What you can publish as a tool

The kinds of program a hub can run in a tool session, and what each one costs you to build. For the pipeline that publishes them, see The contribution process.

The three publishing options

The registration form offers three:

Option	Label on screen	Covers
standard	Rappture or Linux-GUI based tool	Anything with an X11 GUI, including Rappture
jupyter	Web application (Jupyter, Rstudio, ...)	Notebooks, Shiny, Dash, plain web applications
simtool	Sim2L	A notebook published as a callable simulation

The last two appear only where the hub has turned the matching options on. The choice decides the starter invoke script the hub writes for you; see Tool repository structure. (Verified against com_tools.)

Linux GUI applications

A tool that already has a graphical interface under Linux/X11 can usually be published as it stands. Qt, GTK, wxWidgets, Tcl/Tk, Java, and MATLAB interfaces all work. The X output is rendered on the execution host and shown in the member's browser.

Two caveats come with that:

• Graphics-heavy tools do not perform well. Execution containers run on cluster nodes without graphics cards, so OpenGL is emulated in software, and everything rendered is then transmitted to the browser as images. Expect a few frames per second: enough to view and interact with data, nowhere near a desktop machine with a graphics card.
• The tool sees the hub's file system, not the member's desktop. A File > Open dialog inside a tool lists the member's home directory on the hub. Files from their own machine have to get there first, by sftp, WebDAV, or the hub's importfile command. See Accessing your home directory and Importing and exporting user files.

Rappture

Rappture generates a graphical interface from an XML description of a tool's inputs and outputs. You write rappture/tool.xml, and the toolkit builds the form, the Simulate button, and the result plots. It binds to C/C++, Fortran, MATLAB, Python, Perl, Tcl/Tk, and Ruby, so it suits a legacy solver or a simple modelling code that has no interface of its own.

Rappture was written for the hub environment, so it addresses both caveats above: its visualisation uses the hub's rendering hosts, and it has importfile and exportfile built in for moving files to and from the member's desktop.

The introductory course Developing Scientific Tools for the HUBzero Platform is still online and is the most complete Rappture material left. It spells the product name the way it was spelled at the time.

Jupyter notebooks

Notebooks suit teaching, documented workflows, and exploratory work. Hub notebooks are usually Python, R, or Octave; other kernels can be installed. A notebook can also drive an external program in any language: prepare input in Python, run the solver, post-process the output.

Published as a Jupyter tool, the notebook runs automatically and only its graphical output — widgets, plots — is shown. The editing interface is hidden and cannot be reached, so the member sees an application rather than a notebook. Python is the easier language for this, because of the widget libraries, and a notebook written in another language can still have its interface written in Python.

Jupyter notebooks covers deployment styles and the invoke script that selects them.

Sim2L

A Sim2L tool is a notebook published as a callable simulation, with declared inputs and outputs so that other notebooks can run it and reuse its results. Register it with the Sim2L publishing option, which puts a simtool directory in the repository skeleton and writes an invoke script that starts the notebook headless.

Sim2L is the platform's own material and is not documented in this repository beyond the repository layout and the invoke template.

R Shiny, Dash, and web applications

The jupyter publishing option covers web applications generally, not only notebooks:

• R and Shiny — R developers can publish a Shiny application.
• Plotly Dash — Dash builds analytical web applications in Python, with no JavaScript, over Plotly.js, React, and Flask.
• Plain web applications — anything that runs on Linux and serves HTML, CSS, and JavaScript can be published as a tool.

All of these are served through the session in the member's browser in the same way, and all of them are started by the tool's invoke script.