stackhpc.openhpc

This Ansible role installs packages and performs configuration to provide an OpenHPC Slurm cluster. It can also be used to drain and resume nodes.

As a role it must be used from a playbook, for which a simple example is given below. This approach means it is totally modular with no assumptions about available networks or any cluster features except for some hostname conventions. Any desired cluster fileystem or other required functionality may be freely integrated using additional Ansible roles or other approaches.

The minimal image for nodes is a CentOS 7 or RockyLinux 8 GenericCloud image. These use OpenHPC v1 and v2 respectively. Centos8/OpenHPCv2 is generally preferred as it provides additional functionality for Slurm, compilers, MPI and transport libraries.

Role Variables

openhpc_version: Optional. OpenHPC version to install. Defaults provide 1.3 for Centos 7 and 2 for RockyLinux/CentOS 8.

openhpc_extra_repos: Optional list. Extra Yum repository definitions to configure, following the format of the Ansible yum_repository module. Respected keys for each list element:

• name: Required
• description: Optional
• file: Required
• baseurl: Optional
• metalink: Optional
• mirrorlist: Optional
• gpgcheck: Optional
• gpgkey: Optional

openhpc_slurm_service_enabled: boolean, whether to enable the appropriate slurm service (slurmd/slurmctld).

openhpc_slurm_service_started: Optional boolean. Whether to start slurm services. If set to false, all services will be stopped. Defaults to openhpc_slurm_service_enabled.

openhpc_slurm_control_host: Required string. Ansible inventory hostname (and short hostname) of the controller e.g. "{{ groups['cluster_control'] | first }}".

openhpc_slurm_control_host_address: Optional string. IP address or name to use for the openhpc_slurm_control_host, e.g. to use a different interface than is resolved from openhpc_slurm_control_host.

openhpc_packages: additional OpenHPC packages to install.

openhpc_enable:

• control: whether to enable control host
• database: whether to enable slurmdbd
• batch: whether to enable compute nodes
• runtime: whether to enable OpenHPC runtime
• drain: whether to drain compute nodes
• resume: whether to resume compute nodes

openhpc_slurmdbd_host: Optional. Where to deploy slurmdbd if are using this role to deploy slurmdbd, otherwise where an existing slurmdbd is running. This should be the name of a host in your inventory. Set this to none to prevent the role from managing slurmdbd. Defaults to openhpc_slurm_control_host.

openhpc_slurm_configless: Optional, default false. If true then slurm's "configless" mode is used. NB: Requires Centos8/OpenHPC v2.

openhpc_munge_key: Optional. Define a munge key to use. If not provided then one is generated but the openhpc_slurm_control_host must be in the play.

openhpc_login_only_nodes: Optional. If using "configless" mode specify the name of an ansible group containing nodes which are login-only nodes (i.e. not also control nodes), if required. These nodes will run slurmd to contact the control node for config.

openhpc_module_system_install: Optional, default true. Whether or not to install an environment module system. If true, lmod will be installed. If false, You can either supply your own module system or go without one.

slurm.conf

openhpc_slurm_partitions: Optional. List of one or more slurm partitions, default []. Each partition may contain the following values:

• groups: If there are multiple node groups that make up the partition, a list of group objects can be defined here. Otherwise, groups can be omitted and the following attributes can be defined in the partition object:

  • name: The name of the nodes within this group.

  • cluster_name: Optional. An override for the top-level definition openhpc_cluster_name.

  • extra_nodes: Optional. A list of additional node definitions, e.g. for nodes in this group/partition not controlled by this role. Each item should be a dict, with keys/values as per the "NODE CONFIGURATION" docs for slurm.conf. Note the key NodeName must be first.

  • ram_mb: Optional. The physical RAM available in each node of this group (slurm.conf parameter RealMemory) in MiB. This is set using ansible facts if not defined, equivalent to free --mebi total * openhpc_ram_multiplier.

  • ram_multiplier: Optional. An override for the top-level definition openhpc_ram_multiplier. Has no effect if ram_mb is set.

