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// Copyright (c) 2006  Dustin Sallings 

package net.spy.memcached;

import java.io.IOException;
import java.net.ConnectException;
import java.net.InetSocketAddress;
import java.net.SocketAddress;
import java.net.SocketException;
import java.nio.ByteBuffer;
import java.nio.channels.ClosedChannelException;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.SocketChannel;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashSet;
import java.util.IdentityHashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.SortedMap;
import java.util.TreeMap;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.CountDownLatch;

import net.spy.memcached.compat.SpyObject;
import net.spy.memcached.compat.log.LoggerFactory;
import net.spy.memcached.ops.KeyedOperation;
import net.spy.memcached.ops.Operation;
import net.spy.memcached.ops.OperationException;
import net.spy.memcached.ops.OperationState;
import net.spy.memcached.ops.TapOperation;
import net.spy.memcached.ops.VBucketAware;
import net.spy.memcached.protocol.binary.TapAckOperationImpl;
import net.spy.memcached.vbucket.VBucketNodeLocator;
import net.spy.memcached.vbucket.Reconfigurable;
import net.spy.memcached.vbucket.config.Bucket;

/**
 * Connection to a cluster of memcached servers.
 */
public final class MemcachedConnection extends SpyObject implements Reconfigurable {

	// The number of empty selects we'll allow before assuming we may have
	// missed one and should check the current selectors.  This generally
	// indicates a bug, but we'll check it nonetheless.
	private static final int DOUBLE_CHECK_EMPTY = 256;
	// The number of empty selects we'll allow before blowing up.  It's too
	// easy to write a bug that causes it to loop uncontrollably.  This helps
	// find those bugs and often works around them.
	private static final int EXCESSIVE_EMPTY = 0x1000000;

	private volatile boolean shutDown=false;
	// If true, optimization will collapse multiple sequential get ops
	private final boolean shouldOptimize;
	private Selector selector=null;
	private final NodeLocator locator;
	private final FailureMode failureMode;
	// maximum amount of time to wait between reconnect attempts
	private final long maxDelay;
	private int emptySelects=0;
	private final int bufSize;
	private final ConnectionFactory connectionFactory;
	// AddedQueue is used to track the QueueAttachments for which operations
	// have recently been queued.
	private final ConcurrentLinkedQueue addedQueue;
	// reconnectQueue contains the attachments that need to be reconnected
	// The key is the time at which they are eligible for reconnect
	private final SortedMap reconnectQueue;

	private final Collection connObservers =
		new ConcurrentLinkedQueue();
	private final OperationFactory opFact;
	private final int timeoutExceptionThreshold;
        private final Collection retryOps;
	private final ConcurrentLinkedQueue nodesToShutdown;

	/**
	 * Construct a memcached connection.
	 *
	 * @param bufSize the size of the buffer used for reading from the server
	 * @param f the factory that will provide an operation queue
	 * @param a the addresses of the servers to connect to
	 *
	 * @throws IOException if a connection attempt fails early
	 */
	public MemcachedConnection(int bufSize, ConnectionFactory f,
			List a, Collection obs,
			FailureMode fm, OperationFactory opfactory)
		throws IOException {
		connObservers.addAll(obs);
		reconnectQueue=new TreeMap();
		addedQueue=new ConcurrentLinkedQueue();
		failureMode = fm;
		shouldOptimize = f.shouldOptimize();
		maxDelay = f.getMaxReconnectDelay();
		opFact = opfactory;
		timeoutExceptionThreshold = f.getTimeoutExceptionThreshold();
		selector=Selector.open();
		retryOps = new ArrayList();
		nodesToShutdown = new ConcurrentLinkedQueue();
		this.bufSize = bufSize;
		this.connectionFactory = f;
		List connections = createConnections(a);
		locator=f.createLocator(connections);
		}

