HyperQueue

HyperQueue (HQ) is an efficient sub-node task scheduler. Instead of submitting each of your computational tasks as separate Slurm jobs or job steps, you can allocate a large resource block and then use HyperQueue to submit your tasks to this allocation. A single resource allocation will be much less stressful for the batch queue system and is the recommended way to run your high-throughput computing use cases. Furthermore, we can use HyperQueue instead of Slurm as the task executor for other workflow managers, such as Snakemake and Nextflow.

License

Free to use and open source under MIT License

Available

• Puhti: 0.13.0, 0.15.0, 0.16.0
• Mahti: 0.13.0, 0.15.0, 0.16.0

Usage

Task-farming with sbatch-hq tool

For simple task-farming workflows, where you only want to run many similar, independent, and non-MPI parallel programs, you can use the CSC utility tool sbatch-hq. Just specify the list of commands to run in a file, one command per line. The tool sbatch-hq will create and launch a batch job that starts running commands from the file using HyperQueue. You can specify how many nodes you want to run the commands on, and sbatch-hq will keep executing the commands until all are done or the batch job time limit is reached.

Let's assume we have a tasks file with a list of commands we want to run using eight threads each. Do not use srun in the commands! HyperQueue will launch the tasks using the allocated resources as requested. For example,

command1 arguments1
command2 arguments2
# and so on

For example, let's reserve one compute node for the whole job, which means we could run either five tasks simultaneously using Puhti or 16 tasks simultaneously using Mahti.

module load sbatch-hq
sbatch-hq --cores=8 --nodes=1 --account=<project> --partition=test --time=00:15:00 tasks

The number of commands in the file can (usually should) be much larger than the number of tasks that can fit running simultaneously in the reserved nodes. See sbatch-hq --help for more details on usage and input options.

Using HyperQueue in a Slurm batch job

HyperQueue works on a worker-server-client basis. The server manages connections between workers and the client. The client submits tasks to the server, which sends them to the available workers. The client and server may run on login or compute nodes, and the workers run on compute nodes. HyperQueue resembles a Slurm within a Slurm, but you must start the server and workers yourself. We recommend reading the official HyperQueue documentation.

This example consists of a batch script and an executable task script. The batch script starts the HyperQueue server and workers and submits tasks to the workers. The task script is an executable script that we submit to the workers. You can copy the following example, run it as given, and modify it to suit your needs. The directory structure looks as follows:

.             # Current working directory
├── batch.sh  # Batch script for HyperQueue server and workers
└── task      # Executable task script for HyperQueue

Task

We assume that HyperQueue tasks are independent and run on a single node. Here is an example of a simple, executable task script written in Bash.

#!/bin/bash
sleep 1

The overhead per task is around 0.1 milliseconds. Therefore, we can efficiently execute even very small tasks.

Batch job

In a Slurm batch job, each Slurm task corresponds to one HyperQueue worker. We can increase the number of workers by increasing the number of Slurm tasks. We reserve a fraction of the CPUs and memory on a node per worker in a partial node allocation and all the CPUs and memory on a node per worker in a full node allocation.

Puhti partial single nodePuhti partial multinodePuhti full single nodePuhti full multinodeMahti full node

#!/bin/bash
#SBATCH --account=<project>
#SBATCH --partition=small    # single node partition
#SBATCH --nodes=1            # one compute node
#SBATCH --ntasks-per-node=1  # one HyperQueue worker
#SBATCH --cpus-per-task=10   # one or more cpus per worker
#SBATCH --mem-per-cpu=1000   # desired amount of memory per cpu
#SBATCH --time=00:15:00

#!/bin/bash
#SBATCH --account=<project>
#SBATCH --partition=large    # multi node partition
#SBATCH --nodes=2            # two or more nodes
#SBATCH --ntasks-per-node=1  # one HyperQueue worker per node
#SBATCH --cpus-per-task=10   # one or more cpus per worker
#SBATCH --mem-per-cpu=1000   # desired amount of memory per cpu
#SBATCH --time=00:15:00

#!/bin/bash
#SBATCH --account=<project>
#SBATCH --partition=small    # single node partition
#SBATCH --nodes=1            # one compute node
#SBATCH --ntasks-per-node=1  # one HyperQueue worker
#SBATCH --cpus-per-task=40   # all cpus on a node
#SBATCH --mem=0              # reserve all memory on a node
#SBATCH --time=00:15:00

