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/*
* Quasar: lightweight strands and actors for the JVM.
* Copyright (c) 2013-2014, Parallel Universe Software Co. All rights reserved.
*
* This program and the accompanying materials are dual-licensed under
* either the terms of the Eclipse Public License v1.0 as published by
* the Eclipse Foundation
*
* or (per the licensee's choosing)
*
* under the terms of the GNU Lesser General Public License version 3.0
* as published by the Free Software Foundation.
*/
package co.paralleluniverse.strands.channels;
import co.paralleluniverse.common.monitoring.FlightRecorder;
import co.paralleluniverse.common.monitoring.FlightRecorderMessage;
import co.paralleluniverse.common.util.Debug;
import co.paralleluniverse.fibers.SuspendExecution;
import co.paralleluniverse.strands.Strand;
import co.paralleluniverse.strands.Synchronization;
import co.paralleluniverse.strands.Timeout;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.VarHandle;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.ThreadLocalRandom;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicLong;
/**
* Attempts to perform at most one channel operation (send or receive) of a given set.
*
* @author pron
*/
public class Selector implements Synchronization {
/**
* Performs exactly one channel operation of a given set, blocking until any of the actions completes.
*
* @param priority If {@code true} and more than one operation can complete at the same time, the one that appears in the given list first will be the one performed.
* If {@code false} the order of the operations is ignored.
* @param actions a list of actions, one of which will be performed.
* @return the action that has completed successfully
* @throws InterruptedException
*/
public static SelectAction select(boolean priority, SelectAction... actions) throws InterruptedException, SuspendExecution {
return new Selector(priority, Arrays.asList(actions)).select();
}
/**
* Performs exactly one channel operation of a given set, blocking until any of the actions completes, but no longer than the given timeout.
*
* @param priority If {@code true} and more than one operation can complete at the same time, the one that appears in the given list first will be the one performed.
* If {@code false} the order of the operations is ignored.
* @param timeout the maximum duration to block waiting for an operation to complete.
* @param unit the time unit of the given timeout
* @param actions a list of actions, one of which will be performed.
* @return the action that has completed successfully, or {@code null} if the timeout expired before an operation could complete.
* @throws InterruptedException
*/
public static SelectAction select(boolean priority, long timeout, TimeUnit unit, SelectAction... actions) throws InterruptedException, SuspendExecution {
return new Selector(priority, Arrays.asList(actions)).select(timeout, unit);
}
/**
* Performs exactly one channel operation of a given set, blocking until any of the actions completes, but no longer than the given timeout.
*
* @param priority If {@code true} and more than one operation can complete at the same time, the one that appears in the given list first will be the one performed.
* If {@code false} the order of the operations is ignored.
* @param timeout the method will not block for longer than the amount remaining in the {@link Timeout}
* @param actions a list of actions, one of which will be performed.
* @return the action that has completed successfully, or {@code null} if the timeout expired before an operation could complete.
* @throws InterruptedException
*/
public static SelectAction select(boolean priority, Timeout timeout, SelectAction... actions) throws InterruptedException, SuspendExecution {
return new Selector(priority, Arrays.asList(actions)).select(timeout);
}
/**
* Performs exactly one channel operation of a given set, blocking until any of the actions completes.
*
* @param priority If {@code true} and more than one operation can complete at the same time, the one that appears in the given list first will be the one performed.
* If {@code false} the order of the operations is ignored.
* @param actions a list of actions, one of which will be performed.
* @return the action that has completed successfully
* @throws InterruptedException
*/
public static SelectAction select(boolean priority, List> actions) throws InterruptedException, SuspendExecution {
return new Selector(priority, actions instanceof ArrayList ? actions : new ArrayList<>(actions)).select();
}
/**
* Performs exactly one channel operation of a given set, blocking until any of the actions completes, but no longer than the specified timeout.
*
* @param timeout the maximum duration to block waiting for an operation to complete.
