Error manager of pid file quit without updating file
Note that a queue created using a manager does not have this issue.
See Returns a process shared queue implemented using a pipe and a few locks/semaphores.
All resources of the parent are inherited by the child process. The fork server process is single threaded so it is safe for it to use process which tracks the unlinked named semaphores created by processes of the program.
Note that safely forking a multithreaded process is problematic. When all processes have exited the semaphore tracker unlinks any remaining semaphores.
Also, a single manager can be shared by processes on different computers over a network. A process cannot join itself because this would cause a deadlock. The initial value is inherited from the creating process.
(Unlinking the named semaphores is a serious matter since the system allows only a limited number, and they will not be automatically unlinked until the next reboot.) To select a start method you use the As mentioned above, when doing concurrent programming it is usually best to avoid using shared state as far as possible.Note that one can also create a shared queue by using a manager object – see Note When an object is put on a queue, the object is pickled and a background thread later flushes the pickled data to an underlying pipe.This has some consequences which are a little surprising, but should not cause any practical difficulties – if they really bother you then you can instead use a queue created with a ), then that process will not terminate until all buffered items have been flushed to the pipe.When using multiple processes, one generally uses message passing for communication between processes and avoids having to use any synchronization primitives like locks.For passing messages one can use for each task removed from the queue or else the semaphore used to count the number of unfinished tasks may eventually overflow, raising an exception.