If I have 10 hangfire servers running does the disable concurrent attribute apply per server or per datastore?
The enforcing of concurrency is implemented in the datastore by overriding the AcquireDistributedLock method.
Ie. SQL datastore uses the stored procedure sp_getapplock to obtain a distributed lock across all Hangfire servers using the same sql datastore, while store like CompositeC1 doesn’t have such capabilites and can only maintain its locks locally on the same physical server by tracking the locks in-memory.