cylc-admin

Proposal (Feb 2020)

Cylc 8 System Component Naming

Cylc is now a complex multi-component system. It is important that we settle on consistent, unambiguous, and where possible standard, component names so that users and developers can communicate without confusion. (This was not easy even before Cylc 8!).

Proposed Final Names

Note we have already agreed to drop suite for workflow (“suite” is non-standard outside of the NWP community).

Component Name	Code Repository	Config File	Description
Cylc Scheduler	cylc-flow	cylc-flow.conf and cylc-flow-global.conf	an instance of the cylc-flow scheduler program, to manage a single workflow
Cylc Hub	(Jupyter Hub)	<cylc-location>/jupyterhub_config.py	the single point of access that users log in to
Cylc UI Server	cylc-uiserver	N/A? (or cylc-uiserver.conf)	an instance of the cylc-uiserver program, that serves the Cylc Web UI and CLI
Cylc Web UI	cylc-webui	N/A?	an instance of the Cylc Web UI, served to your browser by the Cylc UI Server

Explanatory Comments

Cylc Scheduler

• “workflow server” is ambiguous - it can refer to the host server that the workflows run on
• “workflow server program” is clearer, but too much of a mouthful.
• “workflow daemon” is not strictly correct (--no-detach) and is very Unix-specific (should we ever port to another OS)
• “workflow service” - a cylc-flow instance really stretches the definition of a “service”
• “cylc-flow instance” (as in, an instance of the workflow manager program) was considered but not terribly popular, and compared to “scheduler” it is another very generic term.
• “scheduler” is correct, specific, and obvious. Plus, the program is actually implemented via an instance of the Scheduler class in cylc/flow/scheduler.py.

Cylc config files: cylc-flow.conf, cylc-flow-global.conf

• (we’re dropping the term “suite” - see above)
• the .rc suffix is archaic, rarely used today
• the old global.rc is too generic
• we don’t need to distinguish between user and site global configs - unless there are different config items allowed in each? (In which case we should drop the global and use cylc-flow-user.conf and cylc-flow-site.conf?)
• flow.conf is an option
  • (but cylc-flow.conf is clearer without being too verbose)

Cylc Hub

• A vanilla (so far) JupyterHub instance, configured to show Cylc branding and launch the Cylc UI Server
• To avoid confusion, and in case we ever need to go non-vanilla, we will call it “Cylc Hub” - but we should be clear that it is actually just JupyterHub
• do we need to launch it with a special Cylc command that automatically picks up the Cylc-specific jupyterhub_config.py?

Cylc UI Server

• The word “Server” is not so confusing here (as it could be for the scheduler program) because the UI Server exists only to literally “serve the UI”

Cylc Web UI

• The “Cylc UI” is not just the web interface, it’s also the CLI
• No one uses the term “GUI” for web interfaces

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