I have published a tutorial with a step by step upgrade of a docker based RocketChat deployment. First we show how to upgrade RocketChat to its latest version.
Next, we learn how to migrate the MongoDB database from using the mmap database engine to the new wiredTiger database engine. This is important because this step is a requirement prior to an upgrade to the soon to be released RocketChat 5.0.
Once MongoDB v4.0.x is using the wiredTiger database engine, we show how to perform an iterative upgrade of MongoDB from the deprecated 4.0 version to 4.2. We then upgrade MongoDB from 4.2 to 4.4. Lastly, I show how to upgrade MongoDB from 4.4 to 5.0.