org.jgroups.blocks.ReplicatedHashMap Maven / Gradle / Ivy
package org.jgroups.blocks;
import org.jgroups.*;
import org.jgroups.logging.Log;
import org.jgroups.logging.LogFactory;
import org.jgroups.util.Util;
import java.io.*;
import java.lang.reflect.Method;
import java.util.*;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.CopyOnWriteArraySet;
import java.util.stream.Collectors;
/**
* Implementation of a {@link java.util.concurrent.ConcurrentMap} with replication of the contents across a cluster.
* Any change to the hashmap (clear(), put(), remove() etc) will transparently be propagated to all replicas in the group.
* All read-only methods will always access the local replica.
*
* Keys and values added to the hashmap must be serializable, the reason being that they will be sent
* across the network to all replicas of the group.
* A {@code ReplicatedHashMap} allows one to implement a distributed naming service in just a couple of lines.
*
* An instance of this class will contact an existing member of the group to fetch its initial state.
*
* @author Bela Ban
*/
public class ReplicatedHashMap extends
AbstractMap implements ConcurrentMap, MembershipListener, StateListener, ReplicatedMap, Closeable {
public interface Notification {
void entrySet(K key, V value);
void entryRemoved(K key);
void viewChange(View view, java.util.List mbrs_joined, java.util.List mbrs_left);
void contentsSet(Map new_entries);
void contentsCleared();
}
private static final short PUT=1;
private static final short PUT_IF_ABSENT=2;
private static final short PUT_ALL=3;
private static final short REMOVE=4;
private static final short REMOVE_IF_EQUALS=5;
private static final short REPLACE_IF_EXISTS=6;
private static final short REPLACE_IF_EQUALS=7;
private static final short CLEAR=8;
protected static Map methods;
static {
try {
methods=new HashMap<>(8);
methods.put(PUT, ReplicatedHashMap.class.getMethod("_put",
Object.class,
Object.class));
methods.put(PUT_IF_ABSENT, ReplicatedHashMap.class.getMethod("_putIfAbsent",
Object.class,
Object.class));
methods.put(PUT_ALL, ReplicatedHashMap.class.getMethod("_putAll", Map.class));
methods.put(REMOVE, ReplicatedHashMap.class.getMethod("_remove", Object.class));
methods.put(REMOVE_IF_EQUALS, ReplicatedHashMap.class.getMethod("_remove",
Object.class,
Object.class));
methods.put(REPLACE_IF_EXISTS, ReplicatedHashMap.class.getMethod("_replace",
Object.class,
Object.class));
methods.put(REPLACE_IF_EQUALS, ReplicatedHashMap.class.getMethod("_replace",
Object.class,
Object.class,
Object.class));
methods.put(CLEAR, ReplicatedHashMap.class.getMethod("_clear"));
}
catch(NoSuchMethodException e) {
throw new RuntimeException(e);
}
}
private final JChannel channel;
protected RpcDispatcher disp=null;
private String cluster_name=null;
// to be notified when mbrship changes
private final Set notifs=new CopyOnWriteArraySet<>();
private final List members=new ArrayList<>(); // keeps track of all DHTs
protected final RequestOptions call_options=new RequestOptions(ResponseMode.GET_NONE, 5000);
protected final Log log=LogFactory.getLog(this.getClass());
/** wrapped map instance */
protected ConcurrentMap map=null;
/**
* Constructs a new ReplicatedHashMap with channel. Call {@link #start(long)} to start this map.
*/
public ReplicatedHashMap(JChannel channel) {
this.channel=channel;
this.map=new ConcurrentHashMap<>();
init();
}
/**
* Constructs a new ReplicatedHashMap using provided map instance.
