Docker Rails app with searchkick/elasticsearch - ruby-on-rails

Question

Im porting my rails app from my local machine into a docker container and running into an issue with elasticsearch/searchkick. I can get it working temporarily but Im wondering if there is a better way. So basically the port for elasticsearch isnt matching up with the default localhost:9200 that searchkick uses. Now I have used "docker inspect" on the elasticsearch container and got the actual IP and then set the ENV['ELASTICSEARCH_URL'] variable like the searchkick docs say and it works. The problem Im having is that is a pain if I restart/change the containers the IP changes sometimes and I have to go through the whole process again. Here is my docker-compose.yml:
version: '2'
services:
web:
build: .
command: rails server -p 3000 -b '0.0.0.0'
volumes:
- .:/living-recipe
ports:
- '3000:3000'
env_file:
- .env
depends_on:
- postgres
- elasticsearch
postgres:
image: postgres
elasticsearch:
image: elasticsearch

Answer 1

use elasticsearch:9200 instead of localhost:9200. docker compose exposes the container via it's name.

Answer 2

Here is the docker-compose.yml that is working for me
docker compose will expose the container vaia it's name, so you can set
ELASTICSEARCH_URL: http://elasticsearch:9200 ENV variable in your rails application container
version: "3"
services:
db:
image: postgres:9.6
restart: always
volumes:
- /tmp/db:/var/lib/postgresql/data
environment:
POSTGRES_PASSWORD: password
elasticsearch:
image: docker.elastic.co/elasticsearch/elasticsearch:7.9.2
volumes:
- .:/app
ports:
- 9200:9200
environment:
- discovery.type=single-node
ulimits:
memlock:
soft: -1
hard: -1
api:
build: .
command: bash -c "rm -f tmp/pids/server.pid && bundle exec rails s -p 3000 -b '0.0.0.0'"
volumes:
- ".:/app"
ports:
- "3001:3000"
depends_on:
- db
environment:
DB_HOST: db
DB_PASSWORD: password
ELASTICSEARCH_URL: http://elasticsearch:9200

Answer 3

You don't want to try to map the IP address for elasticsearch manually, as it will change.
Swap out depends_on for links. This will create the same dependency, but also allows the containers to be reached via service name.
Containers for the linked service will be reachable at a hostname identical to the alias, or the service name if no alias was specified.
Links also express dependency between services in the same way as depends_on, so they determine the order of service startup.
Docker Compose File Reference - Links
Then in your rails app where you're setting ENV['ELASTICSEARCH_URL'], use elasticsearch instead.