Running workflow managers - kerblam run

The kerblam run command is used to execute workflow managers for you.

Kerblam! looks for makefiles ending in the .makefile extension and .sh for shell files in the workflows directory (by default src/workflows/). It automatically uses the proper execution strategy based on what extension the file is saved as: either make or bash.

You can use any workflow manager that is installed on your system through Kerblam! (e.g. snakemake or nextflow) by writing thin shell wrappers with the execution command in the src/workflows/ folder. Make has a special execution policy to allow it to work with as little boilerplate as possible.

kerblam run supports the following flags:

• --profile <profile>: Execute this workflow with a profile. Read more about profiles in the section below.
• --desc (-d): Show the description of the workflow, then exit.
• --local (-l): Skip running in a container, if a container is available, preferring a local run.

In short, kerblam run does something similar to this:

• Move your workflow.sh or workflow.makefile file in the root of the project, under the name executor;
• Launch make -f executor or bash executor for you.

This is why workflows are written as if they are executed in the root of the project, because they are.

Listing out workflows

If you just want a list of workflows that Kerblam! can see, just use kerblam run with no workflow specified. Kerblam will reply with something like this:

Error: No runtime specified. Available runtimes:
    ◾📜 process_csv :: Calculate the sums of the input metrics
    🐋◾ save_plots
    ◾◾ generate_metrics

Available profiles: No profiles defined.

Workflows with a 📜 have an associated description, and those with a 🐋 have an associated docker container. You also get a list of available data profiles, which are detailed just below.

Data Profiles - Running the same workflows on different data

You can run your same workflows, as-is, on different data thanks to data profiles.

By default, Kerblam! will leave ./data/in/ untouched when running workflow managers. If you want the same workflows to run on different sets of input data, Kerblam! can temporarily swap out your real data with this 'substitute' data during execution.

For example, a process_csv.makefile requires an input ./data/in/input.csv file. However, you might want to run the same workflow on another, different_input.csv file. You could copy and paste the first workflows and change the paths to the first file to this alternative one, or you might group variables into configuration files for your workflow. However, you then have to maintain two essentially identical workflows (or several different configuration files), and you are prone to adding errors while you modify them (what if you forget to change one reference to the original file?).

You can let Kerblam! handle temporarely swapping input files for you, without touching your workflows. Define in your kerblam.toml file a new section under data.profiles:

# You can use any ASCII name in place of 'alternate'.
[data.profiles.alternate]
# The quotes are important!
"input.csv" = "different_input.csv"

You can then run the same makefile with the new data with:

kerblam run process_csv --profile alternate

Under the hood, Kerblam! will:

• Rename input.csv to input.csv.original;
• Move different_input.csv to input.csv;
• Run the analysis as normal;
• When the run ends (it finishes, it crashes or you kill it), Kerblam! will undo both actions: it moves different_input.csv back to its original place and renames input.csv.original back to input.csv.

This effectively causes the workflow to run with different input data.

Profiles are most commonly useful to run the workflows on test data that is faster to process or that produces pre-defined outputs. For example, you could define something similar to:

[data.profiles.test]
"input.csv" = "test_input.csv"
"configs/config_file.yaml" = "configs/test_config_file.yaml"

And execute your test run with kerblam run workflow --profile test.

The profiles feature is used so commonly for test data that Kerblam! will automatically make a test profile for you, swapping all input files in the ./data/in folder that start with test_xxx with their "regular" counterparts xxx. For example, the profile above is redundant!

If you write a [data.profiles.test] profile yourself, Kerblam! will not modify it in any way, effectively disabling the automatic test profile feature.

Kerblam! tries its best to cleanup after itself (e.g. undo profiles, delete temporary files, etc...) when you use kerblam run, even if the workflow fails, and even if you kill your workflow with CTRL-C.

Detecting if you are in a profiled run

Kerblam! will run the workflows with the environment variable KERBLAM_PROFILE set to whatever the name of the profile is. In this way, you can detect from inside the workflow if you are in a profile or not. This is useful if you want to keep the outputs of different profiles separate, for instance.

File modification times when using profiles

make tracks file creation times to determine if it has to re-run workflows again. This means that if you move files around, like Kerblam! does when it applies profiles, make will always re-run your workflows, even if you run the same workflow with the same profile back-to-back.

To avoid this, Kerblam! will keep track of the last-run profile in your projects and will update the timestamps of the moved files only when strictly necessary.

This means that the profile files will get updated timestamps only when they actually need to be updated, which is:

• When you use a profile for the first time;
• When you switch from one profile to a different one;
• When you don't use a profile, but you just used one the previous run;

To track what was the last profile used, Kerblam! creates a file in $HOME/.cache/kerblam/ for each of your projects.

Sending additional arguments to the worker process

You can send additional arguments to either make or bash after what Kerblam! sets by default by specifying them after kerblam's own run arguments:

kerblam run my_workflow -- extra_arg1 extra_arg_2 ...

Everything after the -- will be passed as-is to the make or bash worker after Kerblam!'s own arguments.

For example, you can tell make to build a different target with this syntax:

kerblam run make_workflow -- other_target

As if you had run make other_target yourself.