Mac OS X Server 10.2: How to Set Up Print Load Balancing Using CUPS

Common UNIX Printing System is based on Internet Printing Protocols (IPP) and works with PostScript and non-PostScript printers. A CUPS printer "class" is a virtual "queue". Its main purpose is to send print jobs to other print queues.

Although not a default feature of Mac OS X Server, a CUPS printer "class" may be configured to distribute print jobs among many printers balancing the print load across multiple printers. Note: Apple does not offer technical support for CUPS.

Setting up a CUPS printer class using Mac OS X Server

1. Create individual queues for each printer.

Note: These queues do not need to be shared in Server Settings since they will be shared in the printer class you are creating.

2. Open a Web browser locally on the server since CUPS by default does not allow remote web administration.

3. Go to the CUPS Web-admin site (http://127.0.0.1:631/).

4. Click "Do Administration Tasks".

5. Click Classes.

6. Click Add Class. The Class admin page appears.

7. Enter a name for the class (and optional location and description).

Note: Spaces are not allowed for class names.

Description is used as the queue name, so it helps to keep the description simple.
Location is the text that appears in Print Center on the Mac OS X 10.2 client.

8. Click Continue. The Class members page appears.

9. Select one or more of the printers in the list add them to the class.

10. Click Continue. The status page appears indicating if the class was added properly.

11. Use Server Settings to enable sharing for the printer class, which appears as another PostScript queue, and to set the sharing name and other Print Service attributes.

• If all the queues added to the class represent PostScript printers, then the class itself appears like another PostScript print queue. This queue can be shared in the Server Settings like an individual print queue.
• You can hold/release the class as a whole or hold/release individual queues attached to the class. Holding the class by itself does not actually hold any of the queues, it just stops jobs from being forwarded to the queues. Once a job is forwarded it falls under the control of the queue that's doing the actual printing (a subtle but important distinction). CUPS performs load balancing and determines which print queue to forward the job to.
• If one or more of the class's queues are held, the jobs are parceled out to the remaining active (non-held) queues. A class can be put on hold to temporarily stop jobs from being forwarded, regardless of hold state of each individual print queue. In this case, the class acts like a queue and maintains its own job list until released.

You can get more information about CUPS by clicking Help on the CUPS Web-admin page.

The Common UNIX Printing System, CUPS, and the CUPS logo are the trademark property of Easy Software Products.

Important: Information about products not manufactured by Apple is provided for information purposes only, and does not constitute Apple's recommendation or endorsement. Please contact the vendor for additional information.

Document 17159, "Locating Vendor Information" can help you search for a particular vendor's address and phone number.