#!/bin/bash
#SBATCH --account=<project>
#SBATCH --partition=large    # multi node partition
#SBATCH --nodes=2            # two or more nodes
#SBATCH --ntasks-per-node=1  # one HyperQueue worker per node
#SBATCH --cpus-per-task=40   # reserve all cpus on a node
#SBATCH --mem=0              # reserve all memory on a node
#SBATCH --time=00:15:00

#!/bin/bash
#SBATCH --account=<project>
#SBATCH --partition=medium   # multi node partition
#SBATCH --nodes=1            # one or more nodes
#SBATCH --ntasks-per-node=1  # one HyperQueue worker per node
#SBATCH --cpus-per-task=128  # all cpus on a node
#SBATCH --mem=0              # reserve all memory on a node
#SBATCH --time=00:15:00

Module

We load the HyperQueue module to make the hq command available.

module load hyperqueue

Server

Next, we specify where HyperQueue places the server files. All hq commands respect this variable, so we set it before using any hq commands. If a server directory is not specified, it will default to the user's home directory. In this case, one has to be careful not to mix up separate computations as well as mind the limited storage space available under $HOME. We recommend starting one server per job in a job-specific directory for simple cases that fit inside one Slurm job.

# Specify a location for the server
export HQ_SERVER_DIR="$PWD/hq-server/$SLURM_JOB_ID"

# Create a directory for the server
mkdir -p "$HQ_SERVER_DIR"

Now, we start the server in the background and wait for it to start. The server keeps running until we stop it; therefore, we place it in the background so it does not block the execution of the rest of the script.

# Start the server in the background
hq server start &

# Wait until the server has started
until hq job list &> /dev/null ; do sleep 1 ; done

Workers

Next, we start HyperQueue workers in the background with the number of CPUs defined in the batch script using the $SLURM_CPUS_PER_TASK environment variable. By starting the workers using the srun command, we create one worker per Slurm task. We also wait for all workers to connect, which is generally good practice as we can notice issues with the workers early.

# Start the workers in the background.
srun --overlap --cpu-bind=none --mpi=none hq worker start \
    --manager slurm \
    --on-server-lost finish-running \
    --cpus="$SLURM_CPUS_PER_TASK" &

# Wait until all workers have started
hq worker wait "$SLURM_NTASKS"

Computing tasks

Now we can submit tasks with hq submit to the server, which executes them on the available workers. It is a non-blocking command; thus, we do not need to run it in the background. Regarding file I/O, we turn off output by setting --stdout=none and --stderr=none. Otherwise, HyperQueue will create output files for each task, which can create excess I/O on the parallel filesystem when there are many tasks. After submitting all the tasks, we wait for them to complete to synchronize the script.

# Submit tasks to workers
hq submit --stdout=none --stderr=none --cpus=1 --array=1-1000 ./task

# Wait for all the tasks to finish
hq job wait all

It is worth reading the sections about Jobs and Tasks and Task Arrays to understand the different ways to run computations with HyperQueue. For more complex task dependencies, we can use HyperQueue as the executor for other workflow managers, such as Snakemake or Nextflow.

Stopping the workers and the server

Once we are done running all of our tasks, we shut down the workers and server to avoid a false error from Slurm when the job ends.

# Shut down the workers and server
hq worker stop all
hq server stop

Using local disks with HyperQueue

We can use temporary local disk areas with HyperQueue to perform I/O intensive tasks. Since a HyperQueue task can run on any allocated node, the local disk of each node must have a copy of all the files that the task may use. A typical workflow consists of

1. Copying and extracting archived input files from the parallel file system to the local disk.
2. Computing the HyperQueue tasks (hq submit) that use the local disk.
3. Archiving and copying the output files from the local disk to the parallel file system.

For steps 1 and 3, we can run an <executable> on each allocated node as a Slurm job step as follows:

srun -m arbitrary -w "$SLURM_JOB_NODELIST" <executable>

Without the options, srun would run the executable on every Slurm task, which could be on the same node. The srun command can be omitted if only a single node is requested.

