/**
* Copyright 2010 Google Inc.
*
* 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.waveprotocol.wave.federation.xmpp;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Function;
import com.google.common.base.Preconditions;
import com.google.common.collect.MapMaker;
import com.google.common.collect.Sets;
import org.dom4j.Attribute;
import org.dom4j.Element;
import org.joda.time.DateTimeUtils;
import org.waveprotocol.wave.federation.FederationErrors;
import org.waveprotocol.wave.federation.FederationErrorProto.FederationError;
import org.xmpp.packet.IQ;
import org.xmpp.packet.Packet;
import java.security.SecureRandom;
import java.util.List;
import java.util.Map;
import java.util.Queue;
import java.util.Random;
import java.util.Set;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicLong;
import java.util.concurrent.atomic.AtomicReference;
import java.util.logging.Logger;
import javax.annotation.Nullable;
/**
* Represents XMPP disco status for a specific remote domain. This class only
* exposes one public method; {@link #discoverRemoteJID}.
*
* @author thorogood@google.com (Sam Thorogood)
*/
public class RemoteDisco {
private static final Logger LOG = Logger.getLogger(RemoteDisco.class.getCanonicalName());
static final int MAXIMUM_DISCO_ATTEMPTS = 5;
static final int MINIMUM_REXMIT_MS = 15000;
static final int REXMIT_JITTER_MS = 2000;
static final int DISCO_INFO_TIMEOUT = 20;
private final long creationTimeMillis;
private final int failExpirySecs;
private final int successExpirySecs;
enum Status {
INIT, PENDING, COMPLETE
}
private final Random random = new SecureRandom();
private final XmppManager manager;
private final String remoteDomain;
private final AtomicReference<Status> status;
private final Queue<SuccessFailCallback<String, String>> pending;
// Result JID field that will be available on COMPLETE status.
private String remoteJid;
// Error field that will be available on COMPLETE status.
private FederationError error;
// These two values are used for tracking success and failure counts.
// Not yet exposed in the fedone waveserver.
public static final Map<String, AtomicLong> statDiscoSuccess =
new MapMaker().makeComputingMap(
new Function<String, AtomicLong>() {
@Override
public AtomicLong apply(String domain) {
return new AtomicLong();
}
});
public static final Map<String, AtomicLong> statDiscoFailed =
new MapMaker().makeComputingMap(
new Function<String, AtomicLong>() {
@Override
public AtomicLong apply(String domain) {
return new AtomicLong();
}
});
/**
* Construct a new RemoteDisco targeting the given domain. This will not kick
* off the disco request itself.
* @param manager XmppManager object, used to send packets
* @param remoteDomain the name of the remote domain (not JID)
* @param failExpirySecs how long to keep alive a failed disco result
* @param successExpirySecs how long to keep alive a successful disco result
*/
public RemoteDisco(XmppManager manager, String remoteDomain, int failExpirySecs,
int successExpirySecs) {
this.manager = manager;
status = new AtomicReference<Status>(Status.INIT);
pending = new ConcurrentLinkedQueue<SuccessFailCallback<String, String>>();
this.remoteDomain = remoteDomain;
this.creationTimeMillis = DateTimeUtils.currentTimeMillis();
this.failExpirySecs = failExpirySecs;
this.successExpirySecs = successExpirySecs;
}
/**
* Construct a new RemoteDisco - purely for testing - with an already
* determined result. Either jid or error must be passed.
*
* @param remoteDomain the name of the remote domain (not JID)
* @param jid the domain's remote JID
* @param error the error from disco
*/
@VisibleForTesting
RemoteDisco(String remoteDomain, String jid, FederationError error) {
Preconditions.checkArgument((jid != null)^(error != null));
manager = null;
status = new AtomicReference<Status>(Status.COMPLETE);
pending = null;
this.remoteDomain = remoteDomain;
this.remoteJid = jid;
this.error = error;
// defaults for testing
this.creationTimeMillis = DateTimeUtils.currentTimeMillis();
this.failExpirySecs = 2 * 60;
this.successExpirySecs = 2 * 60 * 60;
}
/**
* Check whether the request is currently PENDING. Visible only for tests.
