[DOCS] Edited Docker install & tweaked Docker compose file.

[debadair]

Cleaned up the docker install instructions to remove the implication that a two-node cluster is recommended for productions.

Relates to elastic/stack-docs#455

[elasticmachine]

Pinging @elastic/es-docs (>docs)

[elasticmachine]

Pinging @elastic/es-core-infra (:Core/Infra/Packaging)

[rjernst]

@pugnascotia Would you please review this?

Long term it would be great if we could not have the docker compose file embedded in the docs source files, but instead have files that the docs build inserts when building, similar to what we have with some java source files used for examples. This way we can test the exact yml file we are suggesting users use.

[pugnascotia]

I'm trying out the actual compose file, and I'm having trouble getting it work. I'll keep digging.

[pugnascotia]

OK, I figured it out - I was struggling to use the docker-compose.yml setup in Docker for Mac, because I needed to increase the amount of memory available to the Docker Engine. Once I increased it from 2GB to 4GB, everything worked. It might be worth adding a note to the docs about this, since the symptoms I experienced were simply that some of the containers would just exit, without anything in the Docker logs.

After fixing the issue via guesswork, I dug further. The containers were exiting with code 137, which according to a help article from Docker, corresponds to 128 + 9 => 137, in order words a kill -9. By using screen to get into the VM, as per the docs, and running dmesg, I was able to confirm that the the containers were being killed for running out of memory.

[pugnascotia]

Re: elastic/stack-docs#455, are we going to update the example docker-compose.yml file further to enable security?

[debadair]

Thanks for the review @pugnascotia! I synced with the changes to elastic/stack-docs#455 and incorporated your feedback. That PR now has the TLS version, as well.

The goal is indeed to have the sample compose files separate, testable entities. They're separate files now, will work on the testing part once these PRs are merged.

[pugnascotia]

@debadair can we incorporate up the docker-compose.yml changes in https://github.com/elastic/elasticsearch/pull/47650/files too please?

[pugnascotia]

Revisions look good 👍

[debadair]

@elasticmachine run docs build

[debadair]

@elasticmachine, run elasticsearch-ci/docs