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Posted to commits@lucene.apache.org by ma...@apache.org on 2021/01/24 02:18:21 UTC

[lucene-solr] 14/16: wip

This is an automated email from the ASF dual-hosted git repository.

markrmiller pushed a commit to branch reference_impl_dev
in repository https://gitbox.apache.org/repos/asf/lucene-solr.git

commit f1e301577cade8beeb2f16315c817a7ba06c67fd
Author: markrmiller@gmail.com <ma...@gmail.com>
AuthorDate: Fri Jan 22 20:59:55 2021 -0600

    wip
---
 .../java/org/apache/solr/cloud/LeaderElector.java  |  23 ++---
 .../org/apache/solr/cloud/RecoveryStrategy.java    |  34 +++----
 .../solr/cloud/ShardLeaderElectionContext.java     |  35 ++++---
 .../java/org/apache/solr/cloud/ZkController.java   |  26 ++---
 .../java/org/apache/solr/core/CoreContainer.java   |  91 +++++++++---------
 .../java/org/apache/solr/handler/IndexFetcher.java |  11 +--
 .../handler/component/RealTimeGetComponent.java    |   1 +
 .../org/apache/solr/update/AddUpdateCommand.java   |  10 +-
 .../src/java/org/apache/solr/update/PeerSync.java  |  30 +++++-
 .../org/apache/solr/update/PeerSyncWithLeader.java |  13 ++-
 .../src/java/org/apache/solr/update/UpdateLog.java | 107 ++++++++++-----------
 .../org/apache/solr/update/UpdateShardHandler.java |   2 +-
 .../CollectionsAPIDistributedZkTest.java           |   1 +
 .../org/apache/solr/common/SolrInputDocument.java  |   3 +-
 .../apache/solr/common/cloud/SolrZooKeeper.java    |  32 +++---
 .../apache/solr/common/cloud/ZkStateReader.java    |  58 +++++------
 16 files changed, 248 insertions(+), 229 deletions(-)

diff --git a/solr/core/src/java/org/apache/solr/cloud/LeaderElector.java b/solr/core/src/java/org/apache/solr/cloud/LeaderElector.java
index c9b7ffe..ac2cbe9 100644
--- a/solr/core/src/java/org/apache/solr/cloud/LeaderElector.java
+++ b/solr/core/src/java/org/apache/solr/cloud/LeaderElector.java
@@ -184,11 +184,11 @@ public class LeaderElector implements Closeable {
             oldWatcher.close();
           }
 
-          if ((zkController != null && zkController.getCoreContainer().isShutDown())) {
-            if (log.isDebugEnabled()) log.debug("Elector is closed, will not try and run leader processes");
-            state = OUT_OF_ELECTION;
-            return false;
-          }
+//          if ((zkController != null && zkController.getCoreContainer().isShutDown())) {
+//            if (log.isDebugEnabled()) log.debug("Elector is closed, will not try and run leader processes");
+//            state = OUT_OF_ELECTION;
+//            return false;
+//          }
 
           state = POT_LEADER;
           runIamLeaderProcess(context, replacement);
@@ -267,12 +267,12 @@ public class LeaderElector implements Closeable {
   // TODO: get this core param out of here
   protected void runIamLeaderProcess(final ElectionContext context, boolean weAreReplacement) throws KeeperException,
           InterruptedException, IOException {
-    if (state == CLOSED) {
-      throw new AlreadyClosedException();
-    }
-    if (state == LEADER) {
-      throw new IllegalStateException("Already in leader state");
-    }
+//    if (state == CLOSED) {
+//      throw new AlreadyClosedException();
+//    }
+//    if (state == LEADER) {
+//      throw new IllegalStateException("Already in leader state");
+//    }
 
     boolean success = context.runLeaderProcess(context, weAreReplacement, 0);
 
@@ -280,6 +280,7 @@ public class LeaderElector implements Closeable {
       state = LEADER;
     } else {
       state = OUT_OF_ELECTION;
+      throw new SolrException(SolrException.ErrorCode.SERVER_ERROR, "Failed becoming leader");
     }
   }
 
diff --git a/solr/core/src/java/org/apache/solr/cloud/RecoveryStrategy.java b/solr/core/src/java/org/apache/solr/cloud/RecoveryStrategy.java
index eb377d6..ee085b2 100644
--- a/solr/core/src/java/org/apache/solr/cloud/RecoveryStrategy.java
+++ b/solr/core/src/java/org/apache/solr/cloud/RecoveryStrategy.java
@@ -56,7 +56,6 @@ import org.apache.solr.util.plugin.NamedListInitializedPlugin;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import static org.apache.solr.common.cloud.ZkStateReader.COLLECTIONS_ZKNODE;
 import java.io.Closeable;
 import java.io.IOException;
 import java.lang.invoke.MethodHandles;
@@ -230,10 +229,11 @@ public class RecoveryStrategy implements Runnable, Closeable {
 
     log.info("Attempting to replicate from [{}].", leaderprops);
 
-    final String leaderUrl = getReplicateLeaderUrl(leaderprops, zkStateReader);
-
+    String leaderUrl;
     // send commit
     try {
+      Replica leader = zkController.getZkStateReader().getLeaderRetry(coreDescriptor.getCollectionName(), coreDescriptor.getCloudDescriptor().getShardId(), 1500, false);
+      leaderUrl = leader.getCoreUrl();
       commitOnLeader(leaderUrl);
     } catch (Exception e) {
       log.error("Commit on leader failed", e);
@@ -610,20 +610,6 @@ public class RecoveryStrategy implements Runnable, Closeable {
           return false;
         }
 
-        log.info("Begin buffering updates. core=[{}]", coreName);
-        // recalling buffer updates will drop the old buffer tlog
-        ulog.bufferUpdates();
-
-//        try {
-//          if (prevSendPreRecoveryHttpUriRequest != null) {
-//            prevSendPreRecoveryHttpUriRequest.cancel();
-//          }
-//        } catch (NullPointerException e) {
-//          // okay
-//        }
-       // TODO can we do this with commit on leader
-        sendPrepRecoveryCmd(leader.getBaseUrl(), leader.getName(), zkStateReader.getClusterState().getCollection(coreDescriptor.getCollectionName()).getSlice(cloudDesc.getShardId()));
-
         // we wait a bit so that any updates on the leader
         // that started before they saw recovering state
         // are sure to have finished (see SOLR-7141 for
@@ -684,6 +670,20 @@ public class RecoveryStrategy implements Runnable, Closeable {
 
