TORQUE

TORQUE is a resource manager providing control over batch jobs and distributed compute nodes. Basically, one can setup a home or small office Linux cluster and queue jobs with this software. A cluster consists of one head node and many compute nodes. The head node runs the torque-server daemon and the compute nodes run the torque-client daemon. The head node also runs a scheduler daemon.

Note: TORQUE is not free software anymore.

Installation

Note: Although TORQUE is a very powerful queuing system, if the goal of the cluster is solely to increase compilation throughput, distcc is a much easier and elegant solution.

Install the torque^AUR package found in the AUR.

Must haves

/etc/hosts

Make sure that /etc/hosts on all of the boxes in the cluster contains the hostnames of every PC in the cluster. Example, cluster consists of 3 PCs, mars, phobos, and deimos.

192.168.0.20   mars
192.168.0.21   phobos
192.168.0.22   deimos

Firewall configuration (if installed)

Be sure to open TCP for all machines using TORQUE.

The pbs_server (server) and pbs_mom (client) by default use TCP and UDP ports 15001-15004. pbs_mom (client) also uses UDP ports 1023 and below if privileged ports are configured (the default).

NFS

Technically, one does not need to use NFS but doing so simplifies the whole process. An NFS share either on the server or another machine is highly recommended to simplify the process of sharing common build disk space.

Setup

Server (head node) configuration

Follow these steps on the head node/scheduler.

Edit /var/spool/torque/server_name to name the head node. It is recommended to match the hostname in for simplicity's sake.

Create and configure the torque server:

Then start trqauthd by running

A minimal set of options are provided here. Adjust the first line substituting "mars" with the hostname entered in /var/spool/torque/server_name:

qmgr -c "set server acl_hosts = mars"
qmgr -c "set server scheduling=true"
qmgr -c "create queue batch queue_type=execution"
qmgr -c "set queue batch started=true"
qmgr -c "set queue batch enabled=true"
qmgr -c "set queue batch resources_default.nodes=1"
qmgr -c "set queue batch resources_default.walltime=3600"
qmgr -c "set server default_queue=batch"

It may be of interest to keep finished jobs in the queue for a period of time.

qmgr -c "set server keep_completed = 86400"

Here, 86400 sec = 24 h after which point, the job will be auto removed from the queue. One can see the full log of jobs removed from the queue with the switch on qstat:

qstat -f

Verify the server configuration with this command:

# qmgr -c 'p s'

Edit adding all compute nodes. Again, it is recommended to match the hostname(s) of the machines on the LAN. The syntax is HOSTNAME np=x gpus=y properties

• HOSTNAME=the hostname of the machine
• np=number of processors
• gpus=number of gpus
• properties=comments

Only the hostname is required, all other fields are optional.

Example:

mars np=4
phobos np=2
deimos np=2

Note:

• One can run both the server and client on the same box.
• Re-running pbs_server -t create may delete this nodes file.

Restart the server and the new options are sourced.

Client (compute node) configuration

Follow these steps on each compute node in the cluster.

Note: If running both the server and client on the same box, be sure to complete these steps as well for that machine as well as other pure clients on the cluster.

Edit to contain some basic info identifying the server:

$pbsserver      mars          # note: this is the hostname of the headnode
$logevent       255           # bitmap of which events to log

Restart the server

That should be it. Now restart the server so the settings can take effect.

Starting the client(s)

In order to start the clients run the following on each of the clients, including the server if it is also a client:

Verifying cluster status

To check the status of the cluster, issue the following:

$ pbsnodes -a

Each node if up should indicate that it is ready to receive jobs echoing a state of free. If a node is not working, it will report a state of down.

Example output:

Queuing jobs

Queuing to the cluster is accomplished via the qsub command.

A trivial test is to simply run sleep:

$ echo "sleep 30" | qsub

Check the status of the queue via the qstat command described below. At this point, the work will have a status of "Q" which means queued. To start it, run the scheduler:

# pbs_sched

One can modify the torque-server systemd daemon to activate pbs_sched at boot.

Another usage of qsub is to name a job and queue a script:

$ qsub -N x264 /home/facade/bin/x264_HQ.sh

Another example can use a wrapper script to make and queue work en mass automatically.

Checking job status

is used to check work status.

Append the switch to see which nodes are doing which jobs.

See also

• TORQUE short course from University of California, San Francisco - Good guide with templates.
• TORQUE admin manual - Great resource and easy to read.
• Boston College's Torque user guide - Guide not extensive but gives a flavor for how end-users can use a cluster. Probably overkill for home clusters where only one user is submitting work.
• TORQUE mailing lists - The TORQUE community is very knowledgeable and a key asset.
• TORQUE users mailing list archives - Searchable archive of TORQUE-users.