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// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.vespa.curator;
import com.yahoo.path.Path;
import java.time.Clock;
import java.time.Duration;
import java.time.Instant;
import java.util.ArrayList;
import java.util.List;
import java.util.logging.Level;
/**
* Implementation of a Barrier that handles the case where more than number of members can call synchronize.
* Will wait for some time for all servers to do the operation, but will accept the majority of servers to have
* done the operation if it takes longer than a specified amount of time.
*
* @author Vegard Havdal
* @author Ulf Lilleengen
*/
class CuratorCompletionWaiter implements Curator.CompletionWaiter {
private static final java.util.logging.Logger log = java.util.logging.Logger.getLogger(CuratorCompletionWaiter.class.getName());
private final Curator curator;
private final String barrierPath;
private final String myId;
private final Clock clock;
private final Duration waitForAll;
CuratorCompletionWaiter(Curator curator, String barrierPath, String myId, Clock clock, Duration waitForAll) {
this.myId = barrierPath + "/" + myId;
this.curator = curator;
this.barrierPath = barrierPath;
this.clock = clock;
this.waitForAll = waitForAll;
}
@Override
public void awaitCompletion(Duration timeout) {
List<String> respondents;
try {
log.log(Level.FINE, () -> "Synchronizing on barrier " + barrierPath);
respondents = awaitInternal(timeout);
log.log(Level.FINE, () -> "Done synchronizing on barrier " + barrierPath);
} catch (Exception e) {
throw new RuntimeException(e);
}
if (respondents.size() < barrierMemberCount()) {
throw new CompletionTimeoutException("Timed out waiting for config servers to complete operation " +
"(waited for barrier " + barrierPath + ")." +
"Got response from " + respondents + ", but need response from " +
"at least " + barrierMemberCount() + " server(s). " +
"Timeout passed as argument was " + timeout.toMillis() + " ms");
}
}
private List<String> awaitInternal(Duration timeout) throws Exception {
Instant startTime = clock.instant();
Instant endTime = startTime.plus(timeout);
Instant gotQuorumTime = Instant.EPOCH;
List<String> respondents = new ArrayList<>();
do {
respondents.clear();
respondents.addAll(curator.framework().getChildren().forPath(barrierPath));
if (log.isLoggable(Level.FINER)) {
log.log(Level.FINER, respondents.size() + "/" + curator.zooKeeperEnsembleCount() + " responded: " +
respondents + ", all participants: " + curator.zooKeeperEnsembleConnectionSpec());
}
// If all config servers responded, return
if (respondents.size() == curator.zooKeeperEnsembleCount()) {
logBarrierCompleted(respondents, startTime);
break;
}
// If some are missing, quorum is enough, but wait for all up to ´waitForAll´ seconds before returning
if (respondents.size() >= barrierMemberCount()) {
if (gotQuorumTime.isBefore(startTime))
gotQuorumTime = clock.instant();
if (Duration.between(clock.instant(), gotQuorumTime.plus(waitForAll)).isNegative()) {
logBarrierCompleted(respondents, startTime);
break;
}
}
Thread.sleep(100);
} while (clock.instant().isBefore(endTime));
return respondents;
}
private void logBarrierCompleted(List<String> respondents, Instant startTime) {
Duration duration = Duration.between(startTime, Instant.now());
Level level = duration.minus(Duration.ofSeconds(5)).isNegative() ? Level.FINE : Level.INFO;
log.log(level, () -> barrierCompletedMessage(respondents, duration));
}
private String barrierCompletedMessage(List<String> respondents, Duration duration) {
return barrierPath + " completed in " + duration.toString() +
", " + respondents.size() + "/" + curator.zooKeeperEnsembleCount() + " responded: " + respondents;
}
@Override
public void notifyCompletion() {
try {
notifyInternal();
} catch (Exception e) {
throw new RuntimeException(e);
}
}
private void notifyInternal() throws Exception {
curator.framework().create().forPath(myId);
}
@Override
public String toString() {
return "'" + barrierPath + "', " + barrierMemberCount() + " members";
}
public static Curator.CompletionWaiter create(Curator curator, Path barrierPath, String id, Duration waitForAll) {
return new CuratorCompletionWaiter(curator, barrierPath.getAbsolute(), id, Clock.systemUTC(), waitForAll);
}
public static Curator.CompletionWaiter createAndInitialize(Curator curator, Path parentPath, String waiterNode, String id, Duration waitForAll) {
Path waiterPath = parentPath.append(waiterNode);
String debugMessage = log.isLoggable(Level.FINE) ? "Recreating ZK path " + waiterPath : null;
if (debugMessage != null) log.fine(debugMessage);
curator.delete(waiterPath);
curator.createAtomically(waiterPath);
if (debugMessage != null) log.fine(debugMessage + ": Done");
return new CuratorCompletionWaiter(curator, waiterPath.getAbsolute(), id, Clock.systemUTC(), waitForAll);
}
private int barrierMemberCount() {
return (curator.zooKeeperEnsembleCount() / 2) + 1; // majority
}
}
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