The problem occurs on a Windows 2019 server, generally after an upgrade or a new installation of NPrinting.
It is possible to access the NPrinting Web console and click on the start button of a task or on "Reload Metadata" for a connection, but then nothing happens. The execution is not started and no error message is shown.
This error message can be found on Scheduler and Engine logs:
ERROR: RabbitMQ.Client.Exceptions.BrokerUnreachableException: None of the specified endpoints were reachable ---> System.AggregateException: One or more errors occurred. ---> System.Security.Authentication.AuthenticationException: A call to SSPI failed, see inner exception. ---> System.ComponentModel.Win32Exception: The client and server cannot communicate, because they do not possess a common algorithm↓↓ --- End of inner exception stack trace
Resolution
In order to fix the problem, it is necessary to force NPrinting to work with TLS 1.2. This can be done in the RabbitMQ configuration.
- Log in to the NPrinting Server machine as an administrator.
- Stop the NPrinting services.
- Do a backup of "C:\ProgramData\NPrinting\RabbitMQ\advanced.config". It is sufficient to rename it "advanced.config_OLD".
- Paste the "advanced.config" file attached here in the "C:\ProgramData\NPrinting\RabbitMQ\" folder.
- Restart the NPrinting services.
The "advanced.config" file contains a setting forcing NPrinting to use TLS 1.2 for the services communication.
Notice that it may be necessary to repeat this process after an upgrade, because configuration files can be replaced in some cases.
Cause
The problem is due to a defect in the Server Operating System.
Some Windows 2019 machines erroneously advertise TLSv 1.3 as a supported version, so the .NET executables shipped with NPrinting May 2023 try to use TLS 1.3 to connect to the messaging service. But TLS 1.3 is not supported by Windows Server 2019 and the connection fails for this reason.
Some communications between services are then not occurring. For example, the task execution requests are not reaching the Database and can't start.
Environment
- Qlik NPrinting 2023 and higher versions.
