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From ktur...@apache.org
Subject [accumulo] branch master updated: fix #1123 replace observing config with as needed derivation (#1201)
Date Thu, 13 Jun 2019 20:36:18 GMT
This is an automated email from the ASF dual-hosted git repository.

kturner pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/accumulo.git


The following commit(s) were added to refs/heads/master by this push:
     new 17e8f6a  fix #1123 replace observing config with as needed derivation (#1201)
17e8f6a is described below

commit 17e8f6a0b489caf6208a4be3be66dce8726ef7d2
Author: Keith Turner <kturner@apache.org>
AuthorDate: Thu Jun 13 16:36:13 2019 -0400

    fix #1123 replace observing config with as needed derivation (#1201)
---
 .../accumulo/core/conf/AccumuloConfiguration.java  |  86 ++++++++
 .../accumulo/core/conf/ConfigurationObserver.java  |  25 ---
 .../core/conf/ObservableConfiguration.java         | 116 ----------
 .../core/conf/ObservableConfigurationTest.java     |  99 ---------
 .../accumulo/server/conf/NamespaceConfWatcher.java | 121 -----------
 .../server/conf/NamespaceConfiguration.java        |  31 +--
 .../server/conf/ServerConfigurationFactory.java    |  10 -
 .../accumulo/server/conf/TableConfWatcher.java     | 122 -----------
 .../accumulo/server/conf/TableConfiguration.java   | 142 ++++--------
 .../balancer/HostRegexTableLoadBalancer.java       | 241 ++++++++++++---------
 .../server/conf/NamespaceConfigurationTest.java    |  19 +-
 .../conf/ServerConfigurationFactoryTest.java       |   4 +-
 .../server/conf/TableConfigurationTest.java        |  20 +-
 .../BaseHostRegexTableLoadBalancerTest.java        |  13 +-
 ...tRegexTableLoadBalancerReconfigurationTest.java |   8 +-
 .../balancer/HostRegexTableLoadBalancerTest.java   |  94 +-------
 .../org/apache/accumulo/tserver/TabletServer.java  |   8 -
 .../tserver/constraints/ConstraintChecker.java     |  49 +----
 .../org/apache/accumulo/tserver/tablet/Tablet.java | 132 ++---------
 .../apache/accumulo/tserver/tablet/TabletTest.java |  19 +-
 20 files changed, 331 insertions(+), 1028 deletions(-)

diff --git a/core/src/main/java/org/apache/accumulo/core/conf/AccumuloConfiguration.java b/core/src/main/java/org/apache/accumulo/core/conf/AccumuloConfiguration.java
index 450b2f2..4cd7a91 100644
--- a/core/src/main/java/org/apache/accumulo/core/conf/AccumuloConfiguration.java
+++ b/core/src/main/java/org/apache/accumulo/core/conf/AccumuloConfiguration.java
@@ -28,8 +28,10 @@ import java.util.Objects;
 import java.util.Optional;
 import java.util.OptionalInt;
 import java.util.TreeMap;
+import java.util.concurrent.atomic.AtomicReference;
 import java.util.concurrent.locks.Lock;
 import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
 import java.util.function.Predicate;
 
 import org.apache.accumulo.core.conf.PropertyType.PortRange;
@@ -435,6 +437,90 @@ public abstract class AccumuloConfiguration implements Iterable<Entry<String,Str
     return null;
   }
 