           try {
 
+            log.info("Begin buffering updates. core=[{}]", coreName);
+            // recalling buffer updates will drop the old buffer tlog
+            ulog.bufferUpdates();
+
+            //        try {
+            //          if (prevSendPreRecoveryHttpUriRequest != null) {
+            //            prevSendPreRecoveryHttpUriRequest.cancel();
+            //          }
+            //        } catch (NullPointerException e) {
+            //          // okay
+            //        }
+            // TODO can we do this with commit on leader
+            sendPrepRecoveryCmd(leader.getBaseUrl(), leader.getName(), zkStateReader.getClusterState().getCollection(coreDescriptor.getCollectionName()).getSlice(cloudDesc.getShardId()));
+
             IndexFetcher.IndexFetchResult result = replicate(leader);
 
             if (result.getSuccessful()) {
diff --git a/solr/core/src/java/org/apache/solr/cloud/ShardLeaderElectionContext.java b/solr/core/src/java/org/apache/solr/cloud/ShardLeaderElectionContext.java
index 93cfb38..f74f5dc 100644
--- a/solr/core/src/java/org/apache/solr/cloud/ShardLeaderElectionContext.java
+++ b/solr/core/src/java/org/apache/solr/cloud/ShardLeaderElectionContext.java
@@ -38,7 +38,6 @@ import org.apache.solr.logging.MDCLoggingContext;
 import org.apache.solr.update.PeerSync;
 import org.apache.solr.update.UpdateLog;
 import org.apache.zookeeper.KeeperException;
-import org.apache.zookeeper.KeeperException.SessionExpiredException;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -103,19 +102,19 @@ final class ShardLeaderElectionContext extends ShardLeaderElectionContextBase {
         log.error("No SolrCore found, cannot become leader {}", coreName);
         throw new AlreadyClosedException("No SolrCore found, cannot become leader " + coreName);
       }
-      if (core.isClosing() || core.getCoreContainer().isShutDown()) {
-        log.info("We are closed, will not become leader");
-        closed = true;
-        cancelElection();
-        return false;
-      }
+//      if (core.isClosing() || core.getCoreContainer().isShutDown()) {
+//        log.info("We are closed, will not become leader");
+//        closed = true;
+//        cancelElection();
+//        return false;
+//      }
       try {
 
-        core.getSolrCoreState().cancelRecovery(true, false);
+       // core.getSolrCoreState().cancelRecovery(true, false);
 
         ActionThrottle lt;
 
-        MDCLoggingContext.setCore(core);
+      //  MDCLoggingContext.setCore(core);
         lt = core.getUpdateHandler().getSolrCoreState().getLeaderThrottle();
 
         lt.minimumWaitBetweenActions();
@@ -138,7 +137,8 @@ final class ShardLeaderElectionContext extends ShardLeaderElectionContextBase {
         replicaType = cloudCd.getReplicaType();
         // should I be leader?
 
-        ZkShardTerms zkShardTerms = zkController.getShardTerms(collection, shardId);
+        log.info("Check zkShardTerms");
+        ZkShardTerms zkShardTerms = zkController.getShardTermsOrNull(collection, shardId);
         try {
           // if the replica is waiting for leader to see recovery state, the leader should refresh its terms
           if (zkShardTerms != null && zkShardTerms.skipSendingUpdatesTo(coreName)) {
@@ -152,7 +152,7 @@ final class ShardLeaderElectionContext extends ShardLeaderElectionContextBase {
           log.error("Exception while looking at refreshing shard terms", e);
         }
         
-        if (zkShardTerms.registered(coreName) && !zkShardTerms.canBecomeLeader(coreName)) {
+        if (zkShardTerms != null && zkShardTerms.registered(coreName) && !zkShardTerms.canBecomeLeader(coreName)) {
           if (!waitForEligibleBecomeLeaderAfterTimeout(zkShardTerms, coreName, leaderVoteWait)) {
             rejoinLeaderElection(core);
             return false;
@@ -166,9 +166,9 @@ final class ShardLeaderElectionContext extends ShardLeaderElectionContextBase {
 
         PeerSync.PeerSyncResult result = null;
         boolean success = false;
-        if (core.getCoreContainer().isShutDown()) {
-          return false;
-        }
+//        if (core.getCoreContainer().isShutDown()) {
+//          return false;
+//        }
         result = syncStrategy.sync(zkController, core, leaderProps, weAreReplacement);
         log.info("Sync strategy sync result {}", result);
         success = result.isSuccess();
@@ -242,8 +242,11 @@ final class ShardLeaderElectionContext extends ShardLeaderElectionContextBase {
         // in case of leaderVoteWait timeout, a replica with lower term can win the election
         if (setTermToMax) {
           log.error("WARNING: Potential data loss -- Replica {} became leader after timeout (leaderVoteWait) " + "without being up-to-date with the previous leader", coreName);
-          zkController.createCollectionTerms(collection);
-          zkController.getShardTerms(collection, shardId).setTermEqualsToLeader(coreName);
+          try {
+            zkController.getShardTerms(collection, shardId).setTermEqualsToLeader(coreName);
+          } catch (Exception e) {
+            log.error("Exception trying to set shard terms equal to leader", e);
+          }
         }
 
         super.runLeaderProcess(context, weAreReplacement, 0);
diff --git a/solr/core/src/java/org/apache/solr/cloud/ZkController.java b/solr/core/src/java/org/apache/solr/cloud/ZkController.java
index f146d1b..b2abf8f 100644
--- a/solr/core/src/java/org/apache/solr/cloud/ZkController.java
+++ b/solr/core/src/java/org/apache/solr/cloud/ZkController.java
@@ -329,9 +329,8 @@ public class ZkController implements Closeable, Runnable {
     }
 
     public Object call() throws Exception {
-      if (log.isInfoEnabled()) {
-        log.info("Registering core {} afterExpiration? {}", descriptor.getName(), afterExpiration);
-      }
+      log.info("Registering core with ZK {} afterExpiration? {}", descriptor.getName(), afterExpiration);
+
 
       if (zkController.isDcCalled() || zkController.getCoreContainer().isShutDown() || (afterExpiration && !descriptor.getCloudDescriptor().hasRegistered())) {
         return null;
@@ -1422,25 +1421,26 @@ public class ZkController implements Closeable, Runnable {
 
       log.info("Wait to see leader for {}, {}", collection, shardId);
       Replica leader = null;
-      for (int i = 0; i < 30; i++) {
-//        if (leaderElector.isLeader()) {
-//          leader = replica;
-//          break;
-//        }
+      for (int i = 0; i < 15; i++) {
+        if (leaderElector.isLeader()) {
+          leader = replica;
+          break;
+        }
 
         try {
-          if (getCoreContainer().isShutDown() || isDcCalled() || isClosed()) {
-            throw new AlreadyClosedException();
-          }
+//          if (getCoreContainer().isShutDown() || isDcCalled() || isClosed()) {
+//            throw new AlreadyClosedException();
+//          }
 
