Reliably open and lock files

This crates provides a way to reliably open and lock a file, for example for opening lock files, PID files, spool files, mailboxes and other kinds of files which are used for synchronisation between processes.

The OpenAndLock trait implements the algorithm of the flopen function available on BSD systems. It is roughly equivalent to opening a file and calling flock with an operation argument set to LOCK_EX, but it also attempts to detect and handle races between opening or creating the file and locking it.

The trait provides two implementations, a blocking and a non-blocking one.

The open_and_lock() method waits until the file can be locked, so unless an unrelated I/O error occurs, it will eventually succeed once the file has been released if it’s been held by a different process.

The try_open_and_lock() method returns an error immediately when the file cannot be locked, allowing the called to handle it and retry if necessary.

Both methods retry automatically when a race condition occurs and a file gets deleted or recreated directly after the lock has been acquired.

This trait extends OpenOptions, so it can be used the following way:

let file = OpenOptions::new()
    .read(true)
    .write(true)
    .create(true)
    .open_and_lock("/path/to/file")?;

At the moment, this crate supports UNIX-like platforms only.

License

MIT license, also known as the Expat license.

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you shall be licensed as above, without any additional terms or conditions.