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/*
* Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
* or more contributor license agreements. Licensed under the Elastic License
* 2.0 and the Server Side Public License, v 1; you may not use this file except
* in compliance with, at your election, the Elastic License 2.0 or the Server
* Side Public License, v 1.
*/
package org.elasticsearch.transport;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.elasticsearch.action.ActionListener;
import org.elasticsearch.action.support.ContextPreservingActionListener;
import org.elasticsearch.cluster.node.DiscoveryNode;
import org.elasticsearch.common.settings.Settings;
import org.elasticsearch.common.util.concurrent.ConcurrentCollections;
import org.elasticsearch.common.util.concurrent.ListenableFuture;
import org.elasticsearch.common.util.concurrent.RunOnce;
import org.elasticsearch.common.util.concurrent.ThreadContext;
import org.elasticsearch.core.AbstractRefCounted;
import org.elasticsearch.core.Nullable;
import org.elasticsearch.core.RefCounted;
import org.elasticsearch.core.Releasable;
import org.elasticsearch.core.Releasables;
import org.elasticsearch.core.internal.io.IOUtils;
import java.util.Collections;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.atomic.AtomicBoolean;
/**
* This class manages node connections within a cluster. The connection is opened by the underlying transport.
* Once the connection is opened, this class manages the connection. This includes closing the connection when
* the connection manager is closed.
*/
public class ClusterConnectionManager implements ConnectionManager {
private static final Logger logger = LogManager.getLogger(ClusterConnectionManager.class);
private final ConcurrentMap connectedNodes = ConcurrentCollections.newConcurrentMap();
private final ConcurrentMap> pendingConnections = ConcurrentCollections
.newConcurrentMap();
private final AbstractRefCounted connectingRefCounter = AbstractRefCounted.of(this::pendingConnectionsComplete);
private final Transport transport;
private final ThreadContext threadContext;
private final ConnectionProfile defaultProfile;
private final AtomicBoolean closing = new AtomicBoolean(false);
private final CountDownLatch closeLatch = new CountDownLatch(1);
private final DelegatingNodeConnectionListener connectionListener = new DelegatingNodeConnectionListener();
public ClusterConnectionManager(Settings settings, Transport transport, ThreadContext threadContext) {
this(ConnectionProfile.buildDefaultConnectionProfile(settings), transport, threadContext);
}
public ClusterConnectionManager(ConnectionProfile connectionProfile, Transport transport, ThreadContext threadContext) {
this.transport = transport;
this.defaultProfile = connectionProfile;
this.threadContext = threadContext;
}
@Override
public void addListener(TransportConnectionListener listener) {
this.connectionListener.addListener(listener);
}
@Override
public void removeListener(TransportConnectionListener listener) {
this.connectionListener.removeListener(listener);
}
@Override
public void openConnection(DiscoveryNode node, ConnectionProfile connectionProfile, ActionListener listener) {
ConnectionProfile resolvedProfile = ConnectionProfile.resolveConnectionProfile(connectionProfile, defaultProfile);
internalOpenConnection(node, resolvedProfile, listener);
}
/**
* Connects to the given node, or acquires another reference to an existing connection to the given node if a connection already exists.
*
* @param connectionProfile the profile to use if opening a new connection. Only used in tests, this is {@code null} in production.
* @param connectionValidator a callback to validate the connection before it is exposed (e.g. to {@link #nodeConnected}).
* @param listener completed on the calling thread or by the {@link ConnectionValidator}; in production the
* {@link ConnectionValidator} will complete the listener on the generic thread pool (see
* {@link TransportService#connectionValidator}). If successful, completed with a {@link Releasable} which
* will release this connection (and close it if no other references to it are held).
*/
@Override
public void connectToNode(
DiscoveryNode node,
@Nullable ConnectionProfile connectionProfile,
ConnectionValidator connectionValidator,
ActionListener listener
) throws ConnectTransportException {
connectToNodeOrRetry(
node,
connectionProfile,
connectionValidator,
0,
ContextPreservingActionListener.wrapPreservingContext(listener, threadContext)
);
}
/**
* Connects to the given node, or acquires another reference to an existing connection to the given node if a connection already exists.
* If a connection already exists but has been completely released (so it's in the process of closing) then this method will wait for
* the close to complete and then try again (up to 10 times).
