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Use lock free strategy for several Subscription implementations #568

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merged 9 commits into from
Dec 8, 2013
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Merged

Use lock free strategy for several Subscription implementations #568

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d1706bc
Use lock free strategy
jloisel Dec 5, 2013
c728d77
Make unsubscribe + reference modification an atomic operation
jloisel Dec 5, 2013
9897ca8
Lock free strategy using a sentinel (Thanks to akarnokd)
jloisel Dec 5, 2013
d7bd826
Code simplification
jloisel Dec 5, 2013
dba41f0
Simplify code; Junits
jloisel Dec 5, 2013
ec9bd2c
fix: getSubscription should not expose internal sentinel subscription
jloisel Dec 5, 2013
39b9787
JUnit setting subscription concurrently
jloisel Dec 5, 2013
61aea25
Return null on getSubscription() when previously unsubscribed to match
jloisel Dec 6, 2013
078b687
use non-locking state machine based on atomic reference
jloisel Dec 8, 2013
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160 changes: 90 additions & 70 deletions rxjava-core/src/main/java/rx/subscriptions/CompositeSubscription.java
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Original file line number Diff line number Diff line change
Expand Up @@ -15,103 +15,123 @@
*/
package rx.subscriptions;

import static java.util.Arrays.asList;
import static java.util.Collections.unmodifiableSet;

import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.HashSet;
import java.util.Set;
import java.util.concurrent.atomic.AtomicReference;

import rx.Subscription;
import rx.util.CompositeException;

/**
* Subscription that represents a group of Subscriptions that are unsubscribed together.
* Subscription that represents a group of Subscriptions that are unsubscribed
* together.
*
* @see <a href="http://msdn.microsoft.com/en-us/library/system.reactive.disposables.compositedisposable(v=vs.103).aspx">Rx.Net equivalent CompositeDisposable</a>
* @see <a
* href="http://msdn.microsoft.com/en-us/library/system.reactive.disposables.compositedisposable(v=vs.103).aspx">Rx.Net
* equivalent CompositeDisposable</a>
*/
public class CompositeSubscription implements Subscription {
private static final Set<Subscription> MUTATE_STATE = unmodifiableSet(new HashSet<Subscription>());
private static final Set<Subscription> UNSUBSCRIBED_STATE = unmodifiableSet(new HashSet<Subscription>());

private final AtomicReference<Set<Subscription>> reference = new AtomicReference<Set<Subscription>>();

/*
* The reason 'synchronized' is used on 'add' and 'unsubscribe' is because AtomicBoolean/ConcurrentLinkedQueue are both being modified so it needs to be done atomically.
*
* TODO evaluate whether use of synchronized is a performance issue here and if it's worth using an atomic state machine or other non-locking approach
*/
private AtomicBoolean unsubscribed = new AtomicBoolean(false);
private final ConcurrentHashMap<Subscription, Boolean> subscriptions = new ConcurrentHashMap<Subscription, Boolean>();

public CompositeSubscription(List<Subscription> subscriptions) {
for (Subscription s : subscriptions) {
this.subscriptions.put(s, Boolean.TRUE);
}
public CompositeSubscription(final Subscription... subscriptions) {
reference.set(new HashSet<Subscription>(asList(subscriptions)));
}

public CompositeSubscription(Subscription... subscriptions) {
for (Subscription s : subscriptions) {
this.subscriptions.put(s, Boolean.TRUE);
}
public boolean isUnsubscribed() {
return reference.get() == UNSUBSCRIBED_STATE;
}

/**
* Remove and unsubscribe all subscriptions but do not unsubscribe the outer CompositeSubscription.
*/
public void clear() {
Collection<Throwable> es = null;
for (Subscription s : subscriptions.keySet()) {
try {
public void add(final Subscription s) {
do {
final Set<Subscription> existing = reference.get();
if (existing == UNSUBSCRIBED_STATE) {
s.unsubscribe();
this.subscriptions.remove(s);
} catch (Throwable e) {
if (es == null) {
es = new ArrayList<Throwable>();
}
es.add(e);
break;
}
}
if (es != null) {
throw new CompositeException("Failed to unsubscribe to 1 or more subscriptions.", es);
}
}

/**
* Remove the {@link Subscription} and unsubscribe it.
*
* @param s
*/
public void remove(Subscription s) {
this.subscriptions.remove(s);
// also unsubscribe from it: http://msdn.microsoft.com/en-us/library/system.reactive.disposables.compositedisposable.remove(v=vs.103).aspx
s.unsubscribe();
if (reference.compareAndSet(existing, MUTATE_STATE)) {
existing.add(s);
reference.set(existing);
break;
}
} while (true);
}

public boolean isUnsubscribed() {
return unsubscribed.get();
public void remove(final Subscription s) {
do {
final Set<Subscription> subscriptions = reference.get();
if (subscriptions == UNSUBSCRIBED_STATE) {
s.unsubscribe();
break;
}

