Package org.opendaylight.raft.spi

Class AveragingProgressTracker

java.lang.Object

org.opendaylight.raft.spi.ProgressTracker

org.opendaylight.raft.spi.AveragingProgressTracker

public final class AveragingProgressTracker
extends ProgressTracker

A ProgressTracker subclass which uses ticksWorkedPerClosedTask to compute delays.

This class has tasksOpenLimit used as a (weak) limit, as number of open tasks approaches that value, delays computed are increasing.

In order to keep estimateIsolatedDelay values from raising unreasonably high, defaultTicksPerTask acts as a maximal value. openTask may return higher value if there are tasks above the limit.

On the other hand, there is no delay when number of open tasks is half the limit or less, in order to prevent backend from running out of tasks while there may be waiting frontend threads.

This class is NOT thread-safe.

Author:

Vratko Polak

Constructor Summary

Constructors

Constructor	Description
AveragingProgressTracker(long limit)	Create a default idle tracker with given limit.
AveragingProgressTracker(AveragingProgressTracker oldTracker, long now)	Construct a new tracker suitable for a new task queue related to a "reconnect".
AveragingProgressTracker(ProgressTracker oldTracker, long limit, long now)	Construct a new tracker suitable for a new task queue related to a "reconnect".

Method Summary

Modifier and Type	Method	Description
protected long	estimateIsolatedDelay(long now)	Give an estimate of a fair delay, assuming delays caused by other opened tasks are ignored.

Methods inherited from class org.opendaylight.raft.spi.ProgressTracker

cancelDebt, closeTask, defaultTicksPerTask, openTask, ticksStalling, ticksWorkedPerClosedTask

Methods inherited from class java.lang.Object

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

Constructor Details

AveragingProgressTracker

public AveragingProgressTracker(long limit)

Create a default idle tracker with given limit.

Parameters:

limit - of open tasks to avoid exceeding

AveragingProgressTracker

public AveragingProgressTracker(ProgressTracker oldTracker,
 long limit,
 long now)

Construct a new tracker suitable for a new task queue related to a "reconnect".

The limit is set independently of the old tracker.

Parameters:

oldTracker - the tracker used for the previously used backend

limit - of open tasks to avoid exceeding

now - tick number corresponding to caller's present

AveragingProgressTracker

public AveragingProgressTracker(AveragingProgressTracker oldTracker,
 long now)

Construct a new tracker suitable for a new task queue related to a "reconnect".

The limit is copied from the old tracker.

Parameters:

oldTracker - the tracker used for the previously used backend

now - tick number corresponding to caller's present

Method Details

estimateIsolatedDelay

protected long estimateIsolatedDelay(long now)

Give an estimate of a fair delay, assuming delays caused by other opened tasks are ignored.

This implementation returns zero delay if number of open tasks is half of limit or less. Else the delay is computed, aiming to keep number of open tasks at 3/4 of limit, assuming backend throughput remains constant.

As the number of open tasks approaches the limit, the computed delay increases, but it never exceeds defaultTicksPerTask. That means the actual number of open tasks can exceed the limit.

Specified by:

estimateIsolatedDelay in class ProgressTracker

Parameters:

now - tick number corresponding to caller's present

Returns:

delay (in ticks) after which another openTask() would be fair to be called by the same thread again