only update topology when bookie rack changed

It is unnecessary to update  topology, removing and adding the same bookieNode, if the rack of bookie stay unchanged.

Reviewers: Yong Zhang <zhangyong1025.zy@gmail.com>, Nicolò Boschi <boschi1997@gmail.com>, Andrey Yegorov <None>, ZhangJian He <shoothzj@gmail.com>, Enrico Olivelli <eolivelli@gmail.com>

This closes #2790 from gaozhangmin/remove-unnecessary-update-rack

bookkeeper-server/src/main/java/org/apache/bookkeeper/client/TopologyAwareEnsemblePlacementPolicy.java

@@ -749,10 +749,12 @@ public void onBookieRackChange(List<BookieId> bookieAddressList) {
                     if (node != null) {
                         // refresh the rack info if its a known bookie
                         BookieNode newNode = createBookieNode(bookieAddress);
-                        topology.remove(node);
-                        topology.add(newNode);
-                        knownBookies.put(bookieAddress, newNode);
-                        historyBookies.put(bookieAddress, newNode);
+                        if (!newNode.getNetworkLocation().equals(node.getNetworkLocation())) {
+                            topology.remove(node);
+                            topology.add(newNode);
+                            knownBookies.put(bookieAddress, newNode);
+                            historyBookies.put(bookieAddress, newNode);
+                        }
                     }
                 } catch (IllegalArgumentException | NetworkTopologyImpl.InvalidTopologyException e) {
                     LOG.error("Failed to update bookie rack info: {} ", bookieAddress, e);

bookkeeper-server/src/test/java/org/apache/bookkeeper/client/TestRackawareEnsemblePlacementPolicy.java

@@ -2142,6 +2142,55 @@ public void testShuffleWithMask() {
         assertTrue(shuffleOccurred);
     }
 
+    @Test
+    public void testUpdateTopologyWithRackChange() throws Exception {
+        String defaultRackForThisTest = NetworkTopology.DEFAULT_REGION_AND_RACK;
+        repp.uninitalize();
+        updateMyRack(defaultRackForThisTest);
+
+        // Update cluster
+        BookieSocketAddress newAddr1 = new BookieSocketAddress("127.0.0.100", 3181);
+        BookieSocketAddress newAddr2 = new BookieSocketAddress("127.0.0.101", 3181);
+        BookieSocketAddress newAddr3 = new BookieSocketAddress("127.0.0.102", 3181);
+        BookieSocketAddress newAddr4 = new BookieSocketAddress("127.0.0.103", 3181);
+
+        // update dns mapping
+        StaticDNSResolver.addNodeToRack(newAddr1.getHostName(), defaultRackForThisTest);
+        StaticDNSResolver.addNodeToRack(newAddr2.getHostName(), defaultRackForThisTest);
+        StaticDNSResolver.addNodeToRack(newAddr3.getHostName(), defaultRackForThisTest);
+        StaticDNSResolver.addNodeToRack(newAddr4.getHostName(), defaultRackForThisTest);
+
+        TestStatsProvider statsProvider = new TestStatsProvider();
+        TestStatsLogger statsLogger = statsProvider.getStatsLogger("");
+
+        repp = new RackawareEnsemblePlacementPolicy();
+        repp.initialize(conf, Optional.<DNSToSwitchMapping> empty(), timer,
+                DISABLE_ALL, statsLogger, BookieSocketAddress.LEGACY_BOOKIEID_RESOLVER);
+        repp.withDefaultRack(defaultRackForThisTest);
+
+        Gauge<? extends Number> numBookiesInDefaultRackGauge = statsLogger
+                .getGauge(BookKeeperClientStats.NUM_WRITABLE_BOOKIES_IN_DEFAULT_RACK);
+
+        Set<BookieId> writeableBookies = new HashSet<>();
+        Set<BookieId> readOnlyBookies = new HashSet<>();
+        writeableBookies.add(newAddr1.toBookieId());
+        writeableBookies.add(newAddr2.toBookieId());
+        writeableBookies.add(newAddr3.toBookieId());
+        writeableBookies.add(newAddr4.toBookieId());
+        repp.onClusterChanged(writeableBookies, readOnlyBookies);
+        // only writable bookie - newAddr1 in default rack
+        assertEquals("NUM_WRITABLE_BOOKIES_IN_DEFAULT_RACK guage value", 4, numBookiesInDefaultRackGauge.getSample());
+
+        // newAddr4 rack is changed and it is not in default anymore
+        StaticDNSResolver
+                .changeRack(Collections.singletonList(newAddr3), Collections.singletonList("/default-region/r4"));
+        assertEquals("NUM_WRITABLE_BOOKIES_IN_DEFAULT_RACK guage value", 3, numBookiesInDefaultRackGauge.getSample());
+
+        StaticDNSResolver
+                .changeRack(Collections.singletonList(newAddr1), Collections.singletonList(defaultRackForThisTest));
+        assertEquals("NUM_WRITABLE_BOOKIES_IN_DEFAULT_RACK guage value", 3, numBookiesInDefaultRackGauge.getSample());
+    }
+
     @Test
     public void testNumBookiesInDefaultRackGauge() throws Exception {
         String defaultRackForThisTest = NetworkTopology.DEFAULT_REGION_AND_RACK;