JVMCBC-1592 Shuffle node list instead of rotating

Motivation
----------
Avoid a pathological condition where the number of open buckets
is equal to the number of nodes, and the config refresh request
for one of the buckets always goes to a degraded node.

By randomizing the node selection, we ensure the request
eventually goes to one of the other nodes.

Change-Id: I013328fab5286775d796b1cc57ca0ba7933bb460
Reviewed-on: https://review.couchbase.org/c/couchbase-jvm-clients/+/221189
Tested-by: Build Bot <[email protected]>
Reviewed-by: Michael Reiche <[email protected]>

Author: dnault

core-io/src/main/java/com/couchbase/client/core/config/refresher/KeyValueBucketRefresher.java

@@ -46,7 +46,6 @@
 import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.atomic.AtomicInteger;
-import java.util.concurrent.atomic.AtomicLong;
 import java.util.stream.Collectors;
 
 import static com.couchbase.client.core.config.ConfigurationProvider.TRIGGERED_BY_CONFIG_CHANGE_NOTIFICATION;
@@ -97,12 +96,6 @@ public class KeyValueBucketRefresher implements BucketRefresher {
    */
   private final ConfigurationProvider provider;
 
-  /**
-   * The global offset is used to make sure each KV node eventually gets used
-   * by shifting on each invocation.
-   */
-  private final AtomicLong nodeOffset = new AtomicLong(0);
-
   /**
    * Holds all current registrations and their last timestamp when the bucket has been
    * updated.
@@ -242,7 +235,7 @@ private List<NodeInfo> filterEligibleNodes(final String name) {
     }
 
     List<NodeInfo> nodes = new ArrayList<>(config.nodes());
-    shiftNodeList(nodes);
+    Collections.shuffle(nodes);
 
     return nodes
       .stream()
@@ -313,16 +306,6 @@ private ConfigVersion currentVersion(String bucketName) {
     return config == null ? ConfigVersion.ZERO : config.version();
   }
 
-  /**
-   * Helper method to transparently rearrange the node list based on the current global offset.
-   *
-   * @param nodeList the list to shift.
-   */
-  private <T> void shiftNodeList(final List<T> nodeList) {
-    int shiftBy = (int) (nodeOffset.getAndIncrement() % nodeList.size());
-    Collections.rotate(nodeList, -shiftBy);
-  }
-
   @Override
   public Mono<Void> register(final String name) {
     return Mono.defer(() -> {