* @return true if pending else false
*/
@VisibleForTesting
boolean isRequestPending() {
return status.get().equals(Status.PENDING);
}
/**
* Attempt to discover the remote JID for this domain. If the JID has already
* been discovered, then this method will invoke the callback immediately.
* Otherwise, the callback is guaranteed to be invoked at a later point.
*
* @param callback a callback to be invoked when disco is complete
*/
public void discoverRemoteJID(SuccessFailCallback<String, String> callback) {
if (status.get().equals(Status.COMPLETE)) {
complete(callback);
} else if (status.compareAndSet(Status.INIT, Status.PENDING)) {
pending.add(callback);
startDisco();
} else {
pending.add(callback);
// If we've become complete since the start of this method, complete
// all possible callbacks.
if (status.get().equals(Status.COMPLETE)) {
SuccessFailCallback<String, String> item;
while ((item = pending.poll()) != null) {
complete(item);
}
}
}
}
/**
* Returns true if this RemoteDisco's time to live is exceeded.
*
* We can't use MapMaker's expiration code as it won't let us have different expiry for
* successful and failed cases.
*
* @return whether this object should be deleted and recreated
*/
public boolean ttlExceeded() {
if (status.get() == Status.COMPLETE) {
if (remoteJid == null) {
// Failed disco case
if (DateTimeUtils.currentTimeMillis() >
(creationTimeMillis + (1000 * failExpirySecs))) {
return true;
}
} else {
// Successful disco case
if (DateTimeUtils.currentTimeMillis() >
(creationTimeMillis + (1000 * successExpirySecs))) {
return true;
}
}
}
return false;
}
/**
* Complete any specific callback (in the current thread). Requires the status
* to be COMPLETE.
*
* TODO(thorogood): thread model for completing callbacks
* @param callback the callback to complete
*/
private void complete(SuccessFailCallback<String, String> callback) {
Preconditions.checkState(status.get().equals(Status.COMPLETE));
if (remoteJid != null) {
callback.onSuccess(remoteJid);
} else {
// TODO(thorogood): better toString, or change failure type to FederationError
callback.onFailure(error.toString());
}
}
/**
* Start XMPP discovery. Kicks off a retrying call to dial-up the remote
* server and discover its available disco items.
*
* This should only be called by a method holding the PENDING state.
*/
private void startDisco() {
final IQ request = manager.createRequestIQ(remoteDomain);
request.setChildElement("query", XmppNamespace.NAMESPACE_DISCO_ITEMS);
final Runnable requester = new Runnable() {
int attempt = 0;
final PacketCallback callback = new PacketCallback() {
@Override
public void run(Packet result) {
Preconditions.checkArgument(result instanceof IQ, "Manager must provide response IQ");
processDiscoItemsResult((IQ) result);
}
@Override
public void error(FederationError error) {
if (error.getErrorCode().equals(FederationError.Code.REMOTE_SERVER_TIMEOUT)) {
retry();
} else {
LOG.info("Remote server " + remoteDomain + " failed on disco items: "
+ error.getErrorCode());
processDiscoItemsResult(null);
}
}
};
void retry() {
attempt += 1;
if (attempt > MAXIMUM_DISCO_ATTEMPTS) {
finish(null, FederationErrors
.newFederationError(FederationError.Code.REMOTE_SERVER_TIMEOUT));
} else {
// TODO(thorogood): fix ms/seconds!
int timeout = nextDiscoRetransmitTimeout(attempt) / 1000;
request.setID(XmppUtil.generateUniqueId());
LOG.info("Sending disco items request for: " + remoteDomain + ", timeout " + timeout
+ " seconds");
manager.send(request, callback, timeout);
}
}
@Override
public void run() {
retry();
}
};
// Kick off requester!
requester.run();
}
/**
* Calculate the requested timeout for any given request number. Introduces
* random jitter.
*
* @param attempt the attempt count
* @return request timeout in ms
*/
private int nextDiscoRetransmitTimeout(int attempt) {
Preconditions.checkArgument(attempt > 0);
return MINIMUM_REXMIT_MS * (1 << (attempt - 1)) + random.nextInt(REXMIT_JITTER_MS);
}
/**
* Process a returned set of disco items. Invoke a query for each item in
* parallel, searching for any item which supports Wave.
