docker-minecraft-server/elasticsearch/README.md

This Docker image provides an easily configurable Elasticsearch node. Via port mappings, it is easy to create an arbitrarily sized cluster of nodes. As long as the versions match, you can mix-and-match "real" Elasticsearch nodes with container-ized ones.

# NOTE for use on Linux hosts

Elasticsearch 5.x requires that the virtual memory mmap count is set sufficiently for stable,
production use. [Refer to this guide for more information](https://www.elastic.co/guide/en/elasticsearch/reference/current/vm-max-map-count.html).

# Basic Usage

To start an Elasticsearch data node that listens on the standard ports on your host's network interface:

    docker run -d -p 9200:9200 -p 9300:9300 itzg/elasticsearch

You'll then be able to connect to the Elasticsearch HTTP interface to confirm it's alive:

http://DOCKERHOST:9200/

    {
      "status" : 200,
      "name" : "Charon",
      "version" : {
        "number" : "1.3.5",
        "build_hash" : "4a50e7df768fddd572f48830ae9c35e4ded86ac1",
        "build_timestamp" : "2014-11-05T15:21:28Z",
        "build_snapshot" : false,
        "lucene_version" : "4.9"
      },
      "tagline" : "You Know, for Search"
    }

Where `DOCKERHOST` would be the actual hostname of your host running Docker.

# Simple, multi-node cluster

To run a multi-node cluster (3-node in this example) on a single Docker machine use:

    docker run -d --name es0 -p 9200:9200                    itzg/elasticsearch
    docker run -d --name es1 --link es0 -e UNICAST_HOSTS=es0 itzg/elasticsearch
    docker run -d --name es2 --link es0 -e UNICAST_HOSTS=es0 itzg/elasticsearch


and then check the cluster health, such as http://192.168.99.100:9200/_cluster/health?pretty

    {
      "cluster_name" : "elasticsearch",
      "status" : "green",
      "timed_out" : false,
      "number_of_nodes" : 3,
      "number_of_data_nodes" : 3,
      "active_primary_shards" : 0,
      "active_shards" : 0,
      "relocating_shards" : 0,
      "initializing_shards" : 0,
      "unassigned_shards" : 0
    }

If you have a Docker Swarm cluster already initialized you can download this
[docker-compose.yml](https://raw.githubusercontent.com/itzg/dockerfiles/master/elasticsearch/docker-compose.yml) and deploy a cluster using:

    docker stack deploy -c docker-compose.yml es


With a `docker service ls` you can confirm 1 master, 2 data, and 1 gateway nodes are running:

```
ID            NAME        MODE        REPLICAS  IMAGE
9nwnno8hbqgk  es_kibana   replicated  1/1       kibana:latest
f5x7nipwmvkr  es_gateway  replicated  1/1       es
om8rly2yxylw  es_data     replicated  2/2       es
tdvfilj370yn  es_master   replicated  1/1       es
```

As you can see, there is also a Kibana instance included and available at port 5601.

# Health Checks

This container declares a [HEALTHCHECK](https://docs.docker.com/engine/reference/builder/#/healthcheck) that queries the `_cat/health`
endpoint for a quick, one-line gauge of health every 30 seconds.

The current health of the container is shown in the `STATUS` column of `docker ps`, such as

    Up 14 minutes (healthy)

You can also check the history of health checks from `inspect`, such as:

```
> docker inspect -f "{{json .State.Health}}" es
{"Status":"healthy","FailingStreak":0,"Log":[...
```

# Configuration Summary

## Ports

* `9200` - HTTP REST
* `9300` - Native transport

## Volumes

* `/data` - location of `path.data`
* `/conf` - location of `path.conf`

# Configuration Details

The following configuration options are specified using `docker run` environment variables (`-e`) like

    docker run ... -e NAME=VALUE ... itzg/elasticsearch

Since Docker's `-e` settings are baked into the container definition, this image provides an extra feature to change any of the settings below for an existing container. Either create/edit the file `env` in the `/conf` volume mapping or edit within the running container's context using:

    docker exec -it CONTAINER_ID vi /conf/env

replacing `CONTAINER_ID` with the container's ID or name.

The contents of the `/conf/env` file are standard shell

    NAME=VALUE

entries where `NAME` is one of the variables described below.

Configuration options not explicitly supported below can be specified via the `OPTS` environment variable. For example, by default `OPTS` is set with

    OPTS=-Dnetwork.bind_host=_non_loopback_

_NOTE: That option is a default since `bind_host` defaults to `localhost` as of 2.0, which isn't helpful for
port mapping out from the container_.

