Added a AtomicValue distributed primitive.

Change-Id: I00ff165cbd9c6e4f2610af9877ff262527b7b048

+/*
+ * Copyright 2015 Open Networking Laboratory
+ *
+ * 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 org.onosproject.store.service;
+
+/**
+ * Distributed version of java.util.concurrent.atomic.AtomicReference.
+ *
+ * @param <V> value type
+ */
+public interface AtomicValue<V> {
+
+    /**
+     * Atomically sets the value to the given updated value if the current value is equal to the expected value.
+     * <p>
+     * IMPORTANT: Equality is based on the equality of the serialized byte[] representations.
+     * <p>
+     * @param expect  the expected value
+     * @param update  the new value
+     * @return true if successful. false return indicates that the actual value was not equal to the expected value.
+     */
+    boolean compareAndSet(V expect, V update);
+
+    /**
+     * Gets the current value.
+     * @return current value
+     */
+    V get();
+
+    /**
+     * Atomically sets to the given value and returns the old value.
+     * @param value the new value
+     * @return previous value
+     */
+    V getAndSet(V value);
+
+    /**
+     * Sets to the given value.
+     * @param value new value
+     */
+    void set(V value);
+
+    /**
+     * Registers the specified listener to be notified whenever the atomic value is updated.
+     *
+     * @param listener listener to notify about events
+     */
+    void addListener(AtomicValueEventListener<V> listener);
+
+    /**
+     * Unregisters the specified listener such that it will no longer
+     * receive atomic value update notifications.
+     *
+     * @param listener listener to unregister
+     */
+    void removeListener(AtomicValueEventListener<V> listener);
+}

+/*
+ * Copyright 2015 Open Networking Laboratory
+ *
+ * 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 org.onosproject.store.service;
+
+/**
+ * Builder for constructing new AtomicValue instances.
+ *
+ * @param <V> atomic value type
+ */
+public interface AtomicValueBuilder<V> {
+    /**
+     * Sets the name for the atomic value.
+     * <p>
+     * Each atomic value is identified by a unique name.
+     * </p>
+     * <p>
+     * Note: This is a mandatory parameter.
+     * </p>
+     *
+     * @param name name of the atomic value
+     * @return this AtomicValueBuilder for method chaining
+     */
+    AtomicValueBuilder<V> withName(String name);
+
+    /**
+     * Sets a serializer that can be used to serialize the value.
+     * <p>
+     * Note: This is a mandatory parameter.
+     * </p>
+     *
+     * @param serializer serializer
+     * @return this AtomicValueBuilder for method chaining
+     */
+    AtomicValueBuilder<V> withSerializer(Serializer serializer);
+
+    /**
+     * Creates this atomic value on the partition that spans the entire cluster.
+     * <p>
+     * When partitioning is disabled, the value state will be
+     * ephemeral and does not survive a full cluster restart.
+     * </p>
+     * <p>
+     * Note: By default partitions are enabled.
+     * </p>
+     * @return this AtomicValueBuilder for method chaining
+     */
+    AtomicValueBuilder<V> withPartitionsDisabled();
+
+    /**
+     * Builds a AtomicValue based on the configuration options
+     * supplied to this builder.
+     *
+     * @return new AtomicValue
+     * @throws java.lang.RuntimeException if a mandatory parameter is missing
+     */
+    AtomicValue<V> build();
+}