*/
public ReplicatedHashMap(ConcurrentMap map, JChannel channel) {
if(channel == null)
throw new IllegalArgumentException("Cannot create ReplicatedHashMap with null channel");
if(map == null)
throw new IllegalArgumentException("Cannot create ReplicatedHashMap with null map");
this.map=map;
this.cluster_name=channel.getClusterName();
this.channel=channel;
init();
}
protected final void init() {
disp=new RpcDispatcher(channel, this).setMethodLookup(id -> methods.get(id));
disp.setMembershipListener(this).setStateListener(this);
}
public boolean isBlockingUpdates() {
return call_options.mode() == ResponseMode.GET_ALL;
}
/**
* Whether updates across the cluster should be asynchronous (default) or synchronous)
*
* @param blocking_updates
*/
public void setBlockingUpdates(boolean blocking_updates) {
call_options.mode(blocking_updates? ResponseMode.GET_ALL : ResponseMode.GET_NONE);
}
/**
* The timeout (in milliseconds) for blocking updates
*/
public long getTimeout() {
return call_options.timeout();
}
/**
* Sets the cluster call timeout (until all acks have been received)
*
* @param timeout
* The timeout (in milliseconds) for blocking updates
*/
public void setTimeout(long timeout) {
call_options.timeout(timeout);
}
/**
* Fetches the state
* @param state_timeout
*/
public final void start(long state_timeout) throws Exception {
channel.getState(null, state_timeout);
}
public Address getLocalAddress() {
return channel != null? channel.getAddress() : null;
}
public String getClusterName() {
return cluster_name;
}
public JChannel getChannel() {
return channel;
}
public void addNotifier(Notification n) {
if(n != null)
notifs.add(n);
}
public void removeNotifier(Notification n) {
if(n != null)
notifs.remove(n);
}
public void stop() {
if(disp != null) {
disp.stop();
disp=null;
}
Util.close(channel);
}
@Override public void close() throws IOException {
stop();
}
/**
* Maps the specified key to the specified value in this table. Neither the key nor the value can be null.
*
* The value can be retrieved by calling the get method with a key that is equal to the original key.
*
* @param key
* key with which the specified value is to be associated
* @param value
* value to be associated with the specified key
* @return the previous value associated with key, or
* null if there was no mapping for key
* @throws NullPointerException
* if the specified key or value is null
*/
public V put(K key, V value) {
V prev_val=get(key);
try {
MethodCall call=new MethodCall(PUT, key, value);
disp.callRemoteMethods(null, call, call_options);
}
catch(Exception e) {
throw new RuntimeException("put(" + key + ", " + value + ") failed", e);
}
return prev_val;
}
/**
* @return the previous value associated with the specified key, or null if there was no mapping for the key
* @throws NullPointerException if the specified key or value is null
*/
public V putIfAbsent(K key, V value) {
V prev_val=get(key);
try {
MethodCall call=new MethodCall(PUT_IF_ABSENT, key, value);
disp.callRemoteMethods(null, call, call_options);
}
catch(Exception e) {
throw new RuntimeException("putIfAbsent(" + key + ", " + value + ") failed", e);
}
return prev_val;
}
/**
* Copies all of the mappings from the specified map to this one. These
* mappings replace any mappings that this map had for any of the keys
* currently in the specified map.
*
* @param m
* mappings to be stored in this map
*/
public void putAll(Map m) {
try {
MethodCall call=new MethodCall(PUT_ALL, m);
disp.callRemoteMethods(null, call, call_options);
}
catch(Throwable t) {
throw new RuntimeException("putAll() failed", t);
}
}
/**
* Removes all of the mappings from this map.
*/
public void clear() {
try {
MethodCall call=new MethodCall(CLEAR);
disp.callRemoteMethods(null, call, call_options);
}
catch(Exception e) {
throw new RuntimeException("clear() failed", e);
}
}
/**
* Removes the key (and its corresponding value) from this map. This method
* does nothing if the key is not in the map.