Complete example scripts for Puhti

Single nodeMultinode + local disk

File: task

#!/bin/bash
echo "Hello from task $HQ_TASK_ID!" > "output/$HQ_TASK_ID.out"
sleep 1

File: batch.sh

#!/bin/bash
#SBATCH --account=<project>
#SBATCH --partition=small
#SBATCH --nodes=1
#SBATCH --ntasks-per-node=1
#SBATCH --cpus-per-task=10
#SBATCH --mem-per-cpu=1000
#SBATCH --time=00:15:00

module load hyperqueue

# Specify a location and create a directory for the server
export HQ_SERVER_DIR="$PWD/hq-server/$SLURM_JOB_ID"
mkdir -p "$HQ_SERVER_DIR"

# Start the server in the background and wait until it has started
hq server start &
until hq job list &> /dev/null ; do sleep 1 ; done

# Start the workers in the background
srun --overlap --cpu-bind=none --mpi=none hq worker start \
    --manager slurm \
    --on-server-lost finish-running \
    --cpus="$SLURM_CPUS_PER_TASK" &

# Wait until all workers have started
hq worker wait "$SLURM_NTASKS"

# Create a directory for output files
mkdir -p output

# Submit tasks to workers
hq submit --stdout=none --stderr=none --cpus=1 --array=1-1000 ./task

# Wait for all tasks to finish
hq job wait all

# Shut down the workers and server
hq worker stop all
hq server stop

The archive input.tar.gz used in this example extracts into input directory.

File: extract

#!/bin/bash
tar xf input.tar.gz -C "$LOCAL_SCRATCH"
mkdir -p "$LOCAL_SCRATCH/output"

File: task

#!/bin/bash
cd "$LOCAL_SCRATCH"
cat "input/$HQ_TASK_ID.inp" > "output/$HQ_TASK_ID.out"
sleep 1

File: archive

#!/bin/bash
cd "$LOCAL_SCRATCH"
tar czf "output-$SLURMD_NODENAME.tar.gz" output
cp "output-$SLURMD_NODENAME.tar.gz" "$SLURM_SUBMIT_DIR"

File: batch.sh

#!/bin/bash
#SBATCH --account=<project>
#SBATCH --partition=large
#SBATCH --nodes=2
#SBATCH --ntasks-per-node=1
#SBATCH --cpus-per-task=40
#SBATCH --mem=0
#SBATCH --time=00:15:00
#SBATCH --gres=nvme:1

module load hyperqueue

# Specify a location and create a directory for the server
export HQ_SERVER_DIR="$PWD/hq-server/$SLURM_JOB_ID"
mkdir -p "$HQ_SERVER_DIR"

# Start the server in the background and wait until it has started
hq server start &
until hq job list &> /dev/null ; do sleep 1 ; done

# Start the workers in the background
srun --overlap --cpu-bind=none --mpi=none hq worker start \
    --manager slurm \
    --on-server-lost finish-running \
    --cpus="$SLURM_CPUS_PER_TASK" &

# Wait until all workers have started
hq worker wait "$SLURM_NTASKS"

# Download some example input files
wget https://a3s.fi/CSC_training/input.tar.gz

# Extract input files to the local disk and create a directory for outputs
srun -m arbitrary -w "$SLURM_JOB_NODELIST" ./extract

# Submit tasks to workers
hq submit --stdout=none --stderr=none --cpus=1 --array=1-1000 ./task

# Wait for all tasks to finish
hq job wait all

# Archive and copy output from each local disk to working directory on Lustre
srun -m arbitrary -w "$SLURM_JOB_NODELIST" ./archive

# Shut down the workers and server
hq worker stop all
hq server stop

Using Snakemake with HyperQueue

Using Snakemake's --cluster flag, we can use hq submit instead of sbatch:

snakemake --cluster "hq submit --cpus <threads> ..."

If you are porting a more complicated workflow from Slurm, you can do argument parsing and transformations programmatically using Snakemake's job properties.

Using Nextflow with HyperQueue

See a separate tutorial for instructions on using HyperQueue as an executor for Nextflow workflows.

Multinode tasks

Although HyperQueue does not do MPI execution out of the box, it's possible using a combination of the HQ feature Multinode Tasks and orterun, hydra or prrte. This way, one can schedule MPI tasks at a node-level granularity.

Automatic worker allocation

We recommend avoiding using the automatic allocator. It automatically generates and submits batch scripts to start workers, which adds unnecessary complexity. Also, the automatically generated batch scripts have some issues and could be more flexible.

More information

• Using HyperQueue and local disk to process many files
• Farming Gaussian jobs with sbatch-hq

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Last update: January 4, 2024

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