Workflows on OSCAR

This repo tracks the development of a user-friendly CLI tool for installing and configuring Nextflow and Snakemake workflow management tools on Brown's HPC cluster, OSCAR, so that users can easily and efficiently deploy reproducible, scalable pipelines for compute intensive tasks. Please make sure to read this entire README for important information before attempting to run your pipelines using this tool.

Note: This tool is currently in Beta testing. If there are any issues or bugs, please report them to: [email protected]

Running the Installer

To set up Nextflow and/or Snakemake for OSCAR, just git clone this repo into your HOME directory on OSCAR. Once this is done, copy and paste the following command into your terminal:

bash ~/workflows_on_OSCAR/install_me/install.sh && source ~/.bashrc

Running the above command in your terminal will initiate the installation and configuration process, walking the user through a user-friendly guide to setting up and configuring Nextflow and Snakemake to run on OSCAR according to the user's computing needs. You can run the above bash command more than once if you wish to install both workflow management tools or just wish to reconfigure a workflow's HPC defaults to your liking.

NEXTFLOW

When launched, the CLI tool will prompt the user to type the name of the software they wish to install and set up. Just enter Nextflow and you will be guided through the rest of the installation and configuration process. During this process, the guide will prompt you to answer a few simple questions, after which the software handles the majority of the configuration details for you.

Once the installation and configuration process is done, users can run nextflow pipelines using their own custom workflows, workflows from GitHub repos, or workflows from nf-core. The use of singularity containers is automatically enabled and users can flexibly incorporate different containers into their workflow pipelines.

Important Nextflow commands

• nextflow_start makes it so you're able to run Nextflow commands. Specifically, it enters you into a virtual environment module where Nextflow is available to you for use. You can use this command in an interactive session on OSCAR (via interact) or in your sbatch script by putting it before any nextflow commands you use in the script.
• nextflow -h prints helpful information about all the commands and options that exist for Nextflow software. Important Note: this command will only work after you entered the Nextflow session via nextflow_start. For a full list of all the nextflow commands and options you can run, please visit: https://www.nextflow.io/docs/latest/cli.html
• nextflow run executes a pipeline project. This is used with various options along with your project files. Important Note: this command will only work after you entered the Nextflow session via nextflow_start.
• quit_workflow exits you out of the Nextflow working session you entered into. If you run this, you will be taken out of your session and unable to run any Nextflow commands until you run nextflow_start again. Note that you do not put this command in your sbatch scripts.
• nextflow_remove uninstalls (deletes) Nextflow and all of its associated commands (i.e., nextflow_start, nextflow run, nextflow_remove)

Nextflow Template Script for OSCAR

Once Nextflow has been successfully installed and configured on OSCAR, you will find a script called nextflow_template_script.sh in the ~/nextflow_setup directory. This is a template script that you can easily edit and use to run Nextflow pipelines on OSCAR using the sbatch command. To do so, first copy this file to your project directory (or to any other directory you need it) and rename the file. A general example of how to do this would be:

cp ~/nextflow_setup/nextflow_template_script.sh /directory/of/your/choosing/nextflow_run.sh

The above command creates a new script called nextflow_run.sh that is directly copied from the template script. Once this is done, you can open and edit the newly copied file using a text editor of your choice (such as vim). When you are done editing, exit and save and then run the file using the sbatch command. This will run your Nextflow pipeline on OSCAR. Note that inside the nextflow_template_script.sh file you will find more detailed instructions and notes helping you to setup and run pipelines using the template file. Please read and follow these instructions.

File Management using Nextflow

The default configuration sets up Nextflow to use your HOME directory for both slurm logs and job output. Furthermore, singularity caching happens in your scratch directory. As a reminder, the scratch directory is not backed up and files that you do not access for 30 days may be deleted.

SNAKEMAKE

When prompted by the CLI tool to type the name of the software you wish to install and set up, just enter Snakemake and you will be guided through the rest of the installation and configuration process. During this process, the guide will prompt you to answer a few simple questions, after which the software handles the majority of the configuration details for you.

Once the installation and configuration process is done, users can run snakemake pipelines using their own custom workflows or workflows from elsewhere (such as GitHub) via snakefiles. The use of singularity is automatically enabled and users can flexibly incorporate different containers into their workflow pipelines.

Important Snakemake commands

• snakemake_start makes it so you're able to run Snakemake commands. Specifically, it enters you into a virtual environment module where Snakemake software is available to you for use. You can use this command in an interactive session on OSCAR (via interact) or in your sbatch script by putting it before any snakemake commands you use in the script.
• snakemake -h prints helpful information about all the commands and options that exist for Snakemake software. Important Note: this command will only work after you entered the Snakemake session via snakemake_start. For a full list of all the commands and options you can run with Snakemake, please visit: https://snakemake.readthedocs.io/en/stable/executing/cli.html
• snakemake -s executes a workflow, where the -s flag is followed by your snakefile. This is used with various options along with project files. Important Note: this command will only work after you entered the Snakemake session via snakemake_start.
• quit_workflow exits you out of the Snakemake working session you entered into. If you run this, you will be taken out of your session and unable to run any Snakemake commands until you run snakemake_start again. Note that you do not put this command in your sbatch scripts.
• snakemake_remove uninstalls (deletes) Snakemake and all of its associated commands (i.e., snakemake_start, snakemake, snakemake_remove)

Snakemake Template Script for OSCAR

Once Snakemake has been successfully installed and configured on OSCAR, you will find a script called snakemake_template_script.sh in the ~/snakemake_setup directory. This is a template script that you can easily edit and use to run Snakemake pipelines on OSCAR using the sbatch command. To do so, first copy this file to your project directory (or to any other directory you need it) and rename the file.

Once this is done, you can open and edit the newly copied file using a text editor of your choice (such as vim). When you are done editing, exit and save and then run the file using the sbatch command. This will run your Snakemake pipeline on OSCAR. Note that inside the snakemake_template_script.sh file you will find more detailed instructions and notes helping you to setup and run pipelines using the template file. Please read and follow these instructions.

File Management using Snakemake

When Snakemake is installed and configured, it creates a folder called snakemake_folders in your HOME directory. This folder contains three folders used for the storage of output and singularity containers. Specifically, within ~/snakemake_folders is the following:

• snake_error_log this is where slurm error log files go
• snake_output this is where the output from jobs is stored on your filesystem
• singularities this is where singularity files get stored for use by Snakemake

Future updates

A number of updates are forthcoming in order to make future iterations of this tool more user-friendly. Specifically, we hope to do the following:

• Allow users to easily specify where they want slurm and pipeline outputs to go via user prompts during installation process
• Allow for Nextflow to submit jobs to gpu nodes for tasks that require it
• Expand the tool so users do not have to edit the template scripts to run Nextflow and Snakemake pipelines
• Possibly develop GUI and include this software on Brown's Open OnDemand web portal