+  private static class RefCount<T> {
+    T obj;
+    long count;
+
+    RefCount(long c, T r) {
+      this.count = c;
+      this.obj = r;
+    }
+  }
+
+  private class DeriverImpl<T> implements Deriver<T> {
+
+    private final AtomicReference<RefCount<T>> refref = new AtomicReference<>();
+    private final Function<AccumuloConfiguration,T> converter;
+
+    DeriverImpl(Function<AccumuloConfiguration,T> converter) {
+      this.converter = converter;
+    }
+
+    /**
+     * This method was written with the goal of avoiding thread contention and minimizing
+     * recomputation. Configuration can be accessed frequently by many threads. Ideally, threads
+     * working on unrelated task would not impeded each other because of accessing config.
+     *
+     * To avoid thread contention, synchronization and needless calls to compare and set were
+     * avoided. For example if 100 threads are all calling compare and set in a loop this could
+     * cause significant contention.
+     */
+    @Override
+    public T derive() {
+
+      // very important to obtain this before possibly recomputing object
+      long uc = getUpdateCount();
+
+      RefCount<T> rc = refref.get();
+
+      if (rc == null || rc.count != uc) {
+        T newObj = converter.apply(AccumuloConfiguration.this);
+
+        // very important to record the update count that was obtained before recomputing.
+        RefCount<T> nrc = new RefCount<>(uc, newObj);
+
+        /*
+         * The return value of compare and set is intentionally ignored here. This code could loop
+         * calling compare and set inorder to avoid returning a stale object. However after this
+         * function returns, the object could immediately become stale. So in the big picture stale
+         * objects can not be prevented. Looping here could cause thread contention, but it would
+         * not solve the overall stale object problem. That is why the return value was ignored. The
+         * following line is a least effort attempt to make the result of this recomputation
+         * available to the next caller.
+         */
+        refref.compareAndSet(rc, nrc);
+
+        return nrc.obj;
+      }
+
+      return rc.obj;
+    }
+  }
+
+  /**
+   * Automatically regenerates an object whenever configuration changes. When configuration is not
+   * changing, keeps returning the same object. Implementations should be thread safe and eventually
+   * consistent. See {@link AccumuloConfiguration#newDeriver(Function)}
+   */
+  public static interface Deriver<T> {
+    public T derive();
+  }
+
+  /**
+   * Enables deriving an object from configuration and automatically deriving a new object any time
+   * configuration changes.
+   *
+   * @param converter
+   *          This functions is used to create an object from configuration. A reference to this
+   *          function will be kept and called by the returned deriver.
+   * @return The returned supplier will automatically re-derive the object any time this
+   *         configuration changes. When configuration is not changing, the same object is returned.
+   *
+   */
+  public <T> Deriver<T> newDeriver(Function<AccumuloConfiguration,T> converter) {
+    return new DeriverImpl<>(converter);
+  }
+
   private static final String SCAN_EXEC_THREADS = "threads";
   private static final String SCAN_EXEC_PRIORITY = "priority";
   private static final String SCAN_EXEC_PRIORITIZER = "prioritizer";
diff --git a/core/src/main/java/org/apache/accumulo/core/conf/ConfigurationObserver.java b/core/src/main/java/org/apache/accumulo/core/conf/ConfigurationObserver.java
deleted file mode 100644
index 8a62d26..0000000
--- a/core/src/main/java/org/apache/accumulo/core/conf/ConfigurationObserver.java
+++ /dev/null
@@ -1,25 +0,0 @@
-/*
- * Licensed to the Apache Software Foundation (ASF) under one or more
- * contributor license agreements.  See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * The ASF licenses this file to You under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License.  You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package org.apache.accumulo.core.conf;
-
-public interface ConfigurationObserver {
-  void propertyChanged(String key);
-
-  void propertiesChanged();
-
-  void sessionExpired();
-}
diff --git a/core/src/main/java/org/apache/accumulo/core/conf/ObservableConfiguration.java b/core/src/main/java/org/apache/accumulo/core/conf/ObservableConfiguration.java
deleted file mode 100644
index fb49230..0000000
--- a/core/src/main/java/org/apache/accumulo/core/conf/ObservableConfiguration.java
+++ /dev/null
@@ -1,116 +0,0 @@
-/*
- * Licensed to the Apache Software Foundation (ASF) under one or more
- * contributor license agreements.  See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * The ASF licenses this file to You under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License.  You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package org.apache.accumulo.core.conf;
-
-import static java.util.Objects.requireNonNull;
-
-import java.util.Collection;
-import java.util.Collections;
-import java.util.Set;
-
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-
-/**
- * A configuration that can be observed. Handling of observers is thread-safe.
- */
-public abstract class ObservableConfiguration extends AccumuloConfiguration {
-
-  private static final Logger log = LoggerFactory.getLogger(ObservableConfiguration.class);
-
-  private Set<ConfigurationObserver> observers;
-
-  /**
-   * Creates a new observable configuration.
-   */
-  public ObservableConfiguration() {
-    observers = Collections.synchronizedSet(new java.util.HashSet<>());
-  }
-
-  /**
-   * Adds an observer.
-   *
-   * @param co
-   *          observer
-   * @throws NullPointerException
-   *           if co is null
-   */
-  public void addObserver(ConfigurationObserver co) {
-    requireNonNull(co);
-    observers.add(co);
-  }
-
-  /**
-   * Removes an observer.
-   *
-   * @param co
-   *          observer
-   */
-  public void removeObserver(ConfigurationObserver co) {
-    observers.remove(co);
-  }
-
-  /**
-   * Gets the current set of observers. The returned collection is a snapshot, and changes to it do
-   * not reflect back to the configuration.
-   *
-   * @return observers
-   */
-  public Collection<ConfigurationObserver> getObservers() {
-    return snapshot(observers);
-  }
-
-  private static Collection<ConfigurationObserver>
-      snapshot(Collection<ConfigurationObserver> observers) {
-    Collection<ConfigurationObserver> c = new java.util.ArrayList<>();
-    synchronized (observers) {
-      c.addAll(observers);
-    }
-    return c;
-  }
-
-  /**
-   * Expires all observers.
-   */
-  public void expireAllObservers() {
-    Collection<ConfigurationObserver> copy = snapshot(observers);
-    log.info("Expiring {} observers", copy.size());
-    for (ConfigurationObserver co : copy)
-      co.sessionExpired();
-  }
-
-  /**
-   * Notifies all observers that a property changed.
-   *
-   * @param key
-   *          configuration property key
-   */
-  public void propertyChanged(String key) {
-    Collection<ConfigurationObserver> copy = snapshot(observers);
-    for (ConfigurationObserver co : copy)
-      co.propertyChanged(key);
-  }
-
-  /**
-   * Notifies all observers that properties changed.
-   */
-  public void propertiesChanged() {
-    Collection<ConfigurationObserver> copy = snapshot(observers);
-    for (ConfigurationObserver co : copy)
-      co.propertiesChanged();
-  }
-}
diff --git a/core/src/test/java/org/apache/accumulo/core/conf/ObservableConfigurationTest.java b/core/src/test/java/org/apache/accumulo/core/conf/ObservableConfigurationTest.java
deleted file mode 100644
index e6c7169..0000000
--- a/core/src/test/java/org/apache/accumulo/core/conf/ObservableConfigurationTest.java
+++ /dev/null
@@ -1,99 +0,0 @@
-/*
- * Licensed to the Apache Software Foundation (ASF) under one or more
- * contributor license agreements.  See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * The ASF licenses this file to You under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License.  You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package org.apache.accumulo.core.conf;
-
-import static org.easymock.EasyMock.createMock;
-import static org.easymock.EasyMock.replay;
-import static org.easymock.EasyMock.verify;
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertTrue;
-
-import java.util.Collection;
-import java.util.Map;
-import java.util.function.Predicate;
-
-import org.junit.Before;
-import org.junit.Test;
-
-public class ObservableConfigurationTest {
-  private static class TestObservableConfig extends ObservableConfiguration {
-    @Override
-    public String get(Property property) {
-      return null;
-    }
-
-    @Override
-    public void getProperties(Map<String,String> props, Predicate<String> filter) {}
-  }
-
-  private ObservableConfiguration c;
-  private ConfigurationObserver co1;
-
-  @Before
-  public void setUp() {
-    c = new TestObservableConfig();
-    co1 = createMock(ConfigurationObserver.class);
-  }
-
-  @Test
-  public void testAddAndRemove() {
-    ConfigurationObserver co2 = createMock(ConfigurationObserver.class);
-    c.addObserver(co1);
-    c.addObserver(co2);
-    Collection<ConfigurationObserver> cos = c.getObservers();
-    assertEquals(2, cos.size());
-    assertTrue(cos.contains(co1));
-    assertTrue(cos.contains(co2));
-    c.removeObserver(co1);
-    cos = c.getObservers();
-    assertEquals(1, cos.size());
-    assertTrue(cos.contains(co2));
-  }
-
-  @Test(expected = NullPointerException.class)
-  public void testNoNullAdd() {
-    c.addObserver(null);
-  }
-
-  @Test
-  public void testSessionExpired() {
-    c.addObserver(co1);
-    co1.sessionExpired();
-    replay(co1);
-    c.expireAllObservers();
-    verify(co1);
-  }
-
-  @Test
-  public void testPropertyChanged() {
-    String key = "key";
-    c.addObserver(co1);
-    co1.propertyChanged(key);
-    replay(co1);
-    c.propertyChanged(key);
-    verify(co1);
-  }
-
-  @Test
-  public void testPropertiesChanged() {
-    c.addObserver(co1);
-    co1.propertiesChanged();
-    replay(co1);
-    c.propertiesChanged();
-    verify(co1);
-  }
-}
diff --git a/server/base/src/main/java/org/apache/accumulo/server/conf/NamespaceConfWatcher.java b/server/base/src/main/java/org/apache/accumulo/server/conf/NamespaceConfWatcher.java
deleted file mode 100644
index baaee2a..0000000
--- a/server/base/src/main/java/org/apache/accumulo/server/conf/NamespaceConfWatcher.java
+++ /dev/null
@@ -1,121 +0,0 @@
-/*
- * Licensed to the Apache Software Foundation (ASF) under one or more
- * contributor license agreements.  See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * The ASF licenses this file to You under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License.  You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package org.apache.accumulo.server.conf;
-
-import org.apache.accumulo.core.Constants;
-import org.apache.accumulo.core.data.NamespaceId;
-import org.apache.accumulo.server.ServerContext;
-import org.apache.zookeeper.WatchedEvent;
-import org.apache.zookeeper.Watcher;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-
-class NamespaceConfWatcher implements Watcher {
-
-  private static final Logger log = LoggerFactory.getLogger(NamespaceConfWatcher.class);
-  private final ServerContext context;
-  private final String namespacesPrefix;
-  private final int namespacesPrefixLength;
-
-  NamespaceConfWatcher(ServerContext context) {
-    this.context = context;
-    namespacesPrefix = context.getZooKeeperRoot() + Constants.ZNAMESPACES + "/";
-    namespacesPrefixLength = namespacesPrefix.length();
-  }
-
-  static String toString(WatchedEvent event) {
-    return new StringBuilder("{path=").append(event.getPath()).append(",state=")
-        .append(event.getState()).append(",type=").append(event.getType()).append("}").toString();
-  }
-
-  @Override
-  public void process(WatchedEvent event) {
-    String path = event.getPath();
-    if (log.isTraceEnabled()) {
-      log.trace("WatchedEvent : {}", toString(event));
-    }
-
-    String namespaceIdStr = null;
-    String key = null;
-
-    if (path != null) {
-      if (path.startsWith(namespacesPrefix)) {
-        namespaceIdStr = path.substring(namespacesPrefixLength);
-        if (namespaceIdStr.contains("/")) {
-          namespaceIdStr = namespaceIdStr.substring(0, namespaceIdStr.indexOf('/'));
-          if (path
-              .startsWith(namespacesPrefix + namespaceIdStr + Constants.ZNAMESPACE_CONF + "/")) {
-            key = path.substring(
-                (namespacesPrefix + namespaceIdStr + Constants.ZNAMESPACE_CONF + "/").length());
-          }
-        }
-      }
-
-      if (namespaceIdStr == null) {
-        log.warn("Zookeeper told me about a path I was not watching: {}, event {}", path,
-            toString(event));
-        return;
-      }
-    }
-    NamespaceId namespaceId = NamespaceId.of(namespaceIdStr);
-
-    switch (event.getType()) {
-      case NodeDataChanged:
-        if (log.isTraceEnabled()) {
-          log.trace("EventNodeDataChanged {}", event.getPath());
-        }
-        if (key != null) {
-          context.getServerConfFactory().getNamespaceConfiguration(namespaceId)
-              .propertyChanged(key);
-        }
-        break;
-      case NodeChildrenChanged:
-        context.getServerConfFactory().getNamespaceConfiguration(namespaceId).propertiesChanged();
-        break;
-      case NodeDeleted:
-        if (key == null) {
-          ServerConfigurationFactory.removeCachedNamespaceConfiguration(context.getInstanceID(),
-              namespaceId);
-        }
-        break;
-      case None:
-        switch (event.getState()) {
-          case Expired:
-            log.info("Zookeeper node event type None, state=expired. Expire all table observers");
-            ServerConfigurationFactory.expireAllTableObservers();
-            break;
-          case SyncConnected:
-            break;
-          case Disconnected:
-            break;
-          default:
-            log.warn("EventNone event not handled {}", toString(event));
-        }
-        break;
-      case NodeCreated:
-        switch (event.getState()) {
-          case SyncConnected:
-            break;
-          default:
-            log.warn("Event NodeCreated event not handled {}", toString(event));
-        }
-        break;
-      default:
-        log.warn("Event not handled {}", toString(event));
-    }
-  }
-}
diff --git a/server/base/src/main/java/org/apache/accumulo/server/conf/NamespaceConfiguration.java b/server/base/src/main/java/org/apache/accumulo/server/conf/NamespaceConfiguration.java
index eef0248..025a8d8 100644
--- a/server/base/src/main/java/org/apache/accumulo/server/conf/NamespaceConfiguration.java
+++ b/server/base/src/main/java/org/apache/accumulo/server/conf/NamespaceConfiguration.java
@@ -23,19 +23,14 @@ import java.util.function.Predicate;
 import org.apache.accumulo.core.Constants;
 import org.apache.accumulo.core.clientImpl.Namespace;
 import org.apache.accumulo.core.conf.AccumuloConfiguration;
-import org.apache.accumulo.core.conf.ConfigurationObserver;
-import org.apache.accumulo.core.conf.ObservableConfiguration;
 import org.apache.accumulo.core.conf.Property;
 import org.apache.accumulo.core.data.NamespaceId;
 import org.apache.accumulo.fate.zookeeper.ZooCache;
 import org.apache.accumulo.fate.zookeeper.ZooCacheFactory;
 import org.apache.accumulo.server.ServerContext;
 import org.apache.accumulo.server.conf.ZooCachePropertyAccessor.PropCacheKey;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
 
