I'm working on a project where I need to share state between several processes (forked using gunicorn). I'm using dictionaries obtained from a multiprocessing SyncManager to achieve this.

The issue is that if I have multiple forked processes concurrently accessing to different dictionaries created by the same SyncManager, the code will randomly crash while accessing (read-only and read-write) to any of the dictionaries. This behaviour is independent of the way I access the dictionary (i.e. it happens both using the dictionary functions (e.g. has_key) or the built-in keywords (e.g. key in dict).

The attached snippet demonstrates the issue (tested only in python2.7): the function test_manyForkedProcessesSingleThreaded will crash.

The issue is also being discussed here: https://stackoverflow.com/questions/48052148/python-multiprocessing-dict-sharing-between-processes