Setup – Introduction to Workflows with Common Workflow Language

Software

These lessons are best followed using VSCode, and the Benten extension (which is a language server for CWL). We will also be using the CWL reference runner. Instructions for installing these are given below.

VSCode and Benten installation

Download and install VSCode.

Open VSCode and search for Benten in the marketplace. The name of the client extension is Rabix/benten. Follow the usual method to install the extension.

The VSCode Benten extension will require the Benten server to be installed too. It will prompt you to do this the first time you activate the extension.

CWL installation

Windows users first need to install the “Windows Subsystem for Linux 2” (WSL2) and the Docker Desktop before installing the cwltool. Follow these steps. At step 6 follow the venv method below, explained below. Linux users already have a Linux terminal and can start with following the steps below.

In this tutorial the latest version of cwltool is needed. To ensure this, a virtual environment is using pip and venv is used.

python3 -m venv env			# Create a virtual environment named 'env' in the current directory
source env/bin/activate			# Activate the 'env' environment

The virtual environment needs to be activated every time you start the terminal using the source env/bin/activate command.

Next, install cwltool.

pip install cwltool

For the visualisation of the workflow, please install graphviz:

sudo apt install graphviz

Files

You will need to install some example files for this lesson. In this tutorial we will use RNA sequencing data.

Setting up a practice repository

For this tutorial some existing tools are needed to build the workflow. These existing tools will be imported via GitHub. First we need to create an empty git repository for all our files. To do this, use this command:

git init novice-tutorial-exercises

Next, we need to move into our empty git repo:

cd novice-tutorial-exercises

Then import bio-cwl-tools with this command:

git submodule add https://github.com/common-workflow-library/bio-cwl-tools.git

Downloading sample and reference data

Create a new directory inside the novice-tutorial-exercises directory and download the data:

mkdir rnaseq
cd rnaseq
wget --mirror --no-parent --no-host --cut-dirs=1 https://download.jutro.arvadosapi.com/c=9178fe1b80a08a422dbe02adfd439764+925/

Downloading or generating STAR index

To run the STAR tool index files generated from the reference files are needed. This is a large download (4 GB), so it is also possible to generate these files yourself.

Downloading

mkdir hg19-chr1-STAR-index
cd hg19-chr1-STAR-index
wget --mirror --no-parent --no-host --cut-dirs=1 https://download.jutro.arvadosapi.com/c=02a12ce9e2707610991bd29d38796b57+2912/

Generating

Create chr1-star-index.yaml in the the novice-tutorial-exercises directory:

InputFiles:
  - class: File
    location: rnaseq/reference_data/chr1.fa
    format: http://edamontology.org/format_1930
IndexName: 'hg19-chr1-STAR-index'
Gtf:
  class: File
  location: rnaseq/reference_data/chr1-hg19_genes.gtf
Overhang: 99

Generate the index files with cwltool:

cwltool bio-cwl-tools/STAR/STAR-Index.cwl chr1-star-index.yaml

Introduction to Workflows with Common Workflow Language: Setup