	private List createConnections(final Collection a)
		throws IOException {
		List connections=new ArrayList(a.size());
		for(SocketAddress sa : a) {
			SocketChannel ch=SocketChannel.open();
			ch.configureBlocking(false);
			MemcachedNode qa=this.connectionFactory.createMemcachedNode(sa, ch, bufSize);
			int ops=0;
			ch.socket().setTcpNoDelay(!this.connectionFactory.useNagleAlgorithm());
			// Initially I had attempted to skirt this by queueing every
			// connect, but it considerably slowed down start time.
			try {
				if(ch.connect(sa)) {
					getLogger().info("Connected to %s immediately", qa);
					connected(qa);
				} else {
					getLogger().info("Added %s to connect queue", qa);
					ops=SelectionKey.OP_CONNECT;
				}
				qa.setSk(ch.register(selector, ops, qa));
				assert ch.isConnected()
					|| qa.getSk().interestOps() == SelectionKey.OP_CONNECT
					: "Not connected, and not wanting to connect";
			} catch(SocketException e) {
				getLogger().warn("Socket error on initial connect", e);
				queueReconnect(qa);
			}
			connections.add(qa);
		}
		return connections;
	}

	public void reconfigure(Bucket bucket) {
		try {
			// get a new collection of addresses from the received config
			List servers = bucket.getConfig().getServers();
			HashSet newServerAddresses = new HashSet();
			ArrayList newServers = new ArrayList();
			for (String server : servers) {
				int finalColon = server.lastIndexOf(':');
				if (finalColon < 1) {
					throw new IllegalArgumentException("Invalid server ``"
					+ server + "'' in vbucket's server list");
				}
				String hostPart = server.substring(0, finalColon);
				String portNum = server.substring(finalColon + 1);

				InetSocketAddress address = new InetSocketAddress(hostPart,
				Integer.parseInt(portNum));
				// add parsed address to our collections
				newServerAddresses.add(address);
				newServers.add(address);

			}

			// split current nodes to "odd nodes" and "stay nodes"
			ArrayList oddNodes = new ArrayList();
			ArrayList stayNodes = new ArrayList();
			ArrayList stayServers = new ArrayList();
			for (MemcachedNode current : locator.getAll()) {
				if (newServerAddresses.contains(current.getSocketAddress())) {
					stayNodes.add(current);
					stayServers.add((InetSocketAddress) current.getSocketAddress());
				} else {
					oddNodes.add(current);
				}
			}

			// prepare a collection of addresses for new nodes
			newServers.removeAll(stayServers);

			// create a collection of new nodes
			List newNodes = createConnections(newServers);

			// merge stay nodes with new nodes
			List mergedNodes = new ArrayList();
			mergedNodes.addAll(stayNodes);
			mergedNodes.addAll(newNodes);

			// call update locator with new nodes list and vbucket config
			locator.updateLocator(mergedNodes, bucket.getConfig());

			// schedule shutdown for the oddNodes
			nodesToShutdown.addAll(oddNodes);
		} catch (IOException e) {
		    getLogger().error("Connection reconfiguration failed", e);
		}
	}

	private boolean selectorsMakeSense() {
		for(MemcachedNode qa : locator.getAll()) {
			if(qa.getSk() != null && qa.getSk().isValid()) {
				if(qa.getChannel().isConnected()) {
					int sops=qa.getSk().interestOps();
					int expected=0;
					if(qa.hasReadOp()) {
						expected |= SelectionKey.OP_READ;
					}
					if(qa.hasWriteOp()) {
						expected |= SelectionKey.OP_WRITE;
					}
					if(qa.getBytesRemainingToWrite() > 0) {
						expected |= SelectionKey.OP_WRITE;
					}
					assert sops == expected : "Invalid ops:  "
						+ qa + ", expected " + expected + ", got " + sops;
				} else {
					int sops=qa.getSk().interestOps();
					assert sops == SelectionKey.OP_CONNECT
					: "Not connected, and not watching for connect: "
						+ sops;
				}
			}
		}
		getLogger().debug("Checked the selectors.");
		return true;
	}

