[GitHub] [ignite] ololo3000 commented on a change in pull request #7771: IGNITE-12894 Adds ability to wait for the service topology initialization.

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

ololo3000 commented on a change in pull request #7771:
URL: https://github.com/apache/ignite/pull/7771#discussion_r425044202



##########
File path: modules/core/src/main/java/org/apache/ignite/internal/processors/service/IgniteServiceProcessor.java
##########
@@ -823,19 +823,26 @@ else if (prj.predicate() == F.<ClusterNode>alwaysTrue())
 
         long startTime = U.currentTimeMillis();
 
-        Map<UUID, Integer> top;
+        ServiceInfo desc;
 
         while (true) {
-            top = serviceTopology(name);
+             desc = lookupInRegisteredServices(name);

Review comment:
       I got it. If after [1] but before [2] service will be deleted and full message with requested service topology will be received, topology of the local ServiceDescriptor reference will never be updated. Is that what you mean? 
   
   ```
   while (true) {
       desc = lookupInRegisteredServices(name);
   
       if (timeout == 0 && desc == null) // [1]
           return null;
   
       synchronized (servicesTopsUpdateMux) { // [2]
           if (desc != null && desc.topologyInitialized())
               return desc.topologySnapshot();
   
           long wait = 0;
   
           if (timeout != 0) {
               wait = timeout - (U.currentTimeMillis() - startTime);
   
               if (wait <= 0)
                   return desc == null ? null : desc.topologySnapshot();
           }
   
           try {
               servicesTopsUpdateMux.wait(wait);
           }
           catch (InterruptedException e) {
               throw new IgniteInterruptedCheckedException(e);
           }
       }
   }
   ```
   
   It seems that it will be enough to only move 
   
   ```
   desc = lookupInRegisteredServices(name);
   
   if (timeout == 0 && desc == null) // [1]
       return null;
   ```
   
   inside the syncgronization block. 
   In that case if service is removed before synchronization block or full message is received no matter the order, we will retrurn on 
   
   ```
    if (timeout == 0 && desc == null) 
       return null;
   ```
   
   if service is removed during synchronization block execution, we anyway will receive the full message and stop waiting.




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