Jira ticket ECS-5104: Automatically close hutch-python sessions that have been idle for 48 hours or more.

[janeliu-slac]

Summary

This PR adds a timer that automatically closes a hutch-python session that has been idle for 48 hours or more. The timer is implemented as a class called IPython Session Timer that runs in a daemon thread. Using the 'post_run_cell' hook a timestamp is created after every user interaction in the interpreter. This timestamp is compared with the maximum amount of time a session can be idle. If 48 hours have passed, the thread will close the hutch-python session.

Current Issues

I wasn't able to find a way for the ipython interpreter to exit cleanly. I was hoping to get the main thread (the ipython interpreter) to go through standard shutdown procedures and exit the program. The best solution I found is to use get_ipython().ask_exit(). Other methods I tried caused problems (more details in section below).

After get_ipython().ask_exit() runs, the interpreter will display a second prompt. When the user types something at the prompt, ipython will run the code and then exit. This behavior doesn't seem ideal. This can be tested out by running hutch-python in my rhel7 folder at /cds/home/j/janeliu/git/hutch-python.

Other methods to close ipython

I tried a couple of other methods to close the interpreter:

os.kill(os.getpid(), signal.SIGINT) - this raises a KeyboardInterrupt signal and is supposed to allow the main thread to follow standard shutdown procedures, but it generates an error message "KeyboardInterrupt escaped interact()" in hutch-python and the interpreter won't exit.

os._exit(1) - this command doesn't go through standard shutdown procedures. It does force ipython to exit, but my terminal freezes up afterwards. I think it's incorrectly terminating other processes.

Where Has This Been Documented?

This feature was discussed by maintainers of ipython, but it doesn't seem like it was ever implemented: ipython/ipython#9944

Pre-merge checklist

• Code works interactively (a real hutch config file can be loaded)
• Code contains descriptive docstrings, including context and API
• New/changed functions and methods are covered in the test suite where possible
• Test suite passes locally
• Test suite passes on GitHub Actions
• Ran docs/pre-release-notes.sh and created a pre-release documentation page
• Pre-release docs include context, functional descriptions, and contributors as appropriate

[tangkong]

A couple of quick notes before diving into code (really just explaining the PR checklist):

• We usually advocate working on a named branch on your fork, rather than the master branch. This isn't a showstopper but it'll help you keep organized
• There are some pre-commit checks that are failing. These help keep style consistent across our repositories, as well as doing some basic static analysis. You can install these with pre-commit install inside the top-level of a repository, and they'll run before you commit anything locally. (pre-commit is installed in pcds_conda, but is easily pip-installable inside your local environment too)
  • A WIP style guide
• Another little thing is pre-release notes. This helps us auto-generate detailed release notes with every tag. run ./docs/pre-release-notes.sh <issue number> <description, typically branch name> and fill out the generated file.

[tangkong]

Overall I think this works as intended, at least in my interactive testing 👍

Some tests would be good here, possibly monkeypatching the max_time to speed the timeout process up.

[tangkong]

I think it'd be good to expose a way for the user to set this. That'd also help us test this feature.

[tangkong]

We might want to also use the logger here. Currently this doesn't show up in our log files at all, so the session will terminate and uninformed people won't know what happened.

[tangkong]

I'm also not sure if there's a better way. Currently if the session times out, we can actually still request a close with Ctrl+D, though it doesn't matter what we choose.

[ZLLentz]

Taking inspiration from the linked github thread, we apparently need to follow this up with another exit call to kill the prompt that's waiting for input, otherwise as you say in the desc this waits for user input before exiting.

ip = get_ipython()
ip.ask_exit()
ip.pt_app.app.exit()

[tangkong]

I know this is copied from ipython_log.py, but the parameter name is wrong and the type hint is... odd? It should probably be the

ipython : ``IPython.terminal.interactiveshell.TerminalInteractiveShell``

from above

[ZLLentz]

The weird thing about IPython is that there are dozens of shell types

[ZLLentz]

I wonder if there's some way we can warn the user at regular intervals, e.g. "this session will time out in 2 hours if there is no further input"