org.appng.api.messaging.Messaging Maven / Gradle / Ivy
/*
* Copyright 2011-2021 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.appng.api.messaging;
import java.io.Closeable;
import java.io.IOException;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.concurrent.ExecutorService;
import org.appng.api.Environment;
import org.appng.api.Platform;
import org.appng.api.Scope;
import org.appng.api.model.Properties;
import lombok.extern.slf4j.Slf4j;
/**
* A utility class offering static helper methods to create and retrieve a {@link Sender} and to shutdown
* {@link Sender}s and {@link Receiver}s.
*
* @author Matthias Müller
*
* @see Sender
* @see Receiver
*/
@Slf4j
public class Messaging {
/**
* Name of a system property used to identify the node
*/
public static final String APPNG_NODE_ID = "appng.node.id";
/**
* Retrieves the previously created {@link Sender} from the {@link Environment}.
*
* @param env
* the {@link Environment} to use
*
* @return the {@link Sender}, if available
*
* @see #createMessageSender(Environment, ExecutorService)
* @see #createMessageSender(Environment, ExecutorService, String, EventHandler, Iterable)
*/
public static Sender getMessageSender(Environment env) {
return env.getAttribute(Scope.PLATFORM, Platform.Environment.MESSAGE_SENDER);
}
/**
* Creates and returns a new {@link Sender} and a corresponding {@link Receiver}. The class name for the receiver is
* taken from the platform property {@value org.appng.api.Platform.Property#MESSAGING_RECEIVER}. Uses the system
* property {@value #APPNG_NODE_ID} to retrieve the node id for the {@link Serializer}. If this property is absent,
* the local host name is used and the property is set.
*
* @param env
* the {@link Environment} to use
* @param executor
* the {@link ExecutorService} to run the {@link Receiver} with
*
* @return
*
* - the {@link Sender} (if the platform property
* {@value org.appng.api.Platform.Property#MESSAGING_ENABLED} is {@code true}
*
- {@code null} if messaging is disabled or an error occurred while creating the sender
*
*/
public static Sender createMessageSender(Environment env, ExecutorService executor) {
return createMessageSender(env, executor, getNodeId(env), null, null);
}
/**
* Determines the node id for this node. If the system property {@value #APPNG_NODE_ID} is set, this value is used.
* Otherwise, the local host name is used (from {@code java.net.InetAddress.getLocalHost().getHostName()}}).
*
* @param env
* the {@link Environment} to use
*
* @return the node id for this node
*/
public static String getNodeId(Environment env) {
String nodeId = System.getProperty(APPNG_NODE_ID);
if (null == nodeId && getPlatformConfig(env).getBoolean("messagingFallbackToHostName", Boolean.TRUE)) {
try {
nodeId = InetAddress.getLocalHost().getHostName();
LOGGER.info("system property {} is not set, using local host name {} as fallback", APPNG_NODE_ID,
nodeId);
System.setProperty(APPNG_NODE_ID, nodeId);
} catch (UnknownHostException e) {
LOGGER.warn(String.format("error setting system property %s", APPNG_NODE_ID), e);
}
}
return nodeId;
}
protected static Properties getPlatformConfig(Environment env) {
return env.getAttribute(Scope.PLATFORM, Platform.Environment.PLATFORM_CONFIG);
}
/**
* Creates and returns a new {@link Sender} and a corresponding {@link Receiver}. The class name for the receiver is
* taken from the platform property {@value org.appng.api.Platform.Property#MESSAGING_RECEIVER}.
*
* @param env
* the {@link Environment} to use
* @param executor
* the {@link ExecutorService} to run the {@link Receiver} with
* @param nodeId
* the node id for the {@link Serializer}
* @param defaultHandler
* the default {@link EventHandler} for the {@link Receiver} (may be {@code null})
* @param handlers
* a list of {@link EventHandler}s to be registered at the {@link Receiver}
*
* @return
*
* - the {@link Sender} (if the platform property
* {@value org.appng.api.Platform.Property#MESSAGING_ENABLED} is {@code true}
*
- {@code null} if messaging is disabled or an error occurred while creating the sender
*
*/
public static Sender createMessageSender(Environment env, ExecutorService executor, String nodeId,
EventHandler defaultHandler, Iterable> handlers) {
if (isEnabled(env)) {
Sender sender = env.getAttribute(Scope.PLATFORM, Platform.Environment.MESSAGE_SENDER);
if (null == sender) {
try {
LOGGER.info("node id is {}", nodeId);
Serializer eventSerializer = new Serializer(env, nodeId);
String messagingReceiverClassName = getPlatformConfig(env)
.getString(Platform.Property.MESSAGING_RECEIVER);
@SuppressWarnings("unchecked")
Class messagingReceiverClass = (Class) Class
.forName(messagingReceiverClassName);
LOGGER.info("using message receiver {}", messagingReceiverClass);
Receiver eventReceiver = messagingReceiverClass.newInstance().configure(eventSerializer);
if (null != defaultHandler) {
eventReceiver.setDefaultHandler(defaultHandler);
}
if (null != handlers) {
for (EventHandler eventHandler : handlers) {
eventReceiver.registerHandler(eventHandler);
}
}
eventReceiver.runWith(executor);
sender = eventReceiver.createSender();
LOGGER.info("created message sender {}", sender.getClass().getName());
env.setAttribute(Scope.PLATFORM, Platform.Environment.MESSAGE_SENDER, sender);
env.setAttribute(Scope.PLATFORM, Platform.Environment.MESSAGE_RECEIVER, eventReceiver);
return sender;
} catch (ReflectiveOperationException e) {
LOGGER.error("error while initializing messaging", e);
shutdown(env);
}
}
} else {
LOGGER.info("messaging is disabled");
}
return null;
}
public static boolean isEnabled(Environment env) {
return getPlatformConfig(env).getBoolean(Platform.Property.MESSAGING_ENABLED);
}
/**
* Shuts down the messaging system, i.e. calls {@link Closeable#close()} for the {@link Sender} and the
* {@link Receiver} (in case the latter do implement {@link Closeable})
*
* @param env
* then {@link Environment} to use
*/
public static void shutdown(Environment env) {
close(env.getAttribute(Scope.PLATFORM, Platform.Environment.MESSAGE_RECEIVER));
close(env.getAttribute(Scope.PLATFORM, Platform.Environment.MESSAGE_SENDER));
}
private static void close(Object o) {
if (null != o && o instanceof Closeable) {
try {
LOGGER.info("Closing {}", o);
((Closeable) o).close();
} catch (IOException e) {
LOGGER.error("Error while closing " + o, e);
}
}
}
}
© 2015 - 2025 Weber Informatics LLC | Privacy Policy