	/**
	 * MemcachedClient calls this method to handle IO over the connections.
	 */
	public void handleIO() throws IOException {
		if(shutDown) {
			throw new IOException("No IO while shut down");
		}

		// Deal with all of the stuff that's been added, but may not be marked
		// writable.
		handleInputQueue();
		getLogger().debug("Done dealing with queue.");

		long delay=0;
		if(!reconnectQueue.isEmpty()) {
			long now=System.currentTimeMillis();
			long then=reconnectQueue.firstKey();
			delay=Math.max(then-now, 1);
		}
		getLogger().debug("Selecting with delay of %sms", delay);
		assert selectorsMakeSense() : "Selectors don't make sense.";
		int selected=selector.select(delay);
		Set selectedKeys=selector.selectedKeys();

		if(selectedKeys.isEmpty() && !shutDown) {
			getLogger().debug("No selectors ready, interrupted: "
					+ Thread.interrupted());
			if(++emptySelects > DOUBLE_CHECK_EMPTY) {
				for(SelectionKey sk : selector.keys()) {
					getLogger().info("%s has %s, interested in %s",
							sk, sk.readyOps(), sk.interestOps());
					if(sk.readyOps() != 0) {
						getLogger().info("%s has a ready op, handling IO", sk);
						handleIO(sk);
					} else {
						lostConnection((MemcachedNode)sk.attachment());
					}
				}
				assert emptySelects < EXCESSIVE_EMPTY
					: "Too many empty selects";
			}
		} else {
			getLogger().debug("Selected %d, selected %d keys",
					selected, selectedKeys.size());
			emptySelects=0;

			for(SelectionKey sk : selectedKeys) {
				handleIO(sk);
			}

			selectedKeys.clear();
		}


		// see if any connections blew up with large number of timeouts
		for(SelectionKey sk : selector.keys()) {
			MemcachedNode mn = (MemcachedNode)sk.attachment();
			if (mn.getContinuousTimeout() > timeoutExceptionThreshold)
			{
				getLogger().warn("%s exceeded continuous timeout threshold", sk);
				lostConnection(mn);
			}
		}

		if(!shutDown && !reconnectQueue.isEmpty()) {
			attemptReconnects();
		}
        // rehash operations that in retry state
        redistributeOperations(retryOps);
        retryOps.clear();

        // try to shutdown odd nodes
        for (MemcachedNode qa : nodesToShutdown) {
            if (!addedQueue.contains(qa)) {
                nodesToShutdown.remove(qa);
                Collection notCompletedOperations = qa.destroyInputQueue();
                if (qa.getChannel() != null) {
                    qa.getChannel().close();
                    qa.setSk(null);
                    if (qa.getBytesRemainingToWrite() > 0) {
                        getLogger().warn(
                                "Shut down with %d bytes remaining to write",
                                qa.getBytesRemainingToWrite());
                    }
                    getLogger().debug("Shut down channel %s", qa.getChannel());
                }
                redistributeOperations(notCompletedOperations);
            }
        }
	}

	// Handle any requests that have been made against the client.
	private void handleInputQueue() {
		if(!addedQueue.isEmpty()) {
			getLogger().debug("Handling queue");
			// If there's stuff in the added queue.  Try to process it.
			Collection toAdd=new HashSet();
			// Transfer the queue into a hashset.  There are very likely more
			// additions than there are nodes.
			Collection todo=new HashSet();
			MemcachedNode qaNode = null;
			while ((qaNode = addedQueue.poll()) != null) {
				todo.add(qaNode);
			}

			// Now process the queue.
			for(MemcachedNode qa : todo) {
				boolean readyForIO=false;
				if(qa.isActive()) {
					if(qa.getCurrentWriteOp() != null) {
						readyForIO=true;
						getLogger().debug("Handling queued write %s", qa);
					}
				} else {
					toAdd.add(qa);
				}
				qa.copyInputQueue();
				if(readyForIO) {
					try {
						if(qa.getWbuf().hasRemaining()) {
							handleWrites(qa.getSk(), qa);
						}
					} catch(IOException e) {
						getLogger().warn("Exception handling write", e);
						lostConnection(qa);
					}
				}
				qa.fixupOps();
			}
			addedQueue.addAll(toAdd);
		}
	}

