Multiple Retries Required to Get a License from the Zoo

No longer supported
Zoo 4.0 was the license manager for Rhino 4, which reached end of life long ago. This article is kept for historical reference. For current LAN Zoo licensing, see the LAN Zoo guide.

Question

We have a large number of Rhino licenses, over 180, and all of them are managed by a single Zoo server. We have noticed that the Zoo is sometimes a little slow to grant licenses when requests are made. That is, our users often have to keep “retrying” to get a Rhino license before one is finally delivered. It is as if the Zoo times out before it manages to think about delivering a license. Do you have any technical notes or pointers that could help solve this?

Answer

When a network-node version of Rhino starts, it automatically requests a license from the Zoo. If Rhino does not receive any kind of response back from the Zoo in 15 seconds, the following warning message is displayed:

License request retry warning

There are several reasons you might get this message:

  1. Rhino’s message never made it to the Zoo due to a configuration issue or a firewall.
  2. The Zoo was too busy to respond in the timeout period.
  3. The Zoo’s response never made it back to Rhino due to a firewall.

Reasons 1 and 3 are the most common reasons for this message. When a workstation gets this message, open up the Zoo’s Log file (Tools → View Log File), scroll to the end of the file, and look for incoming messages from that workstation. If you don’t see an entry around the time of the license request, then make sure the Rhino workstation is properly configured (Zoo registry key, etc.) and that its firewall is properly configured. You can find configuration details in the Zoo help file or on the Zoo Installation and Configuration page.

Reason 2 can occur on large, busy networks, overloaded servers running the Zoo, or on Zoo servers that host a large number of licenses. One way to ease the load on the Zoo is to increase the period it waits to recover unused licenses. The Zoo’s Recover unused licenses parameter defaults to 3 minutes, which is adequate for most Zoo servers. But for busy Zoo servers, you can increase this value to 12 or even 15 minutes to decrease the load on the Zoo. After changing the value, close and restart the Zoo.

Recover unused licenses setting