(pulsar) 06/06: [improve][misc] Optimize topic list hashing so that potentially large String allocation is avoided (#24525)

[lh...@apache.org]

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lhotari pushed a commit to branch branch-3.3
in repository https://gitbox.apache.org/repos/asf/pulsar.git

commit ab559c6b349fda017c387fe073acc5f7a0bfa5d8
Author: Lari Hotari <lh...@users.noreply.github.com>
AuthorDate: Thu Jul 17 10:18:57 2025 +0300

    [improve][misc] Optimize topic list hashing so that potentially large String allocation is avoided (#24525)
    
    (cherry picked from commit 06f424c4823399ae66608ad9fd0e2133a1055b1a)
---
 .../org/apache/pulsar/common/topics/TopicList.java   | 20 ++++++++++++++------
 .../apache/pulsar/common/topics/TopicListTest.java   | 19 ++++++++++++-------
 2 files changed, 26 insertions(+), 13 deletions(-)

diff --git a/pulsar-common/src/main/java/org/apache/pulsar/common/topics/TopicList.java b/pulsar-common/src/main/java/org/apache/pulsar/common/topics/TopicList.java
index 7a5659c33b5..1e0bde1b0c5 100644
--- a/pulsar-common/src/main/java/org/apache/pulsar/common/topics/TopicList.java
+++ b/pulsar-common/src/main/java/org/apache/pulsar/common/topics/TopicList.java
@@ -18,8 +18,10 @@
  */
 package org.apache.pulsar.common.topics;
 
+import com.google.common.hash.Hasher;
 import com.google.common.hash.Hashing;
 import java.nio.charset.StandardCharsets;
+import java.util.Arrays;
 import java.util.Collection;
 import java.util.HashSet;
 import java.util.List;
@@ -46,6 +48,7 @@ public class TopicList {
         Pattern topicsPattern = Pattern.compile(regex);
         return filterTopics(original, topicsPattern);
     }
+
     public static List<String> filterTopics(List<String> original, Pattern topicsPattern) {
 
         final Pattern shortenedTopicsPattern = Pattern.compile(removeTopicDomainScheme(topicsPattern.toString()));
@@ -68,14 +71,19 @@ public class TopicList {
     }
 
     public static String calculateHash(List<String> topics) {
-        return Hashing.crc32c().hashBytes(topics.stream()
-                .sorted()
-                .collect(Collectors.joining(","))
-                .getBytes(StandardCharsets.UTF_8)).toString();
+        Hasher hasher = Hashing.crc32c().newHasher();
+        String[] sortedTopics = topics.toArray(new String[topics.size()]);
+        Arrays.sort(sortedTopics);
+        for (int i = 0; i < sortedTopics.length; i++) {
+            hasher.putString(sortedTopics[i], StandardCharsets.UTF_8);
+            // Skip the delimiter for the last item so that the hash format is compatible with previous versions
+            if (i < sortedTopics.length - 1) {
+                hasher.putByte((byte) ',');
+            }
+        }
+        return hasher.hash().toString();
     }
 
-
-
     // get topics, which are contained in list1, and not in list2
     public static Set<String> minus(Collection<String> list1, Collection<String> list2) {
         HashSet<String> s1 = new HashSet<>(list1);
diff --git a/pulsar-common/src/test/java/org/apache/pulsar/common/topics/TopicListTest.java b/pulsar-common/src/test/java/org/apache/pulsar/common/topics/TopicListTest.java
index b3a7536ebff..843fe43966a 100644
--- a/pulsar-common/src/test/java/org/apache/pulsar/common/topics/TopicListTest.java
+++ b/pulsar-common/src/test/java/org/apache/pulsar/common/topics/TopicListTest.java
@@ -18,19 +18,18 @@
  */
 package org.apache.pulsar.common.topics;
 
+import static org.testng.Assert.assertEquals;
+import static org.testng.Assert.assertNotEquals;
+import static org.testng.Assert.assertTrue;
+import static org.testng.Assert.fail;
 import com.google.common.collect.Lists;
-import org.testng.annotations.Test;
-
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.List;
 import java.util.Set;
 import java.util.regex.Pattern;
 import java.util.stream.Stream;
-
-import static org.testng.Assert.assertEquals;
-import static org.testng.Assert.assertNotEquals;
-import static org.testng.Assert.assertTrue;
-import static org.testng.Assert.fail;
+import org.testng.annotations.Test;
 
 public class TopicListTest {
 
@@ -102,10 +101,16 @@ public class TopicListTest {
         String hash1 = TopicList.calculateHash(Arrays.asList(topicName3, topicName2, topicName1));
         String hash2 = TopicList.calculateHash(Arrays.asList(topicName1, topicName3, topicName2));
         assertEquals(hash1, hash2, "Hash must not depend on order of topics in the list");
+        assertEquals(hash1, "90d4a04a", "Hash must be equal to the expected value");
 
         String hash3 = TopicList.calculateHash(Arrays.asList(topicName1, topicName2));
         assertNotEquals(hash1, hash3, "Different list must have different hashes");
 
+        String hash4 = TopicList.calculateHash(Arrays.asList(topicName1));
+        assertEquals(hash4, "0d0602ed", "Hash must be equal to the expected value");
+
+        String hash5 = TopicList.calculateHash(Collections.emptyList());
+        assertEquals(hash5, "00000000", "Hash of empty list must be 0");
     }
 
     @Test