-          leader = zkStateReader.getLeaderRetry(collection, shardId, 500, false);
+          leader = zkStateReader.getLeaderRetry(collection, shardId, 1500, false);
 
         } catch (TimeoutException timeoutException) {
-
+           log.info("Timeout waiting to see leader, retry");
         }
       }
 
       if (leader == null) {
+        log.error("No leader found while trying to register " + coreName + " with zookeeper");
         throw new SolrException(ErrorCode.SERVER_ERROR, "No leader found while trying to register " + coreName + " with zookeeper");
       }
 
diff --git a/solr/core/src/java/org/apache/solr/core/CoreContainer.java b/solr/core/src/java/org/apache/solr/core/CoreContainer.java
index ab33eae..26f6a17 100644
--- a/solr/core/src/java/org/apache/solr/core/CoreContainer.java
+++ b/solr/core/src/java/org/apache/solr/core/CoreContainer.java
@@ -102,7 +102,6 @@ import org.apache.solr.util.SystemIdResolver;
 import org.apache.zookeeper.KeeperException;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
-import org.slf4j.MDC;
 
 import static java.util.Objects.requireNonNull;
 import static org.apache.solr.common.params.CommonParams.AUTHC_PATH;
@@ -158,7 +157,6 @@ public class CoreContainer implements Closeable {
   private static final Logger log = LoggerFactory.getLogger(MethodHandles.lookup().lookupClass());
 
   final SolrCores solrCores = new SolrCores(this);
-  private final boolean isZkAware;
   private volatile boolean startedLoadingCores;
   private volatile boolean loaded;
 
@@ -347,19 +345,17 @@ public class CoreContainer implements Closeable {
     assert ObjectReleaseTracker.track(this);
     assert (closeTracker = new CloseTracker()) != null;
     this.containerProperties = new Properties(config.getSolrProperties());
-    String zkHost = System.getProperty("zkHost");
-    if (!StringUtils.isEmpty(zkHost)) {
-      zkSys = new ZkContainer(zkClient);
-      isZkAware = true;
-    } else {
-      isZkAware = false;
-    }
 
     this.loader = config.getSolrResourceLoader();
 
     this.solrHome = config.getSolrHome();
     this.cfg = requireNonNull(config);
 
+    if (zkClient != null) {
+      zkSys = new ZkContainer(zkClient);
+      zkSys.initZooKeeper(this, cfg.getCloudConfig());
+    }
+
     if (null != this.cfg.getBooleanQueryMaxClauseCount()) {
       IndexSearcher.setMaxClauseCount(this.cfg.getBooleanQueryMaxClauseCount());
     }
@@ -403,9 +399,7 @@ public class CoreContainer implements Closeable {
         }
       });
     }
-    if (zkClient != null) {
-      zkSys.initZooKeeper(this, cfg.getCloudConfig());
-    }
+
     coreConfigService = ConfigSetService.createConfigSetService(cfg, loader, zkSys == null ? null : zkSys.zkController);
 
     containerProperties.putAll(cfg.getSolrProperties());
@@ -606,7 +600,6 @@ public class CoreContainer implements Closeable {
     cfg = null;
     containerProperties = null;
     replayUpdatesExecutor = null;
-    isZkAware = false;
   }
 
 
@@ -881,26 +874,26 @@ public class CoreContainer implements Closeable {
     status |= CORE_DISCOVERY_COMPLETE;
     startedLoadingCores = true;
     for (final CoreDescriptor cd : cds) {
-//      if (isZooKeeperAware()) {
-//        String collection = cd.getCollectionName();
-//        try {
-//          zkSys.zkController.zkStateReader.waitForState(collection, 5, TimeUnit.SECONDS, (n, c) -> {
-//            if (c != null) {
-//              Replica replica = c.getReplica(cd.getName());
-//
-//              if (replica.getState().equals(State.DOWN)) {
-//                return true;
-//              }
-//
-//            }
-//            return false;
-//          });
-//        } catch (InterruptedException e) {
-//          ParWork.propagateInterrupt(e);
-//        } catch (TimeoutException e) {
-//          log.error("Timeout", e);
-//        }
-//      }
+      if (isZooKeeperAware()) {
+        String collection = cd.getCollectionName();
+        try {
+          zkSys.zkController.zkStateReader.waitForState(collection, 5, TimeUnit.SECONDS, (n, c) -> {
+            if (c != null) {
+              Replica replica = c.getReplica(cd.getName());
+
+              if (replica.getState().equals(State.DOWN)) {
+                return true;
+              }
+
+            }
+            return false;
+          });
+        } catch (InterruptedException e) {
+          ParWork.propagateInterrupt(e);
+        } catch (TimeoutException e) {
+          log.error("Timeout", e);
+        }
+      }
 
       if (log.isDebugEnabled()) log.debug("Process core descriptor {} {} {}", cd.getName(), cd.isTransient(), cd.isLoadOnStartup());
       if (cd.isTransient() || !cd.isLoadOnStartup()) {
@@ -911,25 +904,20 @@ public class CoreContainer implements Closeable {
       if (cd.isLoadOnStartup()) {
 
         coreLoadFutures.add(solrCoreLoadExecutor.submit(() -> {
-          SolrCore core;
+          SolrCore core = null;
           MDCLoggingContext.setCoreDescriptor(this, cd);
           try {
             try {
 
               core = createFromDescriptor(cd, false);
 
-              if (core.getDirectoryFactory().isSharedStorage()) {
-                if (isZooKeeperAware()) {
-                  zkSys.getZkController().throwErrorIfReplicaReplaced(cd);
-                }
-              }
-
             } finally {
               solrCores.markCoreAsNotLoading(cd);
             }
-            if (isZooKeeperAware()) {
-              new ZkController.RegisterCoreAsync(zkSys.zkController, cd, false).call();
-            }
+
+          } catch (Exception e){
+            log.error("Error creating and register core {}", cd.getName(), e);
+            throw e;
           } finally {
             MDCLoggingContext.clear();
           }
@@ -1409,9 +1397,7 @@ public class CoreContainer implements Closeable {
             throw new AlreadyClosedException("Solr has been shutdown.");
           }
           solrCores.markCoreAsLoading(dcore);
-          if (isZooKeeperAware()) {
-            ParWork.getRootSharedExecutor().submit(new ZkController.RegisterCoreAsync(zkSys.zkController, dcore, false));
-          }
+
           core = new SolrCore(this, dcore, coreConfig);
         } catch (Exception e) {
           core = processCoreCreateException(e, dcore, coreConfig);
@@ -1421,6 +1407,17 @@ public class CoreContainer implements Closeable {
 
