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qsh [-l ignored] [-d spooldir] [-o|-p|-n] [-w|-r] hostname command command.options
This manual page documents GNU Queue load-balancing/batch-processing system and local rsh replacement.
queue with only a -- followed by a command defaults to immediate execution (-i) wait for output (-w) and full-pty emulation (-p).
The defaults for qsh are a slightly different: no-pty emulation is the default, and a hostname argument is required. A plus (+) is the wildcard hostname; specifying + in place of a valid hostname is the same as not using an -h or -H option with queue. qsh is envisioned as a rsh compatibility mode for use with software that expects a rsh-like syntax. This is useful with some MPI implementations; see See section MPI in the Info file.
The options are:
GNU Queue is a UNIX process network load-balancing system that features an innovative 'stub daemon' mechanism which allows users to control their remote jobs in a nearly seamless and transparent fashion. When an interactive remote job is launched, such as say EMACS interfacing Allegro Lisp, a stub daemon runs on the remote end. By sending signals to the remote stub - including hitting the suspend key - the process on the remote end may be controlled. Resuming the stub resumes the remote job. The user's environment is almost completely replicated, including not only environmental variables, but nice values, rlimits, terminal settings are all replicated on the remote end. Together with MIT_MAGIC_COOKIE_1 (or xhost +) the system is X-windows transparent as well, provided the users local DISPLAY variable is set to the fully qualified pathname of the local machine.
One of the most appealing features of the stub system even with experienced users is that asynchronous job control of remote jobs by the shell is possible and intuitive. One simply runs the stub in the background under the local shell; the shell notifies the user when the remote job has a change in status by monitoring the stub daemon.
When the remote process has terminated, the stub returns the exit value to the shell; otherwise, the stub simulates a death by the same signal as that which terminated or suspended the remote job. In this way, control of the remote process is intuitive even to novice users, as it is just like controlling a local job from the shell. Many of my original users had to be reminded that their jobs were, in fact, running remotely.
In addition, Queue also features a more traditional distributed batch processing environment, with results returned to the user via email. In addition, traditional batch processing limitations may be placed on jobs running in either environment (stub or with the email mechanism) such as suspension of jobs if the system exceeds a certain load average, limits on CPU time, disk free requirements, limits on the times in which jobs may run, etc. (These are documented in the sample profile file included.)
In order to use queue to farm out jobs onto the network, the queued must be running on every host in your cluster, as defined in the host Access Control File (default: /usr/local/share/qhostsfile).
Once queued is running, jobs may normally be farmed out to other hosts withing the homogenous cluster. For example, try something like queue -i -w -p -- emacs -nw. You should be able to background and foreground the remote EMACS process from the local shell just as if it were running as a local copy.
Another example command is queue -i -w -n -- hostname which should return the best host, as controlled by options in the profile file (See below) to run a job on.
The options on queue need to be explained:
-i specifies immediate execution mode, placing the job in the now spool. This is the default. Alternatively, you may specify either the -q option, which is shorthand for the wait spool, or use the -d spooldir option to place the job under the control of the profile file in the spooldir subdirectory of the spool directory, which must previously have been created by the Queue administrator.
In any case, execution of the job will wait until it satisfies the conditions of the profile file for that particular spool directory, which may include waiting for a slot to become free. This method of batch processing is completely compatible with the stub mechanism, although it may disorient users to use it in this way as they may be unknowingly forced to wait until a slot on a remote machine becomes available.
-w activates the stub mechanism, which is the default. The queue stub process will terminate when the remote process terminates; you may send signals and suspend/resume the remote process by doing the same to the stub process. Standard input/output will be that of the 'queue' stub process. -r deactivates the stub process; standard input/output will be via email back to the users; the queue process will return immediately.
-p or -n specifies whether or not a virtual tty should be allocated at the remote end, or whether the system should merely use the more efficient socket mechanism. Many interactive processes, such as EMACS or Matlab, require a virtual tty to be present, so the -p option is required for these. Other processes, such as a simple hostname do not require a tty and so may be run without the default -p. Note that queue is intelligent and will override the -p option if it detects both stdio/stdout have been re-directed to a non-terminal; this feature is useful in facilitating system administration scripts that allow users to execute jobs. [At some point we may wish to change the default to -p as the system automatically detects when -n will suffice.] Simple, non-interactive jobs such as hostname do not need the less efficient pty/tty mechanism and so should be run with the -n option. The -n option is the default when queue is invoked in rsh compatibility mode with qsh.
