FR: Multiple Hosts Support about watchtower

[cameronaw13]

After briefly reviewing the internal/pkg code and docker sdk api, it seems that we'd need to rework quite a bit regarding the client setup process. There isn't any way to add multiple hosts directly through the "DOCKER_HOST" env var as its used directly in the sdk api (it can only work with one host at a time). We'd likely need to add a separate environment variable allowing us to parse and iterate through a list of docker hosts (though this may add unneeded complexity). For each iteration we would need to run the update stack changing the docker_host env var each time but I am unsure of how much would need to be updated in order to accommodate this. For example, we'd also need to rework notifications/logs allowing you to differentiate between docker hosts.

And there's likely much more that I missed as I only looked through the code briefly with my limited golang knowledge. Its a bit more complicated than I first thought but I still feel that implementing such a feature would benefit many people's setups including mine in the long run.

[github-actions]

Hi there! 👋🏼 As you're new to this repo, we'd like to suggest that you read our code of conduct as well as our contribution guidelines. Thanks a bunch for opening your first issue! 🙏

[cameronaw13]

+1 on this.
Just to clear the air from the previous discussion; from what I've gathered, I think that both piksel and simskij severely misinterpreted what neo-neo1 was trying to say. He was not asking for a way to implement redundancy for watchtower but was instead commenting on how redundant it is to add a new instance of watchtower for each and every machine he runs docker on. Instead, as spyhuntergenral suggests, we could allow a single instance of watchtower to update multiple remote Docker endpoints (including the local daemon if possible) eliminating the need to start up and maintain multiple instances of watchtower.

[NetRat88]

Good to see, that this FR comes up again.
I also was searching for the possibility to add multi host on my existing and running watchtower instance and also was wandering about the discussion in the past. 😅

In my use case I would like to add my QNAP NAS docker host with paperless, another Raspberry Pi4 with some network docker containers and my Pi5 with home automation containers to my existing watchtower instance in my third management Pi (with Portainer and some other containers).

Just to let you guys know that there are more supporters for this feature request. Thanks for the great work which saves me a lot of admin time!
But understand that you have iterate some more code to add this. I also use pushover notifications and could imagine, that it's not just extending the remote host list.