Re:Maybe You Don't Need Kubernetes (2019)
by falcolas on Monday January 13, 2020 @01:11PM
(#22036961)
> There's a resulting explosion of cognitive complexity as I have to keep track of what's part of the application and what's a system-level service.
If you can start them up with additional lines in a docker file (containers in a pod), it's just another ExecStart line in the unit file that calls Docker with a different container name.
EDIT: You do have to think a bit differently about networking, since the containers will have separate networks by default with Docker, in comparison to a k8s pod. You can make it match, however, by creating a network for the shared containers.
If, however, there's a "this service must be started before the next", systemd's dependency system will be more comprehensible than Kubernetes (since Kubernetes does not create dependency trees; the recommended method is to use init containers for such).
As a side note, unit files can also do things like init containers using the ExecStartPre hook.
If you can start them up with additional lines in a docker file (containers in a pod), it's just another ExecStart line in the unit file that calls Docker with a different container name.
EDIT: You do have to think a bit differently about networking, since the containers will have separate networks by default with Docker, in comparison to a k8s pod. You can make it match, however, by creating a network for the shared containers.
If, however, there's a "this service must be started before the next", systemd's dependency system will be more comprehensible than Kubernetes (since Kubernetes does not create dependency trees; the recommended method is to use init containers for such).
As a side note, unit files can also do things like init containers using the ExecStartPre hook.