-public class NamespaceConfiguration extends ObservableConfiguration {
-  private static final Logger log = LoggerFactory.getLogger(NamespaceConfiguration.class);
+public class NamespaceConfiguration extends AccumuloConfiguration {
 
   private static final Map<PropCacheKey,ZooCache> propCaches = new java.util.HashMap<>();
 
@@ -74,8 +69,7 @@ public class NamespaceConfiguration extends ObservableConfiguration {
       PropCacheKey key = new PropCacheKey(context.getInstanceID(), namespaceId.canonical());
       ZooCache propCache = propCaches.get(key);
       if (propCache == null) {
-        propCache = zcf.getZooCache(context.getZooKeepers(), context.getZooKeepersSessionTimeOut(),
-            new NamespaceConfWatcher(context));
+        propCache = zcf.getZooCache(context.getZooKeepers(), context.getZooKeepersSessionTimeOut());
         propCaches.put(key, propCache);
       }
       return propCache;
@@ -136,27 +130,6 @@ public class NamespaceConfiguration extends ObservableConfiguration {
     return namespaceId;
   }
 
-  @Override
-  public void addObserver(ConfigurationObserver co) {
-    if (namespaceId == null) {
-      String err = "Attempt to add observer for non-namespace configuration";
-      log.error(err);
-      throw new RuntimeException(err);
-    }
-    iterator();
-    super.addObserver(co);
-  }
-
-  @Override
-  public void removeObserver(ConfigurationObserver co) {
-    if (namespaceId == null) {
-      String err = "Attempt to remove observer for non-namespace configuration";
-      log.error(err);
-      throw new RuntimeException(err);
-    }
-    super.removeObserver(co);
-  }
-
   static boolean isIteratorOrConstraint(String key) {
     return key.startsWith(Property.TABLE_ITERATOR_PREFIX.getKey())
         || key.startsWith(Property.TABLE_CONSTRAINT_PREFIX.getKey());
diff --git a/server/base/src/main/java/org/apache/accumulo/server/conf/ServerConfigurationFactory.java b/server/base/src/main/java/org/apache/accumulo/server/conf/ServerConfigurationFactory.java
index 39ae6ec..f2c82f7 100644
--- a/server/base/src/main/java/org/apache/accumulo/server/conf/ServerConfigurationFactory.java
+++ b/server/base/src/main/java/org/apache/accumulo/server/conf/ServerConfigurationFactory.java
@@ -77,16 +77,6 @@ public class ServerConfigurationFactory extends ServerConfiguration {
     }
   }
 
-  static void expireAllTableObservers() {
-    synchronized (tableConfigs) {
-      for (Map<TableId,TableConfiguration> instanceMap : tableConfigs.values()) {
-        for (TableConfiguration c : instanceMap.values()) {
-          c.expireAllObservers();
-        }
-      }
-    }
-  }
-
   private final ServerContext context;
   private final SiteConfiguration siteConfig;
   private final String instanceID;
diff --git a/server/base/src/main/java/org/apache/accumulo/server/conf/TableConfWatcher.java b/server/base/src/main/java/org/apache/accumulo/server/conf/TableConfWatcher.java
deleted file mode 100644
index ffcb7eb..0000000
--- a/server/base/src/main/java/org/apache/accumulo/server/conf/TableConfWatcher.java
+++ /dev/null
@@ -1,122 +0,0 @@
-/*
- * Licensed to the Apache Software Foundation (ASF) under one or more
- * contributor license agreements.  See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * The ASF licenses this file to You under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License.  You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package org.apache.accumulo.server.conf;
-
-import org.apache.accumulo.core.Constants;
-import org.apache.accumulo.core.data.TableId;
-import org.apache.accumulo.server.ServerContext;
-import org.apache.zookeeper.WatchedEvent;
-import org.apache.zookeeper.Watcher;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-
-class TableConfWatcher implements Watcher {
-
-  private static final Logger log = LoggerFactory.getLogger(TableConfWatcher.class);
-  private final ServerContext context;
-  private final String tablesPrefix;
-  private ServerConfigurationFactory scf;
-
-  TableConfWatcher(ServerContext context) {
-    this.context = context;
-    tablesPrefix = context.getZooKeeperRoot() + Constants.ZTABLES + "/";
-    scf = context.getServerConfFactory();
-  }
-
-  static String toString(WatchedEvent event) {
-    return new StringBuilder("{path=").append(event.getPath()).append(",state=")
-        .append(event.getState()).append(",type=").append(event.getType()).append("}").toString();
-  }
-
-  @Override
-  public void process(WatchedEvent event) {
-    String path = event.getPath();
-    if (log.isTraceEnabled()) {
-      log.trace("WatchedEvent : {}", toString(event));
-    }
-
-    String tableIdString = null;
-    String key = null;
-
-    if (path != null) {
-      if (path.startsWith(tablesPrefix)) {
-        tableIdString = path.substring(tablesPrefix.length());
-        if (tableIdString.contains("/")) {
-          tableIdString = tableIdString.substring(0, tableIdString.indexOf('/'));
-          if (path.startsWith(tablesPrefix + tableIdString + Constants.ZTABLE_CONF + "/")) {
-            key = path
-                .substring((tablesPrefix + tableIdString + Constants.ZTABLE_CONF + "/").length());
-          }
-        }
-      }
-
-      if (tableIdString == null) {
-        log.warn("Zookeeper told me about a path I was not watching: {}, event {}", path,
-            toString(event));
-        return;
-      }
-    }
-    TableId tableId = TableId.of(tableIdString);
-
-    switch (event.getType()) {
-      case NodeDataChanged:
-        if (log.isTraceEnabled()) {
-          log.trace("EventNodeDataChanged {}", event.getPath());
-        }
-        if (key != null) {
-          scf.getTableConfiguration(tableId).propertyChanged(key);
-        }
-        break;
-      case NodeChildrenChanged:
-        scf.getTableConfiguration(tableId).propertiesChanged();
-        break;
-      case NodeDeleted:
-        if (key == null) {
-          // only remove the AccumuloConfiguration object when a
-          // table node is deleted, not when a tables property is
-          // deleted.
-          ServerConfigurationFactory.removeCachedTableConfiguration(context.getInstanceID(),
-              tableId);
-        }
-        break;
-      case None:
-        switch (event.getState()) {
-          case Expired:
-            log.info("Zookeeper node event type None, state=expired. Expire all table observers");
-            ServerConfigurationFactory.expireAllTableObservers();
-            break;
-          case SyncConnected:
-            break;
-          case Disconnected:
-            break;
-          default:
-            log.warn("EventNone event not handled {}", toString(event));
-        }
-        break;
-      case NodeCreated:
-        switch (event.getState()) {
-          case SyncConnected:
-            break;
-          default:
-            log.warn("Event NodeCreated event not handled {}", toString(event));
-        }
-        break;
-      default:
-        log.warn("Event not handled {}", toString(event));
-    }
-  }
-}
diff --git a/server/base/src/main/java/org/apache/accumulo/server/conf/TableConfiguration.java b/server/base/src/main/java/org/apache/accumulo/server/conf/TableConfiguration.java
index 28d7e25..a1cd54f 100644
--- a/server/base/src/main/java/org/apache/accumulo/server/conf/TableConfiguration.java
+++ b/server/base/src/main/java/org/apache/accumulo/server/conf/TableConfiguration.java
@@ -28,9 +28,8 @@ import java.util.concurrent.atomic.AtomicReference;
 import java.util.function.Predicate;
 
