does elasticsearch have capability to form es cluster with only one es docker service running multiple replicas of it in docker-swarm
yes it is possible to achieve it.
just add endpoint_mode as dnsrr like below in docker-compose.yaml file.
for deploying one instance/container across all docker-swarm nodes use "mode: global" in docker-compose.yaml file.
For deploying all ES cluster instance/containers in one machine, use "mode: replicated" and specify replicas to deploy as say "replicas: 3" in docker-compose.yaml file.
With usage of "endpoint_mode: dnsrr" we won't able to expose service ports.
For this purpose we should use an external load balancer like nginx or haproxy.
Like below nginx docker-compose.yaml file
version: '3.5'
services:
elasticsearch:
image: elasticsearch:5
deploy:
# mode: replicated
# replicas: 3
mode: global
endpoint_mode: dnsrr
restart_policy:
condition: on-failure
delay: 5s
max_attempts: 3
window: 120s
# placement:
# constraints: [node.role == manager]
environment:
- ES_JAVA_OPTS=${ELASTICSEARCH_MEM}
volumes:
- esdata:/usr/share/elasticsearch/data
configs:
- source: elasticsearch.yml
target: /usr/share/elasticsearch/config/elasticsearch.yml
# ports:
# - 9200:9200
# - 9300:9300
nginx-lb:
image: "nginx:1.15.4"
deploy:
restart_policy:
condition: on-failure
delay: 5s
max_attempts: 3
window: 120s
placement:
constraints: [node.role == manager]
volumes:
- ./nginx.conf:/etc/nginx/nginx.conf
ports:
- 9200:9200
- 9300:9300
volumes:
esdata:
configs:
elasticsearch.yml:
external: true
#elasticsearch.yaml file
transport.host: 0.0.0.0
http.host: 0.0.0.0
network.host: 0.0.0.0
cluster.name: elasticsearch
discovery.zen.ping.unicast.hosts: elasticsearch
discovery.zen.minimum_master_nodes: 1
node.max_local_storage_nodes: 20
#nginx.conf file
events {}
stream {
upstream stream_backend {
server elasticsearch:9300;
}
server {
listen 9300;
proxy_pass stream_backend;
proxy_timeout 3s;
proxy_connect_timeout 1s;
}
}
http {
upstream elasticsearchPort9200 {
server elasticsearch:9200;
}
server {
listen 9200;
server_name _;
location / {
proxy_pass http://elasticsearchPort9200;
}
}
}