	/**
	 * Add a connection observer.
	 *
	 * @return whether the observer was successfully added
	 */
	public boolean addObserver(ConnectionObserver obs) {
		return connObservers.add(obs);
	}

	/**
	 * Remove a connection observer.
	 *
	 * @return true if the observer existed and now doesn't
	 */
	public boolean removeObserver(ConnectionObserver obs) {
		return connObservers.remove(obs);
	}

	private void connected(MemcachedNode qa) {
		assert qa.getChannel().isConnected() : "Not connected.";
		int rt = qa.getReconnectCount();
		qa.connected();
		for(ConnectionObserver observer : connObservers) {
			observer.connectionEstablished(qa.getSocketAddress(), rt);
		}
	}

	private void lostConnection(MemcachedNode qa) {
		queueReconnect(qa);
		for(ConnectionObserver observer : connObservers) {
			observer.connectionLost(qa.getSocketAddress());
		}
	}

	// Handle IO for a specific selector.  Any IOException will cause a
	// reconnect
	private void handleIO(SelectionKey sk) {
		MemcachedNode qa=(MemcachedNode)sk.attachment();
		try {
			getLogger().debug(
					"Handling IO for:  %s (r=%s, w=%s, c=%s, op=%s)",
					sk, sk.isReadable(), sk.isWritable(),
					sk.isConnectable(), sk.attachment());
			if(sk.isConnectable()) {
				getLogger().info("Connection state changed for %s", sk);
				final SocketChannel channel=qa.getChannel();
				if(channel.finishConnect()) {
					connected(qa);
					addedQueue.offer(qa);
					if(qa.getWbuf().hasRemaining()) {
						handleWrites(sk, qa);
					}
				} else {
					assert !channel.isConnected() : "connected";
				}
			} else {
				if(sk.isValid() && sk.isReadable()) {
					handleReads(sk, qa);
				}
				if(sk.isValid() && sk.isWritable()) {
					handleWrites(sk, qa);
				}
			}
		} catch(ClosedChannelException e) {
			// Note, not all channel closes end up here
			if(!shutDown) {
				getLogger().info("Closed channel and not shutting down.  "
					+ "Queueing reconnect on %s", qa, e);
				lostConnection(qa);
			}
		} catch(ConnectException e) {
			// Failures to establish a connection should attempt a reconnect
			// without signaling the observers.
			getLogger().info("Reconnecting due to failure to connect to %s",
					qa, e);
			queueReconnect(qa);
		} catch (OperationException e) {
			qa.setupForAuth(); // noop if !shouldAuth
			getLogger().info("Reconnection due to exception " +
				"handling a memcached operation on %s.  " +
				"This may be due to an authentication failure.", qa, e);
			lostConnection(qa);
		} catch(Exception e) {
			// Any particular error processing an item should simply
			// cause us to reconnect to the server.
			//
			// One cause is just network oddness or servers
			// restarting, which lead here with IOException

			qa.setupForAuth(); // noop if !shouldAuth
			getLogger().info("Reconnecting due to exception on %s", qa, e);
			lostConnection(qa);
		}
		qa.fixupOps();
	}

	private void handleWrites(SelectionKey sk, MemcachedNode qa)
		throws IOException {
		qa.fillWriteBuffer(shouldOptimize);
		boolean canWriteMore=qa.getBytesRemainingToWrite() > 0;
		while(canWriteMore) {
			int wrote=qa.writeSome();
			qa.fillWriteBuffer(shouldOptimize);
			canWriteMore = wrote > 0 && qa.getBytesRemainingToWrite() > 0;
		}
	}

