Fix single server locking #93
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The existing behaviour auto-released the lock once the `schedule:run`command finished execution. For short running tasks (~1 second or less), auto-releasing the lock can lead to a case where if a cron starts slightly later on another server, the lock from the first invocation has already been deleted, and the task is executed for a second time. This change relies on the DEFAULT_TTL constant to tidy-up locks rather than doing so in this extension.
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The existing behaviour auto-released the lock once the
schedule:runcommand finished execution.For short running tasks (~1 second or less), auto-releasing the lock can lead to a case where if a cron starts slightly later on another server, the lock from the first invocation has already been deleted, and the task is executed for a second time. For a cluster of 3 app servers running in the same datacenter using Redis to store locks, I've noticed this happening fairly frequenty on ~1 second jobs (~30% of the time).
This change relies on the DEFAULT_TTL constant to tidy-up locks rather than doing so in this extension. I'm not entirely sure this is the best way of handling things, so I'm open to other ideas!