.. _architecture-reference:

Architecture
============

This section provides an in-depth explanation of the architecture of the
Cylc components intended for developers and system administrators.

The main Cylc 8 system components are:

Cylc Scheduler
--------------

- The workflow engine core, Python 3 based
- Includes the **CLI** (Command Line Interface)
- And **TUI**, a new Terminal UI application

Cylc UI
-------

- In-browser web UI, includes:
- A dashboard with summary information and documentation links
- Integrated gscan (multi-workflow) side-panel
- Responsive web design (from desktop to table to mobile)
- Tabbed interface to display multiple workflow views
- Command integration for interacting with task, jobs, and schedulers

Cylc UI Server
--------------

- Interacts with Schedulers and the filesystem
- Serves the UI to users
- Can be launched by the privileged Hub, for multi-user installations
- Or run standalone for use by a single user
- (The UI Server is a `Jupyter Server
  <https://jupyter-server.readthedocs.io>`_ extension)

Cylc Hub
--------

- For proving the UI in multi-user setups.
- Authenticates users, spawns and proxies Cylc UI Servers
- Can run as a regular or privileged user
- (The Hub is a `Jupyterhub <https://jupyter.org/hub>`_ instance)

Network layers
--------------

- Incremental push updates (c.f. polled full-state updates in Cylc 7)

Further Reading
---------------

.. toctree::
   :maxdepth: 2

   ui-server
   data-flow