Redundant Servers

A redundant server configuration enables you to have three servers managing the same set of license tokens acting as one logical server. This configuration requires that two redundant license servers be operative and able to contact each other. If two redundant license servers are not operative, none of the license tokens will be available. A three-server configuration requires that two servers be available for any tokens to be available. The main advantage of redundant servers is an increased likelihood that if any tokens are available, then all tokens are available. The cost is additional administration.

One of the redundant servers is the master server, the server that issues license tokens and has a heavier processing load. If the master server becomes unavailable, then the next available peer in the configuration becomes the master server.

Figure 1-6 shows the process for getting a license in a redundant server configuration.

Figure 1-6 Process for Getting a License With Redundant License Servers

This is the process for getting a license with redundant license servers:

1. A C++ developer is trying to recompile a program from a desktop machine envoy. The developer has mounted a copy of Sun Visual WorkShop C++ from the machine tools. The developer's system administrator has set up a redundant server configuration on the network: lic1 is the master server, and lic2 and lic3 are alternate servers. The redundant server configuration brokers the 30 license tokens the group purchased.

2. When the developer starts a compile of a program, Sun Visual WorkShop C++ mounted from tools sends a request to lic1 for a license token. The server lic1 first checks for the presence of lic2. If lic2 is not found, then it looks for lic3. If either lic2 or lic3 is found and a license token is available, then the request is granted, and the compile completes.

3. If all 30 license tokens are in use by other developers in the group, the developer would be put in a queue to get the first available license token. If lic1 cannot find either lic2 or lic3 (if both machines were down for repairs), no license tokens would be available. If lic1 is down but lic2 and lic3 are functional, all license tokens are available.