         old = registerCore(dcore, core, true);
         registered = true;
+        solrCores.markCoreAsNotLoading(dcore);
+
+        if (isZooKeeperAware()) {
+          if (!newCollection) {
+            if (core.getDirectoryFactory().isSharedStorage()) {
+              zkSys.getZkController().throwErrorIfReplicaReplaced(dcore);
+            }
+          }
+          new ZkController.RegisterCoreAsync(zkSys.zkController, dcore, false).call();
+        }
+
       } catch (Exception e) {
 
         throw new SolrException(ErrorCode.SERVER_ERROR, e);
@@ -2168,7 +2165,7 @@ public class CoreContainer implements Closeable {
   }
 
   public boolean isZooKeeperAware() {
-    return isZkAware && zkSys != null && zkSys.zkController != null;
+    return zkSys != null && zkSys.zkController != null;
   }
 
   public ZkController getZkController() {
diff --git a/solr/core/src/java/org/apache/solr/handler/IndexFetcher.java b/solr/core/src/java/org/apache/solr/handler/IndexFetcher.java
index 6ac1139..07887b3 100644
--- a/solr/core/src/java/org/apache/solr/handler/IndexFetcher.java
+++ b/solr/core/src/java/org/apache/solr/handler/IndexFetcher.java
@@ -44,10 +44,8 @@ import org.apache.solr.common.SolrException.ErrorCode;
 import org.apache.solr.common.cloud.Replica;
 import org.apache.solr.common.params.CommonParams;
 import org.apache.solr.common.params.ModifiableSolrParams;
-import org.apache.solr.common.util.ExecutorUtil;
 import org.apache.solr.common.util.FastInputStream;
 import org.apache.solr.common.util.NamedList;
-import org.apache.solr.common.util.SolrNamedThreadFactory;
 import org.apache.solr.common.util.SuppressForbidden;
 import org.apache.solr.core.DirectoryFactory;
 import org.apache.solr.core.DirectoryFactory.DirContext;
@@ -522,7 +520,7 @@ public class IndexFetcher {
       }
 
       // Create the sync service
-      fsyncService = ExecutorUtil.newMDCAwareSingleThreadExecutor(new SolrNamedThreadFactory("fsyncService"));
+      fsyncService = ParWork.getExecutorService(15);
       // use a synchronized list because the list is read by other threads (to show details)
       filesDownloaded = Collections.synchronizedList(new ArrayList<Map<String, Object>>());
       // if the generation of master is older than that of the slave , it means they are not compatible to be copied
@@ -812,7 +810,6 @@ public class IndexFetcher {
    * terminate the fsync service and wait for all the tasks to complete. If it is already terminated
    */
   private void terminateAndWaitFsyncService() throws Exception {
-    if (fsyncServiceFuture == null || fsyncService.isTerminated()) return;
     fsyncService.shutdown();
     // give a long wait say 1 hr
     fsyncService.awaitTermination(3600, TimeUnit.SECONDS);
@@ -1722,11 +1719,11 @@ public class IndexFetcher {
         throw e;
       } finally {
         cleanup(null);
-        //if cleanup succeeds . The file is downloaded fully. do an fsync
+        //if cleanup succeeds . The file is downloaded fully
         fsyncServiceFuture = fsyncService.submit(() -> {
           try {
-            log.info("Sync and close fetched file", file);
-            file.sync();
+            log.info("Close fetched file", file);
+            file.close();
           } catch (Exception e) {
             fsyncException = e;
           }
diff --git a/solr/core/src/java/org/apache/solr/handler/component/RealTimeGetComponent.java b/solr/core/src/java/org/apache/solr/handler/component/RealTimeGetComponent.java
index 63eff4b..2c2dd9c 100644
--- a/solr/core/src/java/org/apache/solr/handler/component/RealTimeGetComponent.java
+++ b/solr/core/src/java/org/apache/solr/handler/component/RealTimeGetComponent.java
@@ -1189,6 +1189,7 @@ public class RealTimeGetComponent extends SearchComponent
 
     // TODO: get this from cache instead of rebuilding?
     try (UpdateLog.RecentUpdates recentUpdates = ulog.getRecentUpdates()) {
+      log.info("Get updates  versionsRequested={} params={}", versions.size(), params);
       for (Long version : versions) {
         try {
           Object o = recentUpdates.lookup(version);
diff --git a/solr/core/src/java/org/apache/solr/update/AddUpdateCommand.java b/solr/core/src/java/org/apache/solr/update/AddUpdateCommand.java
index e192fe9..8c945f0 100644
--- a/solr/core/src/java/org/apache/solr/update/AddUpdateCommand.java
+++ b/solr/core/src/java/org/apache/solr/update/AddUpdateCommand.java
@@ -43,7 +43,7 @@ public class AddUpdateCommand extends UpdateCommand {
    * Higher level SolrInputDocument, normally used to construct the Lucene Document(s)
    * to index.
    */
-  public SolrInputDocument solrDoc;
+  public volatile SolrInputDocument solrDoc;
 
   /**
    * This is the version of a document, previously indexed, on which the current
@@ -51,7 +51,7 @@ public class AddUpdateCommand extends UpdateCommand {
    * or a full update. A negative value here, e.g. -1, indicates that this add
    * update does not depend on a previous update.
    */
-  public long prevVersion = -1;
+  public volatile long prevVersion = -1;
 
   public boolean overwrite = true;
 
@@ -62,14 +62,14 @@ public class AddUpdateCommand extends UpdateCommand {
 
   public int commitWithin = -1;
 
-  public boolean isLastDocInBatch = false;
+  public volatile boolean isLastDocInBatch = false;
 
   /** Is this a nested update, null means not yet calculated. */
-  public Boolean isNested = null;
+  public volatile Boolean isNested = null;
 
   // optional id in "internal" indexed form... if it is needed and not supplied,
   // it will be obtained from the doc.
-  private BytesRef indexedId;
+  private volatile BytesRef indexedId;
 
   public AddUpdateCommand(SolrQueryRequest req) {
     super(req);
diff --git a/solr/core/src/java/org/apache/solr/update/PeerSync.java b/solr/core/src/java/org/apache/solr/update/PeerSync.java
index 387f27e..d24f905 100644
--- a/solr/core/src/java/org/apache/solr/update/PeerSync.java
+++ b/solr/core/src/java/org/apache/solr/update/PeerSync.java
@@ -441,7 +441,7 @@ public class PeerSync implements SolrMetricProducer {
     Object fingerprint = srsp.getSolrResponse().getResponse().get("fingerprint");
 
     if (log.isInfoEnabled()) {
-      log.info("{} Received {} versions from {} fingerprint:{}", msg(), otherVersions.size(), sreq.shards[0], fingerprint);
+      log.info("{} Received {} versions from {} {} fingerprint:{}", msg(), otherVersions.size(), otherVersions, sreq.shards[0], fingerprint);
     }
     if (fingerprint != null) {
       sreq.fingerprint = IndexFingerprint.fromObject(fingerprint);
@@ -524,7 +524,7 @@ public class PeerSync implements SolrMetricProducer {
 
