Revert "remove ServerDiscoverySelector from DruidLeaderClient (#9481)"

server/src/main/java/org/apache/druid/discovery/DruidLeaderClient.java

@@ -22,6 +22,8 @@
 import com.google.common.base.Preconditions;
 import com.google.common.base.Throwables;
 import com.google.common.util.concurrent.ListenableFuture;
+import org.apache.druid.client.selector.DiscoverySelector;
+import org.apache.druid.client.selector.Server;
 import org.apache.druid.concurrent.LifecycleLock;
 import org.apache.druid.java.util.common.IOE;
 import org.apache.druid.java.util.common.ISE;
@@ -70,6 +72,9 @@ public class DruidLeaderClient
 
   private final String leaderRequestPath;
 
+  //Note: This is kept for back compatibility with pre 0.11.0 releases and should be removed in future.
+  private final DiscoverySelector<Server> serverDiscoverySelector;
+
   private LifecycleLock lifecycleLock = new LifecycleLock();
   private DruidNodeDiscovery druidNodeDiscovery;
   private AtomicReference<String> currentKnownLeader = new AtomicReference<>();
@@ -78,13 +83,15 @@ public DruidLeaderClient(
       HttpClient httpClient,
       DruidNodeDiscoveryProvider druidNodeDiscoveryProvider,
       NodeRole nodeRoleToWatch,
-      String leaderRequestPath
+      String leaderRequestPath,
+      DiscoverySelector<Server> serverDiscoverySelector
   )
   {
     this.httpClient = httpClient;
     this.druidNodeDiscoveryProvider = druidNodeDiscoveryProvider;
     this.nodeRoleToWatch = nodeRoleToWatch;
     this.leaderRequestPath = leaderRequestPath;
+    this.serverDiscoverySelector = serverDiscoverySelector;
   }
 
   @LifecycleStart
@@ -296,6 +303,16 @@ private String getCurrentKnownLeader(final boolean cached) throws IOException
   @Nullable
   private String pickOneHost()
   {
+    Server server = serverDiscoverySelector.pick();
+    if (server != null) {
+      return StringUtils.format(
+          "%s://%s:%s",
+          server.getScheme(),
+          server.getAddress(),
+          server.getPort()
+      );
+    }
+
     Iterator<DiscoveryDruidNode> iter = druidNodeDiscovery.getAllNodes().iterator();
     if (iter.hasNext()) {
       DiscoveryDruidNode node = iter.next();

server/src/main/java/org/apache/druid/guice/CoordinatorDiscoveryModule.java

@@ -24,6 +24,8 @@
 import com.google.inject.Provides;
 import org.apache.druid.client.coordinator.Coordinator;
 import org.apache.druid.client.coordinator.CoordinatorSelectorConfig;
+import org.apache.druid.curator.discovery.ServerDiscoveryFactory;
+import org.apache.druid.curator.discovery.ServerDiscoverySelector;
 import org.apache.druid.discovery.DruidLeaderClient;
 import org.apache.druid.discovery.DruidNodeDiscoveryProvider;
 import org.apache.druid.discovery.NodeRole;
@@ -40,19 +42,32 @@ public void configure(Binder binder)
     JsonConfigProvider.bind(binder, "druid.selectors.coordinator", CoordinatorSelectorConfig.class);
   }
 
+  @Provides
+  @Coordinator
+  @ManageLifecycle
+  public ServerDiscoverySelector getServiceProvider(
+      CoordinatorSelectorConfig config,
+      ServerDiscoveryFactory serverDiscoveryFactory
+  )
+  {
+    return serverDiscoveryFactory.createSelector(config.getServiceName());
+  }
+
   @Provides
   @Coordinator
   @ManageLifecycle
   public DruidLeaderClient getLeaderHttpClient(
       @EscalatedGlobal HttpClient httpClient,
-      DruidNodeDiscoveryProvider druidNodeDiscoveryProvider
+      DruidNodeDiscoveryProvider druidNodeDiscoveryProvider,
+      @Coordinator ServerDiscoverySelector serverDiscoverySelector
   )
   {
     return new DruidLeaderClient(
         httpClient,
         druidNodeDiscoveryProvider,
         NodeRole.COORDINATOR,
-        "/druid/coordinator/v1/leader"
+        "/druid/coordinator/v1/leader",
+        serverDiscoverySelector
     );
   }
 }

server/src/main/java/org/apache/druid/guice/IndexingServiceDiscoveryModule.java

@@ -24,6 +24,8 @@
 import com.google.inject.Provides;
 import org.apache.druid.client.indexing.IndexingService;
 import org.apache.druid.client.indexing.IndexingServiceSelectorConfig;
+import org.apache.druid.curator.discovery.ServerDiscoveryFactory;
+import org.apache.druid.curator.discovery.ServerDiscoverySelector;
 import org.apache.druid.discovery.DruidLeaderClient;
 import org.apache.druid.discovery.DruidNodeDiscoveryProvider;
 import org.apache.druid.discovery.NodeRole;
@@ -40,19 +42,32 @@ public void configure(Binder binder)
     JsonConfigProvider.bind(binder, "druid.selectors.indexing", IndexingServiceSelectorConfig.class);
   }
 
