Obliterate X-Pack

Summary

The Elasticsearch Docker image used by this role has X-Pack installed. X-Pack is a commercial plug-in and we do not use it.

Steps to reproduce

See container logs, e.g.

docker logs elasticsearch

Expected behavior

All is fine, all is well.

Actual behavior

This is what I got it the logs:

# License [will expire] on [Friday, December 22, 2017]. If you have a new license, please update it.
# Otherwise, please reach out to your support contact.
# 
# Commercial plugins operate with reduced functionality on license expiration:
# - security
#  - Cluster health, cluster stats and indices stats operations are blocked
#  - All data operations (read and write) continue to work
# - watcher
#  - PUT / GET watch APIs are disabled, DELETE watch API continues to work
#  - Watches execute and write to the history
#  - The actions of the watches don't execute
# - monitoring
#  - The agent will stop collecting cluster and indices metrics
#  - The agent will stop automatically cleaning indices older than [xpack.monitoring.history.duration]
# - graph
#  - Graph explore APIs are disabled
# - ml
#  - Machine learning APIs are disabled

Moreover, this X-Pack thing adds some crazy "watchers" for Kibana, Logstash & whatnot, which then produce the following error messages:

[2017-11-30T09:46:59,185][WARN ][o.e.x.w.e.ExecutionService] [b5SU3U6] Failed to execute watch [xBFROtqtRiaGEJKsQaufKg_logstash_version_mismatch_44bbbb0d-d894-4a37-acd2-d9bc2e0c0b9e-2017-11-30T09:46:59.160Z]
[2017-11-30T09:46:59,194][WARN ][o.e.x.w.e.ExecutionService] [b5SU3U6] Failed to execute watch [xBFROtqtRiaGEJKsQaufKg_kibana_version_mismatch_26b4202b-06ac-4412-82c1-f637fb44c10f-2017-11-30T09:46:59.160Z]
[2017-11-30T09:46:59,197][WARN ][o.e.x.w.e.ExecutionService] [b5SU3U6] Failed to execute watch [xBFROtqtRiaGEJKsQaufKg_elasticsearch_version_mismatch_e596a417-0191-4c79-a570-45d2706f5a66-2017-11-30T09:46:59.160Z]
[2017-11-30T09:46:59,219][WARN ][o.e.x.w.e.ExecutionService] [b5SU3U6] Failed to execute watch [xBFROtqtRiaGEJKsQaufKg_elasticsearch_cluster_status_a0fa5159-d7ab-4969-a038-f43d39ee14c3-2017-11-30T09:46:59.160Z]

Relevant logs and/or screenshots

Possible fixes

Zwei easy fixes are possible:

1. [RECOMMENDED] Change the Docker image to elasticsearch-oss, which does not include X-Pack. This image is only available for Elasticsearch 6.0.

2. Disable X-Pack features explicitly in the configuration file, i.e.:

   xpack.security.enabled: false
   xpack.watcher.enabled: false
   xpack.monitoring.enabled: false
   xpack.ml.enabled: false
   xpack.graph.enabled: false