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Version 1.9 Build 803

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AutoLocking working

AutoLocking is a handy mode because it frees the user from having to do explicit locking and unlocking. Furthermore it has the advantage that it does not release a lock before another process needs it. This advantage is at the same time the weakness of AutoLocking, because it may take a while before a process holding a lock recognizes that another process needs a lock. For this to understand it is explained how AutoLocking works.

1. When table I/O is done, it is checked if the table is appropriately locked. If not, it is tried to acquire a lock with TableLock::maxWait as the maximum number of attempts (default is trying forever).
2. Unlocking is also done automatically. After some I/O-s are done, the Table System inspects the list in the lock file to see if another process needs the lock. If so, it releases the lock. The inspection interval can be defined in the TableLock constructor and defaults to 5 seconds.

In general this scheme works fine, but the problem is that if no I/O is done, the Table System does not check if another process needs a lock. This is especially a problem for glish clients as they can be idle for some time waiting for a command to be given. To circumvent this problem the function Table::relinquishAutoLocks can be used to release locks on tables using AutoLocking. Either all such tables are unlocked or only the tables needed by another process.