NX How to set-up a redundant triad license server?

How to set-up a Redundant triad license server for the Siemens license server?

What things to take into account, some tips and tricks.

This article provides guidance on configuring a triad, redundant license server setup with three servers.
What it is and some things to take into account in order to get the best performance.

What is it?

Siemens Software Licensing supports redundant license servers to ensure license availability even if a daemon crashes. This setup requires three servers, each with Siemens Software Licensing installed. The license file includes SERVER lines for these servers.

To implement redundancy:

1. Provide Siemens with the host IDs of the three servers.
2. Siemens generates a license file with three SERVER lines.

Start each server in the order listed in the license file. At least two servers must be active for licenses to be available. If the primary server fails, another server takes over. After resolving any issues, reset the servers by stopping all three and restarting them in the listed order. More info you can find in the Siemens Digital Industries Software Licensing Manual for PLM Products

Although it does give you some failover, it does require some extra care and administration.

When using a redundant-server configuration, be aware of the following:

• A full-time administrator should maintain the redundant-server configuration.
• If one of the three servers goes down, the odds are greater for server failure than on a single-server system. The reason is that if either of the other servers fails, licenses cannot be accessed because at least two of the three servers must be operational.
• To perform as expected, all three license servers must be in the same local area network.
• Some more remarks can be found in the manual

How to set it up?

In a triad setup, three identical license files are used across three distinct servers. If multiple daemons, such as ugslmd, RCTECH, cdlmd, mglmd, and/or saltd, are hosted on the same license server, the same configuration applies. Ensure all license file copies reside in the “active licenses” directory, and all .lic files will be identified and utilized.

In order to get the Triad license server running, you will need to start all 3 license servers, and they need to be able to connect to each other. They will wait till all 3 server are online and running. And only then the licenses will be available. So at startup it will always need all 3 servers. 
The redundancy is there, so that if 1 of the 3 license servers fails, one of the other two will automatically and seamlessly take over. And they will also wait for the first server to come back online again.

It is crucial to note that if two license servers fail or disconnect, the third server will automatically shut down.

The server lines in a license file will look something like this:

################################################################################

SERVER Lic_server1 COMPOSITE=1061596295D2 29000
SERVER Lic_server2 COMPOSITE=A0CC8BC8F00F 29000
SERVER Lic_server3 COMPOSITE=AB6F8DE7D460 29000
VENDOR saltd saltd PORT=29001

Tips and tricks

First tip, if more than one type of daemon is used, ensure the order of license servers is consistent across all files, on all three servers, and for all license types per vendor daemon.

Secondly, ensure you the names are typed consistently, although the license server is not case sensitive, the license server will work just fine, however we have seen some strange anomalies when different upper and lower case characters are used in the different files. 

By default, the first server you start will be the "Master". So this will be the server that actually does the checking OUT and IN of the features. The other two servers serve as backups. 
So when the primary server fails for whatever reason, the secondary server will take over, and will become the "Master"
Even when the primary server is reactivated, the secondary server remains the “Master”.

The Master server can be designated by adding PRIMARY_IS_MASTER to the server line, as shown below:

################################################################################
SERVER Lic_server1 COMPOSITE=A0CC8BC8F00F 29000 PRIMARY_IS_MASTER
SERVER Lic_server2 COMPOSITE=A0CC8BC8F00F 29000
SERVER Lic_server3 COMPOSITE=AB6F8DE7D460 29000
VENDOR saltd saltd PORT=29001

This does the following 2 things:
First of all it will always try to use the appointed server to be the "Master", no matter in what order they are started. And secondly should the first server fail or is disconnected, the secondary server will be the "Master". However, when the primary server is reactivated, it automatically reassumes the “Master” role.

Note that the server assigned as the Tertiary Server will never become the “Master.” Normally, the Primary is the master, and if it fails, the Secondary becomes the new “Master,” either temporarily (forced by the PRIMARY_IS_MASTER) or permanently. Two scenarios can occur:

1) The Primary gets back online, and later the Secondary will fail. The Primary will become master again. The Tertiary is not used in this case.

2) The Primary does not reactivate, and the Secondary also fails. In this case, the License server ceases operation as at least two servers must be online to maintain operation. Again, the Tertiary is not used.

The third server is just there to establish the quorum.