CacheStatus.java

/*
 Licensed to Diennea S.r.l. under one
 or more contributor license agreements. See the NOTICE file
 distributed with this work for additional information
 regarding copyright ownership. Diennea S.r.l. licenses this file
 to you 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 blazingcache.server;

import blazingcache.utils.RawString;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import java.util.logging.Level;
import java.util.logging.Logger;
import java.util.stream.Collectors;

/**
 * Gestione listeners
 *
 * @author enrico.olivelli
 */
public class CacheStatus {

    private static final Logger LOGGER = Logger.getLogger(CacheStatus.class.getName());

    private final Map<RawString, Set<String>> clientsForKey = new HashMap<>();
    private final Map<String, Set<RawString>> keysForClient = new HashMap<>();
    private final Map<RawString, Long> entryExpireTime = new HashMap<>();
    // clientId -> id of the connection that last registered a key for it. Used to make
    // the disconnect cleanup connection-identity aware: a late cleanup of a dead
    // connection must not wipe the registrations a new connection of the same client made
    // after reconnecting. Guarded by {@link #lock}.
    private final Map<String, Long> connectionForClient = new HashMap<>();
    private final ReentrantReadWriteLock lock = new ReentrantReadWriteLock(true);

    @Override
    public String toString() {
        lock.readLock().lock();
        try {
            return "CacheListeners{" + "clientsForKey=" + clientsForKey + ", keysForClient=" + keysForClient + '}';
        } finally {
            lock.readLock().unlock();
        }
    }

    public void registerKeyForClient(RawString key, String client, long connectionId, long expiretime) {
        LOGGER.log(Level.FINEST, "registerKeyForClient key={0} client={1} connection={2}", new Object[]{key, client, connectionId});
        lock.writeLock().lock();
        try {
            Set<String> clients = clientsForKey.get(key);
            if (clients == null) {
                clients = new HashSet<>();
                clientsForKey.put(key, clients);
            }
            clients.add(client);

            Set<RawString> keys = keysForClient.get(client);
            if (keys == null) {
                keys = new HashSet<>();
                keysForClient.put(client, keys);
            }
            keys.add(key);
            // record which connection owns this client's registrations now; a later
            // disconnect of an older connection will not wipe them (see removeClientListeners).
            // Advance the owner FORWARD-ONLY: connection ids are monotonic, so a late
            // registration arriving from an older (already-superseded) connection - e.g. a
            // delayed fetch reply, or a put/load that was queued behind a held lock - must
            // not move ownership back to that dead connection and defeat the guard.
            connectionForClient.merge(client, connectionId, Math::max);
            if (expiretime > 0) {
                entryExpireTime.put(key, expiretime);
            } else {
                entryExpireTime.remove(key);
            }
        } finally {
            lock.writeLock().unlock();
        }
    }

    public Set<String> getClientsForKey(RawString key) {
        lock.readLock().lock();
        try {
            Set<String> clients = clientsForKey.get(key);
            if (clients == null) {
                return Collections.emptySet();
            } else {
                return new HashSet<>(clients);
            }
        } finally {
            lock.readLock().unlock();
        }
    }

    public int getTotalEntryCount() {
        lock.readLock().lock();
        try {
            return clientsForKey.size();
        } finally {
            lock.readLock().unlock();
        }
    }

    public Set<RawString> getKeys() {
        lock.readLock().lock();
        try {
            return new HashSet<>(clientsForKey.keySet());
        } finally {
            lock.readLock().unlock();
        }
    }

    public List<RawString> getKeysForClient(String client) {
        lock.readLock().lock();
        try {
            Set<RawString> keys = keysForClient.get(client);
            if (keys == null) {
                return Collections.emptyList();
            } else {
                return new ArrayList<>(keys);
            }
        } finally {
            lock.readLock().unlock();
        }
    }

    public void removeKeyForClient(RawString key, String client) {
        LOGGER.log(Level.FINEST, "removeKeyForClient key={0} client={1}", new Object[]{key, client});
        lock.writeLock().lock();
        try {
            Set<String> clients = clientsForKey.get(key);
            if (clients != null) {
                clients.remove(client);
                if (clients.isEmpty()) {
                    clientsForKey.remove(key);
                    entryExpireTime.remove(key);
                }
            }

            Set<RawString> keys = keysForClient.get(client);
            if (keys != null) {
                keys.remove(key);
                if (keys.isEmpty()) {
                    keysForClient.remove(client);
                    connectionForClient.remove(client);
                }
            }
        } finally {
            lock.writeLock().unlock();
        }
        LOGGER.log(Level.FINEST, "removeKeyForClient key={0} client={1} -> keysForClient {2}", new Object[]{key, client, keysForClient});
    }

    /**
     * Removes the key listeners of a disconnected connection, but ONLY if that connection
     * is still the one that owns the client's registrations. If a newer connection of the
     * same client (a reconnect) has registered in the meantime, this is a no-op so its
     * fresh registrations are not wiped — the check and the removal happen atomically
     * under the write lock, together with the concurrent registerKeyForClient, so there
     * is no time-of-check/time-of-use gap. The dead connection's now-stale registrations
     * are then left as benign, self-healing phantoms.
     *
     * @return the number of listeners removed. Application locks are released separately
     * by the {@link KeyedScheduler}, which owns the lock lifecycle.
     */
    int removeClientListeners(String clientId, long connectionId) {
        AtomicInteger count = new AtomicInteger();
        lock.writeLock().lock();
        try {
            Long owner = connectionForClient.get(clientId);
            if (owner != null && owner != connectionId) {
                // a newer connection of this client already took over its registrations
                return 0;
            }
            Set<RawString> keys = keysForClient.get(clientId);
            if (keys != null) {
                keys.forEach((key) -> {
                    count.incrementAndGet();
                    Set<String> clients = clientsForKey.get(key);
                    if (clients != null) {
                        clients.remove(clientId);
                        if (clients.isEmpty()) {
                            clientsForKey.remove(key);
                            entryExpireTime.remove(key);
                        }
                    }
                });
            }
            keysForClient.remove(clientId);
            connectionForClient.remove(clientId);
        } finally {
            lock.writeLock().unlock();
        }
        return count.get();
    }

    Set<String> getAllClientsWithListener() {
        lock.readLock().lock();
        try {
            Set<String> clients = keysForClient.keySet();
            return new HashSet<>(clients);
        } finally {
            lock.readLock().unlock();
        }
    }

    List<RawString> selectExpiredEntries(long now, int max) {
        lock.readLock().lock();
        try {
            return entryExpireTime.entrySet().stream().filter(entry -> entry.getValue() < now)
                .map(entry -> entry.getKey()).limit(max).collect(Collectors.toList());
        } finally {
            lock.readLock().unlock();
        }
    }

    void touchKeyFromClient(RawString key, String clientId, long expiretime) {
        LOGGER.log(Level.FINEST, "touchKeyFromClient key={0} client={1} expiretime={2}", new Object[]{key, clientId, expiretime});
        lock.writeLock().lock();
        try {
            if (clientsForKey.containsKey(key)) {
                if (expiretime > 0) {
                    entryExpireTime.put(key, expiretime);
                } else {
                    entryExpireTime.remove(key);
                }
            }
        } finally {
            lock.writeLock().unlock();
        }
    }
}