Clustering Dockerized Elasticsearch with multiple Docker Host - docker

Question

Trying to make it clustering with docker compose.
I have two elasticsearch docker containers which are deployed in different Docker Hosts.
docker version: 18.06.3-ce
elasticsearch : 6.5.2
docker-compose.yml for docker-container-1
services:
elasticsearch:
restart: always
hostname: elasticsearch
image: docker-elk/elasticsearch:1.0.0
build:
context: elasticsearch
dockerfile: Dockerfile
environment:
discovery.type: zen
ports:
- 9200:9200
- 9300:9300
env_file:
- ./elasticsearch/elasticsearch.env
volumes:
- elasticsearch_data:/usr/share/elasticsearch/data
docker-compose.yml for docker-container-2
services:
elasticsearch:
restart: always
hostname: elasticsearch
image: docker-elk/elasticsearch:1.0.0
build:
context: elasticsearch
dockerfile: Dockerfile
environment:
discovery.type: zen
ports:
- 9200:9200
- 9300:9300
env_file:
- ./elasticsearch/elasticsearch.env
volumes:
- elasticsearch_data:/usr/share/elasticsearch/data
elasticsearch.yml on the elasticsearch-docker-container-1 on the Docker-Host 1
xpack.security.enabled: true
cluster.name: es-cluster
node.name: es1
network.host: 0.0.0.0
node.master: true
node.data: true
transport.tcp.port: 9300
path.data: /usr/share/elasticsearch/data
path.logs: /usr/share/elasticsearch/logs
discovery.zen.minimum_master_nodes: 2
gateway.recover_after_nodes: 1
discovery.zen.ping.unicast.hosts: ["host1:9300", "host2:9300","host1:9200", "host2:9200"]
network.publish_host: host1
elasticsearch.yml on the elasticsearch-docker-container-2 on the Docker-Host 2
xpack.security.enabled: true
cluster.name: es-cluster
node.name: es2
network.host: 0.0.0.0
node.master: true
node.data: true
transport.tcp.port: 9300
path.data: /usr/share/elasticsearch/data
path.logs: /usr/share/elasticsearch/logs
discovery.zen.minimum_master_nodes: 2
gateway.recover_after_nodes: 1
discovery.zen.ping.unicast.hosts: ["host1:9300", "host2:9300","host1:9200", "host2:9200"]
network.publish_host: host2
Below is the result of GET /_cluster/health?pretty and it shows that there is only one node.
{
"cluster_name" : "dps_geocluster",
"status" : "yellow",
"timed_out" : false,
"number_of_nodes" : 1,
"number_of_data_nodes" : 1,
"active_primary_shards" : 33,
"active_shards" : 33,
"relocating_shards" : 0,
"initializing_shards" : 0,
"unassigned_shards" : 30,
"delayed_unassigned_shards" : 0,
"number_of_pending_tasks" : 0,
"number_of_in_flight_fetch" : 0,
"task_max_waiting_in_queue_millis" : 0,
"active_shards_percent_as_number" : 52.38095238095239
}
According to the document below at least three elasticsearch nodes are required.
https://www.elastic.co/guide/en/elasticsearch/reference/6.5/modules-node.html
Each elasticsearch container should be at different Docker host?

Answer 1

The following was the cause of error. After increasing the value of vm.max_map_count into 262144 with sysctl, it works fine.
elasticsearch_1 | [1]: max virtual memory areas vm.max_map_count [65530] is too low, increase to at least [262144]
Now number_of_nodes is 2.
{
"cluster_name" : "es-cluster",
"status" : "yellow",
"timed_out" : false,
"number_of_nodes" : 2,
"number_of_data_nodes" : 2,
"active_primary_shards" : 35,
"active_shards" : 37,
"relocating_shards" : 0,
"initializing_shards" : 2,
"unassigned_shards" : 31,
"delayed_unassigned_shards" : 0,
"number_of_pending_tasks" : 0,
"number_of_in_flight_fetch" : 0,
"task_max_waiting_in_queue_millis" : 0,
"active_shards_percent_as_number" : 52.85714285714286
}