Shulou(Shulou.com)06/02 Report--

This article mainly explains "the principle and usage of subscribe and unsubscribe in NacosNamingService". The content of the explanation is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought to study and learn "the principle and usage of subscribe and unsubscribe in NacosNamingService".

Order

This paper mainly studies the subscribe and unsubscribe of NacosNamingService.

NacosNamingService

Nacos-1.1.3/client/src/main/java/com/alibaba/nacos/client/naming/NacosNamingService.java

Public class NacosNamingService implements NamingService {private static final String DEFAULT_PORT = "8080"; private static final long DEFAULT_HEART_BEAT_INTERVAL = TimeUnit.SECONDS.toMillis (5); / * * Each Naming instance should have different namespace. * / private String namespace; private String endpoint; private String serverList; private String cacheDir; private String logName; private HostReactor hostReactor; private BeatReactor beatReactor; private EventDispatcher eventDispatcher; private NamingProxy serverProxy; / /. Override public void subscribe (String serviceName, EventListener listener) throws NacosException {subscribe (serviceName, new ArrayList (), listener);} @ Override public void subscribe (String serviceName, String groupName, EventListener listener) throws NacosException {subscribe (serviceName, groupName, new ArrayList (), listener);} @ Override public void subscribe (String serviceName, List clusters, EventListener listener) throws NacosException {subscribe (serviceName, Constants.DEFAULT_GROUP, clusters, listener) } @ Override public void subscribe (String serviceName, String groupName, List clusters, EventListener listener) throws NacosException {eventDispatcher.addListener (hostReactor.getServiceInfo (NamingUtils.getGroupedName (serviceName, groupName), StringUtils.join (clusters, ","), StringUtils.join (clusters, ","), listener);} @ Override public void unsubscribe (String serviceName, EventListener listener) throws NacosException {unsubscribe (serviceName, new ArrayList (), listener) } @ Override public void unsubscribe (String serviceName, String groupName, EventListener listener) throws NacosException {unsubscribe (serviceName, groupName, new ArrayList (), listener);} @ Override public void unsubscribe (String serviceName, List clusters, EventListener listener) throws NacosException {unsubscribe (serviceName, Constants.DEFAULT_GROUP, clusters, listener) } @ Override public void unsubscribe (String serviceName, String groupName, List clusters, EventListener listener) throws NacosException {eventDispatcher.removeListener (NamingUtils.getGroupedName (serviceName, groupName), StringUtils.join (clusters, ","), listener);} /.}

Subscribe method executes eventDispatcher.addListener;unsubscribe method executes eventDispatcher.removeListener

EventDispatcher

Nacos-1.1.3/client/src/main/java/com/alibaba/nacos/client/naming/core/EventDispatcher.java

Public class EventDispatcher {private ExecutorService executor = null; private BlockingQueue changedServices = new LinkedBlockingQueue (); private ConcurrentMap observerMap = new ConcurrentHashMap (); public EventDispatcher () {executor = Executors.newSingleThreadExecutor (new ThreadFactory () {@ Override public Thread newThread (Runnable r) {Thread thread = newThread (r, "com.alibaba.nacos.naming.client.listener"); thread.setDaemon (true) Return thread;}}); executor.execute (new Notifier ());} public void addListener (ServiceInfo serviceInfo, String clusters, EventListener listener) {NAMING_LOGGER.info ("[LISTENER] adding" + serviceInfo.getName () + "with" + clusters + "to listener map"); List observers = Collections.synchronizedList (new ArrayList ()); observers.add (listener) Observers = observerMap.putIfAbsent (ServiceInfo.getKey (serviceInfo.getName (), clusters), observers); if (observers! = null) {observers.add (listener);} serviceChanged (serviceInfo);} public void removeListener (String serviceName, String clusters, EventListener listener) {NAMING_LOGGER.info ("[LISTENER] removing" + serviceName + "with" + clusters + "from listener map") List observers = observerMap.get (ServiceInfo.getKey (serviceName, clusters)); if (observers! = null) {Iterator iter = observers.iterator (); while (iter.hasNext ()) {EventListener oldListener = iter.next (); if (oldListener.equals (listener)) {iter.remove () }} if (observers.isEmpty ()) {observerMap.remove (ServiceInfo.getKey (serviceName, clusters));} public List getSubscribeServices () {List serviceInfos = new ArrayList (); for (String key: observerMap.keySet ()) {serviceInfos.add (ServiceInfo.fromKey (key)) } return serviceInfos;} public void serviceChanged (ServiceInfo serviceInfo) {if (serviceInfo = = null) {return;} changedServices.add (serviceInfo);} private class Notifier implements Runnable {@ Override public void run () {while (true) {ServiceInfo serviceInfo = null Try {serviceInfo = changedServices.poll (5, TimeUnit.MINUTES);} catch (Exception ignore) {} if (serviceInfo = = null) {continue;} try {List listeners = observerMap.get (serviceInfo.getKey ()) If (! CollectionUtils.isEmpty (listeners)) {for (EventListener listener: listeners) {List hosts = Collections.unmodifiableList (serviceInfo.getHosts ()); listener.onEvent (new NamingEvent (serviceInfo.getName (), serviceInfo.getGroupName (), serviceInfo.getClusters (), hosts)) } catch (Exception e) {NAMING_LOGGER.error ("[NA] notify error for service:" + serviceInfo.getName () + ", clusters:" + serviceInfo.getClusters (), e) } public void setExecutor (ExecutorService executor) {ExecutorService oldExecutor = this.executor; this.executor = executor; oldExecutor.shutdown ();}}

The constructor of EventDispatcher creates executor and executes Notifier;Notifier using a while true loop to continuously execute changedServices.poll (5, TimeUnit.MINUTES) to pull serviceInfo. If pulled, the corresponding EventListener list will be fetched from observerMap, and then the listener.onEvent method will be called back one by one.

The addListener method creates or adds an observers to the observerMap, and then executes the serviceChanged method; removeListener removes the specified listener from the observerMap, and deletes the key if the listener list of the specified key is empty

After the serviceChanged method adds serviceInfo; to the changedServices, the Notifier asynchronous thread can pull the information to perform the listener.onEvent callback

Summary

Subscribe method of NacosNamingService executes eventDispatcher.addListener;unsubscribe method executes eventDispatcher.removeListener

Thank you for your reading, the above is the content of "the principle and usage of subscribe and unsubscribe in NacosNamingService". After the study of this article, I believe you have a deeper understanding of the principle and use of subscribe and unsubscribe in NacosNamingService, and the specific use needs to be verified in practice. Here is, the editor will push for you more related knowledge points of the article, welcome to follow!

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.