Send & handle `JobUpdate.refresh_tasks = true` when many tasks are
updated simultaneously. This applies to things like cancelling &
requeueing an entire job.
This partially rolls back 67bf77de13d99b1bc5d7344951068822c4fadd88, as
it was too slow when 1000+ tasks were being updated all at once.
Worker and Manager implementation of the "may-I-kee-running" protocol.
While running tasks, the Worker will ask the Manager periodically
whether it's still allowed to keep running that task. This allows the
Manager to abort commands on Workers when:
- the Worker should go to another state (typically 'asleep' or
'shutdown'),
- the task changed status from 'active' to something non-runnable
(typically 'canceled' when the job as a whole is canceled).
- the task has been assigned to a different Worker. This can happen when
a Worker loses its connection to its Manager, resulting in a task
timeout (not yet implemented) after which the task can be assigned to
another Worker. If then the connectivity is restored, the first Worker
should abort (last-assigned Worker wins).
The selection mechanism of Tabulator was getting in the way of having nice
navigation, as it would deselect (i.e. nav to "/") before selecting the
next job (i.e. nav to "/jobs/{job-id}").
The active job is now determined by the URL and thus handled by Vue Router.
Clicking on a job simply navigates to its URL, which causes the reactive
system to load & display it.
It is still intended to get job selection for "mass actions", but that's
only possible after normal navigation is working well.
Most of the code moved from `App.vue` to `views/JobsView.vue`.
Notification bar has its own component, and there are placeholder
"views" for Workers and Settings pages.
There is still some clunky handling of updates via SocketIO, as those
are a mix of job-specific and global (like SocketIO reconnection
events). The advantage of the current approach is that SocketIO
connections are closed when you leave the Jobs page, and reopened when
you enter the Workers page. My gut feeling says this is nice because it
ensures that all SocketIO connection-specific things are cleaned up when
you navigate.
