Allow for basic container Orchestration by specifying Container dependency (akin to WatchTower)

[taw123]

I reviewed the doc here, and scared through the Discussions forms but can find no evidence the function exhists. Please feel free to correct if I am wrong.

First I want to say I am quite impressed with what appears to be an incredibly modular and flexible update management system, unfortunately it for my use it looks to be missing only one key function. I am potentially coming to WUD from WatchTower (and before that MANY years using Ouroboros). I say potentially as WatchTower is currently meeting my needs but looking to potentially move to WUD given maintenance state and perceived flexibility. For reference: Link to Watchtower Lifecycle doc and Labeling linked Containers

Unfortunately while it appears that WUD also supports the use of labels for control of a number of functions, it docent APEAR from and thing I have found that WUD supports labeling container DEPENDANCY.

What I am looking for is the ability to add a label to a given container with any dependent containers and then have WUD down any appropriate containers when the prerequisite is to be updated, and restart them BEFORE starting the newly updated container. For example take Home Assistant which I have using both Maria and InfluxDB. Both databases are listed/labeled as dependencies one the Home Assistant container (Label com.centurylinklabs.watchtower.depends-on = InfluxDB,MariaDB). IF Maria needs to be updated, then HA is stopped before updating and likewise after updating Maria is started BEFORE restarting HA. There is no "guarantee" that the prerequisite had completed it's start up though in practice this has not been an issue so either delay Watchtower is imposing sufficient. I of course could add my own delay on start, or implement a health check(not desirable given performance hit) or in this particular case just test for access to the from Home Assistant before starting the container inside a wait loop.

Regardless, I do know that there are a number of ways to implement orchestration from simple wait loops like I mentioned above to full blown orchestration systems, but what I am seeking here is very rudimentary and narrow in scope, but would clearly solve the issue for me and many of my containers that have simple dependencies. I believe that I am clearly NOT alone in my quest for the functionality (given it's longstanding availability as mentioned in WatchTower).

Thanks again for all the effort you have and continue to put into this project and look forward your reply and hopefully the orchestration label I mentioned.

-T

[G-Cyrille]

Totally agree with this.

Personally I currently manage part of this with a custom script that I import into the container :

• ./update-custom.js:/home/node/app/update-custom.js:ro
  This script has access to dockerode (the package used by WUD)

But this is not a good/long term solution as it may break depending on the internals of WUD.
Neither does this have the potential to do all you need.