*
* @param key
* the key that needs to be removed
* @return the previous value associated with key, or
* null if there was no mapping for key
* @throws NullPointerException
* if the specified key is null
*/
public V remove(Object key) {
V retval=get(key);
try {
MethodCall call=new MethodCall(REMOVE, key);
disp.callRemoteMethods(null, call, call_options);
}
catch(Exception e) {
throw new RuntimeException("remove(" + key + ") failed", e);
}
return retval;
}
/** @throws NullPointerException if the specified key is null */
public boolean remove(Object key, Object value) {
Object val=get(key);
boolean removed=val != null && value != null && val.equals(value);
try {
MethodCall call=new MethodCall(REMOVE_IF_EQUALS, key, value);
disp.callRemoteMethods(null, call, call_options);
}
catch(Exception e) {
throw new RuntimeException("remove(" + key + ", " + value + ") failed", e);
}
return removed;
}
/** @throws NullPointerException if any of the arguments are null */
public boolean replace(K key, V oldValue, V newValue) {
Object val=get(key);
boolean replaced=val != null && oldValue != null && val.equals(oldValue);
try {
MethodCall call=new MethodCall(REPLACE_IF_EQUALS, key, oldValue, newValue);
disp.callRemoteMethods(null, call, call_options);
}
catch(Exception e) {
throw new RuntimeException("replace(" + key
+ ", "
+ oldValue
+ ", "
+ newValue
+ ") failed", e);
}
return replaced;
}
/**
*
*
* @return the previous value associated with the specified key, or
* null if there was no mapping for the key
* @throws NullPointerException
* if the specified key or value is null
*/
public V replace(K key, V value) {
V retval=get(key);
try {
MethodCall call=new MethodCall(REPLACE_IF_EXISTS, key, value);
disp.callRemoteMethods(null, call, call_options);
}
catch(Exception e) {
throw new RuntimeException("replace(" + key + ", " + value + ") failed", e);
}
return retval;
}
/*------------------------ Callbacks -----------------------*/
public V _put(K key, V value) {
V retval=map.put(key, value);
for(Notification notif:notifs)
notif.entrySet(key, value);
return retval;
}
public V _putIfAbsent(K key, V value) {
V retval=map.putIfAbsent(key, value);
for(Notification notif:notifs)
notif.entrySet(key, value);
return retval;
}
/**
* @see java.util.Map#putAll(java.util.Map)
*/
public void _putAll(Map map) {
if(map == null)
return;
// Calling the method below seems okay, but would result in ... deadlock !
// The reason is that Map.putAll() calls put(), which we override, which results in
// lock contention for the map.
// ---> super.putAll(m); <--- CULPRIT !!!@#$%$
// That said let's do it the stupid way:
for(Map.Entry entry:map.entrySet()) {
this.map.put(entry.getKey(), entry.getValue());
}
if(!map.isEmpty()) {
for(Notification notif:notifs)
notif.contentsSet(map);
}
}
public void _clear() {
map.clear();
notifs.forEach(Notification::contentsCleared);
}
public V _remove(K key) {
V retval=map.remove(key);
if(retval != null) {
for(Notification notif:notifs)
notif.entryRemoved(key);
}
return retval;
}
public boolean _remove(K key, V value) {
boolean removed=map.remove(key, value);
if(removed) {
for(Notification notif:notifs)
notif.entryRemoved(key);
}
return removed;
}
public boolean _replace(K key, V oldValue, V newValue) {
boolean replaced=map.replace(key, oldValue, newValue);
if(replaced) {
for(Notification notif:notifs)
notif.entrySet(key, newValue);
}
return replaced;
}
public V _replace(K key, V value) {
V retval=map.replace(key, value);
for(Notification notif:notifs)
notif.entrySet(key, value);
return retval;
}
/*----------------------------------------------------------*/
/*-------------------- State Exchange ----------------------*/
public void getState(OutputStream ostream) throws Exception {
HashMap copy=new HashMap<>();
for(Map.Entry entry:entrySet()) {
K key=entry.getKey();
V val=entry.getValue();
copy.put(key, val);
}
try(ObjectOutputStream oos=new ObjectOutputStream(new BufferedOutputStream(ostream, 1024))) {
oos.writeObject(copy);
}
}
public void setState(InputStream istream) throws Exception {
HashMap new_copy=null;
try(ObjectInputStream ois=new ObjectInputStream(istream)) {
new_copy=(HashMap)ois.readObject();
}
if(new_copy != null)
_putAll(new_copy);
log.debug("state received successfully");
}
/*------------------- Membership Changes ----------------------*/
public void viewAccepted(View new_view) {
List new_mbrs=new_view.getMembers();
if(new_mbrs != null) {
sendViewChangeNotifications(new_view, new_mbrs, new ArrayList<>(members)); // notifies observers (joined, left)
members.clear();
members.addAll(new_mbrs);
}
}
/**
* Called when a member is suspected
*/
public void suspect(Address suspected_mbr) {
;
}
/**
* Block sending and receiving of messages until ViewAccepted is called
*/
public void block() {}
void sendViewChangeNotifications(View view, List new_mbrs, List old_mbrs) {
if((notifs.isEmpty()) || (old_mbrs == null) || (new_mbrs == null))
return;
// 1. Compute set of members that joined: all that are in new_mbrs, but not in old_mbrs
List joined=new_mbrs.stream().filter(mbr -> !old_mbrs.contains(mbr)).collect(Collectors.toList());
// 2. Compute set of members that left: all that were in old_mbrs, but not in new_mbrs
List left=old_mbrs.stream().filter(mbr -> !new_mbrs.contains(mbr)).collect(Collectors.toList());
notifs.forEach( notif -> notif.viewChange(view, joined, left));
}
public void unblock() {}
/**
* Creates a synchronized facade for a ReplicatedMap. All methods which
* change state are invoked through a monitor. This is similar to
* {@link java.util.Collections.SynchronizedMap#synchronizedMap(Map)}, but also includes the replication
* methods (starting with an underscore).
