1 files changed, 71 insertions, 0 deletions
diff --git a/yolean/src/main/java/com/yahoo/yolean/system/CatchSignals.java b/yolean/src/main/java/com/yahoo/yolean/system/CatchSignals.java
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index 00000000000..dce70fbbb5f
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+++ b/yolean/src/main/java/com/yahoo/yolean/system/CatchSignals.java
@@ -0,0 +1,71 @@
+// Copyright 2017 Yahoo Holdings. 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.*;
+
+// import sun.misc.Signal;
+// import sun.misc.SignalHandler;
+
+import java.util.concurrent.atomic.AtomicBoolean;
+
+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;
+    }
+}