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Oracle Coherence Community Edition
/*
* Copyright (c) 2000, 2020, Oracle and/or its affiliates.
*
* Licensed under the Universal Permissive License v 1.0 as shown at
* http://oss.oracle.com/licenses/upl.
*/
package com.tangosol.internal.net;
import com.oracle.coherence.common.base.Converter;
import com.oracle.coherence.common.base.NonBlocking;
import java.util.concurrent.atomic.AtomicLong;
/**
* A FlowControl implementation which supports debouncing based on user specified thresholds.
*
* @author mf 2016.02.03
*/
public class DebouncedFlowControl
extends AbstractFlowControl
{
// ----- DebouncedFlowControl interface ---------------------------------
/**
* Construct a flow control object with the specified limits.
*
* @param lLimitNormal the limit below which a backlog is considered to be normal
* @param lLimitExcessive the limit above which a backlog is considered to be excessive
*/
public DebouncedFlowControl(long lLimitNormal, long lLimitExcessive)
{
this (lLimitNormal, lLimitExcessive, null);
}
/**
* Construct a flow control object with the specified limits.
*
* @param lLimitNormal the limit below which a backlog is considered to be normal
* @param lLimitExcessive the limit above which a backlog is considered to be excessive
* @param unitFormatter converter used for format the backlog units
*/
public DebouncedFlowControl(long lLimitNormal, long lLimitExcessive, Converter unitFormatter)
{
f_lLimitNormal = lLimitNormal;
f_lLimitExcessive = lLimitExcessive;
f_unitFormatter = unitFormatter == null ? Object::toString : unitFormatter;
}
// ----- DebouncedFlowControl interface ---------------------------------
/**
* Return the current backlog.
*
* @return the backlog
*/
public long getBacklog()
{
return f_lBacklog.get() >> 1;
}
/**
* Adjust the backlog by the specified amount and evaluate the backlog.
*
* @param c the amount to adjust by
*
* @return this object
*/
public DebouncedFlowControl adjustBacklog(long c)
{
boolean fExitBacklog;
long lBacklogOld;
long lBacklogNew;
long cBacklogNew;
long fBacklogged;
do
{
lBacklogOld = f_lBacklog.get();
cBacklogNew = (lBacklogOld >> 1) + c;
fBacklogged = lBacklogOld & 0x1;
fExitBacklog = false;
if (cBacklogNew >= Long.MAX_VALUE >> 1 || cBacklogNew <= Long.MIN_VALUE >> 1)
{
throw new IllegalArgumentException("adjustment would overflow");
}
else if (fBacklogged == 0 && cBacklogNew >= f_lLimitExcessive)
{
fBacklogged = 1;
}
else if (fBacklogged == 1 && cBacklogNew <= f_lLimitNormal)
{
fBacklogged = 0;
fExitBacklog = true;
}
lBacklogNew = (cBacklogNew << 1) | fBacklogged;
}
while (!f_lBacklog.compareAndSet(lBacklogOld, lBacklogNew));
if (fExitBacklog)
{
// we transitioned from backlogged to normal above
// we may have reentered by now, but it is still safe to trigger the continuations
processContinuations();
}
else if (fBacklogged == 1 && !NonBlocking.isNonBlockingCaller())
{
drainBacklog(0);
}
return this;
}
/**
* Increment and evaluate the backlog.
*
* @return this object
*/
public DebouncedFlowControl incrementBacklog()
{
return adjustBacklog(1);
}
/**
* Decrement and evaluate the backlog.
*
* @return this object
*/
public DebouncedFlowControl decrementBacklog()
{
return adjustBacklog(-1);
}
// ----- AbstractFlowControl interface ----------------------------------
@Override
public boolean isBacklogged()
{
return (f_lBacklog.get() & 0x1) != 0;
}
// ---- Object interface ------------------------------------------------
@Override
public String toString()
{
long lBacklog = f_lBacklog.get();
long cBacklog = lBacklog >> 1;
long fBacklog = lBacklog & 0x1;
return f_unitFormatter.convert(cBacklog) + "/" +
f_unitFormatter.convert(f_lLimitExcessive) + (" " + cBacklog * 100 / f_lLimitExcessive + "%") +
(fBacklog == 0 ? " normal" : " excessive");
}
// ----- data members ---------------------------------------------------
/**
* The limit at which a backlog condition ends.
*/
private final long f_lLimitNormal;
/**
* The limit at which a backlog condition starts.
*/
private final long f_lLimitExcessive;
/**
* The bit 0 is backlog state, remaining 63 bits are the backlog counter.
*/
private final AtomicLong f_lBacklog = new AtomicLong();
/**
* The unit formatter
*/
private final Converter f_unitFormatter;
}