Orchestrating containers question

Hi all,
I would like to know what is the best practice for a following scenario: lets say I have a container running a cronjob, second container running nginx and third one nexus. Let cronjob container be in charge for some periodic task, like renewing certificates. When new certificates are issued, some signal is posted to nginx so it can run nginx -s reload. Similar situation is with nexus: its loading can last and I would like to be able to reload nginx after its running.

Background of this question is actually a strange problem I hit today, when running a compose with nginx container serving as reverse proxy to couple of other containers (nexus, jenkins, etc). I needed to connect to running nginx container and issue reload in order upstreams to work.

I have added:
resolver valid=30s;

To *.conf files but it did not solve it.

Thanks in advance