Safe Haskell | Safe-Inferred |
---|---|
Language | Haskell2010 |
Device for running an action at (i.e. shortly after) a certain time, which can be used to implement things like time-based cache expiry.
This implementation avoids the use of polling and leans on Haskell's scheduler to achieve low-latency without lots of computational overhead.
The alarm can be set multiple times, and in this case the alarm will go off at the earliest requested time. If the alarm is set in the past, the action will run immediately. When the action runs, it clears all future alarms; the action can itself return the time at which it should run again.
To perform time-based cache expiry, create an AlarmClock
whose action flushes
any stale entries from the cache and then calls setAlarm
for the next time
that an entry will expire (if there are any). When expiring entries are added
to the cache, call setAlarm
to ensure that they will expire in a timely
fashion.
- data AlarmClock
- newAlarmClock :: (AlarmClock -> IO ()) -> IO AlarmClock
- destroyAlarmClock :: AlarmClock -> IO ()
- setAlarm :: AlarmClock -> UTCTime -> IO ()
- setAlarmNow :: AlarmClock -> IO ()
Documentation
data AlarmClock Source
An AlarmClock
is a device for running an action at (or shortly after) a certain time.
:: (AlarmClock -> IO ()) | Action to run when the alarm goes off. The action is provided the alarm clock
so it can set a new alarm if desired. Note that |
-> IO AlarmClock |
Create a new AlarmClock
that runs the given action. Initially, there is
no wakeup time set: you must call setAlarm
for anything else to happen.
destroyAlarmClock :: AlarmClock -> IO () Source
Destroy the AlarmClock
so no further alarms will occur. If the alarm is currently going off
then this will block until the action is finished.
setAlarm :: AlarmClock -> UTCTime -> IO () Source
Make the AlarmClock
go off at (or shortly after) the given time. This
can be called more than once; in which case, the alarm will go off at the
earliest given time.
setAlarmNow :: AlarmClock -> IO () Source
Make the AlarmClock
go off right now.