* @param unit the time unit of the given timeout
* @param priority If {@code true} and more than one operation can complete at the same time, the one that appears in the given list first will be the one performed.
* If {@code false} the order of the operations is ignored.
* @param actions a list of actions, one of which will be performed.
* @return the action that has completed successfully
* @throws InterruptedException
*/
public static SelectAction select(boolean priority, long timeout, TimeUnit unit, List> actions) throws InterruptedException, SuspendExecution {
return new Selector(priority, actions instanceof ArrayList ? actions : new ArrayList<>(actions)).select(timeout, unit);
}
/**
* Performs exactly one channel operation of a given set, blocking until any of the actions completes, but no longer than the specified timeout.
*
* @param timeout the method will not block for longer than the amount remaining in the {@link Timeout}
* @param priority If {@code true} and more than one operation can complete at the same time, the one that appears in the given list first will be the one performed.
* If {@code false} the order of the operations is ignored.
* @param actions a list of actions, one of which will be performed.
* @return the action that has completed successfully
* @throws InterruptedException
*/
public static SelectAction select(boolean priority, Timeout timeout, List> actions) throws InterruptedException, SuspendExecution {
return new Selector(priority, actions instanceof ArrayList ? actions : new ArrayList<>(actions)).select(timeout);
}
/**
* Performs exactly one channel operation of a given set, blocking until any of the actions completes.
* Same as calling {@link #select(boolean, co.paralleluniverse.strands.channels.SelectAction[]) select(false, actions)}.
*
* @param actions a list of actions, one of which will be performed.
* @return the action that has completed successfully
* @throws InterruptedException
*/
public static SelectAction select(SelectAction... actions) throws InterruptedException, SuspendExecution {
return select(false, actions);
}
/**
* Performs exactly one channel operation of a given set, blocking until any of the actions completes, but no longer than the given timeout.
* Same as calling {@link #select(long, java.util.concurrent.TimeUnit, co.paralleluniverse.strands.channels.SelectAction[]) select(false, timeout, unit, actions)}.
*
* @param timeout the maximum duration to block waiting for an operation to complete.
* @param unit the time unit of the given timeout
* @param actions a list of actions, one of which will be performed.
* @return the action that has completed successfully, or {@code null} if the timeout expired before an operation could complete.
* @throws InterruptedException
*/
public static SelectAction select(long timeout, TimeUnit unit, SelectAction... actions) throws InterruptedException, SuspendExecution {
return select(false, timeout, unit, actions);
}
/**
* Performs exactly one channel operation of a given set, blocking until any of the actions completes, but no longer than the given timeout.
* Same as calling {@link #select(long, java.util.concurrent.TimeUnit, co.paralleluniverse.strands.channels.SelectAction[]) select(false, timeout, unit, actions)}.
*
* @param timeout the method will not block for longer than the amount remaining in the {@link Timeout}
* @param actions a list of actions, one of which will be performed.
* @return the action that has completed successfully, or {@code null} if the timeout expired before an operation could complete.
* @throws InterruptedException
*/
public static SelectAction select(Timeout timeout, SelectAction... actions) throws InterruptedException, SuspendExecution {
return select(false, timeout, actions);
}
/**
* Performs exactly one channel operation of a given set, blocking until any of the actions completes.
* Same as calling {@link #select(boolean, java.util.List) select(false, actions)}.
*
* @param actions a list of actions, one of which will be performed.
* @return the action that has completed successfully
* @throws InterruptedException
*/
public static SelectAction select(List> actions) throws InterruptedException, SuspendExecution {
return select(false, actions);
}
/**
* Performs exactly one channel operation of a given set, blocking until any of the actions completes, but no longer than the given timeout.
* Same as calling {@link #select(boolean, long, java.util.concurrent.TimeUnit, java.util.List) select(false, timeout, unit, actions)}.
*
* @param timeout the maximum duration to block waiting for an operation to complete.
