When a job or task gets requeued from the web interface, its task
failure lists (i.e. the list of workers that previously failed this
task) will be cleared.
This clearing doesn't happen in other situations, e.g. when a worker
signs off and its task gets requeued, the task's failure list will
remain as-is.
When a Worker indicates a task failed, mark it as `soft-failed` until
enough workers have tried & failed at the same task.
This is the first step in a blocklisting system, where tasks of an
often-failing worker will be requeued to be retried by others.
NOTE: currently the failure list of a task is NOT reset whenever it is
requeued! This will be implemented in a future commit, and is tracked in
`FEATURES.md`.
Update the 'last seen at' timestamp of workers when they:
- sign on
- sign off
- get a task assigned
- send a task update
- check whether they can keep running their task
Note that this commit is necessary to not have the workers time out
immediately ;-)
Requeueing the tasks of a specific worker is now done in the
`TaskStateMachine`, such that it can be called from other services as
well in future commits.
This also makes the `LogStorage` service a dependency of the
`TaskStateMachine`, as it needs to write "this task was requeued" kind
of messages to the task logs.
In the future different services will write to the task log, and thus
it makes sense to move the responsibility of prepending the timestamps
to the log storage service.