+/*
+ * Copyright 2015 Open Networking Laboratory
+ *
+ * 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 org.onosproject.store.service;
+
+import java.util.Objects;
+
+import com.google.common.base.MoreObjects;
+
+/**
+ * Representation of a AtomicValue update notification.
+ *
+ * @param <V> atomic value type
+ */
+public class AtomicValueEvent<V> {
+
+    /**
+     * AtomicValueEvent type.
+     */
+    public enum Type {
+
+        /**
+         * Value was updated.
+         */
+        UPDATE,
+    }
+
+    private final String name;
+    private final Type type;
+    private final V value;
+
+    /**
+     * Creates a new event object.
+     *
+     * @param name AtomicValue name
+     * @param type the type of the event
+     * @param value the new value
+     */
+    public AtomicValueEvent(String name, Type type, V value) {
+        this.name = name;
+        this.type = type;
+        this.value = value;
+    }
+
+    /**
+     * Returns the AtomicValue name.
+     *
+     * @return name of atomic value
+     */
+    public String name() {
+        return name;
+    }
+
+    /**
+     * Returns the type of the event.
+     *
+     * @return the type of the event
+     */
+    public Type type() {
+        return type;
+    }
+
+    /**
+     * Returns the new updated value.
+     *
+     * @return the value
+     */
+    public V value() {
+        return value;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (!(o instanceof AtomicValueEvent)) {
+            return false;
+        }
+
+        AtomicValueEvent<V> that = (AtomicValueEvent) o;
+        return Objects.equals(this.name, that.name) &&
+                Objects.equals(this.type, that.type) &&
+                Objects.equals(this.value, that.value);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(name, type, value);
+    }
+
+    @Override
+    public String toString() {
+        return MoreObjects.toStringHelper(getClass())
+                .add("name", name)
+                .add("type", type)
+                .add("value", value)
+                .toString();
+    }
+}
\ No newline at end of file

+/*
+ * Copyright 2015 Open Networking Laboratory
+ *
+ * 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 org.onosproject.store.service;
+
+/**
+ * Listener to be notified about updates to a AtomicValue.
+ */
+public interface AtomicValueEventListener<V> {
+    /**
+     * Reacts to the specified event.
+     *
+     * @param event the event
+     */
+    void event(AtomicValueEvent<V> event);
+}

@@ -71,6 +71,14 @@ public interface StorageService {
     AtomicCounterBuilder atomicCounterBuilder();
 
     /**
+     * Creates a new AtomicValueBuilder.
+     *
+     * @param <V> atomic value type
+     * @return atomic value builder
+     */
+    <V> AtomicValueBuilder<V> atomicValueBuilder();
+
+    /**
      * Creates a new transaction context builder.
      *
      * @return a builder for a transaction context.

@@ -63,6 +63,7 @@ import org.onosproject.store.cluster.messaging.ClusterCommunicationService;
 import org.onosproject.store.cluster.messaging.MessageSubject;
 import org.onosproject.store.ecmap.EventuallyConsistentMapBuilderImpl;
 import org.onosproject.store.service.AtomicCounterBuilder;
+import org.onosproject.store.service.AtomicValueBuilder;
 import org.onosproject.store.service.ConsistentMapBuilder;
 import org.onosproject.store.service.ConsistentMapException;
 import org.onosproject.store.service.DistributedQueueBuilder;
@@ -383,6 +384,11 @@ public class DatabaseManager implements StorageService, StorageAdminService {
     }
 
     @Override
+    public <V> AtomicValueBuilder<V> atomicValueBuilder() {
+        return new DefaultAtomicValueBuilder<>(this);
+    }
+
+    @Override
     public List<MapInfo> getMapInfo() {
         List<MapInfo> maps = Lists.newArrayList();
         maps.addAll(getMapInfo(inMemoryDatabase));