## Cluster Name

If joining a pre-existing cluster, then you may need to specify a cluster name different than the default "elasticsearch":

    -e CLUSTER=dockers

## Zen Unicast Hosts

When joining a multi-physical-host cluster, multicast may not be supported on the physical network. In that case, your node can reference specific one or more hosts in the cluster via the [Zen Unicast Hosts](http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/modules-discovery-zen.html#unicast) capability as a comma-separated list of `HOST:PORT` pairs:

    -e UNICAST_HOSTS=HOST:PORT[,HOST:PORT]

such as

    -e UNICAST_HOSTS=192.168.0.100:9300

## Plugins

You can install one or more plugins before startup by passing a comma-separated list of plugins.

    -e PLUGINS=ID[,ID]

In this example, it will install the Marvel plugin

    -e PLUGINS=elasticsearch/marvel/latest

Many more plugins [are available here](http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/modules-plugins.html#known-plugins).

## Publish As

Since the container gives the Elasticsearch software an isolated perspective of its networking, it will most likely advertise its published address with a container-internal IP address. This can be overridden with a physical networking name and port using:

    -e PUBLISH_AS=DOCKERHOST:9301

_Author Note: I have yet to hit a case where this was actually necessary. Other
than the cosmetic weirdness in the logs, Elasticsearch seems to be quite tolerant._

## Node Name

Rather than use the randomly assigned node name, you can indicate a specific one using:

    -e NODE_NAME=Docker

## Node Type

If you refer to [the Node section](https://www.elastic.co/guide/en/elasticsearch/reference/2.3/modules-node.html)
of the Elasticsearch reference guide, you'll find that there's three main types of nodes: master-eligible, data, and client.

In larger clusters it is important to dedicate a small number (>= 3) of master nodes. There are also cases where a large cluster may need dedicated gateway nodes that are neither master nor data nodes and purely operate as "smart routers" and have large amounts of CPU and memory to handle client requests and search-reduce.

To simplify all that, this image provides a `TYPE` variable to let you amongst these combinations. The choices are:

* (not set, the default) : the default node type which is both master-eligible and a data node
* `MASTER` : master-eligible, but holds no data. It is good to have three or more of these in a
large cluster
* `DATA` (or `NON_MASTER`) : holds data and serves search/index requests. Scale these out for elastic-y goodness.
* `NON_DATA` : performs all duties except holding data
* `GATEWAY` (or `COORDINATING`) : only operates as a client node or a "smart router". These are the ones whose HTTP port 9200 will need to be exposed
* `INGEST` : operates only as an ingest node and is not master or data eligible

A [Docker Compose](https://docs.docker.com/compose/overview/) file will serve as a good example of these three node types:

```
version: '3'

services:
  gateway:
    image: itzg/elasticsearch
    environment:
      UNICAST_HOSTS: master
      TYPE: GATEWAY
    ports:
      - "9200:9200"

  master:
    image: itzg/elasticsearch
    environment:
      UNICAST_HOSTS: gateway
      TYPE: MASTER
      MIN_MASTERS: 2

  data:
    image: itzg/elasticsearch
    environment:
      UNICAST_HOSTS: master,gateway
      TYPE: DATA

  kibana:
    image: kibana
    ports:
      - "5601:5601"
    environment:
      ELASTICSEARCH_URL: http://gateway:9200

```

## Minimum Master Nodes

In combination with the `TYPE` variable above, you will also want to configure the minimum master nodes to [avoid split-brain](https://www.elastic.co/guide/en/elasticsearch/reference/2.3/modules-node.html#split-brain) during network outages.

The minimum, which can be calculated as `(master_eligible_nodes / 2) + 1`, can be set with the `MIN_MASTERS` variable.

Using the Docker Compose file above, a value of `2` is appropriate when scaling the cluster to 3 master nodes:

    docker-compose scale master=3

## Multiple Network Binding, such as Swarm Mode

When using Docker Swarm mode the container is presented with multiple ethernet
devices. By default, all global, routable IP addresses are configured for
Elasticsearch to use as `network.host`.

That discovery can be overridden by providing a specific ethernet device name
to `DISCOVER_TRANSPORT_IP` and/or `DISCOVER_HTTP_IP`, such as

    -e DISCOVER_TRANSPORT_IP=eth0
    -e DISCOVER_HTTP_IP=eth2

## Heap size and other JVM options

By default this image will run Elasticsearch with a Java heap size of 1 GB. If that value
or any other JVM options need to be adjusted, then replace the `ES_JAVA_OPTS`
environment variable.

For example, this would allow for the use of 16 GB of heap:

    -e ES_JAVA_OPTS="-Xms16g -Xmx16g"

Refer to [this page](https://www.elastic.co/guide/en/elasticsearch/reference/current/heap-size.html)
for more information about why both the minimum and maximum sizes were set to
the same value.