Open OnDemand Documentation

Open OnDemand is an open-source, web-based client portal designed for High-Performance Computing (HPC) centers. It aims to bridge the accessibility gap in HPC by providing advanced web and graphical interfaces, reducing the need for users to have advanced Linux knowledge or to manually configure client software like SSH or VNC.

Key capabilities include:

• Per-user NGINX (PUN) architecture: Provides secure, federated authentication (e.g., via CILogon) and uses Unix domain sockets for secure server-side communication between a web proxy and individual user instances.
• File Management: Includes a web-based file browser and file editor.
• Terminal Access: Provides a web-based terminal interface.
• Accessibility Apps: A suite of applications including a Dashboard, Job Constructor, Job Status, System Status, VDI, and iHPC apps.
• App Development: Uses the Rails-based AweSim AppKit, which enables the creation, sharing, and publishing of both workflow and interactive applications.

Views in the Project Manager are typically .html.erb (Embedded Ruby) files. They use data provided by the controller (stored in instance variables like @project or @workflow) to render the UI.

View Patterns

• Passing Data to JavaScript: Hidden input fields are often used to pass IDs and URL paths from the server-side Ruby view to client-side JavaScript.
• Embedded Ruby (ERB): You can execute Ruby code within the HTML to perform logic, such as conditionally applying CSS classes.
• Rails Helpers: Standard Rails helpers like project_workflow_path or select_tag are available to generate URLs and form elements.

# apps/dashboard/app/views/workflows/show.html.erb

<%= javascript_include_tag 'workflows', nonce: true, defer: true %>

<input type="hidden" id="project-id" value="<%= @project.id %>">
<input type="hidden" id="workflow-id" value="<%= @workflow.id %>">
<input type="hidden" id="base-workflow-url" value="<%= project_workflow_path(@project.id, @workflow.id) %>">
<input type="hidden" id="base-launcher-url" value="<%= project_launchers_path(@project.id) %>">

<div id="workflows_app">
  <div class="toolbar" aria-label="toolbar">
    <% hidden_class = @workflow.editable? ? '' : 'd-none' %>
    <%= select_tag "select_launcher", options_from_collection_for_select(@launchers, :id, :title), include_blank: false, class: "form-control w-25 #{hidden_class}" %>
    <button id="btn-add" class="<%= hidden_class %>">Add Launcher</button>

Models are responsible for managing data and providing the core logic that controllers and views interact with. They isolate complexity, allowing controllers and views to remain simple.

Model Responsibilities

• Data Persistence: In Open OnDemand, models often manage files (like YAML manifests) rather than database rows.
• Logic Encapsulation: Models provide methods to determine state (e.g., editable?) or perform complex operations (e.g., update or submit).
• Abstraction: By using model methods, you can change the underlying implementation (e.g., how a file is checked for writability) without changing the controller or view code.

# apps/dashboard/app/models/workflow.rb

  def manifest_file
    Workflow.workflow_dir(@project_dir).join("#{@id}.yml")
  end

  def update(attributes, override = false)
    update_attrs(attributes, override)
    return false unless valid?(:update)

    save_manifest(:update)
  end

  def update_attrs(attributes, override = false)
    [:name, :description, :launcher_ids, :metadata].each do |attribute|
      next unless override || attributes.key?(attribute)
      instance_variable_set("@#{attribute}".to_sym, attributes.fetch(attribute, ''))
    end
  end

  def editable?
    manifest_file.writable? || !shared?(manifest_file)
  end