/*
* Copyright (c) 2008-2017 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.cometd.oort;
import java.util.Map;
import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.UnavailableException;
import javax.servlet.http.HttpServlet;
import org.cometd.bayeux.Message;
import org.cometd.bayeux.client.ClientSessionChannel;
import org.cometd.bayeux.server.BayeuxServer;
import org.cometd.client.BayeuxClient;
import org.cometd.common.JSONContext;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* <p>This servlet serves as a base class for initializing and configuring an
* instance of the {@link Oort} CometD cluster manager.</p>
* <p>The following servlet init parameters are used to configure the Oort instance:</p>
* <ul>
* <li>{@code oort.url}, the absolute public URL to the CometD servlet</li>
* <li>{@code oort.secret}, the pre-shared secret that Oort servers use to authenticate
* connections from other Oort comets</li>
* <li>{@code oort.channels}, a comma separated list of channels that
* will be passed to {@link Oort#observeChannel(String)}</li>
* <li>{@code clientDebug}, a boolean that enables debugging of the
* clients connected to other oort cluster managers</li>
* </ul>
* <p>Override method {@link #newOort(BayeuxServer, String)} to return a customized
* instance of {@link Oort}.</p>
*
* @see SetiServlet
*/
public abstract class OortConfigServlet extends HttpServlet {
public static final String OORT_URL_PARAM = "oort.url";
public static final String OORT_SECRET_PARAM = "oort.secret";
public static final String OORT_CHANNELS_PARAM = "oort.channels";
public static final String OORT_ENABLE_ACK_EXTENSION_PARAM = "enableAckExtension";
public static final String OORT_ENABLE_BINARY_EXTENSION_PARAM = "enableBinaryExtension";
public static final String OORT_JSON_CONTEXT_PARAM = "jsonContext";
protected static final Logger LOG = LoggerFactory.getLogger(OortConfigServlet.class);
@Override
public void init(ServletConfig config) throws ServletException {
super.init(config);
ServletContext servletContext = config.getServletContext();
BayeuxServer bayeux = (BayeuxServer)servletContext.getAttribute(BayeuxServer.ATTRIBUTE);
if (bayeux == null) {
throw new UnavailableException("Missing " + BayeuxServer.ATTRIBUTE + " attribute");
}
String url = provideOortURL();
if (url == null) {
throw new UnavailableException("Missing " + OORT_URL_PARAM + " init parameter");
}
try {
Oort oort = newOort(bayeux, url);
String secret = config.getInitParameter(OORT_SECRET_PARAM);
if (secret != null) {
oort.setSecret(secret);
}
String enableAckExtension = config.getInitParameter(OORT_ENABLE_ACK_EXTENSION_PARAM);
if (enableAckExtension == null) {
enableAckExtension = "true";
}
oort.setAckExtensionEnabled(Boolean.parseBoolean(enableAckExtension));
String enableBinaryExtension = config.getInitParameter(OORT_ENABLE_BINARY_EXTENSION_PARAM);
if (enableBinaryExtension == null) {
enableBinaryExtension = "true";
}
oort.setBinaryExtensionEnabled(Boolean.parseBoolean(enableBinaryExtension));
String jsonContext = config.getInitParameter(OORT_JSON_CONTEXT_PARAM);
if (jsonContext != null) {
oort.setJSONContextClient((JSONContext.Client)getClass().getClassLoader().loadClass(jsonContext).newInstance());
}
oort.start();
servletContext.setAttribute(Oort.OORT_ATTRIBUTE, oort);
new Thread(new Starter(config, oort)).start();
} catch (Exception x) {
throw new ServletException(x);
}
}
/**
* <p>Retrieves the {@code oort.url} parameter from this servlet init parameters.</p>
* <p>Subclasses can override this method to compute the {@code oort.url} parameter
* dynamically, for example by retrieving the IP address of the host.</p>
*
* @return the {@code oort.url} parameter
*/
protected String provideOortURL() {
return getServletConfig().getInitParameter(OORT_URL_PARAM);
}
/**
* <p>Creates and returns a new Oort instance.</p>
*
* @param bayeux the BayeuxServer instance to which the Oort instance should be associated to
* @param url the {@code oort.url} of the Oort instance
* @return a new Oort instance
*/
protected Oort newOort(BayeuxServer bayeux, String url) {
return new Oort(bayeux, url);
}
/**
* <p>Configures the Oort cloud by establishing connections with other Oort comets.</p>
* <p>Subclasses implement their own strategy to discover and link with other comets.</p>
*
* @param config the servlet configuration to read parameters from
* @param oort the Oort instance associated with this configuration servlet
* @throws Exception if the cloud configuration fails
*/
protected abstract void configureCloud(ServletConfig config, Oort oort) throws Exception;
@Override
public void destroy() {
try {
ServletContext servletContext = getServletConfig().getServletContext();
Oort oort = (Oort)servletContext.getAttribute(Oort.OORT_ATTRIBUTE);
servletContext.removeAttribute(Oort.OORT_ATTRIBUTE);
if (oort != null) {
oort.stop();
}
} catch (Exception x) {
throw new RuntimeException(x);
}
}
private class Starter implements Runnable {
private final ServletConfig config;
private final Oort oort;
private final OortComet oortComet;
private Starter(ServletConfig config, Oort oort) {
this.config = config;
this.oort = oort;
this.oortComet = oort.newOortComet(oort.getURL());
this.oortComet.setOption(BayeuxClient.MAX_BACKOFF_OPTION, 1000L);
}
@Override
public void run() {
// Connect to myself until success. If the handshake fails,
// the normal BayeuxClient retry mechanism will kick-in.
if (LOG.isDebugEnabled()) {
LOG.debug("Connecting to self: {}", oort);
}
Map<String, Object> fields = oort.newOortHandshakeFields(oort.getURL(), null);
oortComet.handshake(fields, new ClientSessionChannel.MessageListener() {
@Override
public void onMessage(ClientSessionChannel channel, Message message) {
// If the handshake fails but has an advice field, it means it
// reached the server but was denied e.g. by a SecurityPolicy.
Map<String, Object> advice = message.getAdvice();
if (message.isSuccessful() || advice != null) {
if (LOG.isDebugEnabled()) {
LOG.debug("Connected to self: {}", oort);
}
oortComet.disconnect();
joinCloud();
}
}
});
}
private void joinCloud() {
try {
if (LOG.isDebugEnabled()) {
LOG.debug("Joining cloud: {}", oort);
}
configureCloud(config, oort);
String channels = config.getInitParameter(OORT_CHANNELS_PARAM);
if (channels != null) {
String[] patterns = channels.split(",");
for (String channel : patterns) {
channel = channel.trim();
if (channel.length() > 0) {
oort.observeChannel(channel);
}
}
}
} catch (Throwable x) {
LOG.warn("Could not start Oort", x);
destroy();
}
}
}
}