the upgrade, and saw that I was running the exact same Docker version before the problems started. This pretty much excludes the Docker version as the culprit. The other variables are app upgrade from 1.9 to 2.1. Also, updated host OS. Still, from the logs, I don’t see how the app could cause such low level problems (cant read Redis). So what is going on here? Maybe some dependencies of Docker changed while updating, which are causing the problem? Something inside the container going wrong? I am clueless.. Edit 2: This is what was going on from a resources point of view when it crashed: [image] But there wasn’t much going on at that point in forum. Something spiked memory though, albeit not in critical range.

I’d recommend un-installing the docker-ce that comes with Ubuntu and installing Docker this way: wget -qO- https://get.docker.com/ | sh

That’s how it was installed in the first place. But see my edit I did (after your post). I believe that the Docker version can nearly be excluded as this point (at least in my case)…

Ugh, site crashed again! It is crashing about every 18 hours now since the update to 2.1, always because of Redis (Redis logs show nothing abnormal). I even removed all plugins now, still crashing. Does anyone have any good tips how I could investigate this?

According to monitoring, no (see chart above). I was also thinking about this, that perhaps Linux’s out-of-memory killer is randomly killing processes. But I have no indication that this is the case. It is also interesting that the server typically runs for about 18 hours then goes down (with Redis connection errors in log well before this). Any idea how I could verify if processes are being killed due to memory pressure?

Redis connection timed out

Product Support Self-hosting

codinghorror (Jeff Atwood) June 28, 2018, 7:57pm 21

Are you running out of memory?

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Redis connection timed out

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