*/
private void connectToNodeOrRetry(
DiscoveryNode node,
@Nullable ConnectionProfile connectionProfile,
ConnectionValidator connectionValidator,
int previousFailureCount,
ActionListener listener
) throws ConnectTransportException {
ConnectionProfile resolvedProfile = ConnectionProfile.resolveConnectionProfile(connectionProfile, defaultProfile);
if (node == null) {
listener.onFailure(new ConnectTransportException(null, "can't connect to a null node"));
return;
}
if (acquireConnectingRef() == false) {
listener.onFailure(new ConnectTransportException(node, "connection manager is closed"));
return;
}
final ActionListener acquiringListener = listener.delegateFailure((delegate, connection) -> {
if (connection.tryIncRef()) {
delegate.onResponse(Releasables.releaseOnce(connection::decRef));
return;
}
// We found a connection that's registered but already fully released, so it'll be removed soon by its close listener. Bad luck,
// let's wait for it to be removed and then try again.
final int failureCount = previousFailureCount + 1;
if (failureCount < 10) {
logger.trace("concurrent connect/disconnect for [{}] ([{}] failures), will try again", node, failureCount);
connection.addRemovedListener(
listener.delegateFailure(
(retryDelegate, ignored) -> connectToNodeOrRetry(
node,
connectionProfile,
connectionValidator,
failureCount,
retryDelegate
)
)
);
} else {
// A run of bad luck this long is probably not bad luck after all: something's broken, just give up.
logger.warn("failed to connect to [{}] after [{}] attempts, giving up", node.descriptionWithoutAttributes(), failureCount);
listener.onFailure(
new ConnectTransportException(
node,
"concurrently connecting and disconnecting even after [" + failureCount + "] attempts"
)
);
}
});
final Transport.Connection existingConnection = connectedNodes.get(node);
if (existingConnection != null) {
connectingRefCounter.decRef();
acquiringListener.onResponse(existingConnection);
return;
}
final ListenableFuture currentListener = new ListenableFuture<>();
final ListenableFuture existingListener = pendingConnections.putIfAbsent(node, currentListener);
if (existingListener != null) {
try {
// wait on previous entry to complete connection attempt
existingListener.addListener(acquiringListener);
} finally {
connectingRefCounter.decRef();
}
return;
}
currentListener.addListener(acquiringListener);
// It's possible that a connection completed, and the pendingConnections entry was removed, between the calls to
// connectedNodes.containsKey and pendingConnections.putIfAbsent above, so we check again to make sure we don't open a redundant
// extra connection to the node. We could _just_ check here, but checking up front skips the work to mark the connection as pending.
final Transport.Connection existingConnectionRecheck = connectedNodes.get(node);
if (existingConnectionRecheck != null) {
ListenableFuture future = pendingConnections.remove(node);
assert future == currentListener : "Listener in pending map is different than the expected listener";
connectingRefCounter.decRef();
future.onResponse(existingConnectionRecheck);
return;
}
final RunOnce releaseOnce = new RunOnce(connectingRefCounter::decRef);
internalOpenConnection(
node,
resolvedProfile,
ActionListener.wrap(
conn -> connectionValidator.validate(conn, resolvedProfile, ActionListener.runAfter(ActionListener.wrap(ignored -> {
assert Transports.assertNotTransportThread("connection validator success");
final RefCounted managerRefs = AbstractRefCounted.of(conn::onRemoved);
try {
if (connectedNodes.putIfAbsent(node, conn) != null) {
assert false : "redundant connection to " + node;
logger.warn("existing connection to node [{}], closing new redundant connection", node);
IOUtils.closeWhileHandlingException(conn);
} else {
logger.debug("connected to node [{}]", node);
managerRefs.incRef();
try {
connectionListener.onNodeConnected(node, conn);
} finally {
conn.addCloseListener(ActionListener.wrap(() -> {
connectedNodes.remove(node, conn);
connectionListener.onNodeDisconnected(node, conn);
managerRefs.decRef();
}));
conn.addCloseListener(ActionListener.wrap(() -> {
if (connectingRefCounter.hasReferences() == false) {
logger.trace("connection manager shut down, closing transport connection to [{}]", node);
} else if (conn.hasReferences()) {
logger.info("transport connection to [{}] closed by remote", node.descriptionWithoutAttributes());
// In production code we only close connections via ref-counting, so this message confirms that a
// 'node-left ... reason: disconnected' event was caused by external factors. Put differently, if a
// node leaves the cluster with "reason: disconnected" but without this message being logged then
// that's a bug.
