Slurm Workload Manager¶

Note

Slurm support is in beta. Feel free to use it, but we suggest contacting our support before putting anything into production.

Slurm is an open source, fault-tolerant, and highly scalable cluster management and job scheduling system. Slurm consists of various services which are represented by separate Flying Circus roles documented below.

The remainder of this documentation assumes that you are aware of the basics of Slurm and understand the general terminology.

We provide version 22.5.0 of Slurm.

Basic architecture and roles¶

Warning

Keep in mind that Slurm is built to execute arbitrary commands on any Slurm node with the permissions of the user starting the command on possibly another machine. Keep sensitive data away from Slurm nodes and isolate Slurm as much as possible, using a dedicated resource group without other applications.

You can run one Slurm cluster per resource group. We generally recommend to use separate clusters (and thus separate resource groups) for independent projects. This will give you the most flexibility and will integrate optimally into our platform aligning well on topics like access management, monitoring, SLAs, maintenance, etc.

A resource group with Slurm roles can have additional machines which provide additional services which may be needed to run jobs in Slurm. Such required machines can also be included in the coordination of automated maintenance as described later.

Machine authentication is handled by munge, using a shared secrets generated by our central management directory. New worker nodes are automatically added to existing clusters.

slurm-controller¶

Note

For new clusters, it’s recommended to first set up a controller and add nodes after that. The controller service will only start if there’s at least one node.

Note

For autoconfiguration, all slurm machines must have the same amount of memory and CPU cores. If that’s not the case, memory and CPU cores must be set manually. See the Configuration reference on how to do that.

This role runs slurmctld. We add basic Cluster readiness monitoring via Sensu and telemetry via Telegraf which can be ingested by a Statshost and displayed using a Grafana dashboard.

At the moment, we only support exactly one controller per cluster.

Maintenance of a machine with this role means that all worker nodes are drained and set to down first. Maintenance activities only start when no jobs are running anymore in the whole cluster.

After finishing a platform management task run (which happens every 10 minutes), the controller sets all nodes to ready that have been set to down by an automated maintenance if the nodes and all external dependency machines are not in maintenance.

slurm-dbdserver¶

Note

At the moment, this role must run on the same machine as slurm-controller.

Runs slurmdbd which is needed for job accounting. Automatically sets up a MySQL database with our platform defaults and monitoring/telemetry.

slurm-node¶

Runs slurmd which is responsible for processing jobs. There should be multiple nodes in your cluster for production use but applying this role to a machine which is also running the controller services is also supported for testing purposes.

Nodes must be ready to accept jobs. The corresponding Slurm states are IDLE when the node isn’t processing jobs at the moment or MIXED/ALLOCATED if some or all of its cores are in use at the moment, respectively.

Before running maintenance activities, the node is drained and stops accepting new jobs. Nodes don’t set themselves to ready after maintenance. Instead, the controller activates nodes which are not in maintenance anymore after its own platform management task run (every 10 minutes).

Warning

Nodes that had an unexpected reboot or have been drained/downed manually are not set to ready automatically by the platform management task. You have to do that manually using one of the ready subcommands described in Managing clusters with the fc-slurm command.

slurm-external-dependency¶

This role does not provide any Slurm services but something that is needed to run jobs via Slurm, for example a database accessed by job scripts. When such machines go into maintenance, all nodes are drained first, like for a controller maintenance. After the external dependency machine has finished maintenance, the next run of the platform management task on the controller will set the nodes to ready.

Cluster interaction using Slurm commands¶

The usual Slurm commands are installed globally on every Slurm machine.

In general, all users can run slurm commands on all machines with a slurm-* role. Some commands require the use of sudo -u slurm to run as slurm user. This is allowed for(human) user accounts with the sudo-srv permission without password.

Use slurm-readme to show dynamically-generated documentation specific for this machine.

Managing clusters with the fc-slurm command¶

Use fc-slurm to manage the state of slurm compute nodes and display status information about the cluster.

This command is also used by our platform management task before and after maintenance, as well as to fetch telemetry data from Slurm and running monitoring checks.