 import org.apache.accumulo.core.Constants;
-import org.apache.accumulo.core.conf.ConfigurationObserver;
+import org.apache.accumulo.core.conf.AccumuloConfiguration;
 import org.apache.accumulo.core.conf.IterConfigUtil;
-import org.apache.accumulo.core.conf.ObservableConfiguration;
 import org.apache.accumulo.core.conf.Property;
 import org.apache.accumulo.core.data.TableId;
 import org.apache.accumulo.core.dataImpl.thrift.IterInfo;
@@ -42,15 +41,12 @@ import org.apache.accumulo.fate.zookeeper.ZooCacheFactory;
 import org.apache.accumulo.server.ServerContext;
 import org.apache.accumulo.server.ServiceEnvironmentImpl;
 import org.apache.accumulo.server.conf.ZooCachePropertyAccessor.PropCacheKey;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
 
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.ImmutableMap.Builder;
 
-public class TableConfiguration extends ObservableConfiguration {
-  private static final Logger log = LoggerFactory.getLogger(TableConfiguration.class);
+public class TableConfiguration extends AccumuloConfiguration {
 
   private static final Map<PropCacheKey,ZooCache> propCaches = new java.util.HashMap<>();
 
@@ -62,7 +58,9 @@ public class TableConfiguration extends ObservableConfiguration {
 
   private final TableId tableId;
 
-  private EnumMap<IteratorScope,AtomicReference<ParsedIteratorConfig>> iteratorConfig;
+  private final EnumMap<IteratorScope,Deriver<ParsedIteratorConfig>> iteratorConfig;
+
+  private final Deriver<ScanDispatcher> scanDispatchDeriver;
 
   public TableConfiguration(ServerContext context, TableId tableId, NamespaceConfiguration parent) {
     this.context = requireNonNull(context);
@@ -71,8 +69,16 @@ public class TableConfiguration extends ObservableConfiguration {
 
     iteratorConfig = new EnumMap<>(IteratorScope.class);
     for (IteratorScope scope : IteratorScope.values()) {
-      iteratorConfig.put(scope, new AtomicReference<>(null));
+      iteratorConfig.put(scope, newDeriver(conf -> {
+        Map<String,Map<String,String>> allOpts = new HashMap<>();
+        List<IterInfo> iters =
+            IterConfigUtil.parseIterConf(scope, Collections.emptyList(), allOpts, conf);
+        return new ParsedIteratorConfig(iters, allOpts, conf.get(Property.TABLE_CLASSPATH));
+
+      }));
     }
+
+    scanDispatchDeriver = newDeriver(conf -> createScanDispatcher(conf, context, tableId));
   }
 
   void setZooCacheFactory(ZooCacheFactory zcf) {
@@ -84,8 +90,7 @@ public class TableConfiguration extends ObservableConfiguration {
       PropCacheKey key = new PropCacheKey(context.getInstanceID(), tableId.canonical());
       ZooCache propCache = propCaches.get(key);
       if (propCache == null) {
-        propCache = zcf.getZooCache(context.getZooKeepers(), context.getZooKeepersSessionTimeOut(),
-            new TableConfWatcher(context));
+        propCache = zcf.getZooCache(context.getZooKeepers(), context.getZooKeepersSessionTimeOut());
         propCaches.put(key, propCache);
       }
       return propCache;
@@ -102,27 +107,6 @@ public class TableConfiguration extends ObservableConfiguration {
         .updateAndGet(pca -> pca == null ? new ZooCachePropertyAccessor(getZooCache()) : pca);
   }
 
-  @Override
-  public void addObserver(ConfigurationObserver co) {
-    if (tableId == null) {
-      String err = "Attempt to add observer for non-table configuration";
-      log.error(err);
-      throw new RuntimeException(err);
-    }
-    iterator();
-    super.addObserver(co);
-  }
-
-  @Override
-  public void removeObserver(ConfigurationObserver co) {
-    if (tableId == null) {
-      String err = "Attempt to remove observer for non-table configuration";
-      log.error(err);
-      throw new RuntimeException(err);
-    }
-    super.removeObserver(co);
-  }
-
   private String getPath() {
     return context.getZooKeeperRoot() + Constants.ZTABLES + "/" + tableId + Constants.ZTABLE_CONF;
   }
@@ -195,10 +179,9 @@ public class TableConfiguration extends ObservableConfiguration {
     private final List<IterInfo> tableIters;
     private final Map<String,Map<String,String>> tableOpts;
     private final String context;
-    private final long updateCount;
 
     private ParsedIteratorConfig(List<IterInfo> ii, Map<String,Map<String,String>> opts,
-        String context, long updateCount) {
+        String context) {
       this.tableIters = ImmutableList.copyOf(ii);
       Builder<String,Map<String,String>> imb = ImmutableMap.builder();
       for (Entry<String,Map<String,String>> entry : opts.entrySet()) {
@@ -206,7 +189,6 @@ public class TableConfiguration extends ObservableConfiguration {
       }
       tableOpts = imb.build();
       this.context = context;
-      this.updateCount = updateCount;
     }
 
     public List<IterInfo> getIterInfo() {
@@ -223,71 +205,43 @@ public class TableConfiguration extends ObservableConfiguration {
   }
 
   public ParsedIteratorConfig getParsedIteratorConfig(IteratorScope scope) {
-    long count = getUpdateCount();
-    AtomicReference<ParsedIteratorConfig> ref = iteratorConfig.get(scope);
-    ParsedIteratorConfig pic = ref.get();
-    if (pic == null || pic.updateCount != count) {
-      Map<String,Map<String,String>> allOpts = new HashMap<>();
-      List<IterInfo> iters =
-          IterConfigUtil.parseIterConf(scope, Collections.emptyList(), allOpts, this);
-      ParsedIteratorConfig newPic =
-          new ParsedIteratorConfig(iters, allOpts, get(Property.TABLE_CLASSPATH), count);
-      ref.compareAndSet(pic, newPic);
-      pic = newPic;
-    }
-
-    return pic;
+    return iteratorConfig.get(scope).derive();
   }
 
-  public static class TablesScanDispatcher {
-    public final ScanDispatcher dispatcher;
-    public final long count;
+  private static ScanDispatcher createScanDispatcher(AccumuloConfiguration conf,
+      ServerContext context, TableId tableId) {
+    ScanDispatcher newDispatcher = Property.createTableInstanceFromPropertyName(conf,
+        Property.TABLE_SCAN_DISPATCHER, ScanDispatcher.class, null);
 
