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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.concurrent.classlock;
import java.util.HashMap;
import java.util.Map;
import java.util.function.BooleanSupplier;
/**
* This class is injectable to Vespa plugins and is used to acquire locks cross
* application deployments.
*
* @author valerijf
*/
public class ClassLocking {
private final Map<String, ClassLock> classLocks = new HashMap<>();
private final Object monitor = new Object();
/**
* Locks key. This will block until the key is acquired.
* Users of this <b>must</b> close any lock acquired.
*/
public ClassLock lock(Class<?> clazz) {
return lockWhile(clazz, () -> true);
}
/**
* Locks key. This will block until the key is acquired or the interrupt condition is
* no longer true. Condition is only checked at the start, everytime a lock is released
* and when {@link #interrupt()} is called.
*
* Users of this <b>must</b> close any lock acquired.
*
* @throws LockInterruptException if interruptCondition returned false before
* the lock could be acquired
*/
public ClassLock lockWhile(Class<?> clazz, BooleanSupplier interruptCondition) {
synchronized (monitor) {
while (classLocks.containsKey(clazz.getName())) {
try {
monitor.wait();
} catch (InterruptedException ignored) {
}
if (!interruptCondition.getAsBoolean()) {
throw new LockInterruptException();
}
}
ClassLock classLock = new ClassLock(this, clazz);
classLocks.put(clazz.getName(), classLock);
return classLock;
}
}
void unlock(Class<?> clazz, ClassLock classLock) {
synchronized (monitor) {
if (classLock.equals(classLocks.get(clazz.getName()))) {
classLocks.remove(clazz.getName());
monitor.notifyAll();
} else {
throw new IllegalArgumentException("Lock has already been released");
}
}
}
/**
* Notifies {@link #lockWhile} to check the interrupt condition
*/
public void interrupt() {
synchronized (monitor) {
monitor.notifyAll();
}
}
}
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