shell shell - 1 month ago 16
Python Question

docker cannot connect to redis from file

I am running docker using docker-compose up.

In a file I am trying to access the redis created using:

import redis

pool = redis.ConnectionPool(host='redis', port=6379, db=0)
r = redis.Redis(connection_pool=pool)
r.flushall()


Here is my docker-compose.yml redis portion:

web:
build: .
ports:
- "8000:8000"
links:
- db
- redis
environment:
- DATABASE_URL=postgres://user:openhouse2016@db:5432/chat
- REDIS_URL=redis://redis:6379/1
volumes:
- .:/opt/app
db:
image: praiskup/postgresql:APIv1.0.1-fedora23
# volumes:
# - ./db:/var/lib/pgsql/data
environment:
- POSTGRESQL_DATABASE=chat
- POSTGRESQL_USER=user
- POSTGRESQL_PASSWORD=openhouse2016
- POSTGRESQL_CONTAINER_OPTS=assert_external_data = false
worker:
build: .
environment:
- DATABASE_URL=postgres://user:openhouse2016@db:5432/chat
- REDIS_URL=redis://redis:6379/1
links:
- db
- redis
volumes:
- .:/opt/app
# we need to wait for database setup
command: bash -c "sleep 7 && exec python /opt/app/channels-example/manage.py runworker -v3"
redis:
image: redis
ports:
- "6379:6379"
migrator:
build: .
environment:
- DATABASE_URL=postgres://user:openhouse2016@db:5432/chat
- REDIS_URL=redis://redis:6379/1
links:
- db
# it indeed takes this long to start the database
command: bash -c "sleep 5 && exec python /opt/app/channels-example/manage.py migrate"


After running:

docker-compose down
docker-compose build
docker-compose up


Everything runs fine and redis says it is ready to accept connections on port 6379.

However, the python code above generates:

redis.exceptions.ConnectionError: Error -5 connecting to redis:6379. No address associated with hostname.


How do I connect to redis from the python file?

EDIT:

docker ps -a


redis shows:

3a494c9da73d redis "docker-entrypoint.sh"
10 seconds ago Up 9 seconds 0.0.0.0:6379->6379/tcp

Answer

The migrator did not link to redis. This fixed it:

migrator:
  build: .
  environment:
   - DATABASE_URL=postgres://user:openhouse2016@db:5432/chat
   - REDIS_URL=redis://redis:6379/1
  links:
   - db
   - redis #this line here was missing
  # it indeed takes this long to start the database
  command: bash -c "sleep 5 && exec python /opt/app/channels-example/manage.py migrate"