/* PollingServerPush.java
Purpose:
Description:
History:
Fri Aug 3 18:53:21 2007, Created by tomyeh
Copyright (C) 2007 Potix Corporation. All Rights Reserved.
{{IS_RIGHT
}}IS_RIGHT
*/
package org.zkoss.zk.ui.impl;
import java.util.LinkedList;
import java.util.List;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.zkoss.zk.au.out.AuScript;
import org.zkoss.zk.ui.Desktop;
import org.zkoss.zk.ui.DesktopUnavailableException;
import org.zkoss.zk.ui.Execution;
import org.zkoss.zk.ui.Executions;
import org.zkoss.zk.ui.UiException;
import org.zkoss.zk.ui.event.Event;
import org.zkoss.zk.ui.event.EventListener;
import org.zkoss.zk.ui.sys.Scheduler;
import org.zkoss.zk.ui.sys.ServerPush;
import org.zkoss.zk.ui.util.Clients;
import org.zkoss.zk.ui.util.Configuration;
/**
* A server-push implementation that is based on client-polling.
*
* <p>Developer can control the frequency of the polling by setting the preferences as follows:
* <dl>
* <dt><code>PollingServerPush.delay.min</code></dt>
* <dd>The minimal delay to send the second polling request (unit: milliseconds). Default: 1000.</dd>
* <dt><code>PollingServerPush.delay.max</code></dt>
* <dd>The maximal delay to send the second polling request (unit: milliseconds). Default: 15000.</dd>
* <dt><code>PollingServerPush.delay.factor</code></dt>
* <dd>the delay factor. The real delay is the processing time multiplies the delay
* factor. For example, if the last request
* took 1 second to process, then the client polling will be delayed
* for <code>1 x factor</code> seconds. Default: 5.
* The larger the factor is, the longer delay it tends to be.</dd>
*
* <p>Another way to control the frequency is to instantiate an instance
* with {@link #PollingServerPush(int, int, int)}, and then assign it
* with {@link org.zkoss.zk.ui.sys.DesktopCtrl#enableServerPush(ServerPush)}.
*
* <pre><code>desktop.enableServerPush(new PollingServerPush(1000, 5000, -1));</code></pre>
*
* @author tomyeh
* @since 5.0.0
*/
public class PollingServerPush implements ServerPush {
private static final Logger log = LoggerFactory.getLogger(PollingServerPush.class);
/** Denote a server-push thread gives up the activation (timeout). */
private static final int GIVEUP = -99;
private Desktop _desktop;
/** List of ThreadInfo. */
private final List<ThreadInfo> _pending = new LinkedList<ThreadInfo>();
/** The active thread. */
private ThreadInfo _active;
/** The info to carry over from onPiggyback to the server-push thread. */
private ExecutionCarryOver _carryOver;
private final int _min, _max, _factor;
/** A mutex that is used by this object to wait for the server-push thread
* to complete.
*/
private final Object _mutex = new Object();
public PollingServerPush() {
this(-1, -1, -1);
}
/**
* @param min the minimal delay before sending the second polling request
* (unit: milliseconds).
* If negative, the default is used (see {@link PollingServerPush}).
* @param max the maximal delay before sending the second polling request
* (unit: milliseconds).
* If negative, the default is used (see {@link PollingServerPush}).
* @param factor the delay factor.
* If negative, the default is used (see {@link PollingServerPush}).
* @since 5.0.4
*/
public PollingServerPush(int min, int max, int factor) {
_min = min;
_max = max;
_factor = factor;
}
/** Sends an AU response to the client to start the server push.
* It is called by {@link #start}.
* <p>The derived class usually overrides this method to support
* different devices, such as ZK Mobile.
* <p>The default implementation is to send {@link AuScript} containing
* the script returned by {@link #getStartScript}.
* Devices that don't support scripts could override this method
* to send a custom AU response ({@link org.zkoss.zk.au.AuResponse}).
*/
protected void startClientPush() {
Clients.response("zk.clientpush", new AuScript(null, getStartScript()));
}
/** Sends an AU response the client to stop the server push.
* <p>The derived class usually overrides this method to support
* different devices, such as ZK Mobile.
* <p>The default implementation is to send {@link AuScript} containing
* the script returned by {@link #getStopScript}.
* Devices that don't support scripts could override this method
* to send a custom AU response ({@link org.zkoss.zk.au.AuResponse}).
*/
protected void stopClientPush() {
Clients.response("zk.clientpush", new AuScript(null, getStopScript()));
}
/** Returns the JavaScript codes to enable (a.k.a., start) the server push.
* It is called by {@link #startClientPush} to prepare the script
* of {@link AuScript} that will be sent to the client.
*/
protected String getStartScript() {
final String start = _desktop.getWebApp().getConfiguration().getPreference("PollingServerPush.start", null);
if (start != null)
return start;
final StringBuffer sb = new StringBuffer(128)
.append("zk.load('zk.cpsp');zk.afterLoad(function(){zk.cpsp.start('").append(_desktop.getId())
.append('\'');
final int min = _min > 0 ? _min : getIntPref("PollingServerPush.delay.min"),
max = _max > 0 ? _max : getIntPref("PollingServerPush.delay.max"),
factor = _factor > 0 ? _factor : getIntPref("PollingServerPush.delay.factor");
if (min > 0 || max > 0 || factor > 0)
sb.append(',').append(min).append(',').append(max).append(',').append(factor);
return sb.append(");});").toString();
}
private int getIntPref(String key) {
final String s = _desktop.getWebApp().getConfiguration().getPreference(key, null);
if (s != null) {
try {
return Integer.parseInt(s);
} catch (NumberFormatException ex) {
log.warn("Not a number specified at " + key);
}
}
return -1;
}
/** Returns the JavaScript codes to disable (a.k.a., stop) the server push.
