About Recreate a Docker container if a container it depends upon is recreated
336
github.com/treyturner/whalewatcher
Recreate a Docker container if a container it depends upon is recreated.
That's a word salad, so here's at least one use case (mine):
You have a containerized app that routes traffic through a containerized VPN client, but when watchtower recreates the VPN client container due to an image update, your app container stops routing traffic until it is removed and recreated.
This small Dockerfile and shell script will monitor the state of containers in these dependent relationships and restart the dependent container as needed.
The following environment variables must be set; no defaults are provided.
| Name | Description | Example value |
|---|---|---|
DEPENDENT_CONTAINER | The container with the dependency | rtorrent |
DEPENDENCY_CONTAINER | The container that is depended upon | vpn-dal |
COMPOSE_PROJECT_NAME | The name of the compose project | rtorrent |
The examples above suggest an rtorrent/docker-compose.yml that looks something like this:
version: "3.2"
services:
rtorrent:
image: crazymax/rtorrent-rutorrent
container_name: rtorrent
network_mode: container:vpn-dal
# whatever environment variables and volumes you need
watcher:
image: whalewatcher
container_name: rtorrent_watcher
volumes:
- /var/run/docker.sock:/var/run/docker.sock
# YOU MUST MODIFY THE HOST PATH TO CORRECTLY MOUNT YOUR docker-compose.yml INSIDE THE CONTAINER
- /mnt/cache/appdata/portainer_data/compose/28/docker-compose.yml:/root/docker-compose.yml
restart: unless-stopped
labels:
- com.centurylinklabs.watchtower.enable=false
environment:
- DEPENDENT_CONTAINER=rtorrent
- DEPENDENCY_CONTAINER=vpn-dal
- COMPOSE_PROJECT_NAME=rtorrent
And here's what the container logs when it's doing its thing. In this case, it happened to poll before vpn-dal had reached it's safe init time (30 seconds), so it waits at least that long before starting the dependency.
2022-11-04 Fri 18:32:20 Waiting 10 seconds for vpn-dal to initialize...
2022-11-04 Fri 18:32:30 rtorrent was started before vpn-dal initialized. Recreating...
Stopping rtorrent ...
Stopping rtorrent ... done
Removing rtorrent ...
Removing rtorrent ... done
Going to remove rtorrent
Creating rtorrent ...
Creating rtorrent ... done
Content type
Image
Digest
sha256:ffb23f823…
Size
93.5 MB
Last updated
almost 2 years ago
docker pull treyturner/whalewatcher