The -- with queue specifies `end of queue options' and everything beyond this point is interpreted as the command, or arguments to be given to the command. Consequently, user options (i.e., when invoking queue through a script front end, may be placed here):
#!/bin/sh exec queue -i -w -p -- big_job $*
#!/bin/sh exec queue -q -w -p -d big_job_queue -- big_job $*
for example. This places queue in immediate mode following instructions in the now spool subdirectory (first example) or in batch-processing mode into the big_job spool subdirectory, provided it has been created by the administrator. In both cases, stubs are being used, which will not terminate until the big_job process terminates on the remote end.
In both cases, pty/ttys will be allocated, unless the user redirects both the standard input and standard output of the simple invoking scripts. Invoking queue through these scripts has the additional advantage that the process name will be that of the script, clarifying what is the process is. For example, the script might called big_job or big_job.remote, causing queue to appear this way in the user's process list.
queue can be used for batch processing by using the -q -r -n options, e.g.,
#!/bin/sh exec queue -q -r -n -d big_job -- big_job $*
would run big_job in batch mode. -q and -d big_job options force Queue to follow instructions in the big_job/profile file under Queue's spool directory and wait for the next available job slot. -r activates batch-processing mode, causing Queue to exit immediately and return results (including stdout and stderr output) via email.
The final option, -n, is the option to disable allocation of a pty on the remote end; it is unnecessary in this case (as batch mode disables ptys anyway) but is here to demonstrate how it might be used in a -i -w -n or -q -w -n invocation.
Under /usr/spool/queue you may create several directories for batch jobs, each identified with the class of the batch job (e.g., big_job or small_job). You may then place restrictions on that class, such as maximum number of jobs running, or total CPU time, by placing a profile file like this one in that directory.
However, the now queue is mandatory; it is the directory used by the -i mode (immediate moe) of queue to launch jobs over the network immediately rather than as batch jobs.
Specify that this queue is turned on:
The next two lines in profile may be set to an email address rather than a file; the leading / identifies then as file logs. Files now beginning with cf,of, or ef are ignored by the queued:
mail /usr/local/com/queue/now/mail_log supervisor /usr/local/com/queue/now/mail_log2
Note that /usr/local/com/queue is our spool directory, and now is the job batch directory for the special now queue (run via the -i or immediate-mode flag to the queue executable), so these files may reside in the job batch directories.
The pfactor command is used to control the likelihood of a job being executed on a given machine. Typically, this is done in conjunction with the host command, which specifies that the option on the rest of the line be honored on that host only.
In this example, pfactor is set to the relative MIPS of each machine, for example:
host fast_host pfactor 100 host slow_host pfactor 50
Where fast_host and slow_host are the hostnames of the respective machines.
This is useful for controlling load balancing. Each queue on each machine reports back an `apparant load average' calculated as follows:
1-min load average/ (( max(0, vmaxexec - maxexec) + 1)*pfactor)
The machine with the lowest apparant load average for that queue is the one most likely to get the job.
Consequently, a more powerful pfactor proportionally reduces the load average that is reported back for this queue, indicating a more powerful system.
Vmaxexec is the ``apparant maximum'' number of jobs allowed to execute in this queue, or simply equal to maxexec if it was not set. The default value of these variables is large value treated by the system as infinity.
host fast_host vmaxexec 2 host slow_host vmaxexec 1 maxexec 3
The purpose of vmaxexec is to make the system appear fully loaded at some point before the maximum number of jobs are already running, so that the likelihood of the machine being used tapers off sharply after vmaxexec slots are filled.
Below vmaxexec jobs, the system aggressively discriminates against hosts already running jobs in this Queue.
In job queues running above vmaxexec jobs, hosts appear more equal to the system, and only the load average and pfactor is used to assign jobs. The theory here is that above vmaxexec jobs, the hosts are fully saturated, and the load average is a better indicator than the simple number of jobs running in a job queue of where to send the next job.
Thus, under lightly-loaded situations, the system routes jobs around hosts already running jobs in this job queue. In more heavily loaded situations, load-averages and pfactors are used in determining where to run jobs.
Additional options in profile
PREFIX/share/qhostsfile Host Access Control List File
PREFIX/com/queue spool directory
PREFIX/local/com/queue/now spool directory for immediate execution
PREFIX/com/queue/wait spool directory for the '-q' shorthand
SPOOLDIR/profile control file for the SPOOLDIR job queue
PREFIX/com/queue/now/profile control file for immediate jobs
PREFIX/var/queue_pid_hostname temporary file
Permission is granted to make and distribute verbatim copies of this manpage provided the copyright notice and this permission notice are preserved on all copies.
See Acknowledgements file for a complete list of contributors.
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