	private void handleReads(SelectionKey sk, MemcachedNode qa)
		throws IOException {
		Operation currentOp = qa.getCurrentReadOp();
		// If it's a tap ack there is no response
		if (currentOp instanceof TapAckOperationImpl) {
			qa.removeCurrentReadOp();
			return;
		}
		ByteBuffer rbuf=qa.getRbuf();
		final SocketChannel channel = qa.getChannel();
		int read=channel.read(rbuf);
		if (read < 0) {
			if (currentOp instanceof TapOperation) {
				// If were doing tap then we won't throw an exception
				currentOp.getCallback().complete();
				((TapOperation)currentOp).streamClosed(OperationState.COMPLETE);
				getLogger().debug(
						"Completed read op: %s and giving the next %d bytes",
						currentOp, rbuf.remaining());
				Operation op=qa.removeCurrentReadOp();
				assert op == currentOp : "Expected to pop " + currentOp + " got " + op;
				currentOp=qa.getCurrentReadOp();
			} else {
			    // our model is to keep the connection alive for future ops
			    // so we'll queue a reconnect if disconnected via an IOException
			    throw new IOException("Disconnected unexpected, will reconnect.");
			}
		}
		while(read > 0) {
			getLogger().debug("Read %d bytes", read);
			rbuf.flip();
			while(rbuf.remaining() > 0) {
				if(currentOp == null) {
					throw new IllegalStateException("No read operation.");
				}
				synchronized(currentOp) {
					currentOp.readFromBuffer(rbuf);
					if(currentOp.getState() == OperationState.COMPLETE) {
						getLogger().debug(
								"Completed read op: %s and giving the next %d bytes",
								currentOp, rbuf.remaining());
						Operation op=qa.removeCurrentReadOp();
						assert op == currentOp
						: "Expected to pop " + currentOp + " got " + op;
					} else if (currentOp.getState() == OperationState.RETRY) {
						getLogger().warn(
								"Reschedule read op due to NOT_MY_VBUCKET error: %s ",
								currentOp);
						((VBucketAware) currentOp).addNotMyVbucketNode(currentOp.getHandlingNode());
						Operation op=qa.removeCurrentReadOp();
						assert op == currentOp
						: "Expected to pop " + currentOp + " got " + op;
						retryOps.add(currentOp);
					}
				}
				currentOp=qa.getCurrentReadOp();
			}
			rbuf.clear();
			read=channel.read(rbuf);
		}
	}

	// Make a debug string out of the given buffer's values
	static String dbgBuffer(ByteBuffer b, int size) {
		StringBuilder sb=new StringBuilder();
		byte[] bytes=b.array();
		for(int i=0; i ops) {
		for(Operation op : ops) {
			op.cancel();
		}
	}

	private void redistributeOperations(Collection ops) {
		for(Operation op : ops) {
			if (op.isCancelled() || op.isTimedOut()) {
				continue;
			}
			if(op instanceof KeyedOperation) {
				KeyedOperation ko = (KeyedOperation)op;
				int added = 0;
				for(String k : ko.getKeys()) {
					for(Operation newop : opFact.clone(ko)) {
						addOperation(k, newop);
						added++;
					}
				}
				assert added > 0
					: "Didn't add any new operations when redistributing";
			} else {
				// Cancel things that don't have definite targets.
				op.cancel();
			}
		}
	}