* @param unit the time unit of the given timeout
* @param actions a list of actions, one of which will be performed.
* @return the action that has completed successfully, or {@code null} if the timeout expired before an operation could complete.
* @throws InterruptedException
*/
public static SelectAction select(long timeout, TimeUnit unit, List> actions) throws InterruptedException, SuspendExecution {
return select(false, timeout, unit, actions);
}
/**
* Performs exactly one channel operation of a given set, blocking until any of the actions completes, but no longer than the given timeout.
* Same as calling {@link #select(boolean, long, java.util.concurrent.TimeUnit, java.util.List) select(false, timeout, unit, actions)}.
*
* @param timeout the method will not block for longer than the amount remaining in the {@link Timeout}
* @param actions a list of actions, one of which will be performed.
* @return the action that has completed successfully, or {@code null} if the timeout expired before an operation could complete.
* @throws InterruptedException
*/
public static SelectAction select(Timeout timeout, List> actions) throws InterruptedException, SuspendExecution {
return select(false, timeout, actions);
}
/**
* Attempts to performs exactly one channel operation of a given set if one can be completed without blocking.
* This method never blocks.
*
* @param priority If {@code true} and more than one operation can complete at the same time, the one that appears in the given list first will be the one performed.
* If {@code false} the order of the operations is ignored.
* @param actions a list of actions, one of which will be performed.
* @return the action that has completed successfully
*/
public static SelectAction trySelect(boolean priority, SelectAction... actions) throws SuspendExecution {
return new Selector(priority, Arrays.asList(actions)).trySelect();
}
/**
* Attempts to performs exactly one channel operation of a given set if one can be completed without blocking.
* This method only blocks if the listeners associated with the select actions block.
*
* @param priority If {@code true} and more than one operation can complete at the same time, the one that appears in the given list first will be the one performed.
* If {@code false} the order of the operations is ignored.
* @param actions a list of actions, one of which will be performed.
* @return the action that has completed successfully
*/
public static SelectAction trySelect(boolean priority, List> actions) throws SuspendExecution {
return new Selector(priority, actions instanceof ArrayList ? actions : new ArrayList<>(actions)).trySelect();
}
/**
* Attempts to performs exactly one channel operation of a given set if one can be completed without blocking.
* This method only blocks if the listeners associated with the select actions block. Same as calling {@link #trySelect(boolean, co.paralleluniverse.strands.channels.SelectAction[]) trySelect(false, actions)}.
*
* @param actions a list of actions, one of which will be performed.
* @return the action that has completed successfully
*/
public static SelectAction trySelect(SelectAction... actions) throws SuspendExecution {
return trySelect(false, actions);
}
/**
* Attempts to performs exactly one channel operation of a given set if one can be completed without blocking.
* This method only blocks if the listeners associated with the select actions block.. Same as calling {@link #trySelect(boolean, java.util.List) trySelect(false, actions)}.
*
* @param actions a list of actions, one of which will be performed.
* @return the action that has completed successfully
*/
public static SelectAction trySelect(List> actions) throws SuspendExecution {
return trySelect(false, actions);
}
//////////////////////
/**
* Creates a {@link SelectAction} for a send operation
*
* @param
* @param ch The channel to which the operation tries to send the message
* @param message the message to send.
* @return a send {@link SelectAction} that can be selected by the selector.
*/
public static SelectAction send(SendPort ch, Message message) {
return send(ch, message, null);
}
/**
* Creates a {@link SelectAction} for a send operation
*
* @param
* @param ch The channel to which the operation tries to send the message
* @param message the message to send.
* @param listener a {@link SelectSendListener} which will be triggered if this operation succeeds.
* @return a send {@link SelectAction} that can be selected by the selector.
*/
public static SelectAction send(SendPort ch, Message message, SelectSendListener listener) {
return new SelectActionImpl((SendPort) ch, message, listener);
}
/**
* Creates a {@link SelectAction} for a receive operation
*
* @param
* @param ch the channel from which the operation tries to receive
* @return a receive {@link SelectAction} that can be selected by the selector.