} else {
logger.debug("closing unused transport connection to [{}]", node);
}
}));
}
}
} finally {
ListenableFuture future = pendingConnections.remove(node);
assert future == currentListener : "Listener in pending map is different than the expected listener";
managerRefs.decRef();
releaseOnce.run();
future.onResponse(conn);
}
}, e -> {
assert Transports.assertNotTransportThread("connection validator failure");
IOUtils.closeWhileHandlingException(conn);
failConnectionListener(node, releaseOnce, e, currentListener);
}), conn::decRef)),
e -> {
assert Transports.assertNotTransportThread("internalOpenConnection failure");
failConnectionListener(node, releaseOnce, e, currentListener);
}
)
);
}
/**
* Returns a connection for the given node if the node is connected.
* Connections returned from this method must not be closed. The lifecycle of this connection is
* maintained by this connection manager
*
* @throws NodeNotConnectedException if the node is not connected
* @see #connectToNode(DiscoveryNode, ConnectionProfile, ConnectionValidator, ActionListener)
*/
@Override
public Transport.Connection getConnection(DiscoveryNode node) {
Transport.Connection connection = connectedNodes.get(node);
if (connection == null) {
throw new NodeNotConnectedException(node, "Node not connected");
}
return connection;
}
/**
* Returns {@code true} if the node is connected.
*/
@Override
public boolean nodeConnected(DiscoveryNode node) {
return connectedNodes.containsKey(node);
}
/**
* Disconnected from the given node, if not connected, will do nothing.
*/
@Override
public void disconnectFromNode(DiscoveryNode node) {
Transport.Connection nodeChannels = connectedNodes.remove(node);
if (nodeChannels != null) {
// if we found it and removed it we close
nodeChannels.close();
}
}
/**
* Returns the number of nodes this manager is connected to.
*/
@Override
public int size() {
return connectedNodes.size();
}
@Override
public Set getAllConnectedNodes() {
return Collections.unmodifiableSet(connectedNodes.keySet());
}
@Override
public void close() {
internalClose(true);
}
@Override
public void closeNoBlock() {
internalClose(false);
}
private void internalClose(boolean waitForPendingConnections) {
assert Transports.assertNotTransportThread("Closing ConnectionManager");
if (closing.compareAndSet(false, true)) {
connectingRefCounter.decRef();
if (waitForPendingConnections) {
try {
closeLatch.await();
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
throw new IllegalStateException(e);
}
}
}
}
private void pendingConnectionsComplete() {
final Iterator> iterator = connectedNodes.entrySet().iterator();
while (iterator.hasNext()) {
final Map.Entry next = iterator.next();
try {
IOUtils.closeWhileHandlingException(next.getValue());
} finally {
iterator.remove();
}
}
closeLatch.countDown();
}
private void internalOpenConnection(
DiscoveryNode node,
ConnectionProfile connectionProfile,
ActionListener listener
) {
transport.openConnection(node, connectionProfile, listener.map(connection -> {
assert Transports.assertNotTransportThread("internalOpenConnection success");
try {
connectionListener.onConnectionOpened(connection);
} finally {
connection.addCloseListener(ActionListener.wrap(() -> connectionListener.onConnectionClosed(connection)));
}
if (connection.isClosed()) {
throw new ConnectTransportException(node, "a channel closed while connecting");
}
return connection;
}));
}
private void failConnectionListener(
DiscoveryNode node,
RunOnce releaseOnce,
Exception e,
ListenableFuture expectedListener
) {
ListenableFuture future = pendingConnections.remove(node);
releaseOnce.run();
if (future != null) {
assert future == expectedListener : "Listener in pending map is different than the expected listener";
future.onFailure(e);
}
}
@Override
public ConnectionProfile getConnectionProfile() {
return defaultProfile;
}
private boolean acquireConnectingRef() {
return closing.get() == false && connectingRefCounter.tryIncRef();
}
}
