4 ms·

Isn't this effectively a non-issue? It's literally just a tiny entry in a table that is held no? Or does it just cause Docker to behave oddly?

• FooBarWidget 12y ago
  There are two issues. First is Murphey's law. 1 zombie process is probably harmless, but if the amount grows then you'll fill up kernel limits and the container cannot create further processes. Second, zombie processes that don't go away can also interfere with software that check for the existence of processes. For example, [the Phusion Passenger application server](https://www.phusionpassenger.com/ https://www.phusionpassenger.com/) manages processes. It restarts processes when they crash. Crash detection is implemented by parsing the output of `ps`, and by sending a 0 signal to the process ID. Zombie processes are displayed in `ps` and respond to the 0 signal, so Phusion Passenger thinks the process is still alive even though it has terminated.
  • tjholowaychuk 12y ago
    Fair enough!
  • davidw 12y ago
    > Crash detection is implemented by parsing the output of `ps` Would there be anything to be gained by actually rooting around in /proc yourselves, rather than relying on ps?
    • FooBarWidget 12y ago
      Ps is implemented by parsing /proc, so the results you get are the same. Having said that, /proc/xxx/status does contain a flag that tells you whether a process is a zombie or not. So on Linux, Phusion Passenger parses that file as an extra check. But not all software does this.