Module io.helidon.common.concurrency.limits

Package io.helidon.common.concurrency.limits

Interface LimitAlgorithm

All Known Subinterfaces:

Limit

All Known Implementing Classes:

AimdLimit, FixedLimit

public interface LimitAlgorithm

Concurrency limit algorithm.

There are two options how to use a limit - by handling a token provided by tryAcquire(), or by invoking a callable or runnable through one of the invoke methods (such as invoke(Runnable).

The invoke methods are backed by the same tryAcquire() methods, so behavior is consistent.

Nested Class Summary

Nested Classes

Modifier and Type	Interface	Description
static interface	LimitAlgorithm.Token	When a token is retrieved from tryAcquire(), one of its methods must be called when the task is over, to release the token back to the pool (such as a permit returned to a Semaphore).

Method Summary

Modifier and Type	Method	Description
default void	invoke(Runnable runnable)	Invoke a runnable within the limits of this limiter.
default <T> T	invoke(Callable<T> callable)	Invoke a callable within the limits of this limiter.
default Optional<LimitAlgorithm.Token>	tryAcquire()	Try to acquire a token, waiting for available permits for the configured amount of time, if queuing is enabled.
Optional<LimitAlgorithm.Token>	tryAcquire(boolean wait)	Try to acquire a token, waiting for available permits for the configured amount of time, if wait is enabled, returning immediately otherwise.

Method Details

invoke

default <T> T invoke(Callable<T> callable)
              throws LimitException,
Exception

Invoke a callable within the limits of this limiter.

Limit implementors note: Make sure to catch IgnoreTaskException from the callable, and call its IgnoreTaskException.handle() to either return the provided result, or throw the exception after ignoring the timing for future decisions.

Type Parameters:

T - the callable return type

Parameters:

callable - callable to execute within the limit

Returns:

result of the callable

Throws:

LimitException - in case the limiter did not have an available permit

Exception - in case the task failed with an exception

invoke

default void invoke(Runnable runnable)
             throws LimitException,
Exception

Invoke a runnable within the limits of this limiter.

Limit implementors note: Make sure to catch IgnoreTaskException from the runnable, and call its IgnoreTaskException.handle() to either return the provided result, or throw the exception after ignoring the timing for future decisions.

Parameters:

runnable - runnable to execute within the limit

Throws:

LimitException - in case the limiter did not have an available permit

Exception - in case the task failed with an exception

tryAcquire

default Optional<LimitAlgorithm.Token> tryAcquire()

Try to acquire a token, waiting for available permits for the configured amount of time, if queuing is enabled.

If acquired, the caller must call one of the LimitAlgorithm.Token operations to release the token. If the response is empty, the limit does not have an available token.

Returns:

acquired token, or empty if there is no available token

tryAcquire

Optional<LimitAlgorithm.Token> tryAcquire(boolean wait)

Try to acquire a token, waiting for available permits for the configured amount of time, if wait is enabled, returning immediately otherwise.

If acquired, the caller must call one of the LimitAlgorithm.Token operations to release the token. If the response is empty, the limit does not have an available token.

Parameters:

wait - whether to wait in the queue (if one is configured/available in the limit), or to return immediately

Returns:

acquired token, or empty if there is no available token