     SyncShardRequest sreq = (SyncShardRequest) srsp.getShardRequest();
     if (updates.size() < sreq.totalRequestedUpdates) {
-      log.error("{} Requested {} updates from {} but retrieved {}", msg(), sreq.totalRequestedUpdates, sreq.shards[0], updates.size());
+      log.error("{} Requested {} updates from {} but retrieved {} {}", msg(), sreq.totalRequestedUpdates, sreq.shards[0], updates.size(), srsp.getSolrResponse().getResponse());
       return false;
     }
     
@@ -746,7 +746,7 @@ public class PeerSync implements SolrMetricProducer {
       return true;
     }
 
-    MissedUpdatesRequest handleVersionsWithRanges(List<Long> otherVersions, boolean completeList) {
+    static MissedUpdatesRequest handleVersionsWithRanges(List<Long> ourUpdates, List<Long> otherVersions, boolean completeList, long ourLowThreshold) {
       // we may endup asking for updates for too many versions, causing 2MB post payload limit. Construct a range of
       // versions to request instead of asking individual versions
       List<String> rangesToRequest = new ArrayList<>();
@@ -788,9 +788,31 @@ public class PeerSync implements SolrMetricProducer {
       }
 
       String rangesToRequestStr = rangesToRequest.stream().collect(Collectors.joining(","));
+
+      log.info("handleVersionsWithRanges rangesToRequestStr={} otherVersions={} ourVersions={} completeList={} totalRequestedVersions={}", rangesToRequestStr, otherVersions, ourUpdates, completeList, totalRequestedVersions);
+
       return MissedUpdatesRequest.of(rangesToRequestStr, totalRequestedVersions);
     }
 
+    public static void main(String[] args) {
+
+      List<Long> ourUpdates = new ArrayList<>();
+      ourUpdates.add(1689636098592997376l);
+      ourUpdates.add(1689636098591948800l);
+      ourUpdates.add(1689636098531131395l);
+      ourUpdates.add(1689636098531131394l);
+
+//1689636098592997376, 1689636098591948800, 1689636098585657345
+      List<Long> otherVersions = new ArrayList<>();
+      otherVersions.add(1689636098531131395l);
+      otherVersions.add(1689636098531131394l);
+      otherVersions.add(0l);
+//1689636098531131395, 1689636098531131394, 0
+      MissedUpdatesRequest result = handleVersionsWithRanges(ourUpdates, otherVersions, false, 0);
+      System.out.println(result.versionsAndRanges);
+      System.out.println(result.totalRequestedUpdates);
+    }
+
     MissedUpdatesRequest handleIndividualVersions(List<Long> otherVersions, boolean completeList) {
       List<Long> toRequest = new ArrayList<>();
       for (Long otherVersion : otherVersions) {
@@ -867,7 +889,7 @@ public class PeerSync implements SolrMetricProducer {
 
       MissedUpdatesRequest updatesRequest;
       if (canHandleVersionRanges.get()) {
-        updatesRequest = handleVersionsWithRanges(otherVersions, completeList);
+        updatesRequest = handleVersionsWithRanges(ourUpdates, otherVersions, completeList, ourLowThreshold);
       } else {
         updatesRequest = handleIndividualVersions(otherVersions, completeList);
       }
diff --git a/solr/core/src/java/org/apache/solr/update/PeerSyncWithLeader.java b/solr/core/src/java/org/apache/solr/update/PeerSyncWithLeader.java
index 4582fc6..b670372 100644
--- a/solr/core/src/java/org/apache/solr/update/PeerSyncWithLeader.java
+++ b/solr/core/src/java/org/apache/solr/update/PeerSyncWithLeader.java
@@ -244,7 +244,7 @@ public class PeerSyncWithLeader implements SolrMetricProducer {
 
     MissedUpdatesRequest updatesRequest = missedUpdatesFinder.find(otherVersions, leaderUrl, () -> core.getSolrConfig().useRangeVersionsForPeerSync && canHandleVersionRanges());
     if (updatesRequest == MissedUpdatesRequest.EMPTY) {
-      if (doFingerprint) return MissedUpdatesRequest.UNABLE_TO_SYNC;
+      if (doFingerprint && updatesRequest.totalRequestedUpdates > 0) return MissedUpdatesRequest.UNABLE_TO_SYNC;
       return MissedUpdatesRequest.ALREADY_IN_SYNC;
     }
 
@@ -273,7 +273,7 @@ public class PeerSyncWithLeader implements SolrMetricProducer {
     List<Object> updates = (List<Object>)rsp.get("updates");
 
     if (updates.size() < numRequestedUpdates) {
-      log.error("{} Requested {} updated from {} but retrieved {}", msg(), numRequestedUpdates, leaderUrl, updates.size());
+      log.error("{} Requested {} updated from {} but retrieved {} {}", msg(), numRequestedUpdates, leaderUrl, updates.size(), rsp);
       return false;
     }
 
@@ -298,13 +298,16 @@ public class PeerSyncWithLeader implements SolrMetricProducer {
         // only DBI or DBQ in the gap (above) will satisfy this predicate
         return version > leaderFingerprint.getMaxVersionEncountered() && (oper == UpdateLog.DELETE || oper == UpdateLog.DELETE_BY_QUERY);
       });
+      log.info("existDBIOrDBQInTheGap={}", existDBIOrDBQInTheGap);
       if (!existDBIOrDBQInTheGap) {
         // it is safe to use leaderFingerprint.maxVersionEncountered as cut point now.
         updates.removeIf(e -> {
           @SuppressWarnings({"unchecked"})
           List<Object> u = (List<Object>) e;
           long version = (Long) u.get(1);
-          return version > leaderFingerprint.getMaxVersionEncountered();
+          boolean success = version > leaderFingerprint.getMaxVersionEncountered();
+          log.info("existDBIOrDBQInTheGap version={}  leaderFingerprint.getMaxVersionEncountered={} success={}", version, leaderFingerprint.getMaxVersionEncountered(), success);
+          return success;
         });
       }
     }
@@ -312,6 +315,7 @@ public class PeerSyncWithLeader implements SolrMetricProducer {
     try {
       updater.applyUpdates(updates, leaderUrl);
     } catch (Exception e) {
+      log.error("Could not apply updates", e);
       return false;
     }
     return true;
@@ -386,6 +390,7 @@ public class PeerSyncWithLeader implements SolrMetricProducer {
       if (cmp != 0) {
         if (log.isDebugEnabled()) log.debug("Leader fingerprint: {}, Our fingerprint: {}", leaderFingerprint , ourFingerprint);
       }
+
       return cmp == 0;  // currently, we only check for equality...
     } catch (IOException e) {
       log.warn("Could not confirm if we are already in sync. Continue with PeerSync");
@@ -426,7 +431,7 @@ public class PeerSyncWithLeader implements SolrMetricProducer {
       boolean completeList = leaderVersions.size() < nUpdates;
       MissedUpdatesRequest updatesRequest;
       if (canHandleVersionRanges.get()) {
-        updatesRequest = handleVersionsWithRanges(leaderVersions, completeList);
+        updatesRequest = handleVersionsWithRanges(ourUpdates, leaderVersions, completeList, ourLowThreshold);
       } else {
         updatesRequest = handleIndividualVersions(leaderVersions, completeList);
       }
diff --git a/solr/core/src/java/org/apache/solr/update/UpdateLog.java b/solr/core/src/java/org/apache/solr/update/UpdateLog.java
index 0f51d41..39fa5de 100644
--- a/solr/core/src/java/org/apache/solr/update/UpdateLog.java
+++ b/solr/core/src/java/org/apache/solr/update/UpdateLog.java
@@ -190,25 +190,25 @@ public class UpdateLog implements PluginInfoInitialized, SolrMetricProducer {
   protected volatile TransactionLog bufferTlog;
   protected volatile TransactionLog tlog;
 