	private void attemptReconnects() throws IOException {
		final long now=System.currentTimeMillis();
		final Map seen=
			new IdentityHashMap();
		final List rereQueue=new ArrayList();
		SocketChannel ch = null;
		for(Iterator i=
				reconnectQueue.headMap(now).values().iterator(); i.hasNext();) {
			final MemcachedNode qa=i.next();
			i.remove();
			try {
				if(!seen.containsKey(qa)) {
					seen.put(qa, Boolean.TRUE);
					getLogger().info("Reconnecting %s", qa);
					ch=SocketChannel.open();
					ch.configureBlocking(false);
					int ops=0;
					if(ch.connect(qa.getSocketAddress())) {
						getLogger().info("Immediately reconnected to %s", qa);
						assert ch.isConnected();
					} else {
						ops=SelectionKey.OP_CONNECT;
					}
					qa.registerChannel(ch, ch.register(selector, ops, qa));
					assert qa.getChannel() == ch : "Channel was lost.";
				} else {
					getLogger().debug(
						"Skipping duplicate reconnect request for %s", qa);
				}
			} catch(SocketException e) {
				getLogger().warn("Error on reconnect", e);
				rereQueue.add(qa);
			}
			catch (Exception e) {
                getLogger().error("Exception on reconnect, lost node %s", qa, e);
            } finally {
                //it's possible that above code will leak file descriptors under abnormal
                //conditions (when ch.open() fails and throws IOException.
                //always close non connected channel
                if (ch != null && !ch.isConnected()
                        && !ch.isConnectionPending()) {
                    try {
                        ch.close();
                    } catch (IOException x) {
                        getLogger().error("Exception closing channel: %s", qa, x);
                    }
                }
            }
		}
		// Requeue any fast-failed connects.
		for(MemcachedNode n : rereQueue) {
			queueReconnect(n);
		}
	}

	/**
	 * Get the node locator used by this connection.
	 */
	NodeLocator getLocator() {
		return locator;
	}

	/**
	 * Add an operation to the given connection.
	 *
	 * @param key the key the operation is operating upon
	 * @param o the operation
	 */
	public void addOperation(final String key, final Operation o) {
		MemcachedNode placeIn=null;
		MemcachedNode primary = locator.getPrimary(key);
		if(primary.isActive() || failureMode == FailureMode.Retry) {
			placeIn=primary;
		} else if(failureMode == FailureMode.Cancel) {
			o.cancel();
		} else {
			// Look for another node in sequence that is ready.
			for(Iterator i=locator.getSequence(key);
				placeIn == null && i.hasNext(); ) {
				MemcachedNode n=i.next();
				if(n.isActive()) {
					placeIn=n;
				}
			}
			// If we didn't find an active node, queue it in the primary node
			// and wait for it to come back online.
			if(placeIn == null) {
				placeIn = primary;
				this.getLogger().warn("Could not redistribute " +
					"to another node, retrying primary node for %s.", key);
			}
		}

		assert o.isCancelled() || placeIn != null
			: "No node found for key " + key;
		if(placeIn != null) {
			// add the vbucketIndex to the operation
			if (locator instanceof VBucketNodeLocator) {
				VBucketNodeLocator vbucketLocator = (VBucketNodeLocator) locator;
				short vbucketIndex = (short)vbucketLocator.getVBucketIndex(key);
				if (o instanceof VBucketAware) {
					VBucketAware vbucketAwareOp = (VBucketAware) o;
					vbucketAwareOp.setVBucket(key, vbucketIndex);
					if (!vbucketAwareOp.getNotMyVbucketNodes().isEmpty()) {
						MemcachedNode alternative = vbucketLocator.
						getAlternative(key, vbucketAwareOp.getNotMyVbucketNodes());
							if (alternative != null) {
								placeIn = alternative;
							}
					}
				}
			}
			addOperation(placeIn, o);
			} else {
				assert o.isCancelled() : "No node found for "
					+ key + " (and not immediately cancelled)";
			}
	}

	public void insertOperation(final MemcachedNode node, final Operation o) {
		o.setHandlingNode(node);
		o.initialize();
		node.insertOp(o);
		addedQueue.offer(node);
		Selector s=selector.wakeup();
		assert s == selector : "Wakeup returned the wrong selector.";
		getLogger().debug("Added %s to %s", o, node);
	}

	private void addOperation(final MemcachedNode node, final Operation o) {
		o.setHandlingNode(node);
		o.initialize();
		node.addOp(o);
		addedQueue.offer(node);
		Selector s=selector.wakeup();
		assert s == selector : "Wakeup returned the wrong selector.";
		getLogger().debug("Added %s to %s", o, node);
	}