-    public TablesScanDispatcher(ScanDispatcher dispatcher, long count) {
-      this.dispatcher = dispatcher;
-      this.count = count;
-    }
-  }
+    Builder<String,String> builder = ImmutableMap.builder();
+    conf.getAllPropertiesWithPrefix(Property.TABLE_SCAN_DISPATCHER_OPTS).forEach((k, v) -> {
+      String optKey = k.substring(Property.TABLE_SCAN_DISPATCHER_OPTS.getKey().length());
+      builder.put(optKey, v);
+    });
 
-  private AtomicReference<TablesScanDispatcher> scanDispatcherRef = new AtomicReference<>();
+    Map<String,String> opts = builder.build();
 
-  public ScanDispatcher getScanDispatcher() {
-    long count = getUpdateCount();
-    TablesScanDispatcher currRef = scanDispatcherRef.get();
-    if (currRef == null || currRef.count != count) {
-      ScanDispatcher newDispatcher = Property.createTableInstanceFromPropertyName(this,
-          Property.TABLE_SCAN_DISPATCHER, ScanDispatcher.class, null);
-
-      Builder<String,String> builder = ImmutableMap.builder();
-      getAllPropertiesWithPrefix(Property.TABLE_SCAN_DISPATCHER_OPTS).forEach((k, v) -> {
-        String optKey = k.substring(Property.TABLE_SCAN_DISPATCHER_OPTS.getKey().length());
-        builder.put(optKey, v);
-      });
-
-      Map<String,String> opts = builder.build();
-
-      newDispatcher.init(new ScanDispatcher.InitParameters() {
-        @Override
-        public TableId getTableId() {
-          return tableId;
-        }
-
-        @Override
-        public Map<String,String> getOptions() {
-          return opts;
-        }
-
-        @Override
-        public ServiceEnvironment getServiceEnv() {
-          return new ServiceEnvironmentImpl(context);
-        }
-      });
-
-      TablesScanDispatcher newRef = new TablesScanDispatcher(newDispatcher, count);
-      scanDispatcherRef.compareAndSet(currRef, newRef);
-      currRef = newRef;
-    }
+    newDispatcher.init(new ScanDispatcher.InitParameters() {
+      @Override
+      public TableId getTableId() {
+        return tableId;
+      }
+
+      @Override
+      public Map<String,String> getOptions() {
+        return opts;
+      }
+
+      @Override
+      public ServiceEnvironment getServiceEnv() {
+        return new ServiceEnvironmentImpl(context);
+      }
+    });
 
-    return currRef.dispatcher;
+    return newDispatcher;
+  }
+
+  public ScanDispatcher getScanDispatcher() {
+    return scanDispatchDeriver.derive();
   }
 }
diff --git a/server/base/src/main/java/org/apache/accumulo/server/master/balancer/HostRegexTableLoadBalancer.java b/server/base/src/main/java/org/apache/accumulo/server/master/balancer/HostRegexTableLoadBalancer.java
index 905ec71..f4e13e8 100644
--- a/server/base/src/main/java/org/apache/accumulo/server/master/balancer/HostRegexTableLoadBalancer.java
+++ b/server/base/src/main/java/org/apache/accumulo/server/master/balancer/HostRegexTableLoadBalancer.java
@@ -31,10 +31,12 @@ import java.util.Random;
 import java.util.Set;
 import java.util.SortedMap;
 import java.util.TreeMap;
+import java.util.concurrent.TimeUnit;
 import java.util.regex.Pattern;
 
 import org.apache.accumulo.core.client.admin.TableOperations;
-import org.apache.accumulo.core.conf.ConfigurationObserver;
+import org.apache.accumulo.core.conf.AccumuloConfiguration;
+import org.apache.accumulo.core.conf.AccumuloConfiguration.Deriver;
 import org.apache.accumulo.core.conf.ConfigurationTypeHelper;
 import org.apache.accumulo.core.conf.Property;
 import org.apache.accumulo.core.data.TableId;
@@ -43,7 +45,6 @@ import org.apache.accumulo.core.master.thrift.TableInfo;
 import org.apache.accumulo.core.master.thrift.TabletServerStatus;
 import org.apache.accumulo.core.tabletserver.thrift.TabletStats;
 import org.apache.accumulo.server.ServerContext;
-import org.apache.accumulo.server.conf.ServerConfiguration;
 import org.apache.accumulo.server.master.state.TServerInstance;
 import org.apache.accumulo.server.master.state.TabletMigration;
 import org.apache.commons.lang.builder.ToStringBuilder;
@@ -52,6 +53,9 @@ import org.apache.thrift.TException;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import com.google.common.cache.CacheBuilder;
+import com.google.common.cache.CacheLoader;
+import com.google.common.cache.LoadingCache;
 import com.google.common.collect.HashMultimap;
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.Iterables;
@@ -82,7 +86,7 @@ import com.google.common.collect.Multimap;
  * <b>table.custom.balancer.host.regex.max.outstanding.migrations</b>
  *
  */
-public class HostRegexTableLoadBalancer extends TableLoadBalancer implements ConfigurationObserver {
+public class HostRegexTableLoadBalancer extends TableLoadBalancer {
 
   private static final String PROP_PREFIX = Property.TABLE_ARBITRARY_PROP_PREFIX.getKey();
 
@@ -101,22 +105,83 @@ public class HostRegexTableLoadBalancer extends TableLoadBalancer implements Con
   public static final String HOST_BALANCER_OUTSTANDING_MIGRATIONS_KEY =
       PROP_PREFIX + "balancer.host.regex.max.outstanding.migrations";
 
-  protected long oobCheckMillis =
-      ConfigurationTypeHelper.getTimeInMillis(HOST_BALANCER_OOB_DEFAULT);
+  private static Map<String,String> getRegexes(AccumuloConfiguration aconf) {
+    Map<String,String> regexes = new HashMap<>();
+    Map<String,String> customProps =
+        aconf.getAllPropertiesWithPrefix(Property.TABLE_ARBITRARY_PROP_PREFIX);
+
+    if (customProps != null && customProps.size() > 0) {
+      for (Entry<String,String> customProp : customProps.entrySet()) {
+        if (customProp.getKey().startsWith(HOST_BALANCER_PREFIX)) {
+          if (customProp.getKey().equals(HOST_BALANCER_OOB_CHECK_KEY)
+              || customProp.getKey().equals(HOST_BALANCER_REGEX_USING_IPS_KEY)
+              || customProp.getKey().equals(HOST_BALANCER_REGEX_MAX_MIGRATIONS_KEY)
+              || customProp.getKey().equals(HOST_BALANCER_OUTSTANDING_MIGRATIONS_KEY)) {
+            continue;
+          }
+          String tableName = customProp.getKey().substring(HOST_BALANCER_PREFIX.length());
+          String regex = customProp.getValue();
+          regexes.put(tableName, regex);
+        }
+      }
+    }
+
+    return ImmutableMap.copyOf(regexes);
+  }
+
+  /**
+   * Host Regex Table Load Balance Config
+   */
+  static class HrtlbConf {
+
+    protected long oobCheckMillis =
+        ConfigurationTypeHelper.getTimeInMillis(HOST_BALANCER_OOB_DEFAULT);
+    private int maxTServerMigrations = HOST_BALANCER_REGEX_MAX_MIGRATIONS_DEFAULT;
+    private int maxOutstandingMigrations = DEFAULT_OUTSTANDING_MIGRATIONS;
+    private boolean isIpBasedRegex = false;
+    private Map<String,String> regexes;
+    private Map<String,Pattern> poolNameToRegexPattern = null;
+
+    HrtlbConf(AccumuloConfiguration aconf) {
+      System.out.println("building hrtlb conf");
+      String oobProperty = aconf.get(HOST_BALANCER_OOB_CHECK_KEY);
+      if (oobProperty != null) {
+        oobCheckMillis = ConfigurationTypeHelper.getTimeInMillis(oobProperty);
+      }
+      String ipBased = aconf.get(HOST_BALANCER_REGEX_USING_IPS_KEY);
+      if (ipBased != null) {
+        isIpBasedRegex = Boolean.parseBoolean(ipBased);
+      }
+      String migrations = aconf.get(HOST_BALANCER_REGEX_MAX_MIGRATIONS_KEY);
+      if (migrations != null) {
+        maxTServerMigrations = Integer.parseInt(migrations);
+      }
+      String outstanding = aconf.get(HOST_BALANCER_OUTSTANDING_MIGRATIONS_KEY);
+      if (outstanding != null) {
+        maxOutstandingMigrations = Integer.parseInt(outstanding);
+      }
+
+      this.regexes = getRegexes(aconf);
+
+      Map<String,Pattern> poolNameToRegexPatternBuilder = new HashMap<>();
+      regexes.forEach((k, v) -> {
+        poolNameToRegexPatternBuilder.put(k, Pattern.compile(v));
+      });
+
+      poolNameToRegexPattern = ImmutableMap.copyOf(poolNameToRegexPatternBuilder);
+    }
+  }
 