-  protected TransactionLog prevTlog;
+  protected volatile TransactionLog prevTlog;
   protected TransactionLog prevTlogOnPrecommit;
   protected final Deque<TransactionLog> logs = new LinkedList<>();  // list of recent logs, newest first
   protected final LinkedList<TransactionLog> newestLogsOnStartup = new LinkedList<>();
-  protected int numOldRecords;  // number of records in the recent logs
+  protected volatile int numOldRecords;  // number of records in the recent logs
 
   protected volatile Map<BytesRef,LogPtr> map = new ConcurrentHashMap<>(32);
   protected volatile Map<BytesRef,LogPtr> prevMap;  // used while committing/reopening is happening
   protected volatile Map<BytesRef,LogPtr> prevMap2;  // used while committing/reopening is happening
-  protected TransactionLog prevMapLog;  // the transaction log used to look up entries found in prevMap
-  protected TransactionLog prevMapLog2;  // the transaction log used to look up entries found in prevMap2
+  protected volatile TransactionLog prevMapLog;  // the transaction log used to look up entries found in prevMap
+  protected volatile TransactionLog prevMapLog2;  // the transaction log used to look up entries found in prevMap2
 
   protected final int numDeletesToKeep = 1000;
   protected final int numDeletesByQueryToKeep = 100;
-  protected int numRecordsToKeep;
+  protected volatile int numRecordsToKeep;
   protected volatile int maxNumLogsToKeep;
   protected volatile int numVersionBuckets = 65536; // This should only be used to initialize VersionInfo... the actual number of buckets may be rounded up to a power of two.
-  protected Long maxVersionFromIndex = null;
-  protected boolean existOldBufferLog = false;
+  protected volatile Long maxVersionFromIndex = null;
+  protected volatile boolean existOldBufferLog = false;
 
   // keep track of deletes only... this is not updated on an add
   protected Map<BytesRef, LogPtr> oldDeletes = Collections.synchronizedMap(new LinkedHashMap<BytesRef, LogPtr>(numDeletesToKeep) {
@@ -1142,22 +1142,18 @@ public class UpdateLog implements PluginInfoInitialized, SolrMetricProducer {
   // synchronization is needed for stronger guarantees (as VersionUpdateProcessor does).
   public Long lookupVersion(BytesRef indexedId) {
     LogPtr entry;
-    tlogLock.lock();
-    try {
-      entry = map.get(indexedId);
-      // SolrCore.verbose("TLOG: lookup ver: for id ",indexedId.utf8ToString(),"in map",System.identityHashCode(map),"got",entry,"lookupLog=",lookupLog);
-      if (entry == null && prevMap != null) {
-        entry = prevMap.get(indexedId);
-        // something found in prevMap will always be found in prevMapLog (which could be tlog or prevTlog)
-        // SolrCore.verbose("TLOG: lookup ver: for id ",indexedId.utf8ToString(),"in prevMap",System.identityHashCode(map),"got",entry,"lookupLog=",lookupLog);
-      }
-      if (entry == null && prevMap2 != null) {
-        entry = prevMap2.get(indexedId);
-        // something found in prevMap2 will always be found in prevMapLog2 (which could be tlog or prevTlog)
-        // SolrCore.verbose("TLOG: lookup ver: for id ",indexedId.utf8ToString(),"in prevMap2",System.identityHashCode(map),"got",entry,"lookupLog=",lookupLog);
-      }
-    } finally {
-      tlogLock.unlock();
+
+    entry = map.get(indexedId);
+    // SolrCore.verbose("TLOG: lookup ver: for id ",indexedId.utf8ToString(),"in map",System.identityHashCode(map),"got",entry,"lookupLog=",lookupLog);
+    if (entry == null && prevMap != null) {
+      entry = prevMap.get(indexedId);
+      // something found in prevMap will always be found in prevMapLog (which could be tlog or prevTlog)
+      // SolrCore.verbose("TLOG: lookup ver: for id ",indexedId.utf8ToString(),"in prevMap",System.identityHashCode(map),"got",entry,"lookupLog=",lookupLog);
+    }
+    if (entry == null && prevMap2 != null) {
+      entry = prevMap2.get(indexedId);
+      // something found in prevMap2 will always be found in prevMapLog2 (which could be tlog or prevTlog)
+      // SolrCore.verbose("TLOG: lookup ver: for id ",indexedId.utf8ToString(),"in prevMap2",System.identityHashCode(map),"got",entry,"lookupLog=",lookupLog);
     }
 
 
@@ -1174,12 +1170,8 @@ public class UpdateLog implements PluginInfoInitialized, SolrMetricProducer {
 
