From 2b9fed863f19510007f4bce08082ee42fb867eac Mon Sep 17 00:00:00 2001
From: huzheng <openinx@gmail.com>
Date: Tue, 20 Mar 2018 10:13:15 +0800
Subject: [PATCH] HBASE-20116 Optimize the region last pushed sequence id
 layout on zk

---
 .../ZKReplicationQueueStorage.java            | 22 ++++++++++++++-----
 .../TestReplicationStateBasic.java            |  3 ++-
 .../TestZKReplicationQueueStorage.java        | 10 +++++++++
 3 files changed, 28 insertions(+), 7 deletions(-)

diff --git a/hbase-replication/src/main/java/org/apache/hadoop/hbase/replication/ZKReplicationQueueStorage.java b/hbase-replication/src/main/java/org/apache/hadoop/hbase/replication/ZKReplicationQueueStorage.java
index 63f43e85347..6c9752a9f70 100644
--- a/hbase-replication/src/main/java/org/apache/hadoop/hbase/replication/ZKReplicationQueueStorage.java
+++ b/hbase-replication/src/main/java/org/apache/hadoop/hbase/replication/ZKReplicationQueueStorage.java
@@ -33,6 +33,7 @@ import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.Path;
 import org.apache.hadoop.hbase.HConstants;
 import org.apache.hadoop.hbase.ServerName;
+import org.apache.hadoop.hbase.client.RegionInfo;
 import org.apache.hadoop.hbase.exceptions.DeserializationException;
 import org.apache.hadoop.hbase.util.Bytes;
 import org.apache.hadoop.hbase.util.Pair;
@@ -138,19 +139,28 @@ class ZKReplicationQueueStorage extends ZKReplicationStorageBase
    * So the final znode path will be format like this:
    *
    * <pre>
-   * /hbase/replication/regions/254/dd04e76a6966d4ffa908ed0586764767-100
+   * /hbase/replication/regions/e1/ff/dd04e76a6966d4ffa908ed0586764767-100
    * </pre>
    *
-   * The 254 indicate the hash of encoded region name, the 100 indicate the peer id.
+   * The e1 indicate the first level hash of encoded region name, and the ff indicate the second
+   * level hash of encoded region name, the 100 indicate the peer id. <br>
+   * Note that here we use two-level hash because if only one-level hash (such as mod 65535), it
+   * will still lead to too many children under the /hbase/replication/regions znode.
    * @param encodedRegionName the encoded region name.
    * @param peerId peer id for replication.
    * @return ZNode path to persist the max sequence id that we've pushed for the given region and
    *         peer.
    */
-  private String getSerialReplicationRegionPeerNode(String encodedRegionName, String peerId) {
-    int hash = encodedRegionName.hashCode() & 0x0000FFFF;
-    String hashPath = ZNodePaths.joinZNode(regionsZNode, String.valueOf(hash));
-    return ZNodePaths.joinZNode(hashPath, String.format("%s-%s", encodedRegionName, peerId));
+  @VisibleForTesting
+  public String getSerialReplicationRegionPeerNode(String encodedRegionName, String peerId) {
+    if (encodedRegionName == null || encodedRegionName.length() != RegionInfo.MD5_HEX_LENGTH) {
+      throw new IllegalArgumentException(
+          "Invalid encoded region name: " + encodedRegionName + ", length should be 32.");
+    }
+    return new StringBuilder(regionsZNode).append(ZNodePaths.ZNODE_PATH_SEPARATOR)
+        .append(encodedRegionName.substring(0, 2)).append(ZNodePaths.ZNODE_PATH_SEPARATOR)
+        .append(encodedRegionName.substring(2, 4)).append(ZNodePaths.ZNODE_PATH_SEPARATOR)
+        .append(encodedRegionName).append("-").append(peerId).toString();
   }
 
   @Override
diff --git a/hbase-replication/src/test/java/org/apache/hadoop/hbase/replication/TestReplicationStateBasic.java b/hbase-replication/src/test/java/org/apache/hadoop/hbase/replication/TestReplicationStateBasic.java
index 21b09aa89b4..3ed41217ce6 100644
--- a/hbase-replication/src/test/java/org/apache/hadoop/hbase/replication/TestReplicationStateBasic.java
+++ b/hbase-replication/src/test/java/org/apache/hadoop/hbase/replication/TestReplicationStateBasic.java
@@ -285,7 +285,8 @@ public abstract class TestReplicationStateBasic {
     ServerName serverName1 = ServerName.valueOf("127.0.0.1", 8000, 10000);
     assertTrue(rqs.getAllQueues(serverName1).isEmpty());
     String queue1 = "1";
-    String region0 = "region0", region1 = "region1";
+    String region0 = "6b2c8f8555335cc9af74455b94516cbe",
+        region1 = "6ecd2e9e010499f8ddef97ee8f70834f";
     for (int i = 0; i < 10; i++) {
       rqs.addWAL(serverName1, queue1, getFileName("file1", i));
     }
diff --git a/hbase-replication/src/test/java/org/apache/hadoop/hbase/replication/TestZKReplicationQueueStorage.java b/hbase-replication/src/test/java/org/apache/hadoop/hbase/replication/TestZKReplicationQueueStorage.java
index c8138703c00..28cdff17f44 100644
--- a/hbase-replication/src/test/java/org/apache/hadoop/hbase/replication/TestZKReplicationQueueStorage.java
+++ b/hbase-replication/src/test/java/org/apache/hadoop/hbase/replication/TestZKReplicationQueueStorage.java
@@ -38,6 +38,7 @@ import org.apache.hadoop.hbase.util.Pair;
 import org.apache.zookeeper.KeeperException;
 import org.junit.After;
 import org.junit.AfterClass;
+import org.junit.Assert;
 import org.junit.BeforeClass;
 import org.junit.ClassRule;
 import org.junit.Test;
@@ -251,4 +252,13 @@ public class TestZKReplicationQueueStorage {
     assertEquals(1, allHFileRefs.size());
     assertThat(allHFileRefs, hasItems("test"));
   }
+
+  @Test
+  public void testRegionsZNodeLayout() throws Exception {
+    String peerId = "1";
+    String encodedRegionName = "31d9792f4435b99d9fb1016f6fbc8dc7";
+    String expectedPath = "/hbase/replication/regions/31/d9/" + encodedRegionName + "-" + peerId;
+    String path = STORAGE.getSerialReplicationRegionPeerNode(encodedRegionName, peerId);
+    Assert.assertEquals(expectedPath, path);
+  }
 }