Re: Mysterious Disapperance of file contents

[Ajnabi]

I had the same problem. I suspected some sort of racing condition. It can also happen with Server or Web-Server crash.

I am taking a similar approach, but with two files in place of one. If main counter file is blank, use values from counter.bak file.

Lock Counter_File

  Read Count 

    On Fail 

      Read Counter_File.bak

  Increment

  Write Data to Counter_File

  Copy Counter_File to .bak file.

Release Lock

[aquarium]

Gorby is also chomping an array instead of just using a scalar all the way through. There's 3 opens and closes for the counterfile: first open in append, second open in RW, and third open in write. this spells disaster when not locking the lock/semaphore file properly using sysopen and flock. Therefore, when the server is busy, and the semaphore lock fails, the counter file is clobberred by another instance of the prog. It could have been written with just a single lock on the counter file itself: but locked properly (sysopen/flock) and openned and closed once, not 3 times.

[Abigail-II]

Therefore, when the server is busy, and the semaphore lock fails, the counter file is clobberred by another instance of the prog.

No. The code says:

flock(SEM, LOCK_EX) || die "Lock failed: $!"

If a lock fails, the program exits, so it can't clobber.

Abigail