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// Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.vespa.config.server;
import com.yahoo.path.Path;
import com.yahoo.transaction.AbstractTransaction;
import com.yahoo.transaction.Transaction;
import com.yahoo.vespa.config.GenerationCounter;
import com.yahoo.vespa.curator.recipes.CuratorCounter;
import com.yahoo.vespa.curator.Curator;
/**
* Distributed global generation counter for the super model.
*
* @author lulf
* @since 5.9
*/
public class SuperModelGenerationCounter implements GenerationCounter {
private static final Path counterPath = Path.fromString("/config/v2/RPC/superModelGeneration");
private final CuratorCounter counter;
public SuperModelGenerationCounter(Curator curator) {
this.counter = new CuratorCounter(curator, counterPath.getAbsolute());
}
/**
* Increment counter and return next value. This method is thread safe and provides an atomic value
* across zookeeper clusters.
*
* @return incremented counter value.
*/
public synchronized long increment() {
return counter.next();
}
/**
* @return current counter value.
*/
public synchronized long get() {
return counter.get();
}
/** Returns a transaction which increments this */
public IncrementTransaction incrementTransaction() {
return new IncrementTransaction(counter);
}
/** An increment transaction */
public static class IncrementTransaction extends AbstractTransaction {
/** Creates a counting curator transaction containing a single increment operation */
public IncrementTransaction(CuratorCounter counter) {
add(new IncrementOperation(counter));
}
@Override
public void prepare() { }
@Override
public void commit() {
for (Operation operation : operations())
((IncrementOperation)operation).commit();
}
@Override
public void rollbackOrLog() {
for (Operation operation : operations())
((IncrementOperation)operation).rollback();
}
public static class IncrementOperation implements Transaction.Operation {
private final CuratorCounter counter;
public IncrementOperation(CuratorCounter counter) {
this.counter = counter;
}
public void commit() {
counter.next();
}
public void rollback() {
// ok; we're just losing a generation number
}
public String toString() { return "increment " + counterPath + " operation"; }
}
}
}
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