On Fri, 28.06.13 13:23, P J P (pj.pandit@xxxxxxxxxxx) wrote: > > The systemd-journald takes care of all of: receiving messages, writing > > them to storage, and rotating the storage. > > > > We do synchronous rotation before each write. i.e. the moment we append > > to a file we check if the write would cause the disk usage to be out of > > limits, and then do the rotation right away. > > I see. While doing this rotation, I guess systemd uses flock(2) or similar > mechanism to pause writing to a log file, move/rename or copy-truncate that > file and continue writes again? journald is the only writer, it doesn't need locking. The changes it does are done in a way so that concurrent readers will either see the changes or not, but never half-written changes. Also note that locking on Linux is seriously broken. You can get a lock on any file you can read, thus you can freeze everybody else who might want a lock. Or in other words: if a logging daemon takes a lock on its lock files, then you can use this to make that service freeze forever. File system locking on Unix cannot really work. Lennart -- Lennart Poettering - Red Hat, Inc. -- devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxxx https://admin.fedoraproject.org/mailman/listinfo/devel
