How critical is dumb-init for Docker?

Question

I hope that this question will not be marked as primarily opinion-based, but that there is an objective answer to it.

I have read Introducing dumb-init, an init system for Docker containers, which extensively describes why and how to use dumb-init. To be honest, for someone not too experienced with how the Linux process structure works, this sounds pretty dramatic - and it feels as if you are doing things entirely wrong if you don't use dumb-init.

This is why I'm thinking about using it within my very own Docker images… what keeps me from doing this is the fact that I have not yet found an official Docker image that uses it.

• Take mongo as an example: They call mongod directly.
• Take postgres as an example: They call postgres directly.
• Take node as an example: They call node directly.
• …

If dumb-init is so important - why is apparently nobody using it? What am I missing here?

Answer 1

Something like dumb-init or tini can be used if you have a process that spawns new processes and you don't have good signal handlers implemented to catch child signals and stop your child if your process should be stopped etc.

If your process doesn't spawn new processes (e.g. Node.js), then this may not be necessary.

I guess that MongoDB, PostgreSQL, ... which may run child processes have good signal handlers implemented. Otherwise there would have been zombie processes and someone would have filed an issue to fix this.

Only problem may be the official language images, like node, ruby, golang. They don't have dumb-init/tini in it as you normally don't need them. But it's up to the developer which may implement bad child execution code to either fix the signal handlers or use helper as PID 1.