*
* @param result IQ stanza provided from disco items, if null try default items
*/
private void processDiscoItemsResult(@Nullable IQ result) {
Set<String> candidates = Sets.newHashSet();
// Traverse the source list, finding possible JID candidates.
if (result != null) {
List<Element> items = XmppUtil.toSafeElementList(result.getChildElement().elements("item"));
for (Element item : items) {
Attribute jid = item.attribute("jid");
if (jid != null) {
candidates.add(jid.getValue());
}
}
}
// Returned nothing for the items list. Try the domain itself.
if (candidates.isEmpty()) {
candidates.add(remoteDomain);
}
// Always query 'wave.', as an automatic fallback.
candidates.add("wave." + remoteDomain);
// Iterate over all candidates, requesting information in parallel.
AtomicInteger sharedLatch = new AtomicInteger(candidates.size());
for (String candidate : candidates) {
requestDiscoInfo(candidate, sharedLatch);
}
}
/**
* Request disco info from a specific target JID. Accepts a target JID as well
* as a shared latch: on a result, the latch should be decremented and if it
* reaches zero, finish() must be invoked with an error.
*
* @param target the target JID
* @param sharedLatch a shared latch
*/
private void requestDiscoInfo(String target, final AtomicInteger sharedLatch) {
final IQ request = manager.createRequestIQ(target);
request.setChildElement("query", XmppNamespace.NAMESPACE_DISCO_INFO);
PacketCallback callback = new PacketCallback() {
@Override
public void error(FederationError error) {
int currentCount = sharedLatch.decrementAndGet();
Preconditions.checkState(currentCount >= 0,
"Info latch should not count down past zero for domain: %s", remoteDomain);
if (currentCount == 0) {
finish(null, error);
}
}
@Override
public void run(Packet packet) {
Preconditions.checkArgument(packet instanceof IQ);
IQ result = (IQ) packet;
List<Element> features =
XmppUtil.toSafeElementList(result.getChildElement().elements("feature"));
for (Element feature : features) {
Attribute var = feature.attribute("var");
if (var != null && var.getValue().equals(XmppNamespace.NAMESPACE_WAVE_SERVER)) {
String targetJID = packet.getFrom().toString();
finish(targetJID, null);
// Decrement the latch *after* finishing, so we don't allow an error
// callback to be kicked off.
Preconditions.checkState(sharedLatch.decrementAndGet() >= 0,
"Info latch should not count down past zero for domain: %s", remoteDomain);
return;
}
}
// This result didn't contain a useful result JID, so cause an error.
error(FederationErrors.newFederationError(FederationError.Code.ITEM_NOT_FOUND));
}
};
LOG.info("Sending disco info request for: " + target);
manager.send(request, callback, DISCO_INFO_TIMEOUT);
}
/**
* Finish this disco attempt with either a success or error result. This
* method should only be called on a thread that owns the PENDING state and
* will (if successful) result in a transition to COMPLETE. If the disco
* attempt is already complete, return false and do nothing (safe operation).
*
* @param jid success JID, or null
* @param error error proto, or null
* @return true if successful, false if already finished
*/
@VisibleForTesting
boolean finish(String jid, FederationError error) {
Preconditions.checkArgument((jid != null)^(error != null));
if (!status.compareAndSet(Status.PENDING, Status.COMPLETE)) {
return false;
}
// Set either the result JID or error state.
if (jid != null) {
this.remoteJid = jid;
LOG.info("Discovered remote JID: " + jid + " for " + remoteDomain);
statDiscoSuccess.get(remoteDomain).incrementAndGet();
} else if (error != null) {
this.error = error;
LOG.info("Could not discover remote JID: " + error + " for " + remoteDomain);
statDiscoFailed.get(remoteDomain).incrementAndGet();
} else {
throw new IllegalArgumentException("At least one of jid/error must be set");
}
// Complete all available callbacks.
SuccessFailCallback<String, String> item;
while ((item = pending.poll()) != null) {
complete(item);
}
return true;
}
}