[GitHub] [samza] vjagadish1989 commented on a change in pull request #952: Improved standby-aware container allocation for active-containers on job redeploys

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

vjagadish1989 commented on a change in pull request #952: Improved standby-aware container allocation for active-containers on job redeploys
URL: https://github.com/apache/samza/pull/952#discussion_r267638815
 
 

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 File path: samza-core/src/main/java/org/apache/samza/clustermanager/StandbyContainerManager.java
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 @@ -226,15 +244,35 @@ private void initiateActiveContainerFailover(String containerID, String resource
         // use this standby if there was no previous failover for which this standbyResource was used
         if (!(failoverMetadata.isPresent() && failoverMetadata.get().isStandbyResourceUsed(standbyContainerResource.getResourceID()))) {
 
-          log.info("Returning standby container {} in running state for active container {}", standbyContainerID,
-              activeContainerID);
-          return Optional.of(new Entry<>(standbyContainerID, standbyContainerResource));
+          log.info("Returning standby container {} in running state on host {} for active container {}", standbyContainerID, standbyContainerResource.getHost(), activeContainerID);
+          return standbyContainerResource.getHost();
         }
       }
     }
-
     log.info("Did not find any running standby container for active container {}", activeContainerID);
-    return Optional.empty();
+
+    // Now, we iterate over the list of last-known standbyHosts to check if anyone of them has not already been tried
+    Map<String, String> containerToHostMapping = this.samzaApplicationState.jobModelManager.jobModel().getAllContainerLocality();
+
+    for (String standbyContainerID : this.standbyContainerConstraints.get(activeContainerID)) {
+      String standbyHost = containerToHostMapping.get(standbyContainerID);
+
+      // if there is no last-known host for the standby, continue
+      if (standbyHost == null) {
+        continue;
 
 Review comment:
   the flow is a bit circuitous. avoid the `continue` and consider returning `any-host` here?

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