*/
public static SelectAction receive(ReceivePort ch) {
return receive(ch, null);
}
/**
* Creates a {@link SelectAction} for a receive operation
*
* @param
* @param ch the channel from which the operation tries to receive
* @param listener a {@link SelectReceiveListener} which will be triggered if this operation succeeds.
* @return a receive {@link SelectAction} that can be selected by the selector.
*/
public static SelectAction receive(ReceivePort ch, SelectReceiveListener listener) {
return new SelectActionImpl(ch, listener);
}
///////////////////
private static final AtomicLong selectorId = new AtomicLong(); // used to break symmetry to prevent deadlock in transfer channel
private static final Object LEASED = new Object() {
@Override
public String toString() {
return "LEASED";
}
};
final long id;
private volatile Object winner;
private Strand waiter;
private final List> actions;
private int lastRegistered;
private final boolean priority;
SelectAction res;
Selector(boolean priority, List> actions) {
this.id = selectorId.incrementAndGet();
this.waiter = Strand.currentStrand();
this.actions = (List>) actions;
this.priority = priority;
for (int i = 0; i < actions.size(); i++) {
SelectActionImpl sa = (SelectActionImpl) actions.get(i);
sa.setSelector(this);
sa.setIndex(i);
record("", "%s added %s", this, sa);
}
}
private void selectInit() {
if (!priority)
Collections.shuffle(actions, ThreadLocalRandom.current());
}
void reset() {
waiter = null;
for (SelectActionImpl sa : actions)
sa.resetReceive();
winner = null;
}
SelectAction select() throws InterruptedException, SuspendExecution {
return select(-1, null);
}
@Override
public Object register() {
Strand s = Strand.currentStrand();
if (waiter != null && !waiter.equals(s))
throw new IllegalMonitorStateException("A strand is already registered");
this.waiter = Strand.currentStrand();
final int n = actions.size();
res = null;
// register
lastRegistered = -1;
for (int i = 0; i < n; i++) {
SelectActionImpl sa = actions.get(i);
sa.token = sa.port.register((SelectActionImpl) sa);
lastRegistered = i;
if (sa.isDone()) {
assert winner == sa; // seen to have failed in co.paralleluniverse.strands.channels.GeneralSelectorTest > testFans1[5]
res = sa;
break;
} else {
Object w = winner;
if (w != null & w != LEASED)
break;
}
}
return null;
}
@Override
public void unregister(Object registrationToken) {
for (int i = 0; i <= lastRegistered; i++) {
SelectActionImpl sa = actions.get(i);
sa.port.unregister(sa.token);
sa.token = null; // for GC
}
this.waiter = null;
}
SelectAction select(Timeout timeout) throws InterruptedException, SuspendExecution {
return select(timeout.nanosLeft(), TimeUnit.NANOSECONDS);
}
SelectAction select(long timeout, TimeUnit unit) throws InterruptedException, SuspendExecution {
if (timeout == 0 && unit != null)
return trySelect();
selectInit();
final boolean timed = (timeout > 0 && unit != null);
long lastTime = timed ? System.nanoTime() : 0L;
long nanos = timed ? unit.toNanos(timeout) : 0L;
Object token = register();
try {
if (res == null) {
tryloop:
for (;;) {
if (timed && nanos <= 0)
break;
for (int i = 0; i <= lastRegistered; i++) {
SelectActionImpl sa = actions.get(i);
if (sa.port.tryNow(sa.token)) {
res = sa;
break tryloop;
}
}
if (timed) {
long now = System.nanoTime();
if ((nanos -= now - lastTime) > 0)
Strand.parkNanos(this, nanos);
lastTime = now;
} else
Strand.park(this);
}
}
} finally {
unregister(token);
}
if (res != null)
((SelectActionImpl) res).fire();
return res;
}
