Spool Queue Processing

LPRng Reference Manual: 24 Sep 2004 (For LPRng-3.8.28)
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# 15.4. Spool Queue Processing

Options used:

- lpd_force_poll=Force lpd to periodically poll print queues

- lpd_poll_time=Time between polls

- max_servers_active=Maximum number of active servers

When the lpd server starts, it will fork a set of subserver processes, each which will handle an individual queue.

If a system has a large number of queues, then this forking operation may result in the lpd server exhausting the process resources. To control this, the max_servers_active value restricts the number of active children to the specified value. If this value is 0, then 50% of the maximum system processes value will be used.

Due to the limits on the number of processes, there may be times when a job is placed in a queue, but the lpd server is unable to start handling the job. When all of the children of the main lpd server have exited, the server starts a timer. After lpd_poll_time seconds, it will scan the queues, looking for jobs to process, and starts a process to service them. If it does not find any jobs it remains idle.

The lpd_force_poll flag causes the server to periodically poll the queues. This is useful when there is a high possibility that jobs could fail to be printed due to high loads on the server.

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