Re^12: [threads] Open a file in one thread and allow others to write to it

The AUTOFLUSH does not solve the problem

The SEEK works !!! and it works without the lock in $sem and the AUTOFLUSH in LOG. However, IMHO the lock in $sem must be used

In overall i've understand your tip, but it's not clear for me how all the file pointers are syncked in a thread concurrency level, without conflicts. With the lock in $sem it's obvious , because only one thread can SEEK the Filehandle and write to it. However, I'm getting the log file syncked without using the lock in $sem. But these are other discussions

Thanks for the tip it will be very useful for me...

Comment on Re^12: [threads] Open a file in one thread and allow others to write to it

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Re^13: [threads] Open a file in one thread and allow others to write to it by ikegami (Patriarch) on Nov 16, 2009 at 19:56 UTC
and it works without the AUTOFLUSH in LOG. `seek` apparently forces a flush. Assuming it's safe to rely on that, it's not good enough. The catch is that it's forcing the flush at the wrong time. You want to flush immediately after the `print`, not at the start of the thread's next `print`. and it works without the lock in $sem You're relying on your OS to do writes atomically. That might be reliable for small writes, but why chance it. If you do find a performance bottleneck, you might be better off using a separate log file for each thread and merge them later.	[reply] [d/l] [select]

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Re^13: [threads] Open a file in one thread and allow others to write to it
by ikegami (Patriarch) on Nov 16, 2009 at 19:56 UTC

and it works without the AUTOFLUSH in LOG.

seek apparently forces a flush. Assuming it's safe to rely on that, it's not good enough. The catch is that it's forcing the flush at the wrong time. You want to flush immediately after the print, not at the start of the thread's next print.

and it works without the lock in $sem

You're relying on your OS to do writes atomically. That might be reliable for small writes, but why chance it. If you do find a performance bottleneck, you might be better off using a separate log file for each thread and merge them later.

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