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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.yolean.system;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.concurrent.atomic.AtomicBoolean;
// import sun.misc.Signal;
// import sun.misc.SignalHandler;
public class CatchSignals {
/**
* Sets up a signal handler for SIGTERM and SIGINT, where a given AtomicBoolean
* gets a true value when the signal is caught.
*
* Callers basically have two options for acting on the signal:
*
* They may choose to synchronize and wait() on this variable,
* and they will be notified when it changes state to true. To avoid
* problems with spurious wakeups, use a while loop and wait()
* again if the state is still false. As soon as the caller has been
* woken up and the state is true, the application should exit as
* soon as possible.
*
* They may also choose to poll the state of this variable. As soon
* as its state becomes true, the signal has been received, and the
* application should exit as soon as possible.
*
* @param signalCaught set to false initially, will be set to true when SIGTERM or SIGINT is caught.
*/
@SuppressWarnings("rawtypes")
public static void setup(final AtomicBoolean signalCaught) {
signalCaught.set(false);
try {
Class shc = Class.forName("sun.misc.SignalHandler");
Class ssc = Class.forName("sun.misc.Signal");
InvocationHandler ihandler = new InvocationHandler() {
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
synchronized (signalCaught) {
signalCaught.set(true);
signalCaught.notifyAll();
}
return null;
}
};
Object shandler = Proxy.newProxyInstance(CatchSignals.class.getClassLoader(),
new Class[] { shc },
ihandler);
Constructor[] c = ssc.getDeclaredConstructors();
assert c.length == 1;
Object sigterm = c[0].newInstance("TERM");
Object sigint = c[0].newInstance("INT");
Method m = findMethod(ssc, "handle");
assert m != null; // "NoSuchMethodException"
m.invoke(null, sigterm, shandler);
m.invoke(null, sigint, shandler);
} catch (ClassNotFoundException | InvocationTargetException | InstantiationException | IllegalAccessException e) {
System.err.println("FAILED setting up signal catching: "+e);
}
}
private static Method findMethod(Class<?> c, String name) {
for (Method m : c.getDeclaredMethods()) {
if (m.getName().equals(name)) {
return m;
}
}
return null;
}
}
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