     // We can't get any version info for deletes from the index, so if the doc
     // wasn't found, check a cache of recent deletes.
-    tlogLock.lock();
-    try {
-      entry = oldDeletes.get(indexedId);
-    } finally {
-      tlogLock.unlock();
-    }
+
+    entry = oldDeletes.get(indexedId);
 
     if (entry != null) {
       return entry.version;
@@ -1195,15 +1187,10 @@ public class UpdateLog implements PluginInfoInitialized, SolrMetricProducer {
     if (syncLevel == SyncLevel.NONE) {
       return;
     }
-    TransactionLog currLog;
-    tlogLock.lock();
-    try {
-      currLog = tlog;
-      if (currLog == null) return;
-      currLog.incref();
-    } finally {
-      tlogLock.unlock();
-    }
+
+    TransactionLog currLog = tlog;
+    if (currLog == null) return;
+    currLog.incref();
 
     try {
       currLog.finish(syncLevel);
@@ -1327,20 +1314,16 @@ public class UpdateLog implements PluginInfoInitialized, SolrMetricProducer {
   public void commitAndSwitchToNewTlog(CommitUpdateCommand cuc) {
     versionInfo.blockUpdates();
     try {
-      tlogLock.lock();
+      if (tlog == null) {
+        return;
+      }
+      preCommit(cuc);
       try {
-        if (tlog == null) {
-          return;
-        }
-        preCommit(cuc);
-        try {
-          copyOverOldUpdates(cuc.getVersion());
-        } finally {
-          postCommit(cuc);
-        }
+        copyOverOldUpdates(cuc.getVersion());
       } finally {
-        tlogLock.unlock();
+        postCommit(cuc);
       }
+
     } finally {
       versionInfo.unblockUpdates();
     }
@@ -1611,19 +1594,29 @@ public class UpdateLog implements PluginInfoInitialized, SolrMetricProducer {
       for (List<Update> singleList : updateList) {
         for (Update ptr : singleList) {
           if(Math.abs(ptr.version) > Math.abs(maxVersion)) continue;
-          ret.add(ptr.version);
+          if (ptr.version != 0) {
+            ret.add(ptr.version);
+          }
           if (--n <= 0) return ret;
         }
       }
+      log.info("Return getVersions {} {}", n, ret);
 
       return ret;
     }
 
     public Object lookup(long version) {
+      log.info("lookup {}", version);
       Update update = updates.get(version);
       if (update == null) return null;
 
-      return update.log.lookup(update.pointer);
+      log.info("found update from updates {} {}", update.version, updates.size());
+
+      Object object = update.log.lookup(update.pointer);
+
+      log.info("found update from log {} {} ptr={} object={}", update.version, update.log, update.pointer, object);
+
+      return object;
     }
 
     /** Returns the list of deleteByQueries that happened after the given version */
@@ -1640,7 +1633,7 @@ public class UpdateLog implements PluginInfoInitialized, SolrMetricProducer {
 
     private void update() {
       int numUpdates = 0;
-      updateList = new ArrayList<>(logList.size());
+      updateList = new ArrayList<>(numRecordsToKeep);
       deleteByQueryList = new ArrayList<>();
       deleteList = new ArrayList<>();
       updates = new HashMap<>(numRecordsToKeep);
@@ -1705,12 +1698,14 @@ public class UpdateLog implements PluginInfoInitialized, SolrMetricProducer {
               // would be caused by a corrupt transaction log
             } catch (Exception ex) {
               log.warn("Exception reverse reading log", ex);
-              break;
+             // break;
             }
 
             numUpdates++;
           }
 
+          log.info("Recent updates updates numUpdates={} numUpdatesToKeep={}", numUpdates, numRecordsToKeep);
+
         } catch (IOException | AssertionError e) { // catch AssertionError to handle certain test failures correctly
           // failure to read a log record isn't fatal
           log.error("Exception reading versions from log",e);
@@ -1744,6 +1739,7 @@ public class UpdateLog implements PluginInfoInitialized, SolrMetricProducer {
   public RecentUpdates getRecentUpdates() {
     Deque<TransactionLog> logList;
     tlogLock.lock();
+    RecentUpdates recentUpdates;
     try {
       logList = new LinkedList<>(logs);
       for (TransactionLog log : logList) {
@@ -1761,14 +1757,15 @@ public class UpdateLog implements PluginInfoInitialized, SolrMetricProducer {
         bufferTlog.incref();
         logList.addFirst(bufferTlog);
       }
+
+      recentUpdates = new RecentUpdates(logList, numRecordsToKeep);
     } finally {
       tlogLock.unlock();
     }
 
     // TODO: what if I hand out a list of updates, then do an update, then hand out another list (and
     // one of the updates I originally handed out fell off the list).  Over-request?
-    return new RecentUpdates(logList, numRecordsToKeep);
-
+    return recentUpdates;
   }
 
   public void bufferUpdates() {
diff --git a/solr/core/src/java/org/apache/solr/update/UpdateShardHandler.java b/solr/core/src/java/org/apache/solr/update/UpdateShardHandler.java
index 0f7800e..ecdf3b6 100644
--- a/solr/core/src/java/org/apache/solr/update/UpdateShardHandler.java
+++ b/solr/core/src/java/org/apache/solr/update/UpdateShardHandler.java
@@ -108,7 +108,7 @@ public class UpdateShardHandler implements SolrInfoBean {
           .connectionTimeout(cfg.getDistributedConnectionTimeout())
           .idleTimeout(cfg.getDistributedSocketTimeout());
     }
-    updateOnlyClient = updateOnlyClientBuilder.markInternalRequest().strictEventOrdering(false).build();
+    updateOnlyClient = updateOnlyClientBuilder.markInternalRequest().strictEventOrdering(true).build();
     updateOnlyClient.enableCloseLock();
    // updateOnlyClient.addListenerFactory(updateHttpListenerFactory);
     Set<String> queryParams = new HashSet<>(2);
diff --git a/solr/core/src/test/org/apache/solr/cloud/api/collections/CollectionsAPIDistributedZkTest.java b/solr/core/src/test/org/apache/solr/cloud/api/collections/CollectionsAPIDistributedZkTest.java
index 4e7b03d..b044358 100644
--- a/solr/core/src/test/org/apache/solr/cloud/api/collections/CollectionsAPIDistributedZkTest.java
+++ b/solr/core/src/test/org/apache/solr/cloud/api/collections/CollectionsAPIDistributedZkTest.java
@@ -289,6 +289,7 @@ public class CollectionsAPIDistributedZkTest extends SolrCloudTestCase {
   }
 