*
* @param map
* @return
*/
public static ReplicatedMap synchronizedMap(ReplicatedMap map) {
return new SynchronizedReplicatedMap<>(map);
}
private static final class SynchronizedReplicatedMap
implements ReplicatedMap {
private final ReplicatedMap map;
private final Object mutex;
private SynchronizedReplicatedMap(ReplicatedMap map) {
this.map=map;
this.mutex=this;
}
public int size() {
synchronized(mutex) {
return map.size();
}
}
public boolean isEmpty() {
synchronized(mutex) {
return map.isEmpty();
}
}
public boolean containsKey(Object key) {
synchronized(mutex) {
return map.containsKey(key);
}
}
public boolean containsValue(Object value) {
synchronized(mutex) {
return map.containsValue(value);
}
}
public V get(Object key) {
synchronized(mutex) {
return map.get(key);
}
}
public V put(K key, V value) {
synchronized(mutex) {
return map.put(key, value);
}
}
public void putAll(Map m) {
synchronized(mutex) {
map.putAll(m);
}
}
public void clear() {
synchronized(mutex) {
map.clear();
}
}
public V putIfAbsent(K key, V value) {
synchronized(mutex) {
return map.putIfAbsent(key, value);
}
}
public boolean remove(Object key, Object value) {
synchronized(mutex) {
return map.remove(key, value);
}
}
public boolean replace(K key, V oldValue, V newValue) {
synchronized(mutex) {
return map.replace(key, oldValue, newValue);
}
}
public V replace(K key, V value) {
synchronized(mutex) {
return map.replace(key, value);
}
}
private Set keySet=null;
private Set> entrySet=null;
private Collection values=null;
public Set keySet() {
synchronized(mutex) {
if(keySet == null)
keySet=Collections.synchronizedSet(map.keySet());
return keySet;
}
}
public Collection values() {
synchronized(mutex) {
if(values == null)
values=Collections.synchronizedCollection(map.values());
return values;
}
}
public Set> entrySet() {
synchronized(mutex) {
if(entrySet == null)
entrySet=Collections.synchronizedSet(map.entrySet());
return entrySet;
}
}
public V remove(Object key) {
synchronized(mutex) {
return map.remove(key);
}
}
public V _put(K key, V value) {
synchronized(mutex) {
return map._put(key, value);
}
}
public void _putAll(Map map) {
synchronized(mutex) {
this.map._putAll(map);
}
}
public void _clear() {
synchronized(mutex) {
map._clear();
}
}
public V _remove(K key) {
synchronized(mutex) {
return map._remove(key);
}
}
public V _putIfAbsent(K key, V value) {
synchronized(mutex) {
return map._putIfAbsent(key, value);
}
}
public boolean _remove(K key, V value) {
synchronized(mutex) {
return map._remove(key, value);
}
}
public boolean _replace(K key, V oldValue, V newValue) {
synchronized(mutex) {
return map._replace(key, oldValue, newValue);
}
}
public V _replace(K key, V value) {
synchronized(mutex) {
return map._replace(key, value);
}
}
public String toString() {
synchronized(mutex) {
return map.toString();
}
}
public int hashCode() {
synchronized(mutex) {
return map.hashCode();
}
}
public boolean equals(Object obj) {
synchronized(mutex) {
return map.equals(obj);
}
}
}
// Delegate Methods
@Override
public boolean containsKey(Object key) {
return map.containsKey(key);
}
@Override
public boolean containsValue(Object value) {
return map.containsValue(value);
}
@Override
public Set> entrySet() {
return map.entrySet();
}
@Override
public V get(Object key) {
return map.get(key);
}
@Override
public Set keySet() {
return map.keySet();
}
@Override
public int size() {
return map.size();
}
@Override
public Collection values() {
return map.values();
}
}