.NetCore client connection throwing " Unable to connect to any of the specified MySQL hosts."
Posted by: Robin Johnson
Date: October 19, 2020 09:15AM

On a system that processes 500,000 requests daily (i.e. very moderate workload) running against an AWS Aurora RDS database server, very unexpectedly in that last two weeks we have gotten a storm of these errors. We've been using Aurora for years. This particular version of our client app [IIS Worker Process] has been in production for several weeks without any changes (the core code unchanged in years).

Can someone tell me what would CAUSE this error?

We have two Windows 2016 systems running four client app instances. Only one instance experienced this error and only resolved after a restart of the IIS worker process.

Since the other instances continued to work without any issues, it doesn't seem like a networking issue. The ADO connection pool is standard default and the logs showed no errors of interest - just suddenly started getting these errors.

Oracle MySql.Data.MySqlClient .Net Core Class Library 8.0.20

MySql.Data.MySqlClient.MySqlException (0x80004005): Unable to connect to any of the specified MySQL hosts. ---> MySql.Data.MySqlClient.MySqlException (0x80004005): Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding. at MySql.Data.Common.StreamCreator.GetTcpStream(MySqlConnectionStringBuilder settings) at MySql.Data.MySqlClient.NativeDriver.Open() at MySql.Data....'

Any guidance in tracking down root cause or better configuration would be welcome.


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.NetCore client connection throwing " Unable to connect to any of the specified MySQL hosts."
October 19, 2020 09:15AM

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