/* * Copyright (c) 2014, 2022, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package javacserver.server; import java.util.Timer; import java.util.TimerTask; import java.util.function.Consumer; import javacserver.util.RunnableTimerTask; /** * Monitors the javacserver daemon, shutting it down if it recieves no new requests * after a certain amount of time. */ public class IdleMonitor { // Accept 120 seconds of inactivity before quitting. private static final int KEEPALIVE = 120; private final Consumer onShutdown; private final Timer idlenessTimer = new Timer(); private int outstandingCalls = 0; // Class invariant: idlenessTimerTask != null <-> idlenessTimerTask is scheduled private TimerTask idlenessTimerTask; public IdleMonitor(Consumer onShutdown) { this.onShutdown = onShutdown; scheduleTimeout(); } public synchronized void startCall() { // Was there no outstanding calls before this call? if (++outstandingCalls == 1) { // Then the timer task must have been scheduled if (idlenessTimerTask == null) throw new IllegalStateException("Idle timeout already cancelled"); // Cancel timeout task idlenessTimerTask.cancel(); idlenessTimerTask = null; } } public synchronized void endCall() { if (--outstandingCalls == 0) { // No more outstanding calls. Schedule timeout. scheduleTimeout(); } } private void scheduleTimeout() { if (idlenessTimerTask != null) throw new IllegalStateException("Idle timeout already scheduled"); idlenessTimerTask = new RunnableTimerTask(() -> { Server.restoreServerErrorLog(); onShutdown.accept("Server has been idle for " + KEEPALIVE + " seconds."); }); idlenessTimer.schedule(idlenessTimerTask, KEEPALIVE * 1000); } public void shutdown() { idlenessTimer.cancel(); } }