* Switch from nouislider to simpler <input type="range">
* Move it to a sidebar
Also, fix a bug in _get_events where the "start" local variable
got clobbered, and made the date range for the Notification
query wrong.
* Add Check.last_start_rid field
* Fill Check.last_start_rid on every start event
* Clear Check.last_start on every "fail" event
* Clear Check.last_start on success event if either case is true:
- the event's rid matches Check.last_start_rid
- the event does not specify rid
In human terms, the alerting logic will be: we track the
execution time of the most recent "start" event only. It would
take a major redesign to track the execution time of all
concurrent "start" events and send alerts when *any* of them
overshoots the time budget. So, whenever we see a "start" event,
the timer resets.
Example:
* 00:00 client sends start signal with rid=A, timer starts
* 00:10 client sends start signal with rid=B, timer resets
* 00:20 client sends success signal with rid=A, timer
does not reset because rid A does not match the rid seen in
the most recent start signal (it was B)
* 00:30 the grace time runs out, the check's status shows
as started + failed
At this point the check can be reset to a healthy state in 3
different ways:
* send a success signal with rid=B
* send a failure signal with any rid value or without it
* send a success signal without a rid value
* Added duration to ping details. This is useful on a device with a small screen, since the duration cannot be seen in the main view so now one can see it in the ping's details.
* Changed terms across the board from "delta" to "duration"
* timedelta is now consistently imported as "td" across the entire project (even in Django generated migration files)
Check.n_pings now stores the total number of pings the check has ever received. Running "prunepings" command doesn't affect this field. +a new "prunepingsslow" command which works in smaller chunks so is appropriate for initial pruning of a huge api_ping table.