  • gres: Optional. List of dicts defining generic resources. Each dict must define:

    • conf: A string with the resource specification but requiring the format <name>:<type>:<number>, e.g. gpu:A100:2. Note the type is an arbitrary string.
    • file: A string with the File (path to device(s)) for this resource, e.g. /dev/nvidia[0-1] for the above example.

    Note GresTypes must be set in openhpc_config if this is used.

• default: Optional. A boolean flag for whether this partion is the default. Valid settings are YES and NO.

• maxtime: Optional. A partition-specific time limit following the format of slurm.conf parameter MaxTime. The default value is given by openhpc_job_maxtime. The value should be quoted to avoid Ansible conversions.

• partition_params: Optional. Mapping of additional parameters and values for partition configuration.

For each group (if used) or partition any nodes in an ansible inventory group <cluster_name>_<group_name> will be added to the group/partition. Note that:

• Nodes may have arbitrary hostnames but these should be lowercase to avoid a mismatch between inventory and actual hostname.
• Nodes in a group are assumed to be homogenous in terms of processor and memory.
• An inventory group may be empty or missing, but if it is not then the play must contain at least one node from it (used to set processor information).
• Nodes may not appear in more than one group.

openhpc_job_maxtime: Maximum job time limit, default '60-0' (60 days). See slurm.conf parameter MaxTime for format. The default is 60 days. The value should be quoted to avoid Ansible conversions.

openhpc_cluster_name: name of the cluster.

openhpc_config: Optional. Mapping of additional parameters and values for slurm.conf. Note these will override any included in templates/slurm.conf.j2.

openhpc_ram_multiplier: Optional, default 0.95. Multiplier used in the calculation: total_memory * openhpc_ram_multiplier when setting RealMemory for the partition in slurm.conf. Can be overriden on a per partition basis using openhpc_slurm_partitions.ram_multiplier. Has no effect if openhpc_slurm_partitions.ram_mb is set.

openhpc_state_save_location: Optional. Absolute path for Slurm controller state (slurm.conf parameter StateSaveLocation)

Accounting

By default, no accounting storage is configured. OpenHPC v1.x and un-updated OpenHPC v2.0 clusters support file-based accounting storage which can be selected by setting the role variable openhpc_slurm_accounting_storage_type to accounting_storage/filetxt¹. Accounting for OpenHPC v2.1 and updated OpenHPC v2.0 clusters requires the Slurm database daemon, slurmdbd (although job completion may be a limited alternative, see below. To enable accounting:

• Configure a mariadb or mysql server as described in the slurm accounting documentation on one of the nodes in your inventory and set openhpc_enable.database to true for this node.
• Set openhpc_slurm_accounting_storage_type to accounting_storage/slurmdbd.
• Configure the variables for slurmdbd.conf below.

The role will take care of configuring the following variables for you:

openhpc_slurm_accounting_storage_host: Where the accounting storage service is running i.e where slurmdbd running.

openhpc_slurm_accounting_storage_port: Which port to use to connect to the accounting storage.

openhpc_slurm_accounting_storage_user: Username for authenticating with the accounting storage.

openhpc_slurm_accounting_storage_pass: Mungekey or database password to use for authenticating.

For more advanced customisation or to configure another storage type, you might want to modify these values manually.

Job accounting

This is largely redundant if you are using the accounting plugin above, but will give you basic accounting data such as start and end times. By default no job accounting is configured.

openhpc_slurm_job_comp_type: Logging mechanism for job accounting. Can be one of jobcomp/filetxt, jobcomp/none, jobcomp/elasticsearch.

openhpc_slurm_job_acct_gather_type: Mechanism for collecting job accounting data. Can be one of jobacct_gather/linux, jobacct_gather/cgroup and jobacct_gather/none.

openhpc_slurm_job_acct_gather_frequency: Sampling period for job accounting (seconds).

openhpc_slurm_job_comp_loc: Location to store the job accounting records. Depends on value of openhpc_slurm_job_comp_type, e.g for jobcomp/filetxt represents a path on disk.

