[GitHub] [dubbo] qixiaobo commented on issue #8515: Dubbo ProviderConsumerRegTable class cause outOfMemory while no provider available exception occurs

[GitBox <gi...@apache.org>]

qixiaobo commented on issue #8515:
URL: https://github.com/apache/dubbo/issues/8515#issuecomment-899382144


   I found this in ReferenceConfig
   ```java
   
               if (urls.size() == 1) {
                   invoker = refprotocol.refer(interfaceClass, urls.get(0));
               } else {
                   List<Invoker<?>> invokers = new ArrayList<Invoker<?>>();
                   URL registryURL = null;
                   for (URL url : urls) {
                       invokers.add(refprotocol.refer(interfaceClass, url));
                       if (Constants.REGISTRY_PROTOCOL.equals(url.getProtocol())) {
                           registryURL = url; // use last registry url
                       }
                   }
                   if (registryURL != null) { // registry url is available
                       // use AvailableCluster only when register's cluster is available
                       URL u = registryURL.addParameterIfAbsent(Constants.CLUSTER_KEY, AvailableCluster.NAME);
                       invoker = cluster.join(new StaticDirectory(u, invokers));
                   } else { // not a registry url
                       invoker = cluster.join(new StaticDirectory(invokers));
                   }
               }
           }
   
           Boolean c = check;
           if (c == null && consumer != null) {
               c = consumer.isCheck();
           }
           if (c == null) {
               c = true; // default true
           }
           if (c && !invoker.isAvailable()) {
               // make it possible for consumer to retry later if provider is temporarily unavailable
               initialized = false;
               throw new IllegalStateException("Failed to check the status of the service " + interfaceName + ". No provider available for the service " + (group == null ? "" : group + "/") + interfaceName + (version == null ? "" : ":" + version) + " from the url " + invoker.getUrl() + " to the consumer " + NetUtils.getLocalHost() + " use dubbo version " + Version.getVersion());
           }
           if (logger.isInfoEnabled()) {
               logger.info("Refer dubbo service " + interfaceClass.getName() + " from url " + invoker.getUrl());
           }
           // create service proxy
           return (T) proxyFactory.getProxy(invoker);
       }
   ```
   We may see like this since "No provider available" 
   But with this code <code>refprotocol.refer</code> It may work below
   ```java
    private <T> Invoker<T> doRefer(Cluster cluster, Registry registry, Class<T> type, URL url) {
           RegistryDirectory<T> directory = new RegistryDirectory<T>(type, url);
           directory.setRegistry(registry);
           directory.setProtocol(protocol);
           // all attributes of REFER_KEY
           Map<String, String> parameters = new HashMap<String, String>(directory.getUrl().getParameters());
           URL subscribeUrl = new URL(Constants.CONSUMER_PROTOCOL, parameters.remove(Constants.REGISTER_IP_KEY), 0, type.getName(), parameters);
           if (!Constants.ANY_VALUE.equals(url.getServiceInterface())
                   && url.getParameter(Constants.REGISTER_KEY, true)) {
               URL registeredConsumerUrl = getRegisteredConsumerUrl(subscribeUrl, url);
               registry.register(registeredConsumerUrl);
               directory.setRegisteredConsumerUrl(registeredConsumerUrl);
           }
           directory.subscribe(subscribeUrl.addParameter(Constants.CATEGORY_KEY,
                   Constants.PROVIDERS_CATEGORY
                           + "," + Constants.CONFIGURATORS_CATEGORY
                           + "," + Constants.ROUTERS_CATEGORY));
   
           Invoker invoker = cluster.join(directory);
           ProviderConsumerRegTable.registerConsumer(invoker, url, subscribeUrl, directory);
           return invoker;
       }
   ```
   You may see registerConsumer executed before.
   So while we never remove consumerInvokers 
   This may cause oom


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