org.threadly.concurrent.future

Class Watchdog

java.lang.Object

org.threadly.concurrent.future.Watchdog

public class Watchdog
extends java.lang.Object

This class is to guarantee that a given ListenableFuture is completed within a timeout. Once the timeout is reached, if the future has not already completed this will attempt to invoke Future.cancel(boolean). The future should then throw a CancellationException on a Future.get() call.

Since:

4.0.0

Constructor Summary

Constructors

Constructor and Description
Watchdog(long timeoutInMillis, boolean sendInterruptOnFutureCancel) Constructs a new Watchdog.
Watchdog(SubmitterScheduler scheduler, long timeoutInMillis, boolean sendInterruptOnFutureCancel) Constructs a new Watchdog with a scheduler of your choosing.

Method Summary

Modifier and Type	Method and Description
long	getTimeoutInMillis() Request the timeout in milliseconds until futures that have not completed are canceled.
boolean	isActive() Checks to see if this watchdog is currently active.
void	watch(ListenableFuture<?> future) Watch a given ListenableFuture to ensure that it completes within the constructed time limit.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Watchdog

public Watchdog(long timeoutInMillis,
                boolean sendInterruptOnFutureCancel)

Constructs a new Watchdog. This constructor will use a default static scheduler (which is lazily constructed). This should be fine in most cases, but you can provide your own scheduler if you want to avoid the thread creation (which is shared among all instances that were constructed with this constructor or WatchdogCache.WatchdogCache(boolean)).

Parameters:

timeoutInMillis - Time in milliseconds that futures will be set to error if they are not done

sendInterruptOnFutureCancel - If true, and a thread is provided with the future, an interrupt will be sent on timeout

Watchdog

public Watchdog(SubmitterScheduler scheduler,
                long timeoutInMillis,
                boolean sendInterruptOnFutureCancel)

Constructs a new Watchdog with a scheduler of your choosing. It is critical that this scheduler has a free thread available to inspect futures which may not have completed in the given timeout. You may want to use a org.threadly.concurrent.limiter to ensure that there are threads available.

Parameters:

scheduler - Scheduler to schedule task to look for expired futures

timeoutInMillis - Time in milliseconds that futures will be set to error if they are not done

sendInterruptOnFutureCancel - If true, and a thread is provided with the future, an interrupt will be sent on timeout

Method Detail

getTimeoutInMillis

public long getTimeoutInMillis()

Request the timeout in milliseconds until futures that have not completed are canceled. This is the timeout that the class was constructed with (since it can not be changed after construction).

Returns:

Time in milliseconds till incomplete futures have Future.cancel(boolean) invoked

isActive

public boolean isActive()

Checks to see if this watchdog is currently active. Meaning there are futures on it which either have not been completed yet, or have not been inspected for completion. If this returns false, it means that there are no futures waiting to complete, and no scheduled tasks currently scheduled to inspect them.

Returns:

true if this watchdog is currently in use

watch

public void watch(ListenableFuture<?> future)

Watch a given ListenableFuture to ensure that it completes within the constructed time limit. If the future is not marked as done by the time limit then it will be completed by invoking Future.cancel(boolean). Weather a true or false will be provided to interrupt the running thread is dependent on how this Watchdog was constructed.

Parameters:

future - Future to inspect to ensure completion