Some subcommands that modify state require sudo. This is allowed for (human) user accounts with the sudo-srv permission without password.

The output and availability of subcommands depends on the role of the machine.

Global Node Management¶

The fc-slurm all-nodes subcommand can be run on every machine with a slurm role and operates on all nodes in the cluster.

Mark all nodes as ready:

sudo fc-slurm all-nodes ready

This is needed when nodes are out because they had an unexpected reboot or have been drained/downed manually.

Note

all-nodes ready skips nodes that are still in maintenance.

You can specify a reason to restrict the affected nodes. Their reason for being in a down state must contain the given string:

sudo fc-slurm all-nodes ready --reason-must-match "my node maintenance"

Drain all nodes (no new jobs allowed) and set them to down afterwards:

sudo fc-slurm all-nodes drain-and-down --reason "my global maintenance"

Dump node state info as JSON:

fc-slurm all-nodes state

Single Node Management¶

Manage the state of nodes individually, by running fc-slurm directly on the node:

sudo fc-slurm drain-and-down --reason "my node maintenance"
sudo fc-slurm ready

Check the state of the node, also used by the slurm Sensu check:

fc-slurm check

Controller Management¶

Controllers don’t have management commands that affect their state at the moment but you can run fc-slurm all-nodes on controller machines or look at check output.

Check the state of the controller and all nodes, also used by the slurm Sensu check:

fc-slurm check

Command Cheat sheet¶

Set all nodes to ready:

sudo fc-slurm all-nodes ready

View the dynamically-generated documentation for a machine:

slurm-readme

Show the current configuration:

slurm-show-configuration

Show running/pending jobs

squeue

Show partition state:

sinfo

Show node info:

sinfo -N

Show job accounting info:

sacct

Known limitations¶

For autoconfiguration, all nodes and the controller must have the same amount of memory and CPU cores. If that’s not the case, memory and CPU must be set manually via Nix config to the same value on all Slurm machines because Slurm expects the config file to be the same everywhere.
slurm-dbdserver and slurm-controller roles must be on the same machine.
we support only one slurm-controller per cluster at the moment.

Configuration reference¶

Warning

Memory and CPU cores must be set to the same value on all Slurm machines because Slurm expects the config file to be the same everywhere.

This also applies to machines that don’t have the slurm-node role even if the memory and CPU settings have no effect there.

flyingcircus.slurm.realMemory

Memory in MiB used by a slurm compute node.

flyingcircus.slurm.cpus

Number of CPU cores used by a slurm compute node.

flyingcircus.slurm.clusterName

Name of the cluster. Defaults to the name of the resource group.

The cluster name is used in various places like state files or accounting table names and should normally stay unchanged. Changing this requires manual intervention in the state dir or slurmctld will not start anymore!

flyingcircus.slurm.partitionName

Name of the default partition which includes the machines defined via the nodes option. Don’t use default as partition name, it will fail!

flyingcircus.slurm.accountingStorageEnforce

This controls what level of association-based enforcement to impose on job submissions. Valid options are any combination of associations, limits, nojobs, nosteps, qos, safe, and wckeys, or all for all things (except nojobs and nosteps, which must be requested as well). If limits, qos, or wckeys are set, associations will automatically be set.

By setting associations, no new job is allowed to run unless a corresponding association exists in the system. If limits are enforced, users can be limited by association to whatever job size or run time limits are defined.

flyingcircus.slurm.nodes

Names of the nodes that are added to the automatically generated partition. By default, all Slurm nodes in a resource group are part of the partition called partitionName.

services.slurm.extraConfig

Extra configuration options that will be added verbatim at the end of the slurm configuration file.

services.slurm.dbdserver.extraConfig

Extra configuration for slurmdbd.conf See also: slurmdbd.conf(8).

Example custom local config¶

{ ... }:

{
  flyingcircus.slurm = {
    accountingStorageEnforce = true;
    partitionName = "processing";
    realMemory = 62000;
    cpus = 16;
  };

  services.slurm.extraConfig = ''
    AccountingStorageEnforce=associations
  '';
}