Pass in configuration using environment variable

[xaka]

As we live in era where containers taking over place, it would be nice to assign configuration to environment variable, may be $LOGSTASH, and make sure logstash consumes it when no configuration file (-f) or configuration string (-e) is provided. The reason is pretty simple - I don't want to build my own image from base one just to inject some file nor I want to mess around with volumes nor I'm happy with -e because you end up with a long unreadable line and at the same, when you use docker compose for instance, you can come up with (take a look at magical pipe | supported by YAML):

image: logstash
environment:
  LOGSTASH: |
    input {
      ...
    }

Which is pretty readable and allows one to use existing official image.

[xaka]

For now I'm using the following workaround to stick to official image without need for building my own:

image: logstash
command: bash -c 'echo $$LOGSTASH > logstash.conf; exec logstash -f logstash.conf'
environment:
  LOGSTASH: |
    input {
      ...
    }

[suyograo]

Fixed in #3944, will be available in 2.3