May 18, 2022

Launching workflows from external sources using web interface

If you host your analysis workflows on publicly accessible external sources such as source code repositories (GitHub, GitLab), digital repositories (Zenodo), or simply other locations on the web (generic URL), it is now possible to launch your workflows directly on the web using the brand new REANA launcher web page.

An alternative way to execute workflows

The traditional and the most-used way of executing REANA workflows is by means of the reana-client command-line tool. You can use it to create workflows, upload files to workspaces, start workflow execution, consult logs, download results, and more. A short tutorial on using reana-client can be found on the First example documentation page.

Another, even more low-level way to manage workflows, is to use the Python API. This can be useful if you want to interact with REANA from your Python application. A short tutorial on using REANA Python API can be found in the How to run REANA workflows using Python API blog post.

Both of these approaches require installing reana-client locally, which can be non-desirable in certain usage scenarios. For example, if you only want to execute an already-published workflow to check its results, or re-execute it with modified input parameters, it may be easier to launch such a workflow using directly the web interface, saving the work of manually cloning the repository and editing its input files. The new REANA launcher functionality enables exactly this kind of usage scenarios.

Launching workflows using web interface

If you have a valid CERN account, please go to the reana.cern.ch/launch where you will see the launcher home page with several demo examples:

Launchhome

You can click on one of the presented examples to launch the workflow on the REANA web site. For example, clicking on the RooFit demo will redirect you to the following page:

LaunchRooFit

where you can further click on the Launch button. REANA will then fetch the workflow from the remote GitHub repository and start its execution.

Constructing your own launch URLs

If you look at the browser address bar, you will see the following full URL before launching the RooFit demo example:

https://reana.cern.ch/launch?url=https%3A%2F%2Fgithub.com%2Freanahub%2Freana-demo-root6-roofit&name=reana-demo-root6-roofit

The launcher functionality is handled by the /launch endpoint which executes the workflow specified by the url argument. By pointing url to where you host your workflow, you can construct your own launch URLs for your analyses.

You can also optionally provide a custom workflow run name via a name argument, or choose a path to a specific reana.yaml specification file via the specification argument. Finally, you can also modify workflow’s input parameters via specially encoded parameters argument.

For a detailed description of all launcher arguments, please see the Launcher arguments documentation page.

Using launch badges

We have prepared a set of Launch-on-REANA badges that you can use to make your workflows runnable by simply clicking on them:

Launch on REANA atCERN

Badges are just images that will redirect users to the launch URLs constructed above. This means that you can include them wherever you want, for example in the README file of your Git repositories.

Here is an example of a badge used in the README file of the RooFit demo example:

Launch RooFitbadges

For more information on available badges, please see the Launcher badges documentation page.

Availability

REANA launcher will be coming with the REANA 0.9.0 release series. The launcher functionality is already deployed for a preview on the reana.cern.ch instance. The launcher currently supports launching workflows from publicly accessible URLs only. Please give it a try and let us know what you think!

See also

© CERN 2022