slurmdbd.conf

The following options affect slurmdbd.conf. Please see the slurm documentation for more details. You will need to configure these variables if you have set openhpc_enable.database to true.

openhpc_slurmdbd_port: Port for slurmdb to listen on, defaults to 6819.

openhpc_slurmdbd_mysql_host: Hostname or IP Where mariadb is running, defaults to openhpc_slurm_control_host.

openhpc_slurmdbd_mysql_database: Database to use for accounting, defaults to slurm_acct_db.

openhpc_slurmdbd_mysql_password: Password for authenticating with the database. You must set this variable.

openhpc_slurmdbd_mysql_username: Username for authenticating with the database, defaults to slurm.

Example Inventory

And an Ansible inventory as this:

[openhpc_login]
openhpc-login-0 ansible_host=10.60.253.40 ansible_user=centos

[openhpc_compute]
openhpc-compute-0 ansible_host=10.60.253.31 ansible_user=centos
openhpc-compute-1 ansible_host=10.60.253.32 ansible_user=centos

[cluster_login:children]
openhpc_login

[cluster_control:children]
openhpc_login

[cluster_batch:children]
openhpc_compute

Example Playbooks

To deploy, create a playbook which looks like this:

---
- hosts:
  - cluster_login
  - cluster_control
  - cluster_batch
  become: yes
  roles:
    - role: openhpc
      openhpc_enable:
        control: "{{ inventory_hostname in groups['cluster_control'] }}"
        batch: "{{ inventory_hostname in groups['cluster_batch'] }}"
        runtime: true
      openhpc_slurm_service_enabled: true
      openhpc_slurm_control_host: "{{ groups['cluster_control'] | first }}"
      openhpc_slurm_partitions:
        - name: "compute"
      openhpc_cluster_name: openhpc
      openhpc_packages: []
...

To drain nodes, for example, before scaling down the cluster to 6 nodes:

---
- hosts: openstack
  gather_facts: false
  vars:
    partition: "{{ cluster_group.output_value | selectattr('group', 'equalto', item.name) | list }}"
    openhpc_slurm_partitions:
      - name: "compute"
        flavor: "compute-A"
        image: "CentOS7.5-OpenHPC"
        num_nodes: 6
        user: "centos"
    openhpc_cluster_name: openhpc
  roles:
    # Our stackhpc.cluster-infra role can be invoked in `query` mode which
    # looks up the state of the cluster by querying the Heat API.
    - role: stackhpc.cluster-infra
      cluster_name: "{{ cluster_name }}"
      cluster_state: query
      cluster_params:
        cluster_groups: "{{ cluster_groups }}"
  tasks:
    # Given that the original cluster that was created had 8 nodes and the
    # cluster we want to create has 6 nodes, the computed desired_state
    # variable stores the list of instances to leave untouched.
    - name: Count the number of compute nodes per slurm partition
      set_fact:
        desired_state: "{{ (( partition | first).nodes | map(attribute='name') | list )[:item.num_nodes] + desired_state | default([]) }}"
      when: partition | length > 0
      with_items: "{{ openhpc_slurm_partitions }}"
    - debug: var=desired_state

- hosts: cluster_batch
  become: yes
  vars:
    desired_state: "{{ hostvars['localhost']['desired_state'] | default([]) }}"
  roles:
    # Now, the stackhpc.openhpc role is invoked in drain/resume modes where
    # the instances in desired_state are resumed if in a drained state and
    # drained if in a resumed state.
    - role: stackhpc.openhpc
      openhpc_slurm_control_host: "{{ groups['cluster_control'] | first }}"
      openhpc_enable:
        drain: "{{ inventory_hostname not in desired_state }}"
        resume: "{{ inventory_hostname in desired_state }}"
...

---

1 Slurm 20.11 removed accounting_storage/filetxt as an option. This version of Slurm was introduced in OpenHPC v2.1 but the OpenHPC repos are common to all OpenHPC v2.x releases. ↩