   private static final long ONE_HOUR = 60 * 60 * 1000;
   private static final Set<KeyExtent> EMPTY_MIGRATIONS = Collections.emptySet();
-
-  private volatile Map<TableId,String> tableIdToTableName = null;
-  private volatile Map<String,Pattern> poolNameToRegexPattern = null;
   private volatile long lastOOBCheck = System.currentTimeMillis();
-  private volatile boolean isIpBasedRegex = false;
   private Map<String,SortedMap<TServerInstance,TabletServerStatus>> pools = new HashMap<>();
-  private volatile int maxTServerMigrations = HOST_BALANCER_REGEX_MAX_MIGRATIONS_DEFAULT;
-  private volatile int maxOutstandingMigrations = DEFAULT_OUTSTANDING_MIGRATIONS;
   private final Map<KeyExtent,TabletMigration> migrationsFromLastPass = new HashMap<>();
   private final Map<String,Long> tableToTimeSinceNoMigrations = new HashMap<>();
 
+  private Deriver<HrtlbConf> hrtlbConf;
+  private LoadingCache<TableId,Deriver<Map<String,String>>> tablesRegExCache;
+
   /**
    * Group the set of current tservers by pool name. Tservers that don't match a regex are put into
    * a default pool. This could be expensive in the terms of the amount of time to recompute the
@@ -170,7 +235,7 @@ public class HostRegexTableLoadBalancer extends TableLoadBalancer implements Con
    */
   protected List<String> getPoolNamesForHost(String host) {
     String test = host;
-    if (!isIpBasedRegex) {
+    if (!hrtlbConf.derive().isIpBasedRegex) {
       try {
         test = getNameFromIp(host);
       } catch (UnknownHostException e1) {
@@ -180,7 +245,7 @@ public class HostRegexTableLoadBalancer extends TableLoadBalancer implements Con
       }
     }
     List<String> pools = new ArrayList<>();
-    for (Entry<String,Pattern> e : poolNameToRegexPattern.entrySet()) {
+    for (Entry<String,Pattern> e : hrtlbConf.derive().poolNameToRegexPattern.entrySet()) {
       if (e.getValue().matcher(test).matches()) {
         pools.add(e.getKey());
       }
@@ -195,6 +260,24 @@ public class HostRegexTableLoadBalancer extends TableLoadBalancer implements Con
     return InetAddress.getByName(hostIp).getHostName();
   }
 
+  private void checkTableConfig(TableId tableId) {
+    Map<String,String> tableRegexes = tablesRegExCache.getUnchecked(tableId).derive();
+
+    if (!hrtlbConf.derive().regexes.equals(tableRegexes)) {
+      LoggerFactory.getLogger(HostRegexTableLoadBalancer.class).warn(
+          "Table id {} has different config than system.  The per table config is ignored.",
+          tableId);
+    }
+  }
+
+  private Map<TableId,String> createdTableNameMap(Map<String,String> tableIdMap) {
+    HashMap<TableId,String> tableNameMap = new HashMap<>();
+    tableIdMap.forEach((tableName, tableId) -> {
+      tableNameMap.put(TableId.of(tableId), tableName);
+    });
+    return tableNameMap;
+  }
+
   /**
    * Matches table name against pool names, returns matching pool name or DEFAULT_POOL.
    *
@@ -206,106 +289,58 @@ public class HostRegexTableLoadBalancer extends TableLoadBalancer implements Con
     if (tableName == null) {
       return DEFAULT_POOL;
     }
-    return poolNameToRegexPattern.containsKey(tableName) ? tableName : DEFAULT_POOL;
-  }
-
-  /**
-   * Parse configuration and extract properties
-   *
-   * @param conf
-   *          server configuration
-   */
-  protected void parseConfiguration(ServerConfiguration conf) {
-    TableOperations t = getTableOperations();
-    if (t == null) {
-      throw new RuntimeException("Table Operations cannot be null");
-    }
-    Map<TableId,String> tableIdToTableNameBuilder = new HashMap<>();
-    Map<String,Pattern> poolNameToRegexPatternBuilder = new HashMap<>();
-    for (Entry<String,String> table : t.tableIdMap().entrySet()) {
-      TableId tableId = TableId.of(table.getValue());
-      tableIdToTableNameBuilder.put(tableId, table.getKey());
-      conf.getTableConfiguration(tableId).addObserver(this);
-      Map<String,String> customProps = conf.getTableConfiguration(tableId)
-          .getAllPropertiesWithPrefix(Property.TABLE_ARBITRARY_PROP_PREFIX);
-      if (customProps != null && customProps.size() > 0) {
-        for (Entry<String,String> customProp : customProps.entrySet()) {
-          if (customProp.getKey().startsWith(HOST_BALANCER_PREFIX)) {
-            if (customProp.getKey().equals(HOST_BALANCER_OOB_CHECK_KEY)
-                || customProp.getKey().equals(HOST_BALANCER_REGEX_USING_IPS_KEY)
-                || customProp.getKey().equals(HOST_BALANCER_REGEX_MAX_MIGRATIONS_KEY)
-                || customProp.getKey().equals(HOST_BALANCER_OUTSTANDING_MIGRATIONS_KEY)) {
-              continue;
-            }
-            String tableName = customProp.getKey().substring(HOST_BALANCER_PREFIX.length());
-            String regex = customProp.getValue();
-            poolNameToRegexPatternBuilder.put(tableName, Pattern.compile(regex));
-          }
-        }
-      }
-    }
-
-    tableIdToTableName = ImmutableMap.copyOf(tableIdToTableNameBuilder);
-    poolNameToRegexPattern = ImmutableMap.copyOf(poolNameToRegexPatternBuilder);
-
-    String oobProperty = conf.getSystemConfiguration().get(HOST_BALANCER_OOB_CHECK_KEY);
-    if (oobProperty != null) {
-      oobCheckMillis = ConfigurationTypeHelper.getTimeInMillis(oobProperty);
-    }
-    String ipBased = conf.getSystemConfiguration().get(HOST_BALANCER_REGEX_USING_IPS_KEY);
-    if (ipBased != null) {
-      isIpBasedRegex = Boolean.parseBoolean(ipBased);
-    }
-    String migrations = conf.getSystemConfiguration().get(HOST_BALANCER_REGEX_MAX_MIGRATIONS_KEY);
-    if (migrations != null) {
-      maxTServerMigrations = Integer.parseInt(migrations);
-    }
-    String outstanding =
-        conf.getSystemConfiguration().get(HOST_BALANCER_OUTSTANDING_MIGRATIONS_KEY);
-    if (outstanding != null) {
-      this.maxOutstandingMigrations = Integer.parseInt(outstanding);
-    }
-    LOG.info("{}", this);
+    return hrtlbConf.derive().poolNameToRegexPattern.containsKey(tableName) ? tableName
+        : DEFAULT_POOL;
   }
 
