“Error: System.InvalidOperationException: Timeout expired” in rcmctrl.log when the .NET Connection pool is full

“Error: System.InvalidOperationException: Timeout expired” in rcmctrl.log when the .NET Connection pool is full

I’ve noticed that the SCCM Replication Configuration Monitor component is failing with an InvalidOperationException error when the .NET Connection pool is full.

If I look in rcmctrl.log I see:

Error: Received unhandled SQL exception, printing info and throwing it again. This will be retried in next cycle.
Error: Exception message: [The target database, 'TESTDB', is participating in an availability group and is currently not accessible for queries. Either data movement is suspended or the availability replica is not enabled for read access.
…
DRS sync started.
Error: Received unhandled exception, printing info and throwing it again. This will be retried in next cycle.
Error: System.InvalidOperationException: Timeout expired. The timeout period elapsed prior to obtaining a connection from the pool. This may have occurred because all pooled connections were in use and max pool size was reached.