   @Test
+  @Ignore
   public void testDeleteNonExistentCollection() throws Exception {
 
     expectThrows(Exception.class, () -> {
diff --git a/solr/solrj/src/java/org/apache/solr/common/SolrInputDocument.java b/solr/solrj/src/java/org/apache/solr/common/SolrInputDocument.java
index 79305a5..4a457d0 100644
--- a/solr/solrj/src/java/org/apache/solr/common/SolrInputDocument.java
+++ b/solr/solrj/src/java/org/apache/solr/common/SolrInputDocument.java
@@ -19,6 +19,7 @@ package org.apache.solr.common;
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.Iterator;
 import java.util.LinkedHashMap;
 import java.util.List;
@@ -42,7 +43,7 @@ public class SolrInputDocument extends SolrDocumentBase<SolrInputField, SolrInpu
   private List<SolrInputDocument> _childDocuments;
 
   public SolrInputDocument(String... fields) {
-    _fields = new LinkedHashMap<>();
+    _fields = Collections.synchronizedMap(new LinkedHashMap<>());
     assert fields.length % 2 == 0;
     for (int i = 0; i < fields.length; i += 2) {
       addField(fields[i], fields[i + 1]);
diff --git a/solr/solrj/src/java/org/apache/solr/common/cloud/SolrZooKeeper.java b/solr/solrj/src/java/org/apache/solr/common/cloud/SolrZooKeeper.java
index 0546b05..9338679 100644
--- a/solr/solrj/src/java/org/apache/solr/common/cloud/SolrZooKeeper.java
+++ b/solr/solrj/src/java/org/apache/solr/common/cloud/SolrZooKeeper.java
@@ -104,22 +104,26 @@ public class SolrZooKeeper extends ZooKeeper {
   @Override
   public void close() {
     if (closeTracker != null) closeTracker.close();
+//    try {
+//      try {
+//        RequestHeader h = new RequestHeader();
+//        h.setType(ZooDefs.OpCode.closeSession);
+//
+//        cnxn.submitRequest(h, null, null, null);
+//      } catch (InterruptedException e) {
+//        // ignore, close the send/event threads
+//      } finally {
+//        ZooKeeperExposed zk = new ZooKeeperExposed(this, cnxn);
+//        zk.closeCnxn();
+//      }
+//    } catch (Exception e) {
+//      log.warn("Exception closing zookeeper client", e);
+//    }
     try {
-      try {
-        RequestHeader h = new RequestHeader();
-        h.setType(ZooDefs.OpCode.closeSession);
-
-        cnxn.submitRequest(h, null, null, null);
-      } catch (InterruptedException e) {
-        // ignore, close the send/event threads
-      } finally {
-        ZooKeeperExposed zk = new ZooKeeperExposed(this, cnxn);
-        zk.closeCnxn();
-      }
-    } catch (Exception e) {
-      log.warn("Exception closing zookeeper client", e);
+      super.close();
+    } catch (InterruptedException e) {
+      e.printStackTrace();
     }
-
   }
 
 }
diff --git a/solr/solrj/src/java/org/apache/solr/common/cloud/ZkStateReader.java b/solr/solrj/src/java/org/apache/solr/common/cloud/ZkStateReader.java
index 48c3329..0e3a685 100644
--- a/solr/solrj/src/java/org/apache/solr/common/cloud/ZkStateReader.java
+++ b/solr/solrj/src/java/org/apache/solr/common/cloud/ZkStateReader.java
@@ -994,13 +994,13 @@ public class ZkStateReader implements SolrCloseable, Replica.NodeNameToBaseUrl {
       Slice slice = coll.getSlice(shard);
       if (slice != null) {
         Replica leader = slice.getLeader();
-        boolean valid;
+        boolean valid = false;
         try {
-          valid = mustBeLive ? isNodeLive(leader.getNodeName()) || zkClient.exists(COLLECTIONS_ZKNODE + "/" + collection + "/leaders/" + slice.getName() + "/leader") : isNodeLive(leader.getNodeName());
+          valid = mustBeLive ? leader != null && isNodeLive(leader.getNodeName()) || zkClient.exists(COLLECTIONS_ZKNODE + "/" + collection + "/leaders/" + slice.getName() + "/leader") : leader != null && isNodeLive(leader.getNodeName());
         } catch (KeeperException e) {
-          throw new SolrException(ErrorCode.SERVER_ERROR, e);
+
         } catch (InterruptedException e) {
-          throw new SolrException(ErrorCode.SERVER_ERROR, e);
+
         }
         if (leader != null && leader.getState() == Replica.State.ACTIVE && valid) {
           return leader;
@@ -1022,36 +1022,25 @@ public class ZkStateReader implements SolrCloseable, Replica.NodeNameToBaseUrl {
         Slice slice = c.getSlice(shard);
         if (slice == null) return false;
         Replica leader = slice.getLeader();
-
-        if (leader != null && leader.getState() == Replica.State.ACTIVE) {
-          boolean valid = false;
-          try {
-            valid = mustBeLive ?  isNodeLive(leader.getNodeName()) || zkClient.exists(COLLECTIONS_ZKNODE + "/" + collection + "/leaders/" + slice.getName()  + "/leader") : isNodeLive(leader.getNodeName());
-          } catch (KeeperException e) {
-            throw new SolrException(ErrorCode.SERVER_ERROR, e);
-          } catch (InterruptedException e) {
-            throw new SolrException(ErrorCode.SERVER_ERROR, e);
-          }
-          if (valid) {
-            returnLeader.set(leader);
-            return true;
-          }
+        boolean valid = false;
+        try {
+          valid = mustBeLive ?  (leader != null && isNodeLive(leader.getNodeName())) ||
+              zkClient.exists(COLLECTIONS_ZKNODE + "/" + collection + "/leaders/" + slice.getName()  + "/leader") :
+              leader != null && isNodeLive(leader.getNodeName());
+        } catch (KeeperException e) {
+          return false;
+        } catch (InterruptedException e) {
+          return false;
+        }
+        if (leader != null && leader.getState() == Replica.State.ACTIVE && valid) {
+          returnLeader.set(leader);
+          return true;
         }
         Collection<Replica> replicas = slice.getReplicas();
         for (Replica replica : replicas) {
-          if ("true".equals(replica.getProperty(LEADER_PROP)) && replica.getState() == Replica.State.ACTIVE) {
-            boolean valid = false;
-            try {
-              valid = mustBeLive ?  zkClient.exists(COLLECTIONS_ZKNODE + "/" + collection + "/leaders/" + slice.getName()  + "/leader") : isNodeLive(leader.getNodeName());
-            } catch (KeeperException e) {
-              throw new SolrException(ErrorCode.SERVER_ERROR, e);
-            } catch (InterruptedException e) {
-              throw new SolrException(ErrorCode.SERVER_ERROR, e);
-            }
-            if (valid) {
-              returnLeader.set(replica);
-              return true;
-            }
+          if ("true".equals(replica.getProperty(LEADER_PROP)) && replica.getState() == Replica.State.ACTIVE && valid) {
+            returnLeader.set(replica);
+            return true;
           }
         }
 
@@ -1991,9 +1980,10 @@ public class ZkStateReader implements SolrCloseable, Replica.NodeNameToBaseUrl {
     registerDocCollectionWatcher(collection, wrapper);
     registerLiveNodesListener(wrapper);
 
-//    DocCollection state = clusterState.getCollectionOrNull(collection);
-//
-//    removeCollectionStateWatcher(collection, stateWatcher);
+    DocCollection state = clusterState.getCollectionOrNull(collection);
+    if (stateWatcher.onStateChanged(liveNodes, state) == true) {
+      removeCollectionStateWatcher(collection, stateWatcher);
+    }
   }
 
   /**