Configuring logstash

[r-glyde]

Currently the logstash config looks for whether the KMS_LOGGING_LOGSTASH variable is defined to determine whether to enable logging or not.

<if condition='isDefined("KMS_LOGGING_LOGSTASH")'>

I think it is expected that a variable is passed in when the container is run that would set this value i.e. KMS_LOGGING_LOGSTASH: "true" to turn logging on. By only checking whether the variable is defined, something like KMS_LOGGING_LOGSTASH: "false" would also enable logging which is quite counterintuitive/wrong.

I think the condition should be adjusted to something where the configuration makes more sense e.g:

<if condition='p("KMS_LOGGING_LOGSTASH").equalsIgnoreCase("true")'>

I'm not sure if there are better ways of doing this e.g. parsing the env variable to a real boolean rather than true/false wrapped in a string.

Also, this config should probably be documented in the how-to-run-it section of the README.