docker: php name resolution issue

Question

I'm facing an issue on raspberry pi 4 with php in Docker saying it cannot resolve the name of my redis server.

I'm using the nextcloud image linuxserver/nextcloud which relies on nginx+php-fpm with the following docker-compose.yml:

services:
  db:
    image: yobasystems/alpine-mariadb
    volumes:
      - "./db/mysql:/var/lib/mysql" # location where you persist DB files
      - "./db/restore:/restore" # mount folder to store mysql_dump file
    environment:
      - TZ=Europe/Paris
    env_file: .env
    restart: always

  redis:
    image: redis:alpine
    restart: always
    volumes:
      - "./redis:/data"

  nextcloud:
    depends_on:
      - db
      - redis
    image: linuxserver/nextcloud
    container_name: nextcloud
    environment:
      - PUID=1000
      - PGID=1000
      - TZ=Europe/Paris
   ...

and in my nextcloud config.php:

  'memcache.local' => '\OC\Memcache\Redis',
  'redis' =>
     array (
       'host' => 'redis',
       'port' => 6379,
     ),
  'memcache.locking' => '\OC\Memcache\Redis',

Running this, I get the error "php_network_getaddresses: getaddrinfo failed: Name does not resolve" although pinging redis from the container using the following command works fine:

pi@raspberrypi /docker/nextcloud $ docker exec nextcloud ping redis
PING redis (172.19.0.2): 56 data bytes
64 bytes from 172.19.0.2: seq=0 ttl=64 time=0.247 ms
64 bytes from 172.19.0.2: seq=1 ttl=64 time=0.303 ms
64 bytes from 172.19.0.2: seq=2 ttl=64 time=0.172 ms
64 bytes from 172.19.0.2: seq=3 ttl=64 time=0.341 ms

When I change 'redis' by the redis IP in "host"=>'redis' in the nextcloud config.php, everything works fine in nextcloud/redis communication but I don't like to hardcode this.

I looked at the different questions around the same topic but didn't find something really usefull...

Any help appreciated...

docker: php name resolution issue

0 Answers