[GitHub] clebertsuconic commented on a change in pull request #2548: ARTEMIS-2118 Enhanced Message Groups Support

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clebertsuconic commented on a change in pull request #2548: ARTEMIS-2118 Enhanced Message Groups Support
URL: https://github.com/apache/activemq-artemis/pull/2548#discussion_r259099336
 
 

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 File path: artemis-server/src/main/java/org/apache/activemq/artemis/core/server/impl/BucketMessageGroups.java
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+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.activemq.artemis.core.server.impl;
+
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.function.Predicate;
+import org.apache.activemq.artemis.api.core.SimpleString;
+
+/**
+ * BucketMessageGroups, stores values against a bucket, where the bucket used is based on the provided key objects hash.
+ *
+ * As such where keys compute to the same bucket they will act on that stored value, not the unique specific key.
+ *
+ * The number of buckets is provided at construction.
+ */
+public class BucketMessageGroups<C> implements MessageGroups<C> {
+
+   //This _AMQ_GROUP_BUCKET_INT_KEY uses the post-fixed value after this key, as an int, it is used for a few cases:
+   //1) For the admin screen we need to show a group key so we have to map back from int to something, as it expects SimpleString.
+   //2) Admin users still need to interact with a specific bucket/group e.g. they may need to reset a bucket.
+   //3) Choice of key is we want to avoid risk of clashing with users groups keys.
+   //4) Actually makes testing a little easier as we know how the parsed int will hash.
+   private static SimpleString _AMQ_GROUP_BUCKET_INT_KEY = new SimpleString("_AMQ_GROUP_BUCKET_INT_KEY_");
+
+   private final int bucketCount;
+   private C[] buckets;
+   private int size = 0;
+
+   public BucketMessageGroups(int bucketCount) {
+      if (bucketCount < 1) {
+         throw new IllegalArgumentException("Bucket count must be greater than 0");
+      }
+      this.bucketCount = bucketCount;
+   }
+
+   private int getBucket(SimpleString key) {
+      Object bucketKey = key;
+      if (key.startsWith(_AMQ_GROUP_BUCKET_INT_KEY)) {
+         bucketKey = retrieveBucketIntFromKey(key);
+      }
+      return getHashBucket(bucketKey, bucketCount);
+   }
+
+   private static int getHashBucket(final Object key, final int bucketCount) {
+      return (key.hashCode() & Integer.MAX_VALUE) % bucketCount;
 
 Review comment:
   Did you implement this from scratch or did you base it on the ActiveMQ5 bucket?
   
   We had an outstanding task to implement it based on AMQ5 version.

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