[discussed at CylcCon2020]

We want the Cylc Hub to be able to start UI Servers on any one of a group of hosts.

There is already [at least one] JupyterHub spawner which is able to start servers on remote hosts, the remote spawner.

We would like to add basic load-balancing to this. Cylc has load-balancing built-in, see the cylc.flow.host_select module.

The idea is to try and build a new JupyterHub spawner which handles load balancing to work out where to start the server, then uses the configured spawner (e.g. the remote spawner) to actually start the server.

This would give sites a lot of flexibility with which spawners they install.

As, depending on the nature of the installation this spawner may be running as a privileged user the code should be kept to a minimum.