Scheduler

Input Parameters for the Cluster

These parameters is located in input/omnia_config.yml

Variable	Required (?)	Default, Choices	Description
mariadb_password	Optional	“password”	Password used for Slurm database. The password must not contain -,, ‘,” The Length of the password should be at least 8.
k8s_version	Optional	“1.19.3”, 1.16.7	Kubernetes version.
k8s_cni	Optional	“calico”, “flannel”	Kubernetes SDN network.
k8s_pod_network_cidr	Optional	“10.244.0.0/16”	Kubernetes pod network CIDR. Make sure this value does not overlap with any of the host networks.
docker_username	Optional		Username for Dockerhub account A kubernetes secret will be created and patched to service account in default namespace. This kubernetes secret can be used to pull images from private repositories This value is optional but suggested avoiding docker pull limit issues
docker_password	Optional		Password for Dockerhub account This value is mandatory if docker username is provided
ansible_config_file_path	Optional	/etc/ansible	Path to directory hosting ansible config file (ansible.cfg file) This directory is on the host running ansible, if ansible is installed using dnf If ansible is installed using pip, this path should be set
login_node_required	Optional	false, true	Boolean indicating whether login node is required or not.

Before You Build Clusters

• Verify that all inventory files are updated.

• If the target cluster requires more than 10 kubernetes nodes, use a docker enterprise account to avoid docker pull limits.

• Verify that all nodes are assigned a group. Use the inventory as a reference.

  • The manager group should have exactly 1 manager node.

  • The compute group should have at least 1 node.

  • The login_node group is optional. If present, it should have exactly 1 node.

  • Users should also ensure that all repos are available on the target nodes running RHEL.

Note

The inventory file accepts both IPs and FQDNs as long as they can be resolved by DNS.

• For RedHat clusters, ensure that RedHat subscription is enabled on all target nodes. Every target node will require a RedHat subscription.

Features enabled by omnia.yml

• Slurm: Once all the required parameters in omnia_config.yml are filled in, omnia.yml can be used to set up slurm.

• Login Node (Additionally secure login node)

• Kubernetes: Once all the required parameters in omnia_config.yml are filled in, omnia.yml can be used to set up kubernetes.

• BeeGFS bolt on installation

• NFS bolt on support

Building Clusters

1. In the input/omnia_config.yml file, provide the required details.

Note

Without the login node, Slurm jobs can be scheduled only through the manager node.

2. Create an inventory file in the omnia folder. Add login node IP address under the manager node IP address under the [manager] group, compute node IP addresses under the [compute] group, and Login node IP under the [login_node] group,. Check out the sample inventory for more information.

Note

• Omnia checks for red hat subscription being enabled on RedHat nodes as a pre-requisite. Not having Red Hat subscription enabled on the manager node will cause omnia.yml to fail. If compute nodes do not have Red Hat subscription enabled, omnia.yml will skip the node entirely.

• Omnia creates a log file which is available at: /var/log/omnia.log.

• If only Slurm is being installed on the cluster, docker credentials are not required.

3. To run omnia.yml:

ansible-playbook omnia.yml -i inventory

Note

• To visualize the cluster (Slurm/Kubernetes) metrics on Grafana (On the control plane) during the run of omnia.yml, add the parameters grafana_username and grafana_password (That is ansible-playbook omnia.yml -i inventory -e grafana_username="" -e grafana_password=""). Alternatively, Grafana is not installed by omnia.yml if it’s not available on the Control Plane.

• Having the same node in the manager and login_node groups in the inventory is not recommended by Omnia.

Using Skip Tags

Using skip tags, the scheduler running on the cluster can be set to Slurm or Kubernetes while running the omnia.yml playbook. This choice can be made depending on the expected HPC/AI workloads.

• Kubernetes: ansible-playbook omnia.yml -i inventory --skip-tags "kubernetes" (To set Slurm as the scheduler)

• Slurm: ansible-playbook omnia.yml -i inventory --skip-tags "slurm" (To set Kubernetes as the scheduler)

Note

• If you want to view or edit the omnia_config.yml file, run the following command:

  • ansible-vault view omnia_config.yml --vault-password-file .omnia_vault_key – To view the file.

