[fix][test] Fix flaky ModularLoadManagerImplTest and IsolatedBookieEnsemblePlacementPolicyTest (#25496)

Author: lhotari

pulsar-broker-common/src/test/java/org/apache/pulsar/bookie/rackawareness/IsolatedBookieEnsemblePlacementPolicyTest.java

@@ -522,11 +522,13 @@ public void testSecondaryIsolationGroupsBookies() throws Exception {
         defaultBookieGroup.put(BOOKIE5, BookieInfo.builder().rack("rack1").build());
 
         Map<String, BookieInfo> primaryIsolatedBookieGroup = new HashMap<>();
-        primaryIsolatedBookieGroup.put(BOOKIE1, BookieInfo.builder().rack("rack1").build());
+        // Use the same rack as in the default group to avoid non-deterministic rack
+        // resolution when the same bookie appears in multiple groups with different racks.
+        primaryIsolatedBookieGroup.put(BOOKIE1, BookieInfo.builder().rack("rack0").build());
 
         Map<String, BookieInfo> secondaryIsolatedBookieGroup = new HashMap<>();
-        secondaryIsolatedBookieGroup.put(BOOKIE2, BookieInfo.builder().rack("rack0").build());
-        secondaryIsolatedBookieGroup.put(BOOKIE4, BookieInfo.builder().rack("rack0").build());
+        secondaryIsolatedBookieGroup.put(BOOKIE2, BookieInfo.builder().rack("rack1").build());
+        secondaryIsolatedBookieGroup.put(BOOKIE4, BookieInfo.builder().rack("rack1").build());
 
         bookieMapping.put("default", defaultBookieGroup);
         bookieMapping.put(isolatedGroup, primaryIsolatedBookieGroup);

pulsar-broker/src/test/java/org/apache/pulsar/broker/loadbalance/impl/ModularLoadManagerImplTest.java

@@ -1063,6 +1063,11 @@ public void testRemoveNonExistBundleData()
         executorService.submit(latch::countDown);
         latch.await();
 
+        // Ensure lm1 has loaded broker data from both brokers before writing bundle data.
+        // Without this, lm1 may only see bundles from one broker, causing fewer than
+        // bundleNumbers bundles to be written to the metadata store.
+        lm1.updateAll();
+
         loadManagerWrapper.writeResourceQuotasToZooKeeper();
 
         MetadataCache<BundleData> bundlesCache = pulsar1.getLocalMetadataStore().getMetadataCache(BundleData.class);