+/*
+ * Copyright 2015 Open Networking Laboratory
+ *
+ * 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 org.onosproject.store.consistent.impl;
+
+import java.util.Set;
+import java.util.concurrent.CopyOnWriteArraySet;
+
+import org.onosproject.store.service.AtomicValue;
+import org.onosproject.store.service.AtomicValueEvent;
+import org.onosproject.store.service.AtomicValueEventListener;
+import org.onosproject.store.service.ConsistentMap;
+import org.onosproject.store.service.MapEvent;
+import org.onosproject.store.service.MapEventListener;
+import org.onosproject.store.service.Serializer;
+import org.onosproject.store.service.Versioned;
+
+/**
+ * Default implementation of AtomicValue.
+ *
+ * @param <V> value type
+ */
+public class DefaultAtomicValue<V> implements AtomicValue<V> {
+
+    private final Set<AtomicValueEventListener<V>> listeners = new CopyOnWriteArraySet<>();
+    private final ConsistentMap<String, byte[]> valueMap;
+    private final String name;
+    private final Serializer serializer;
+    private final MapEventListener<String, byte[]> mapEventListener = new InternalMapEventListener();
+
+    public DefaultAtomicValue(ConsistentMap<String, byte[]> valueMap,
+            String name,
+            Serializer serializer) {
+        this.valueMap = valueMap;
+        this.name = name;
+        this.serializer = serializer;
+    }
+
+    @Override
+    public boolean compareAndSet(V expect, V update) {
+        if (expect == null) {
+            if (update == null) {
+                return true;
+            }
+            return valueMap.putIfAbsent(name, serializer.encode(update)) == null;
+        } else {
+            if (update == null) {
+                return valueMap.remove(name, serializer.encode(expect));
+            }
+            return valueMap.replace(name, serializer.encode(expect), serializer.encode(update));
+        }
+    }
+
+    @Override
+    public V get() {
+        Versioned<byte[]> rawValue = valueMap.get(name);
+        return rawValue == null ? null : serializer.decode(rawValue.value());
+    }
+
+    @Override
+    public V getAndSet(V value) {
+        Versioned<byte[]> previousValue = value == null ?
+                valueMap.remove(name) : valueMap.put(name, serializer.encode(value));
+        return previousValue == null ? null : serializer.decode(previousValue.value());
+    }
+
+    @Override
+    public void set(V value) {
+        getAndSet(value);
+    }
+
+    @Override
+    public void addListener(AtomicValueEventListener<V> listener) {
+        synchronized (listeners) {
+            if (listeners.add(listener)) {
+                if (listeners.size() == 1) {
+                    valueMap.addListener(mapEventListener);
+                }
+            }
+        }
+    }
+
+    @Override
+    public void removeListener(AtomicValueEventListener<V> listener) {
+        synchronized (listeners) {
+            if (listeners.remove(listener)) {
+                if (listeners.size() == 0) {
+                    valueMap.removeListener(mapEventListener);
+                }
+            }
+        }
+    }
+
+    private class InternalMapEventListener implements MapEventListener<String, byte[]> {
+
+        @Override
+        public void event(MapEvent<String, byte[]> mapEvent) {
+            V newValue = mapEvent.type() == MapEvent.Type.REMOVE ? null : serializer.decode(mapEvent.value().value());
+            AtomicValueEvent<V> atomicValueEvent = new AtomicValueEvent<>(name, AtomicValueEvent.Type.UPDATE, newValue);
+            listeners.forEach(l -> l.event(atomicValueEvent));
+        }
+    }
+}

+/*
+ * Copyright 2015 Open Networking Laboratory
+ *
+ * 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 org.onosproject.store.consistent.impl;
+
+import org.onosproject.store.serializers.KryoNamespaces;
+import org.onosproject.store.service.AtomicValue;
+import org.onosproject.store.service.AtomicValueBuilder;
+import org.onosproject.store.service.ConsistentMapBuilder;
+import org.onosproject.store.service.Serializer;
+
+/**
+ * Default implementation of AtomicValueBuilder.
+ *
+ * @param <V> value type
+ */
+public class DefaultAtomicValueBuilder<V> implements AtomicValueBuilder<V> {
+
+    private Serializer serializer;
+    private String name;
+    private ConsistentMapBuilder<String, byte[]> mapBuilder;
+
+    public DefaultAtomicValueBuilder(DatabaseManager manager) {
+        mapBuilder = manager.<String, byte[]>consistentMapBuilder()
+                            .withName("onos-atomic-values")
+                            .withSerializer(Serializer.using(KryoNamespaces.BASIC));
+    }
+
+    @Override
+    public AtomicValueBuilder<V> withName(String name) {
+        this.name = name;
+        return this;
+    }
+
+    @Override
+    public AtomicValueBuilder<V> withSerializer(Serializer serializer) {
+        this.serializer = serializer;
+        return this;
+    }
+
+    @Override
+    public AtomicValueBuilder<V> withPartitionsDisabled() {
+        mapBuilder.withPartitionsDisabled();
+        return this;
+    }
+
+    @Override
+    public AtomicValue<V> build() {
+        return new DefaultAtomicValue<>(mapBuilder.build(), name, serializer);
+    }
+}
\ No newline at end of file