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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.hosted.node.admin.nodeagent;
import com.yahoo.jdisc.Timer;
import java.time.Duration;
import java.time.Instant;
import java.util.Objects;
/**
* This class should be used by exactly 2 threads, 1 for each interface it implements.
*
* @author freva
*/
public class NodeAgentContextManager implements NodeAgentContextSupplier, NodeAgentScheduler {
private final Object monitor = new Object();
private final Timer timer;
private NodeAgentContext currentContext;
private NodeAgentContext nextContext;
private Instant nextContextAt;
private boolean wantFrozen = false;
private boolean isFrozen = true;
private boolean interrupted = false;
private boolean isWaitingForNextContext = false;
public NodeAgentContextManager(Timer timer, NodeAgentContext context) {
this.timer = timer;
this.currentContext = context;
}
@Override
public void scheduleTickWith(NodeAgentContext context, Instant at) {
synchronized (monitor) {
nextContext = Objects.requireNonNull(context);
nextContextAt = Objects.requireNonNull(at);
monitor.notifyAll(); // Notify of new context
}
}
@Override
public boolean setFrozen(boolean frozen, Duration timeout) {
synchronized (monitor) {
if (wantFrozen != frozen) {
wantFrozen = frozen;
monitor.notifyAll(); // Notify the supplier of the wantFrozen change
}
boolean successful;
long remainder;
long end = timer.currentTime().plus(timeout).toEpochMilli();
while (!(successful = isFrozen == frozen) && (remainder = end - timer.currentTimeMillis()) > 0) {
try {
monitor.wait(remainder); // Wait with timeout until the supplier is has reached wanted frozen state
} catch (InterruptedException ignored) { }
}
return successful;
}
}
@Override
public NodeAgentContext nextContext() throws ContextSupplierInterruptedException {
synchronized (monitor) {
nextContext = null; // Reset any previous context and wait for the next one
isWaitingForNextContext = true;
monitor.notifyAll();
Duration untilNextContext = Duration.ZERO;
while (true) {
if (interrupted) throw new ContextSupplierInterruptedException();
if (!setAndGetIsFrozen(wantFrozen) &&
nextContext != null &&
(untilNextContext = Duration.between(Instant.now(), nextContextAt)).toMillis() <= 0)
break;
try {
monitor.wait(Math.max(untilNextContext.toMillis(), 0L)); // Wait until scheduler provides a new context
} catch (InterruptedException ignored) { }
}
isWaitingForNextContext = false;
currentContext = nextContext;
return currentContext;
}
}
@Override
public NodeAgentContext currentContext() {
synchronized (monitor) {
return currentContext;
}
}
@Override
public void interrupt() {
synchronized (monitor) {
interrupted = true;
monitor.notifyAll();
}
}
private boolean setAndGetIsFrozen(boolean isFrozen) {
synchronized (monitor) {
if (this.isFrozen != isFrozen) {
this.isFrozen = isFrozen;
monitor.notifyAll(); // Notify the scheduler of the isFrozen change
}
return this.isFrozen;
}
}
/** FOR TESTING ONLY */
void waitUntilWaitingForNextContext() {
synchronized (monitor) {
while (!isWaitingForNextContext) {
try {
monitor.wait();
} catch (InterruptedException ignored) { }
}
}
}
}
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