   @Override
   public String toString() {
+    HrtlbConf myConf = hrtlbConf.derive();
     ToStringBuilder buf = new ToStringBuilder(this, ToStringStyle.SHORT_PREFIX_STYLE);
-    buf.append("\nTablet Out Of Bounds Check Interval", this.oobCheckMillis);
-    buf.append("\nMax Tablet Server Migrations", this.maxTServerMigrations);
-    buf.append("\nRegular Expressions use IPs", this.isIpBasedRegex);
-    buf.append("\nPools", this.poolNameToRegexPattern);
+    buf.append("\nTablet Out Of Bounds Check Interval", myConf.oobCheckMillis);
+    buf.append("\nMax Tablet Server Migrations", myConf.maxTServerMigrations);
+    buf.append("\nRegular Expressions use IPs", myConf.isIpBasedRegex);
+    buf.append("\nPools", myConf.poolNameToRegexPattern);
     return buf.toString();
   }
 
-  public Map<TableId,String> getTableIdToTableName() {
-    return tableIdToTableName;
-  }
-
   public Map<String,Pattern> getPoolNameToRegexPattern() {
-    return poolNameToRegexPattern;
+    return hrtlbConf.derive().poolNameToRegexPattern;
   }
 
   public int getMaxMigrations() {
-    return maxTServerMigrations;
+    return hrtlbConf.derive().maxTServerMigrations;
   }
 
   public int getMaxOutstandingMigrations() {
-    return maxOutstandingMigrations;
+    return hrtlbConf.derive().maxOutstandingMigrations;
   }
 
   public long getOobCheckMillis() {
-    return oobCheckMillis;
+    return hrtlbConf.derive().oobCheckMillis;
   }
 
   public boolean isIpBasedRegex() {
-    return isIpBasedRegex;
+    return hrtlbConf.derive().isIpBasedRegex;
   }
 
   @Override
   public void init(ServerContext context) {
     super.init(context);
-    parseConfiguration(context.getServerConfFactory());
+
+    this.hrtlbConf =
+        context.getServerConfFactory().getSystemConfiguration().newDeriver(HrtlbConf::new);
+
+    tablesRegExCache = CacheBuilder.newBuilder().expireAfterAccess(1, TimeUnit.HOURS)
+        .build(new CacheLoader<TableId,Deriver<Map<String,String>>>() {
+          @Override
+          public Deriver<Map<String,String>> load(TableId key) throws Exception {
+            return context.getServerConfFactory().getTableConfiguration(key)
+                .newDeriver(conf -> getRegexes(conf));
+          }
+        });
+
+    LOG.info("{}", this);
   }
 
   @Override
@@ -324,6 +359,9 @@ public class HostRegexTableLoadBalancer extends TableLoadBalancer implements Con
       }
       tableUnassigned.put(e.getKey(), e.getValue());
     }
+
+    Map<TableId,String> tableIdToTableName = createdTableNameMap(getTableOperations().tableIdMap());
+
     // Send a view of the current servers to the tables tablet balancer
     for (Entry<TableId,Map<KeyExtent,TServerInstance>> e : groupedUnassigned.entrySet()) {
       Map<KeyExtent,TServerInstance> newAssignments = new HashMap<>();
@@ -357,14 +395,19 @@ public class HostRegexTableLoadBalancer extends TableLoadBalancer implements Con
       return minBalanceTime;
 
     Map<String,String> tableIdMap = t.tableIdMap();
+    Map<TableId,String> tableIdToTableName = createdTableNameMap(tableIdMap);
+    tableIdToTableName.keySet().forEach(tid -> checkTableConfig(tid));
+
     long now = System.currentTimeMillis();
 
+    HrtlbConf myConf = hrtlbConf.derive();
+
     Map<String,SortedMap<TServerInstance,TabletServerStatus>> currentGrouped =
         splitCurrentByRegex(current);
-    if ((now - this.lastOOBCheck) > this.oobCheckMillis) {
+    if ((now - this.lastOOBCheck) > myConf.oobCheckMillis) {
       try {
         // Check to see if a tablet is assigned outside the bounds of the pool. If so, migrate it.
-        for (String table : t.list()) {
+        for (String table : tableIdMap.keySet()) {
           LOG.debug("Checking for out of bounds tablets for table {}", table);
           String tablePoolName = getPoolNameForTable(table);
           for (Entry<TServerInstance,TabletServerStatus> e : current.entrySet()) {
@@ -406,7 +449,7 @@ public class HostRegexTableLoadBalancer extends TableLoadBalancer implements Con
                   LOG.info("Tablet {} is currently outside the bounds of the"
                       + " regex, migrating from {} to {}", ke, e.getKey(), nextTS);
                   migrationsOut.add(new TabletMigration(ke, e.getKey(), nextTS));
-                  if (migrationsOut.size() >= this.maxTServerMigrations) {
+                  if (migrationsOut.size() >= myConf.maxTServerMigrations) {
                     break;
                   }
                 } else {
@@ -433,7 +476,7 @@ public class HostRegexTableLoadBalancer extends TableLoadBalancer implements Con
     }
 
     if (migrations != null && migrations.size() > 0) {
-      if (migrations.size() >= maxOutstandingMigrations) {
+      if (migrations.size() >= myConf.maxOutstandingMigrations) {
         LOG.warn("Not balancing tables due to {} outstanding migrations", migrations.size());
         if (LOG.isTraceEnabled()) {
           LOG.trace("Sample up to 10 outstanding migrations: {}", Iterables.limit(migrations, 10));
@@ -490,7 +533,7 @@ public class HostRegexTableLoadBalancer extends TableLoadBalancer implements Con
       }
 
       migrationsOut.addAll(newMigrations);
-      if (migrationsOut.size() >= this.maxTServerMigrations) {
+      if (migrationsOut.size() >= myConf.maxTServerMigrations) {
         break;
       }
     }
@@ -530,18 +573,4 @@ public class HostRegexTableLoadBalancer extends TableLoadBalancer implements Con
     }
     return newInfo;
   }
-
-  @Override
-  public void propertyChanged(String key) {
-    parseConfiguration(context.getServerConfFactory());
-  }
-
-  @Override
-  public void propertiesChanged() {
-    parseConfiguration(context.getServerConfFactory());
-  }
-
-  @Override
-  public void sessionExpired() {}
-
 }
diff --git a/server/base/src/test/java/org/apache/accumulo/server/conf/NamespaceConfigurationTest.java b/server/base/src/test/java/org/apache/accumulo/server/conf/NamespaceConfigurationTest.java
index 7f023e7..1b53027 100644
--- a/server/base/src/test/java/org/apache/accumulo/server/conf/NamespaceConfigurationTest.java
+++ b/server/base/src/test/java/org/apache/accumulo/server/conf/NamespaceConfigurationTest.java
@@ -17,7 +17,6 @@
 package org.apache.accumulo.server.conf;
 
 import static java.nio.charset.StandardCharsets.UTF_8;
-import static org.easymock.EasyMock.anyObject;
 import static org.easymock.EasyMock.createMock;
 import static org.easymock.EasyMock.eq;
 import static org.easymock.EasyMock.expect;
@@ -25,9 +24,7 @@ import static org.easymock.EasyMock.replay;
 import static org.easymock.EasyMock.verify;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNull;
-import static org.junit.Assert.assertTrue;
 
-import java.util.Collection;
 import java.util.List;
 import java.util.Map;
 import java.util.Properties;
@@ -37,7 +34,6 @@ import java.util.function.Predicate;
 import org.apache.accumulo.core.Constants;
 import org.apache.accumulo.core.clientImpl.Namespace;
 import org.apache.accumulo.core.conf.AccumuloConfiguration;
-import org.apache.accumulo.core.conf.ConfigurationObserver;
 import org.apache.accumulo.core.conf.Property;
 import org.apache.accumulo.core.data.NamespaceId;
 import org.apache.accumulo.fate.zookeeper.ZooCache;
@@ -78,8 +74,7 @@ public class NamespaceConfigurationTest {
     c.setZooCacheFactory(zcf);
 
     zc = createMock(ZooCache.class);
-    expect(zcf.getZooCache(eq(ZOOKEEPERS), eq(ZK_SESSION_TIMEOUT),
-        anyObject(NamespaceConfWatcher.class))).andReturn(zc);
+    expect(zcf.getZooCache(eq(ZOOKEEPERS), eq(ZK_SESSION_TIMEOUT))).andReturn(zc);
     replay(zcf);
   }
 
