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Open OnDemand

Drona Workflow Engine is designed to run as a Passenger app within Open OnDemand (OOD). This page covers how to deploy Drona as both a development and production OOD application.

How It Works​

Open OnDemand serves Drona through Phusion Passenger, which acts as the application server for the Flask backend. The entry point is passenger_wsgi.py, which exposes the Flask app to Passenger. Drona automatically detects whether it's running in a dev or sys (production) directory and loads the corresponding configuration from config.yml.

Development Deployment​

OOD development apps live under your personal dev directory:

/var/www/ood/apps/dev/<username>/gateway/<app-name>/

Clone the repository into this location and run the setup script:

cd /var/www/ood/apps/dev/$USER/gateway/
git clone https://github.com/tamu-edu/dor-hprc-drona-composer.git
cd dor-hprc-drona-composer
./setup

The app will be accessible from the OOD dashboard under the Jobs category. Development apps are only visible to you.

Restarting the App​

To restart the Passenger process after making changes, touch the restart file:

touch tmp/restart.txt

OOD will pick up the change and restart the app on the next request.

Production Deployment​

Production apps are installed system-wide under:

/var/www/ood/apps/sys/<app-name>/

The setup process is the same. The app detects the sys path and automatically uses the production configuration block from config.yml.

Configuration Differences​

The config.yml file uses YAML anchors to share common settings between environments, with production overriding specific values:

development: &common_settings
  cluster_name: "Grace"
  dashboard_url: "/pun/dev/dor-hprc-drona-composer"
  driver_scripts_path: "/var/www/ood/apps/dev/<user>/gateway/dor-hprc-drona-composer/machine_driver_scripts"

production:
  <<: *common_settings
  dashboard_url: "/pun/sys/dor-hprc-drona-composer"
  driver_scripts_path: "/var/www/ood/apps/sys/dor-hprc-drona-composer/machine_driver_scripts"

Key settings to update for your deployment:

  • dashboard_url — Must match the OOD URL path for your app
  • driver_scripts_path — Absolute path to machine_driver_scripts/ in the deployment location
  • file_app_url — URL for the OOD file browser (typically /pun/sys/files/fs)
  • file_editor_url — URL for the OOD file editor (typically /pun/sys/file-editor/edit)

manifest.yml​

OOD uses manifest.yml to register the app in the dashboard:

---
name: Drona Workflow Engine
category: Jobs
description: Drona Workflow Engine
icon: ''

The category field determines which tab the app appears under in the OOD navigation. The setup script automatically populates the cluster name and app name in this file.

OOD Integration Points​

Drona uses several OOD features beyond basic app hosting:

  • File Browser — Links to the OOD file browser for navigating job output directories, configured via file_app_url
  • File Editor — Links to the OOD file editor for viewing and editing scripts, configured via file_editor_url
  • User Identity — Reads the $USER environment variable provided by OOD's per-user Nginx (PUN) to determine user-specific paths and permissions

Troubleshooting​

App Not Appearing in Dashboard​

  • Verify manifest.yml exists and is valid YAML
  • Check that the app directory is in the correct OOD path (dev or sys)
  • Restart the PUN if needed: the OOD admin panel or sudo /opt/ood/nginx_stage/sbin/nginx_stage nginx_clean

App Fails to Start​

  • Check Passenger logs, typically at /var/log/ondemand-nginx/<user>/error.log
  • Verify the Python virtual environment was created correctly (.venv/ directory exists)
  • Ensure passenger_wsgi.py is present in the app root
  • Try touch tmp/restart.txt to force a restart

Wrong Configuration Loading​

Drona detects the environment by checking if the current working directory contains dev or sys. If neither is found, it defaults to unknown. Ensure the app is installed in a standard OOD directory structure.

Texas A&M University High Performance Research Computing