Default config should be valid, but no-op.

[ninaspitfire]

When a user passes the pipeline configuration via ENV (see #30), that config is merged with the default config resulting in unexpected behaviour. The default config should do nothing, successfully.

[slavniyteo]

Will it be done?
Now we run elk in rancher and pass pipeline through env CONFIG_STRING. And should pass PATH_CONFIG=/dev/null to avoid config merge. It is weird.

[jordansissel]

Maybe it's really a bug that there's any default configuration in the docker container.

Anyway, it is a feature of Logstash that the config_string (-e flag to logstash) merges with the configuration on disk.

However, in Logstash starting with 6.0 (unreleased), this merging behavior is gone:

• Is the merging of -e and -f still a desirable behaviour? #4619
• make e and f flags mutually exclusive #6976

Once 6.0 is released (though 6.0-beta2 is available),