Bram Cohen (bramcohen) wrote,

print() experiencing deja vu

I have a very multithreaded Python3 app I'm running which I have a whole bunch of calls to print() in. I don't generally do multithreading, but this is spinning up a whole bunch of servers to check if they're working right. I have another test which is non-multithreaded and reproducible, and will of course have another test of actually running everything on multiple machines, but this is the intermediate step.

Anyhow, my problem is that print() appears to be sometimes causing the same line to be printed out repeatedly. I'm loathe to draw the conclusion that the underlying libraries are misbehaving, but I've taken the following precautions:

The amount of data it's spitting out is extensive
The code is asserting that the exact string hasn't been printed before
The thread and object id's are included in what's printed
There's a call to randrange() included at the end, just to make sure

And yet, I'm still getting identical lines of output.

My questions are:

What the fuck?

Is there some config setup to make this stop?

If not, is there a workaround?

My next step is to try making everything dump objects to be printed on a queue and have a single thread to all the printing, in the hopes that that will get the duplicates to go away, or at least be next to each other instead of obnoxiously interleaved. But first I'm taking a break for lunch, I've already wasted a day on this crap.
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