It's not. Most apps rightfully expect that they're not PID 1, and that the real PID 1 takes care of that sort of stuff. Only in a container does it happen often that your totally-not-designed-to-be-a-PID-1 app, actually is PID 1.
What if you're creating a PostgreSQL container, and your init script spawns a daemon, after which it exec()s the PostgreSQL server process as PID 1? The daemon then spawns a few processes that fork a few times. PostgreSQL only waitpid()s on its own postmaster worker processes and so those other processes become zombies. Are you telling me that PostgreSQL is broken and that you have to patch PostgreSQL?
I think using a proper init system, and running PostgreSQL under it, is a much saner view on things. The small wrapper that you mentioned is exactly the /sbin/my_init provided by baseimage-docker.
What if you're creating a PostgreSQL container, and your init script spawns a daemon, after which it exec()s the PostgreSQL server process as PID 1? The daemon then spawns a few processes that fork a few times. PostgreSQL only waitpid()s on its own postmaster worker processes and so those other processes become zombies. Are you telling me that PostgreSQL is broken and that you have to patch PostgreSQL?
I think using a proper init system, and running PostgreSQL under it, is a much saner view on things. The small wrapper that you mentioned is exactly the /sbin/my_init provided by baseimage-docker.