killed by SIGPIPE, anyone?

[bjorndown]

I am taking over maintenance of a webchanges setup which monitors 1111 sites, whic has stopped working around end of July this year. --verbose only shows that webchanges stops without any error or stacktrace but with a return code of 141. Running it with strace ends with killed by SIGPIPE. I was not able to find anyone having similar problems.

For lack of better ideas I commented out these two lines in the local package and after that it ran successfully for the first time.

I am wondering why these lines are there in the first place, when the docs say that SIGPIPE is ignored by default and that BrokenPipeError is raised instead.

I am running webchanges 3.9.2 with python 3.10 on Ubuntu 22.04.

[mborsetti]

Thanks for taking the time to share this discovery and fix; really appreciated.

It puzzles me as well, and this code is from 2016, well before my time.

From my research, this call to the signal.signal function changes the signal handler for SIGPIPE from the default Python behavior of raising a BrokenPipeError exception to SIG_DFL, which stands for "default action", restoring the standard Unix behavior of terminating the process on a broken pipe.

Why would one want that? Not sure, but an LLM says that

this is generally desirable for a command-line tool to ensure it behaves correctly when used in shell pipelines.

Pressed further, it says that

the developers are making a deliberate choice to have their tool behave like a traditional Unix command-line utility. They are saying, "If this tool is part of a pipeline and the downstream process closes the pipe, terminate this process silently." This ensures that this tool integrates smoothly and predictably into shell scripts and command-line workflows.

In summary, restoring the default SIGPIPE handler is a way of making a Python program a better-behaved citizen in the command-line ecosystem, ensuring it interacts with other tools in the expected way."

Now that you have commented out these lines, are any of the jobs you're running reporting a BrokenPipeError?