	public void addOperations(final Map ops) {

		for(Map.Entry me : ops.entrySet()) {
			final MemcachedNode node=me.getKey();
			Operation o=me.getValue();
			// add the vbucketIndex to the operation
			if (locator instanceof VBucketNodeLocator) {
				if (o instanceof KeyedOperation && o instanceof VBucketAware) {
					Collection keys = ((KeyedOperation)o).getKeys();
					VBucketNodeLocator vbucketLocator = (VBucketNodeLocator) locator;
					for (String key : keys) {
						short vbucketIndex = (short)vbucketLocator.getVBucketIndex(key);
						VBucketAware vbucketAwareOp = (VBucketAware) o;
						vbucketAwareOp.setVBucket(key, vbucketIndex);
					}
				}
			}
			o.setHandlingNode(node);
			o.initialize();
			node.addOp(o);
			addedQueue.offer(node);
		}
		Selector s=selector.wakeup();
		assert s == selector : "Wakeup returned the wrong selector.";
	}

	/**
	 * Broadcast an operation to all nodes.
	 */
	public CountDownLatch broadcastOperation(BroadcastOpFactory of) {
		return broadcastOperation(of, locator.getAll());
	}

	/**
	 * Broadcast an operation to a specific collection of nodes.
	 */
	public CountDownLatch broadcastOperation(final BroadcastOpFactory of,
			Collection nodes) {
		final CountDownLatch latch=new CountDownLatch(locator.getAll().size());
		for(MemcachedNode node : nodes) {
			Operation op = of.newOp(node, latch);
			op.initialize();
			node.addOp(op);
			op.setHandlingNode(node);
			addedQueue.offer(node);
		}
		Selector s=selector.wakeup();
		assert s == selector : "Wakeup returned the wrong selector.";
		return latch;
	}

	/**
	 * Shut down all of the connections.
	 */
	public void shutdown() throws IOException {
		shutDown=true;
		Selector s=selector.wakeup();
		assert s == selector : "Wakeup returned the wrong selector.";
		for(MemcachedNode qa : locator.getAll()) {
			if(qa.getChannel() != null) {
				qa.getChannel().close();
				qa.setSk(null);
				if(qa.getBytesRemainingToWrite() > 0) {
					getLogger().warn(
						"Shut down with %d bytes remaining to write",
							qa.getBytesRemainingToWrite());
				}
				getLogger().debug("Shut down channel %s", qa.getChannel());
			}
		}
		selector.close();
		getLogger().debug("Shut down selector %s", selector);
	}

	@Override
	public String toString() {
		StringBuilder sb=new StringBuilder();
		sb.append("{MemcachedConnection to");
		for(MemcachedNode qa : locator.getAll()) {
			sb.append(" ");
			sb.append(qa.getSocketAddress());
		}
		sb.append("}");
		return sb.toString();
	}

    /**
     * helper method: increase timeout count on node attached to this op
     *
     * @param op
     */
    public static void opTimedOut(Operation op) {
        MemcachedConnection.setTimeout(op, true);
    }

    /**
     * helper method: reset timeout counter
     *
     * @param op
     */
    public static void opSucceeded(Operation op) {
        MemcachedConnection.setTimeout(op, false);
    }

    /**
     * helper method: do some error checking and set timeout boolean
     *
     * @param op
     * @param isTimeout
     */
    private static void setTimeout(Operation op, boolean isTimeout) {
        try {
            if (op == null || op.isTimedOutUnsent()) {
                return; // op may be null in some cases, e.g. flush
            }
            MemcachedNode node = op.getHandlingNode();
            if (node == null) {
                LoggerFactory.getLogger(MemcachedConnection.class).warn("handling node for operation is not set");
            }
            else {
                node.setContinuousTimeout(isTimeout);
            }
        } catch (Exception e) {
            LoggerFactory.getLogger(MemcachedConnection.class).error(e.getMessage());
        }
    }

}




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