Generate keyfile for the cluster on container build

[jshimko]

All members of a replica set require the same keyfile for encrypted/authenticated communication between replica nodes. That file is currently static in this repo and copied over on container build. Ideally, key generation would happen at build time. The main reason the pre-generated keyfile is included as a static file now is because each member of a set could potentially be built at different times, so random key generators at build time aren't an option. The key needs to match on every node in a set, so environment variables seem to be the simplest way to keep them in sync while also keeping the ability to be unique.

Maybe set it up to use env vars to set the key and then just handle the random key generation in Launchdock?

[timchunght]

@jshimko Would it be possible to generate the key by reading from the environment variable on run time? It can be added in the entrypoint. Thanks.

[jshimko]

I forgot to update this issue when I updated how the keyfile is generated recently. A unique key is now generated at build time, so you just have to make sure you use the same build in each location.

I suppose an env var would be useful as well. I'd be happy to accept a PR if you want to take care of that.

[timchunght]

@jshimko I just submitted a PR. Thanks! Please check #3

[timchunght]

@jshimko Any update or question in regards to the PR? Thanks.

[createbuildship]

Could you add docs on how to depoy this as there are many sh file and yml files. I can seem to understand what file i need to focus to run the docker builder and get this working.