  • ansible-vault edit omnia_config.yml --vault-password-file .omnia_vault_key – To edit the file.

• It is suggested that you use the ansible-vault view or edit commands and that you do not use the ansible-vault decrypt or encrypt commands. If you have used the ansible-vault decrypt or encrypt commands, provide 644 permission to omnia_config.yml.

Kubernetes Roles

As part of setting up Kubernetes roles, omnia.yml handles the following tasks on the manager and compute nodes:

• Docker is installed.

• Kubernetes is installed.

• Helm package manager is installed.

• All required services are started (Such as kubelet).

• Different operators are configured via Helm.

• Prometheus is installed.

Slurm Roles

As part of setting up Slurm roles, omnia.yml handles the following tasks on the manager and compute nodes:

• Slurm is installed.

• All required services are started (Such as slurmd, slurmctld, slurmdbd).

• Prometheus is installed to visualize slurm metrics.

• Lua and Lmod are installed as slurm modules.

• Slurm restd is set up.

Login node

If a login node is available and mentioned in the inventory file, the following tasks are executed:

• Slurmd is installed.

• All required configurations are made to slurm.conf file to enable a slurm login node.

Hostname requirements

• In the examples folder, a mapping_host_file.csv template is provided which can be used for DHCP configuration. The header in the template file must not be deleted before saving the file. It is recommended to provide this optional file as it allows IP assignments provided by Omnia to be persistent across control plane reboots.

• The Hostname should not contain the following characters: , (comma), . (period) or _ (underscore). However, the domain name is allowed commas and periods.

• The Hostname cannot start or end with a hyphen (-).

• No upper case characters are allowed in the hostname.

• The hostname cannot start with a number.

• The hostname and the domain name (that is: hostname00000x.domain.xxx) cumulatively cannot exceed 64 characters. For example, if the node_name provided in input/provision_config.yml is ‘node’, and the domain_name provided is ‘omnia.test’, Omnia will set the hostname of a target compute node to ‘node00001.omnia.test’. Omnia appends 6 digits to the hostname to individually name each target node.

Note

• To enable the login node, ensure that login_node_required in input/omnia_config.yml is set to true.

Slurm job based user access

To ensure security while running jobs on the cluster, users can be assigned permissions to access compute nodes only while their jobs are running. To enable the feature:

cd scheduler
ansible-playbook job_based_user_access.yml -i inventory

Note

• The inventory queried in the above command is to be created by the user prior to running omnia.yml as scheduler.yml is invoked by omnia.yml

• Only users added to the ‘slurm’ group can execute slurm jobs. To add users to the group, use the command: usermod -a -G slurm <username>.

Running Slurm MPI jobs on clusters

To enhance the productivity of the cluster, Slurm allows users to run jobs in a parallel-computing architecture. This is used to efficiently utilize all available computing resources.

Note

• Omnia does not install MPI packages by default. Users hoping to leverage the Slurm-based MPI execution feature are required to install the relevant packages from a source of their choosing.

• Running jobs as individual users (and not as root) requires that passwordSSH be enabled between compute nodes for the user.

For Intel

To run an MPI job on an intel processor, set the following environmental variables on the head nodes or within the job script:

• I_MPI_PMI_LIBRARY = /usr/lib64/pmix/

• FI_PROVIDER = sockets (When InfiniBand network is not available, this variable needs to be set)

• LD_LIBRARY_PATH (Use this variable to point to the location of the Intel/Python library folder. For example: $LD_LIBRARY_PATH:/mnt/jobs/intelpython/python3.9/envs/2022.2.1/lib/)

For AMD

To run an MPI job on an AMD processor, set the following environmental variables on the head nodes or within the job script:

• PATH (Use this variable to point to the location of the OpenMPI binary folder. For example: PATH=$PATH:/appshare/openmpi/bin)

• LD_LIBRARY_PATH (Use this variable to point to the location of the OpenMPI library folder. For example: $LD_LIBRARY_PATH:/appshare/openmpi/lib)

• OMPI_ALLOW_RUN_AS_ROOT = 1 (To run jobs as a root user, set this variable to 1)

• OMPI_ALLOW_RUN_AS_ROOT_CONFIRM = 1 (To run jobs as a root user, set this variable to 1)