NAME
qer, runq – queue management for spooled files

SYNOPSIS
qer [ –q subdir ] [ –f file ] root tag reply args
runq [ –adsER ] [ –f file ] [ –q subdir ] [ –l load ] [ –t time ] [ –r nfiles ] [ –n nprocs ] root cmd

DESCRIPTION
Qer creates a control and a data file in a queue directory. The control file contents consist of the tag, reply, and args separated by spaces. The data file contains the standard input to qer. The files are created in the directory root/subdir, where subdir is the argument to –q if present, else the contents of /dev/user. The names of the control and data files differ only in the first character which is `C' and `D' respectively. Mktemp(2) is used to create the actual names of the control and data file.

Some commands, such as fax (see telco(4)), must queue more files than just the data file. Each file following a –f flag is copied into the queue directory. The names of the copies differ from the name of the data file only in the first character. The first one starts with 'F', the second 'G', etc.

Runq processes the files queued by qer. Without the –a option, runq processes all requests in the directory root/subdir, where subdir is the argument to –q if present, else the contents of /dev/user. With the –a it processes all requests. Each request is processed by executing the command cmd with the contents of the control file as its arguments, the contents of the data file as its standard input, and standard error appended to the error file E.XXXXXX.

The action taken by runq depends on the return status of cmd. If cmd returns a null status, the processing is assumed successful and the control, data, and error files are removed. If cmd returns an error status containing the word Retry, the files are left to be reprocessed at a later time. For any other status, an error message is mailed to the requester and the files are removed. Runq uses the reply field in the control file as a mail address to which to send an error notification. The notification contains the contents of the control file to identify the failed request.

To avoid reprocessing files too often, the following algorithm is used: a data file younger than one hour will not be processed if its error file exists and was last modified within the preceding 10 minutes. A data file older than one hour will not be processed if its error file exists and was last modified within the preceding hour. The –E flag causes all files to be reprocessed regardless of the file times.

The –R flag instructs runq never to give up on a failed queue job, instead leaving it in the queue to be retried.

The –d option causes debugging output on standard error describing the progress through the queues.

The –t flags specifies the number of hours that retries will continue after a send failure. The default is 48 hours.

The –r flag limits the number of files that are processed in a single pass of a queue. Runq accumulates the entire directory containing a queue before processing any files. When a queue contains many files and the system does not have enough memory, runq exits without making progress. This flag forces runq to process the directory in chunks, allowing the queue to be drained incrementally. It is most useful in combination with the –q flag.

The –s, –n, and –l flags are only meaningful with the –a flag. They control amount of parallelism that is used when sweeping all of the queues. The argument following the –n flag specifies the number of queues that are swept in parallel; the default is 50. The argument following the –l flag specifies the total number of queues that are being swept. By default, there is no limit. The number of active sweeps is cumulative over all active executions of runq. The –s flag forces each queue directory to be processed by exactly one instance of runq. This is useful on systems that connect to slow external systems and prevents all the queue sweeps from piling up trying to process a few slow systems.

Runq is often called from cron(8) by an entry such as
0,10,20,30,40,50 * * * * kremvax
/bin/upas/runq –a /mail/queue /mail/lib/remotemail

The entry must be a single line; it is folded here only so it fits on the page.

FILES
root/user               queue directory for user
root
/user/D.XXXXXX       data file
root/user/C.XXXXXX       control file
root/user/E.XXXXXX       error file
root/user/[F–Z].XXXXXX   secondary data files

SOURCE
/sys/src/cmd/upas/q

SEE ALSO
mail(1)