I have an idea how to make one OS image that can be used for both the HTCondor cluster and Slurm Cluster such that we can have HTCondor jobs glidein to the Slurm cluster.
CONDOR_CONFIG
The condor_startd reads the CONDOR_CONFIG environment variable as its config file instead of the default /etc/condor/condor_config and exits with an error if there is a problem reading that file.
DAEMON_SHUTDOWN
The condor_startd daemon will shutdown gracefully and not be restarted if the ClassAd STARTD.DAEMON_SHUTDOWN evlauates to True. E.g.
STARTD.DAEMON_SHUTDONW = State == "Unclaimed" && Activity == "Idle" && (CurrentTime - EnteredCurrentActivity) > 600
MASTER.DAEMON_SHUTDOWN = STARTD_StartTime == 0
https://htcondor.readthedocs.io/en/latest/admin-manual/configuration-macros.html
https://htcondor.readthedocs.io/en/latest/classad-attributes/machine-classad-attributes.html
sysconfig
The condor.service unit in systemd reads /etc/sysconfig/condor but does not evaluate it. So adding something like the following to /etc/sysconfig/condor won't work
CONDOR_CONFIG=$(cat /var/run/condor/config)
I could instead add a second EnvironmentFile like so
EnvironmentFile=-/etc/sysconfig/condor
EnvironmentFile=-/var/run/condor/config
where /var/run/condor/config sets CONDOR_CONFIG=/etc/condor/condor_config
But I can use this to keep HTCondor from starting, just like I do with Torque and Slurm. I can set CONDOR_CONFIG=/dontstartcondor in /etc/syconfig/condor in the OS image and override it with a snapshot. Then stop setting 99-nrao as a snapshot.
OS image
All three schedulers (Torque, slurm, condor) will be configured to start via systemd. The file pbs_mom, slurm, and condor in /etc/sysconfig will be set such that all of these schedulers will fail to start on boot.
/etc/sysconfig/pbs_mom:
/etc/sysconfig/slurm:
/etc/sysconfig/condor: CONDOR_CONFIG=/nosuchfile
If any of these schedulers are wanted to start on boot, the appropriate /etc/sysconfig file (pbs_mom, slurm, condor) will be altered via a snapshot.
/etc/sysconfig/pbs_mom:
/etc/sysconfig/slurm:
/etc/sysconfig/condor: CONDOR_CONFIG=/etc/condor/condor_config
Change the LOCAL_CONFIG_FILE in HTCondor to a file that will contain the configurations needed for a Slurm node to run an HTCondor Pilot job (e.g. STARTD.DAEMON_SHUTDOWN). This file will be created by the Pilot job.
echo 'LOCAL_CONFIG_FILE = /var/run/condor/condor_config.local' >> /etc/condor/condor_config
The alternative was to make a complete copy of condor_config and all its sub-config files into an /etc/condor/glidein-slurm.conf and add the DAEMON_SHUTDOWN ad as well. This seems dangerous to me as now those two config files can drift.
Pilot Job
The Pilot job submitted to Slurm will do the following
echo 'CONDOR_CONFIG=/etc/condor/glidein-slurm.conf' > /var/run/condor/config
echo 'STARTD.DAEMON_SHUTDONW = State == "Unclaimed" && Activity == "Idle" && (MyCurrentTime - EnteredCurrentActivity) > 600' > /var/run/condor/condor_config.localecho 'MASTER.DAEMON_SHUTDOWN = STARTD_StartTime == 0' >> /var/run/condor/condor_config.local
systemctl start condor
# loop until condor_startd is no longer a running process
systemctl stop condor
rm -f /var/run/condor/condor_config.local
rm -f /var/run/condor/config
exit
If the Payload job is very small and exits before the Pilot job can start blocking on condor_startd then the Pilot job may never end. So, it may need some code to exit after some amount of time if condor_stard hasn't been seen.
Factory
The factory process that watches the clusters and launches Pilot jobs should be pretty simple
If jobs are waiting in the HTCondor cluster (perhaps only vlapipe jobs)
If nodes are available in the Slurm Cluster (If not perhaps send email)
Launch one Pilot job
Sleep some amount of time, presumably more than the time HTCondor takes to launch a job
Problems
Ideas
Instead of using systemd to start condor, I could run condor_master -f from the Pilot script. I can set set both STARTD and MASTER DAEMON_SHUTDOWN variables which will cause condor_master to exit and therefore I won't need to watch the condor_startd process. Don't tell james he was right :^)