| Safe Haskell | None |
|---|---|
| Language | Haskell2010 |
Control.Concurrent.AlarmClock
Description
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 set the next alarm time.
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 t
- newAlarmClock :: TimeScale t => (AlarmClock t -> IO ()) -> IO (AlarmClock t)
- newAlarmClock' :: TimeScale t => (AlarmClock t -> t -> IO ()) -> IO (AlarmClock t)
- destroyAlarmClock :: AlarmClock t -> IO ()
- withAlarmClock :: TimeScale t => (AlarmClock t -> t -> IO ()) -> (AlarmClock t -> IO a) -> IO a
- setAlarm :: TimeScale t => AlarmClock t -> t -> IO ()
- setAlarmSTM :: TimeScale t => AlarmClock t -> t -> STM ()
- setAlarmNow :: TimeScale t => AlarmClock t -> IO ()
- isAlarmSet :: AlarmClock t -> IO Bool
- isAlarmSetSTM :: AlarmClock t -> STM Bool
- class TimeScale t where
- newtype MonotonicTime = MonotonicTime TimeSpec
Documentation
data AlarmClock t Source #
An AlarmClock is a device for running an action at (or shortly after) a certain time.
Arguments
| :: TimeScale t | |
| => (AlarmClock t -> 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 t) |
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.
Arguments
| :: TimeScale t | |
| => (AlarmClock t -> t -> 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, and the current time.
Note that |
| -> IO (AlarmClock t) |
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 t -> 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.
withAlarmClock :: TimeScale t => (AlarmClock t -> t -> IO ()) -> (AlarmClock t -> IO a) -> IO a Source #
The action withAlarmClock onWakeUp inner runs inner with a new AlarmClock which
is destroyed when inner exits.
setAlarm :: TimeScale t => AlarmClock t -> t -> 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.
setAlarmSTM :: TimeScale t => AlarmClock t -> t -> STM () 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 :: TimeScale t => AlarmClock t -> IO () Source #
Make the AlarmClock go off right now.
isAlarmSet :: AlarmClock t -> IO Bool Source #
Is the alarm set - i.e. will it go off at some point in the future even if setAlarm is not called?
isAlarmSetSTM :: AlarmClock t -> STM Bool Source #
Is the alarm set - i.e. will it go off at some point in the future even if setAlarm is not called?
class TimeScale t where Source #
Minimal complete definition
newtype MonotonicTime Source #
Representation of system monotonic clock. #
Constructors
| MonotonicTime TimeSpec |
Instances