* It is called by {@link #stopClientPush} to prepare the script
* of {@link AuScript} that will be sent to the client.
*/
protected String getStopScript() {
final String stop = _desktop.getWebApp().getConfiguration().getPreference("PollingServerPush.stop", null);
return stop != null ? stop : "zk.cpsp.stop('" + _desktop.getId() + "');";
}
//ServerPush//
public boolean isActive() {
return _active != null && _active.nActive > 0;
}
public void start(Desktop desktop) {
if (_desktop != null) {
log.warn("Ignored: Sever-push already started");
return;
}
_desktop = desktop;
startClientPush();
}
/**
* ZK-1777 resume serverpush after DesktopRecycling
*/
public void resume() {
if (_desktop == null) {
throw new IllegalStateException(
"ServerPush cannot be resumed without desktop, or has been stopped!call #start(desktop)} instead");
}
startClientPush();
}
public void stop() {
if (_desktop == null) {
log.warn("Ignored: Sever-push not started");
return;
}
final Execution exec = Executions.getCurrent();
final boolean inexec = exec != null && exec.getDesktop() == _desktop;
//it might be caused by DesktopCache expunge (when creating another desktop)
try {
if (inexec && _desktop.isAlive()) //Bug 1815480: don't send if timeout
stopClientPush();
} finally {
_desktop = null; //to cause DesktopUnavailableException being thrown
wakePending();
//if inexec, either in working thread, or other event listener
//if in working thread, we cannot notify here (too early to wake).
//if other listener, no need notify (since onPiggyback not running)
if (!inexec) {
synchronized (_mutex) {
_mutex.notify(); //wake up onPiggyback
}
}
}
}
private void wakePending() {
synchronized (_pending) {
for (ThreadInfo info : _pending) {
synchronized (info) {
info.notify();
}
}
_pending.clear();
}
}
public void onPiggyback() {
// B65-ZK-2105: Need to check if desktop is null.
if (_desktop == null)
return;
final Configuration config = _desktop.getWebApp().getConfiguration();
long tmexpired = 0;
for (int cnt = 0; !_pending.isEmpty();) {
//Don't hold the client too long.
//In addition, an ill-written code might activate again
//before onPiggyback returns. It causes dead-loop in this case.
if (tmexpired == 0) { //first time
tmexpired = System.currentTimeMillis() + (config.getMaxProcessTime() >> 1);
cnt = _pending.size() + 3;
} else if (--cnt < 0 || System.currentTimeMillis() > tmexpired) {
break;
}
final ThreadInfo info;
synchronized (_pending) {
if (_pending.isEmpty())
return; //nothing to do
info = _pending.remove(0);
}
//Note: we have to sync _mutex before info. Otherwise,
//sync(info) might cause deactivate() to run before _mutex.wait
synchronized (_mutex) {
_carryOver = new ExecutionCarryOver(_desktop);
synchronized (info) {
if (info.nActive == GIVEUP)
continue; //give up and try next
info.nActive = 1; //granted
info.notify();
}
if (_desktop == null) //just in case
break;
try {
_mutex.wait(); //wait until the server push is done
} catch (InterruptedException ex) {
throw UiException.Aide.wrap(ex);
}
}
}
}
public <T extends Event> void schedule(EventListener<T> listener, T event, Scheduler<T> scheduler) {
scheduler.schedule(listener, event); //delegate back
}
public boolean activate(long timeout) throws InterruptedException, DesktopUnavailableException {
final Thread curr = Thread.currentThread();
if (_active != null && _active.thread.equals(curr)) { //re-activate
++_active.nActive;
return true;
}
final ThreadInfo info = new ThreadInfo(curr);
synchronized (_pending) {
if (_desktop != null)
_pending.add(info);
}
boolean loop;
do {
loop = false;
synchronized (info) {
if (_desktop != null) {
if (info.nActive == 0) //not granted yet
info.wait(timeout <= 0 ? 10 * 60 * 1000 : timeout);
if (info.nActive <= 0) { //not granted
boolean bTimeout = timeout > 0;
boolean bDead = _desktop == null || !_desktop.isAlive();
if (bTimeout || bDead) { //not timeout
info.nActive = GIVEUP; //denote timeout (and give up)
synchronized (_pending) { //undo pending
_pending.remove(info);
}
if (bDead)
throw new DesktopUnavailableException("Stopped");
return false; //timeout
}
log.debug("Executions.activate() took more than 10 minutes");
loop = true; //try again
}
}
}
} while (loop);
if (_desktop == null)
throw new DesktopUnavailableException("Stopped");
_carryOver.carryOver();
_active = info;
return true;
//Note: we don't mimic inEventListener since 1) ZK doesn't assume it
//2) Window depends on it
}
public boolean deactivate(boolean stop) {
boolean stopped = false;
if (_active != null && Thread.currentThread().equals(_active.thread)) {
if (--_active.nActive <= 0) {
if (stop)
stopClientPush();
_carryOver.cleanup();
_carryOver = null;
_active.nActive = 0; //just in case
_active = null;
if (stop) {
wakePending();
_desktop = null;
stopped = true;
}
//wake up onPiggyback
synchronized (_mutex) {
_mutex.notify();
}
try {
Thread.sleep(100);
} catch (Throwable ex) {
}
//to minimize the chance that the server-push thread
//activate again, before onPiggback polls next _pending
}
}
return stopped;
}
/** The info of a server-push thread.
* It is also a mutex used to start a pending server-push thread.
*/
private static class ThreadInfo {
private final Thread thread;
/** # of activate() was called. */
private int nActive;
private ThreadInfo(Thread thread) {
this.thread = thread;
}
public String toString() {
return "[" + thread + ',' + nActive + ']';
}
}
}