Internal error triggered with large caplog texts

This behavior is reproducible (at least) for pytest==6.2.5 and pytest-xdist==2.4.0.

Consider the following code (let's call this test_large_caplog.py):

import logging


def large_string_generator(n=2147483650):
    return "x" * n


def test_1(caplog):
    caplog.set_level(logging.INFO)
    logging.info(large_string_generator())
    caplog.clear()
    assert True

If we run pytest test_large_caplog.py, it runs fine. However, pytest -n 1 test_large_caplog.py triggers an internal error.

Start by reproducing the issue with the shown test_large_caplog.py example under both pytest test_large_caplog.py and pytest -n 1 test_large_caplog.py. Inspect the internal error and the xdist path handling the large caplog output. Done means the distributed run no longer raises an internal error while the normal run continues to pass.