Where can I find the default docker ulimit settings? - docker

Question

I have been trying to understand an issue I've had when running roribio16/alpine-sqs docker image on one of my machines. Whenever I try to run the image without specifying any other settings, docker run roribio16/alpine-sqs
[xxxx#yyyy ~]$ docker run roribio16/alpine-sqs
2021-05-29 15:48:41,216 INFO Included extra file "/etc/supervisor/conf.d/elasticmq.conf" during parsing
2021-05-29 15:48:41,216 INFO Included extra file "/etc/supervisor/conf.d/insight.conf" during parsing
2021-05-29 15:48:41,216 INFO Included extra file "/etc/supervisor/conf.d/sqs-init.conf" during parsing
2021-05-29 15:48:41,216 INFO Set uid to user 0 succeeded
2021-05-29 15:48:41,222 INFO RPC interface 'supervisor' initialized
2021-05-29 15:48:41,222 CRIT Server 'unix_http_server' running without any HTTP authentication checking
2021-05-29 15:48:41,222 INFO supervisord started with pid 1
2021-05-29 15:48:42,225 INFO spawned: 'sqs-init' with pid 9
2021-05-29 15:48:42,229 INFO spawned: 'elasticmq' with pid 10
2021-05-29 15:48:42,230 INFO spawned: 'insight' with pid 11
cp: can't stat '/opt/custom/*.conf': No such file or directory
> sqs-insight#0.3.0 start /opt/sqs-insight
> node index.js
15:48:42.605 [main] INFO org.elasticmq.server.Main$ - Starting ElasticMQ server (0.15.0) ...
Loading config file from "/opt/sqs-insight/lib/../config/config_local.json"
15:48:42.929 [elasticmq-akka.actor.default-dispatcher-2] INFO akka.event.slf4j.Slf4jLogger - Slf4jLogger started
Unable to load queues for undefined
Config contains 0 queues.
library initialization failed - unable to allocate file descriptor table - out of memorylistening on port 9325
2021-05-29 15:48:43,233 INFO success: sqs-init entered RUNNING state, process has stayed up for > than 1 seconds (startsecs)
2021-05-29 15:48:43,233 INFO success: elasticmq entered RUNNING state, process has stayed up for > than 1 seconds (startsecs)
2021-05-29 15:48:43,234 INFO success: insight entered RUNNING state, process has stayed up for > than 1 seconds (startsecs)
2021-05-29 15:48:43,234 INFO exited: sqs-init (exit status 0; expected)
2021-05-29 15:48:44,318 INFO exited: elasticmq (terminated by SIGABRT (core dumped); not expected)
2021-05-29 15:48:45,322 INFO spawned: 'elasticmq' with pid 67
15:48:45.743 [main] INFO org.elasticmq.server.Main$ - Starting ElasticMQ server (0.15.0) ...
15:48:46.044 [elasticmq-akka.actor.default-dispatcher-2] INFO akka.event.slf4j.Slf4jLogger - Slf4jLogger started
library initialization failed - unable to allocate file descriptor table - out of memory2021-05-29 15:48:47,223 INFO success: elasticmq entered RUNNING state, process has stayed up for > than 1 seconds (startsecs)
2021-05-29 15:48:47,389 INFO exited: elasticmq (terminated by SIGABRT (core dumped); not expected)
2021-05-29 15:48:48,393 INFO spawned: 'elasticmq' with pid 89
15:48:48.766 [main] INFO org.elasticmq.server.Main$ - Starting ElasticMQ server (0.15.0) ...
15:48:49.066 [elasticmq-akka.actor.default-dispatcher-3] INFO akka.event.slf4j.Slf4jLogger - Slf4jLogger started
library initialization failed - unable to allocate file descriptor table - out of memory^C2021-05-29 15:48:49,559 INFO success: elasticmq entered RUNNING state, process has stayed up for > than 1 seconds (startsecs)
2021-05-29 15:48:49,559 WARN received SIGINT indicating exit request
2021-05-29 15:48:49,559 INFO waiting for insight, elasticmq to die
2021-05-29 15:48:49,566 INFO stopped: insight (terminated by SIGTERM)
2021-05-29 15:48:50,431 INFO stopped: elasticmq (terminated by SIGABRT (core dumped))
With a bit of googling I found this post where somebody had the same issue when running some other random image, and then posted that they managed to get the image running by setting some ulimits when running the image, which also worked for me (docker run --ulimit nofile=122880:122880 roribio16/alpine-sqs).
I checked the ulimits set inside the container when I didn't use this configuration
docker exec -it ca bash
$ ulimit -a
and found that the nofile setting was ridiculously high, which I assume is what is causing the container to run out of memory, if too many files are being opened simultaneously. I don't have a particulary good understanding of how this works though so would appreciate any clarification somebody could shed on that particular topic also.
Anyway the point of that ramble is that I want to try and find where the default docker container ulimits are set as I don't understand why they are so high on the machine I am using. I have another machine that does not have this problem.
I can find lots of ways to change the default limits but there does not seem to be much information about where these limits get set in the first place. I understand according to the docker documentation that if custom values are not set then the ulimits should be inherited from my system but as far as I can tell my system nofile settings are much lower than what I'm seeing in the container.
(Both machines run manjaro linux however the one that doesn't have this issue is XFCE and the one that does is KDE).