[helix] 41/50: Update listClusters() in ZkHelixAdmin (#895)

[hu...@apache.org]

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hulee pushed a commit to branch zooscalability_merge
in repository https://gitbox.apache.org/repos/asf/helix.git

commit e4fad83cbe13ad3a8ba8107550e2b6fc0fa6988f
Author: Hunter Lee <hu...@linkedin.com>
AuthorDate: Fri Mar 13 17:28:01 2020 -0700

    Update listClusters() in ZkHelixAdmin (#895)
    
    This PR updates getClusters() in ZkHelixAdmin in realm-aware mode. It is difficult to reason about getting all clusters - and this method, on single-realm mode, is also broken anyways because in the case users create nested clusters, this method will end up returning nothing. This update is backward-compatible for single-realm users.
    
    Ideally, users should use Metadata Store Directory Service to get the list of all clusters.
---
 .../main/java/org/apache/helix/manager/zk/ZKHelixAdmin.java   | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/helix-core/src/main/java/org/apache/helix/manager/zk/ZKHelixAdmin.java b/helix-core/src/main/java/org/apache/helix/manager/zk/ZKHelixAdmin.java
index 7beaed8..689d3c9 100644
--- a/helix-core/src/main/java/org/apache/helix/manager/zk/ZKHelixAdmin.java
+++ b/helix-core/src/main/java/org/apache/helix/manager/zk/ZKHelixAdmin.java
@@ -955,6 +955,12 @@ public class ZKHelixAdmin implements HelixAdmin {
 
   @Override
   public List<String> getClusters() {
+    if (Boolean.getBoolean(SystemPropertyKeys.MULTI_ZK_ENABLED)
+        || _zkClient instanceof FederatedZkClient) {
+      throw new UnsupportedOperationException(
+          "getClusters() is not supported in multi-realm mode! Use Metadata Store Directory Service instead!");
+    }
+
     List<String> zkToplevelPathes = _zkClient.getChildren("/");
     List<String> result = new ArrayList<String>();
     for (String pathName : zkToplevelPathes) {
@@ -1953,7 +1959,10 @@ public class ZKHelixAdmin implements HelixAdmin {
 
       // Resolve RealmAwareZkClientConfig
       if (realmAwareZkClientConfig == null) {
-        realmAwareZkClientConfig = new RealmAwareZkClient.RealmAwareZkClientConfig();
+        // ZkHelixAdmin should have ZNRecordSerializer set by default
+        realmAwareZkClientConfig = new RealmAwareZkClient.RealmAwareZkClientConfig()
+            .setZkSerializer(
+                new org.apache.helix.zookeeper.datamodel.serializer.ZNRecordSerializer());
       }
 
       // Resolve RealmAwareZkConnectionConfig