Mixing OAR3 and OAR2

OAR2 and OAR3 are divided in different modules (see Modules descriptions). Using the modularity, one can mix modules from OAR3 with modules from OAR2. This can be useful, for instance, to do the migration from OAR2 to OAR3.

This page explain how to install and use OAR3 scheduler and metascheduler on a working OAR2 server.

Note

Whereas section Using OAR3 metascheduler with OAR2 and section target_schedulers_oar3_with_oar2 can be setup independently, it is also possible to use them together in the same OAR2 server.

Installation

There is no official package for OAR3 yet, but it can be generated from sources. The only required tool to generate the package is docker.

dependencies

First install oar3’s dependencies.

apt-get update && \
apt-get install -y python3 \
python3-sqlalchemy python3-alembic \
python3-click python3-flask \
python3-passlib python3-psutil python3-requests \
python3-simplejson python3-sqlalchemy-utils  \
python3-tabulate python3-toml python3-yaml \
python3-zmq python3-psycopg2 python3-fastapi

Install from pre-generated .deb

The packages can be downloaded at : https://github.com/oar-team/oar3/releases/latest. Also download the debian package for ProcSet (which is an OAR3 dependency).

Note

The steps to generate the package from sources are described in this section.

Using OAR3 schedulers with OAR2

This documentation describe how to install OAR3 scheduler (named kamelot) on a standard OAR2 installation.

Active scheduler for the default queue

Once installed the schedulers can be activated with the following manipulations.

Activate OAR3 scheduler (named kamelot) for default queue:

# Link the scheduler to the folder expected by OAR2
ln -s /usr/lib/oar/kamelot /usr/lib/oar/schedulers/kamelot

# Delete the default queue
oarnotify --remove-queue default

# add kamelot as default queue scheduler
oarnotify --add-queue default,3,kamelot

Kamelot configuration

In order for kamelot to work, the resources hierarchy of the cluster must be provided in order to be used in resource request. To do so, add the variable HIERARCHY_LABELS to OAR2 configuration. Labels’ order does not matter here.

Example:

# Default value is "resource_id,network_address,cpu,core"
HIERARCHY_LABELS="resource_id,network_address,cpu,core"

Note

In case of issue with kamelot, It is possible to restore OAR2 scheduler with oarnotify.

oarnotify --remove-queue default
oarnotify --add-queue default,3,<you-scheduler>

Using OAR3 metascheduler with OAR2

This section explain how to setup kao in OAR2.

The metascheduler should be available at /usr/lib/oar/kao. Activating the kao for OAR2 requires to edit oar configuration (/etc/oar/oar.conf).

# Change the metascheduler command
META_SCHED_CMD="kao"
# Configuration variable that tells kao to enable compatibility with OAR2
METASCHEDULER_OAR3_WITH_OAR2="yes"

If the changes are applied to a running server, it might be necessary to restart OAR2.

systemctl restart oar-server

Note

To restore OAR2’s metascheduler, set back the META_SCHED_CMD to “oar_meta_sched”. and restart oar-server service systemctl restart oar-server.