This Docker images provides the opensearchproject/opensearch image as base with the mDNS/ZeroConf stack on top. So you can enjoy OpenSearch while it is accessible by default as opensearch.local. (Port 9200, 9600, 80 via proxy)

• Requirements
• Getting starting
• docker-compose usage example
• Host configs
• Configure a different mDNS hostname
• Other top level domains
• Further reading

Requirements

• Host enabled Avahi daemon
• Host enabled mDNS NSS lookup

Getting starting

You just need to run it like that, to get a working opensearch:

$ docker run --rm hausgold/opensearch

The port 9200 is proxied by haproxy to port 80 to make opensearch.local directly accessible. The port 9200 and 9600 are untouched.

Checkout the working with plugins documentation if you have to deal with custom plugins.

In order to enable the Elasticsearch version compatibility add this environment variable:

compatibility.override_main_response_version='true'

docker-compose usage example

opensearch:
  image: hausgold/opensearch
  environment:
    # Mind the .local suffix
    MDNS_HOSTNAME=opensearch.test.local
    OPENSEARCH_JAVA_OPTS: -Xms96m -Xmx96m
    discovery.type: single-node
    compatibility.override_main_response_version: false
  ports:
    # The ports are just for you to know when configure your
    # container links, on depended containers
    - "9200"
    - "9300"
    - "9600"
  ulimits:
    # Due to systemd/pam RLIMIT_NOFILE settings (max int inside the
    # container), the Java process seams to allocate huge limits which result
    # in a +unable to allocate file descriptor table - out of memory+ error.
    # Lowering this value fixes the issue for now.
    #
    # See: http://bit.ly/2U62A80
    # See: http://bit.ly/2T2Izit
    nofile:
      soft: 100000
      hard: 100000

Host configs

Install the nss-mdns package, enable and start the avahi-daemon.service. Then, edit the file /etc/nsswitch.conf and change the hosts line like this:

hosts: ... mdns4_minimal [NOTFOUND=return] resolve [!UNAVAIL=return] dns ...

Configure a different mDNS hostname

The magic environment variable is MDNS_HOSTNAME. Just pass it like that to your docker run command:

$ docker run --rm -e MDNS_HOSTNAME=something.else.local hausgold/opensearch

This will result in something.else.local.

You can also configure multiple aliases (CNAME's) for your container by passing the MDNS_CNAMES environment variable. It will register all the comma separated domains as aliases for the container, next to the regular mDNS hostname.

$ docker run --rm \
  -e MDNS_HOSTNAME=something.else.local \
  -e MDNS_CNAMES=nothing.else.local,special.local \
  hausgold/opensearch

This will result in something.else.local, nothing.else.local and special.local.

Other top level domains

By default .local is the default mDNS top level domain. This images does not force you to use it. But if you do not use the default .local top level domain, you need to configure your host avahi to accept it.

Further reading

• Docker/mDNS demo: https://github.com/Jack12816/docker-mdns
• Archlinux howto: https://wiki.archlinux.org/index.php/avahi
• Ubuntu/Debian howto: https://wiki.ubuntuusers.de/Avahi/