+  @Provides
+  @IndexingService
+  @ManageLifecycle
+  public ServerDiscoverySelector getServiceProvider(
+      IndexingServiceSelectorConfig config,
+      ServerDiscoveryFactory serverDiscoveryFactory
+  )
+  {
+    return serverDiscoveryFactory.createSelector(config.getServiceName());
+  }
+
   @Provides
   @IndexingService
   @ManageLifecycle
   public DruidLeaderClient getLeaderHttpClient(
       @EscalatedGlobal HttpClient httpClient,
-      DruidNodeDiscoveryProvider druidNodeDiscoveryProvider
+      DruidNodeDiscoveryProvider druidNodeDiscoveryProvider,
+      @IndexingService ServerDiscoverySelector serverDiscoverySelector
   )
   {
     return new DruidLeaderClient(
         httpClient,
         druidNodeDiscoveryProvider,
         NodeRole.OVERLORD,
-        "/druid/indexer/v1/leader"
+        "/druid/indexer/v1/leader",
+        serverDiscoverySelector
     );
   }
 }

server/src/test/java/org/apache/druid/discovery/DruidLeaderClientTest.java

@@ -29,6 +29,7 @@
 import com.google.inject.name.Named;
 import com.google.inject.name.Names;
 import com.google.inject.servlet.GuiceFilter;
+import org.apache.druid.curator.discovery.ServerDiscoverySelector;
 import org.apache.druid.guice.GuiceInjectors;
 import org.apache.druid.guice.Jerseys;
 import org.apache.druid.guice.JsonConfigProvider;
@@ -122,7 +123,8 @@ public void testSimple() throws Exception
         httpClient,
         druidNodeDiscoveryProvider,
         NodeRole.PEON,
-        "/simple/leader"
+        "/simple/leader",
+        EasyMock.createNiceMock(ServerDiscoverySelector.class)
     );
     druidLeaderClient.start();
 
@@ -146,7 +148,8 @@ public void testNoLeaderFound() throws Exception
         httpClient,
         druidNodeDiscoveryProvider,
         NodeRole.PEON,
-        "/simple/leader"
+        "/simple/leader",
+        EasyMock.createNiceMock(ServerDiscoverySelector.class)
     );
     druidLeaderClient.start();
 
@@ -172,7 +175,8 @@ public void testRedirection() throws Exception
         httpClient,
         druidNodeDiscoveryProvider,
         NodeRole.PEON,
-        "/simple/leader"
+        "/simple/leader",
+        EasyMock.createNiceMock(ServerDiscoverySelector.class)
     );
     druidLeaderClient.start();
 
@@ -184,6 +188,9 @@ public void testRedirection() throws Exception
   @Test
   public void testServerFailureAndRedirect() throws Exception
   {
+    ServerDiscoverySelector serverDiscoverySelector = EasyMock.createMock(ServerDiscoverySelector.class);
+    EasyMock.expect(serverDiscoverySelector.pick()).andReturn(null).anyTimes();
+
     DruidNodeDiscovery druidNodeDiscovery = EasyMock.createMock(DruidNodeDiscovery.class);
     DiscoveryDruidNode dummyNode = new DiscoveryDruidNode(
         new DruidNode("test", "dummyhost", false, 64231, null, true, false),
@@ -196,13 +203,14 @@ public void testServerFailureAndRedirect() throws Exception
     DruidNodeDiscoveryProvider druidNodeDiscoveryProvider = EasyMock.createMock(DruidNodeDiscoveryProvider.class);
     EasyMock.expect(druidNodeDiscoveryProvider.getForNodeRole(NodeRole.PEON)).andReturn(druidNodeDiscovery).anyTimes();
 
-    EasyMock.replay(druidNodeDiscovery, druidNodeDiscoveryProvider);
+    EasyMock.replay(serverDiscoverySelector, druidNodeDiscovery, druidNodeDiscoveryProvider);
 
     DruidLeaderClient druidLeaderClient = new DruidLeaderClient(
         httpClient,
         druidNodeDiscoveryProvider,
         NodeRole.PEON,
-        "/simple/leader"
+        "/simple/leader",
+        serverDiscoverySelector
     );
     druidLeaderClient.start();
 
@@ -228,7 +236,8 @@ public void testFindCurrentLeader()
         httpClient,
         druidNodeDiscoveryProvider,
         NodeRole.PEON,
-        "/simple/leader"
+        "/simple/leader",
+        EasyMock.createNiceMock(ServerDiscoverySelector.class)
     );
     druidLeaderClient.start();
 

server/src/test/java/org/apache/druid/server/coordinator/duty/CompactSegmentsTest.java

@@ -360,7 +360,7 @@ private class TestDruidLeaderClient extends DruidLeaderClient
 
     private TestDruidLeaderClient(ObjectMapper jsonMapper)
     {
-      super(null, new TestNodeDiscoveryProvider(), null, null);
+      super(null, new TestNodeDiscoveryProvider(), null, null, null);
       this.jsonMapper = jsonMapper;
     }
 

sql/src/test/java/org/apache/druid/sql/calcite/util/CalciteTests.java

@@ -773,7 +773,10 @@ NodeRole.COORDINATOR, new FakeDruidNodeDiscovery(ImmutableMap.of(NodeRole.COORDI
         new FakeHttpClient(),
         provider,
         NodeRole.COORDINATOR,
-        "/simple/leader"
+        "/simple/leader",
+        () -> {
+          throw new UnsupportedOperationException();
+        }
     );
 
     return new SystemSchema(