if (reference.compareAndSet(subscriptions, MUTATE_STATE)) {
// also unsubscribe from it:
// http://msdn.microsoft.com/en-us/library/system.reactive.disposables.compositedisposable.remove(v=vs.103).aspx
subscriptions.remove(s);
reference.set(subscriptions);
s.unsubscribe();
break;
}
} while (true);
}

public synchronized void add(Subscription s) {
if (unsubscribed.get()) {
s.unsubscribe();
} else {
subscriptions.put(s, Boolean.TRUE);
}
public void clear() {
do {
final Set<Subscription> subscriptions = reference.get();
if (subscriptions == UNSUBSCRIBED_STATE) {
break;
}

if (reference.compareAndSet(subscriptions, MUTATE_STATE)) {
final Set<Subscription> copy = new HashSet<Subscription>(
subscriptions);
subscriptions.clear();
reference.set(subscriptions);

for (final Subscription subscription : copy) {
subscription.unsubscribe();
}
break;
}
} while (true);
}

@Override
public synchronized void unsubscribe() {
if (unsubscribed.compareAndSet(false, true)) {
Collection<Throwable> es = null;
for (Subscription s : subscriptions.keySet()) {
try {
s.unsubscribe();
} catch (Throwable e) {
if (es == null) {
es = new ArrayList<Throwable>();
public void unsubscribe() {
do {
final Set<Subscription> subscriptions = reference.get();
if (subscriptions == UNSUBSCRIBED_STATE) {
break;
}

if (subscriptions == MUTATE_STATE) {
continue;
}

if (reference.compareAndSet(subscriptions, UNSUBSCRIBED_STATE)) {
final Collection<Throwable> es = new ArrayList<Throwable>();
for (final Subscription s : subscriptions) {
try {
s.unsubscribe();
} catch (final Throwable e) {
es.add(e);
}
es.add(e);
}
if (es.isEmpty()) {
break;
}
throw new CompositeException(
"Failed to unsubscribe to 1 or more subscriptions.", es);
}
if (es != null) {
throw new CompositeException("Failed to unsubscribe to 1 or more subscriptions.", es);
}
}
} while (true);
}
}
132 changes: 62 additions & 70 deletions rxjava-core/src/main/java/rx/subscriptions/SerialSubscription.java
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Original file line number Diff line number Diff line change
@@ -1,70 +1,62 @@
/**
* Copyright 2013 Netflix, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package rx.subscriptions;

import rx.Subscription;

/**
* Represents a subscription whose underlying subscription can be swapped for another subscription
* which causes the previous underlying subscription to be unsubscribed.
*
* @see <a href="http://msdn.microsoft.com/en-us/library/system.reactive.disposables.serialdisposable(v=vs.103).aspx">Rx.Net equivalent SerialDisposable</a>
*/
public class SerialSubscription implements Subscription {
private boolean unsubscribed;
private Subscription subscription;
private final Object gate = new Object();

@Override
public void unsubscribe() {
Subscription toUnsubscribe = null;
synchronized (gate) {
if (!unsubscribed) {
if (subscription != null) {
toUnsubscribe = subscription;
subscription = null;
}
unsubscribed = true;
}
}
if (toUnsubscribe != null) {
toUnsubscribe.unsubscribe();
}
}

public Subscription getSubscription() {
synchronized (gate) {
return subscription;
}
}

public void setSubscription(Subscription subscription) {
Subscription toUnsubscribe = null;
synchronized (gate) {
if (!unsubscribed) {
if (this.subscription != null) {
toUnsubscribe = this.subscription;
}
this.subscription = subscription;
} else {
toUnsubscribe = subscription;
}
}
if (toUnsubscribe != null) {
toUnsubscribe.unsubscribe();
}
}
}
/**
* Copyright 2013 Netflix, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package rx.subscriptions;

import static rx.subscriptions.Subscriptions.empty;

import java.util.concurrent.atomic.AtomicReference;

import rx.Subscription;

/**
* Represents a subscription whose underlying subscription can be swapped for another subscription
* which causes the previous underlying subscription to be unsubscribed.
*
* @see <a href="http://msdn.microsoft.com/en-us/library/system.reactive.disposables.serialdisposable(v=vs.103).aspx">Rx.Net equivalent SerialDisposable</a>
*/
public class SerialSubscription implements Subscription {
private final AtomicReference<Subscription> reference = new AtomicReference<Subscription>(empty());

private static final Subscription UNSUBSCRIBED = new Subscription() {
@Override
public void unsubscribe() {
}
};

@Override
public void unsubscribe() {
setSubscription(UNSUBSCRIBED);
}

public void setSubscription(final Subscription subscription) {
do {
final Subscription current = reference.get();
if (current == UNSUBSCRIBED) {
subscription.unsubscribe();
break;
}
if (reference.compareAndSet(current, subscription)) {
current.unsubscribe();
break;
}
} while (true);
}

public Subscription getSubscription() {
final Subscription subscription = reference.get();
return subscription == UNSUBSCRIBED ? null : subscription;
}
}
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