Detect parent change in more cases on unix #1271
Conversation
New behaviour: poll getppid and exit if this value is no longer equal to the original parent pid. For backwards compatibility: keep old behaviour when parent_pid is 0 or not given. Parentpoller only watches for parent change to pid 1 (init), but in modern linux environments processes are usually reparented to the systemd user session process. In this situation, ipykernel never noticies that its parent has exited. jupyter-client already sets JPY_PARENT_PID with the pid of the parent process. We could trust this environment variable directly, but in this change, it is only used if it is equal to the actual parent id when the poller starts. (A side effect: if the parent dies quickly enough, ipykernel does not notice.)
|
First PR, tell me if I did something wrong |
|
The ci failures are similar to failures on other PRs here, so it's possible - not certain - that they are unrelated errors. |
| # We cannot use os.waitpid because it works only for child processes. | ||
| from errno import EINTR | ||
|
|
||
| # before start, check if the passed-in parent pid is valid |
There was a problem hiding this comment.
Maybe this whole thing is overly complicated? We could also elect to just trust JPY_PARENT_PID directly - the only problem is if it's a stale environment variable from somewhere.
There was a problem hiding this comment.
Thanks for merging!
My updated thoughts on this comment here is that it's good that we check if JPY_PARENT_PID is the actual parent before using it. It's actually possible (is it common?) to have situations like papermill -> bash -> ipykernel or with similar intermediate processes, where JPY_PARENT_PID will point to papermill but the ipykernel ppid will be bash.
A kernel provisioner could cause such situations (I'm guilty of that..)
|
That looks reasonable to me. |
|
Downstream failures seem unrelated. Merging. |
2 participants
New behaviour: poll getppid and exit if this value is no longer equal to the original parent pid.
For backwards compatibility: keep old behaviour when parent_pid is 0 or not given.
Parentpoller only watches for parent change to pid 1 (init), but in modern linux environments processes are usually reparented to the systemd user session process. In this situation, ipykernel never noticies that its parent has exited.
jupyter-client already sets JPY_PARENT_PID with the pid of the parent process. We could trust this environment variable directly, but in this change, it is only used if it is equal to the actual parent id when the poller starts. (A side effect: if the parent dies quickly enough, ipykernel does not notice.)
Fixes #517