public SelectAction trySelect() throws SuspendExecution {
selectInit();
for (int i = 0; i < actions.size(); i++) {
SelectActionImpl sa = actions.get(i);
if (sa.isData()) {
if (((SendPort) sa.port).trySend(sa.message())) {
sa.fire();
return sa;
}
} else {
Object m = ((ReceivePort) sa.port).tryReceive();
if (m != null || ((ReceivePort) sa.port).isClosed()) {
sa.setItem(m);
sa.fire();
return sa;
}
}
}
return null;
}
// private volatile StackTraceElement st[];
boolean lease() {
record("lease", "trying lease %s", this);
Object w;
int i = 0;
long start = 0;
do {
w = winner;
if (w != null & w != LEASED)
return false;
if (i++ > (1 << 22)) {
if (start == 0)
start = System.nanoTime();
else if (TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - start) > 10000)
throw new RuntimeException("Unable to obtain selector lease in 10 seconds: " + w);
i = 0;
Thread.yield();
}
} while (!casWinner(null, LEASED));
// st = Thread.currentThread().getStackTrace();
record("lease", "got lease %s", this);
return true;
}
void setWinner(SelectAction action) {
record("setWinner", "won %s: %s", this, action);
assert winner == LEASED;
// st = null;
winner = action;
}
void returnLease() {
record("returnLease", "returned lease %s", this);
assert winner == LEASED;
// st = null;
winner = null;
}
Strand getWaiter() {
return waiter;
}
void signal() {
waiter.unpark(this);
}
public SelectAction getWinner() {
return (SelectAction) winner;
}
private static int[] randomIntArray(int n) {
final ThreadLocalRandom random = ThreadLocalRandom.current();
final int[] a = new int[n];
for (int i = 1; i < n; i++) {
int x = random.nextInt(i);
a[i] = a[x];
a[x] = i;
}
return a;
}
@Override
public String toString() {
return Selector.class.getName() + '@' + Long.toHexString(id);
}
private static final VarHandle WINNER;
static {
try {
MethodHandles.Lookup l = MethodHandles.lookup();
WINNER = l.findVarHandle(Selector.class, "winner", Object.class);
} catch (ReflectiveOperationException e) {
throw new ExceptionInInitializerError(e);
}
}
private boolean casWinner(Object expected, Object update) {
return WINNER.compareAndSet(this, expected, update);
}
static final FlightRecorder RECORDER = Debug.isDebug() ? Debug.getGlobalFlightRecorder() : null;
boolean isRecording() {
return RECORDER != null;
}
static void record(String method, String format) {
if (RECORDER != null)
RECORDER.record(1, new FlightRecorderMessage("Selector", method, format, null));
}
static void record(String method, String format, Object arg1) {
if (RECORDER != null)
RECORDER.record(1, new FlightRecorderMessage("Selector", method, format, new Object[]{arg1}));
}
static void record(String method, String format, Object arg1, Object arg2) {
if (RECORDER != null)
RECORDER.record(1, new FlightRecorderMessage("Selector", method, format, new Object[]{arg1, arg2}));
}
static void record(String method, String format, Object arg1, Object arg2, Object arg3) {
if (RECORDER != null)
RECORDER.record(1, new FlightRecorderMessage("Selector", method, format, new Object[]{arg1, arg2, arg3}));
}
static void record(String method, String format, Object arg1, Object arg2, Object arg3, Object arg4) {
if (RECORDER != null)
RECORDER.record(1, new FlightRecorderMessage("Selector", method, format, new Object[]{arg1, arg2, arg3, arg4}));
}
static void record(String method, String format, Object arg1, Object arg2, Object arg3, Object arg4, Object arg5) {
if (RECORDER != null)
RECORDER.record(1, new FlightRecorderMessage("Selector", method, format, new Object[]{arg1, arg2, arg3, arg4, arg5}));
}
}
