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DistributedLock.MySql.md

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DistributedLock.MySql

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The DistributedLock.MySql package offers distributed synchronization primitives based on MySQL/MariaDB user locks. For example:

var @lock = new MySqlDistributedLock("mylockname"), connectionString);
await using (await @lock.AcquireAsync())
{
   // I have the lock
}

APIs

  • The MySqlDistributedLock class implements the IDistributedLock interface.
  • The MySqlDistributedSynchronizationProvider class implements the IDistributedLockProvider and IDistributedReaderWriterLockProvider interfaces.

Implementation notes

MySQL-based locks have been tested against and work with both the MySQL and MariaDB.

MySQL-based locks locks can be constructed with a connectionString, an IDbConnection or an IDbTransaction as a means of connecting to the database. In most cases, using a connectionString is preferred because it allows for the library to efficiently multiplex connections under the hood and eliminates the risk that the passed-in IDbConnection gets used in a way that disrupts the locking process. Using an IDbTransaction is generally equivalent to using an IDbConnection (the lock is still connection-scoped), but it allows the lock to participate in an ongoing transaction.

Natively, MySQL's locking functions are case-insensitive with respect to the lock name. Since the DistributedLock library as a whole uses case-sensitive names, lock names containing uppercase characters will be transformed/hashed under the hood (as will empty names or names that are too long). If your program needs to coordinate with other code that is using GET_LOCK directly, be sure to express the name in lower case and to pass exactName: true when constructing the lock instance (in exactName mode, an invalid name will throw an exception rather than silently being transformed into a valid one).

Options

In addition to specifying the name, several tuning options are available for connectionString-based locks:

  • KeepaliveCadence allows you to have the implementation periodically issue a cheap query on a connection holding a lock. This helps in configurations which are set up to aggressively kill idle connections. Defaults to OFF (Timeout.InfiniteTimeSpan).
  • UseMultiplexing allows the implementation to re-use connections under the hood to hold multiple locks under certain scenarios, leading to lower resource consumption. This behavior defaults to ON; you should not disable it unless you suspect that it is causing issues for you (please file an issue here if so!).