[GitHub] [helix] pkuwm commented on a change in pull request #787: Fix tests in apache/zooscalability and rebase from apache/master

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

pkuwm commented on a change in pull request #787: Fix tests in apache/zooscalability and rebase from apache/master
URL: https://github.com/apache/helix/pull/787#discussion_r382276544
 
 

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 File path: helix-core/src/main/java/org/apache/helix/task/TaskUtil.java
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 @@ -1043,23 +1043,40 @@ public static void purgeExpiredJobs(String workflow, WorkflowConfig workflowConf
    * @param dataProvider
    * @param manager
    */
-  public static void workflowGarbageCollection(WorkflowControllerDataProvider dataProvider,
+  public static void workflowGarbageCollection(final WorkflowControllerDataProvider dataProvider,
       final HelixManager manager) {
     // Garbage collections for conditions where workflow context exists but config is missing.
-    Map<String, ZNRecord> contexts = dataProvider.getContexts();
-    HelixDataAccessor accessor = manager.getHelixDataAccessor();
-    HelixPropertyStore<ZNRecord> propertyStore = manager.getHelixPropertyStore();
 
+    Set<String> existingContexts;
+    /*
+     * Here try-catch is used to avoid concurrent modification exception while doing deep copy.
+     * Map.keySet() can produce concurrent modification exception.
+     * Reason: If the map is modified while an iteration over the set is in progress, concurrent
+     * modification exception will be thrown.
+     */
+    try {
+      existingContexts = new HashSet<>(dataProvider.getContexts().keySet());
+    } catch (Exception e) {
 
 Review comment:
   If we are catching concurrent modification exception, I think it is better to just catch this exception, instead of the general Exception.

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