@@ -144,18 +139,6 @@ public class NamespaceConfigurationTest {
   }
 
   @Test
-  public void testObserver() {
-    ConfigurationObserver o = createMock(ConfigurationObserver.class);
-    c.addObserver(o);
-    Collection<ConfigurationObserver> os = c.getObservers();
-    assertEquals(1, os.size());
-    assertTrue(os.contains(o));
-    c.removeObserver(o);
-    os = c.getObservers();
-    assertEquals(0, os.size());
-  }
-
-  @Test
   public void testInvalidateCache() {
     // need to do a get so the accessor is created
     Property p = Property.INSTANCE_SECRET;
diff --git a/server/base/src/test/java/org/apache/accumulo/server/conf/ServerConfigurationFactoryTest.java b/server/base/src/test/java/org/apache/accumulo/server/conf/ServerConfigurationFactoryTest.java
index 8f29544..bf9dbb9 100644
--- a/server/base/src/test/java/org/apache/accumulo/server/conf/ServerConfigurationFactoryTest.java
+++ b/server/base/src/test/java/org/apache/accumulo/server/conf/ServerConfigurationFactoryTest.java
@@ -37,6 +37,7 @@ import org.apache.accumulo.core.data.NamespaceId;
 import org.apache.accumulo.fate.zookeeper.ZooCache;
 import org.apache.accumulo.fate.zookeeper.ZooCacheFactory;
 import org.apache.accumulo.server.ServerContext;
+import org.easymock.EasyMock;
 import org.junit.After;
 import org.junit.Before;
 import org.junit.BeforeClass;
@@ -56,8 +57,7 @@ public class ServerConfigurationFactoryTest {
   public static void setUpClass() {
     zcf = createMock(ZooCacheFactory.class);
     zc = createMock(ZooCache.class);
-    expect(zcf.getZooCache(eq(ZK_HOST), eq(ZK_TIMEOUT), anyObject(NamespaceConfWatcher.class)))
-        .andReturn(zc);
+    expect(zcf.getZooCache(eq(ZK_HOST), eq(ZK_TIMEOUT), EasyMock.anyObject())).andReturn(zc);
     expectLastCall().anyTimes();
     expect(zcf.getZooCache(ZK_HOST, ZK_TIMEOUT)).andReturn(zc);
     expectLastCall().anyTimes();
diff --git a/server/base/src/test/java/org/apache/accumulo/server/conf/TableConfigurationTest.java b/server/base/src/test/java/org/apache/accumulo/server/conf/TableConfigurationTest.java
index af932aa..aaa0a95 100644
--- a/server/base/src/test/java/org/apache/accumulo/server/conf/TableConfigurationTest.java
+++ b/server/base/src/test/java/org/apache/accumulo/server/conf/TableConfigurationTest.java
@@ -17,16 +17,13 @@
 package org.apache.accumulo.server.conf;
 
 import static java.nio.charset.StandardCharsets.UTF_8;
-import static org.easymock.EasyMock.anyObject;
 import static org.easymock.EasyMock.createMock;
 import static org.easymock.EasyMock.eq;
 import static org.easymock.EasyMock.expect;
 import static org.easymock.EasyMock.replay;
 import static org.easymock.EasyMock.verify;
 import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertTrue;
 
-import java.util.Collection;
 import java.util.List;
 import java.util.Map;
 import java.util.Properties;
@@ -34,7 +31,6 @@ import java.util.UUID;
 import java.util.function.Predicate;
 
 import org.apache.accumulo.core.Constants;
-import org.apache.accumulo.core.conf.ConfigurationObserver;
 import org.apache.accumulo.core.conf.Property;
 import org.apache.accumulo.core.data.TableId;
 import org.apache.accumulo.fate.zookeeper.ZooCache;
@@ -75,9 +71,7 @@ public class TableConfigurationTest {
     c.setZooCacheFactory(zcf);
 
     zc = createMock(ZooCache.class);
-    expect(
-        zcf.getZooCache(eq(ZOOKEEPERS), eq(ZK_SESSION_TIMEOUT), anyObject(TableConfWatcher.class)))
-            .andReturn(zc);
+    expect(zcf.getZooCache(eq(ZOOKEEPERS), eq(ZK_SESSION_TIMEOUT))).andReturn(zc);
     replay(zcf);
   }
 
@@ -132,18 +126,6 @@ public class TableConfigurationTest {
   }
 
   @Test
-  public void testObserver() {
-    ConfigurationObserver o = createMock(ConfigurationObserver.class);
-    c.addObserver(o);
-    Collection<ConfigurationObserver> os = c.getObservers();
-    assertEquals(1, os.size());
-    assertTrue(os.contains(o));
-    c.removeObserver(o);
-    os = c.getObservers();
-    assertEquals(0, os.size());
-  }
-
-  @Test
   public void testInvalidateCache() {
     // need to do a get so the accessor is created
     Property p = Property.INSTANCE_SECRET;
diff --git a/server/base/src/test/java/org/apache/accumulo/server/master/balancer/BaseHostRegexTableLoadBalancerTest.java b/server/base/src/test/java/org/apache/accumulo/server/master/balancer/BaseHostRegexTableLoadBalancerTest.java
index f53cd62..e7944a0 100644
--- a/server/base/src/test/java/org/apache/accumulo/server/master/balancer/BaseHostRegexTableLoadBalancerTest.java
+++ b/server/base/src/test/java/org/apache/accumulo/server/master/balancer/BaseHostRegexTableLoadBalancerTest.java
@@ -23,7 +23,6 @@ import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
-import java.util.Map.Entry;
 import java.util.Properties;
 import java.util.SortedMap;
 import java.util.SortedSet;
@@ -94,15 +93,17 @@ public abstract class BaseHostRegexTableLoadBalancerTest extends HostRegexTableL
   protected static class TestServerConfigurationFactory extends ServerConfigurationFactory {
 
     final ServerContext context;
+    private ConfigurationCopy config;
 
     public TestServerConfigurationFactory(ServerContext context) {
       super(context, siteConfg);
       this.context = context;
+      this.config = new ConfigurationCopy(DEFAULT_TABLE_PROPERTIES);
     }
 
     @Override
     public synchronized AccumuloConfiguration getSystemConfiguration() {
-      return new ConfigurationCopy(DEFAULT_TABLE_PROPERTIES);
+      return config;
     }
 
     @Override
@@ -114,16 +115,12 @@ public abstract class BaseHostRegexTableLoadBalancerTest extends HostRegexTableL
       return new TableConfiguration(context, tableId, dummyConf) {
         @Override
         public String get(Property property) {
-          return DEFAULT_TABLE_PROPERTIES.get(property.name());
+          return getSystemConfiguration().get(property.name());
         }
 
         @Override
         public void getProperties(Map<String,String> props, Predicate<String> filter) {
-          for (Entry<String,String> e : DEFAULT_TABLE_PROPERTIES.entrySet()) {
-            if (filter.test(e.getKey())) {
-              props.put(e.getKey(), e.getValue());
-            }
-          }
+          getSystemConfiguration().getProperties(props, filter);
         }
 
         @Override
diff --git a/server/base/src/test/java/org/apache/accumulo/server/master/balancer/HostRegexTableLoadBalancerReconfigurationTest.java b/server/base/src/test/java/org/apache/accumulo/server/master/balancer/HostRegexTableLoadBalancerReconfigurationTest.java
index 40a28c1..105b6d5 100644
--- a/server/base/src/test/java/org/apache/accumulo/server/master/balancer/HostRegexTableLoadBalancerReconfigurationTest.java
+++ b/server/base/src/test/java/org/apache/accumulo/server/master/balancer/HostRegexTableLoadBalancerReconfigurationTest.java
@@ -31,6 +31,7 @@ import java.util.Map;
 import java.util.Map.Entry;
 import java.util.Set;
 
+import org.apache.accumulo.core.conf.ConfigurationCopy;
 import org.apache.accumulo.core.data.TableId;
 import org.apache.accumulo.core.dataImpl.KeyExtent;
 import org.apache.accumulo.core.tabletserver.thrift.TabletStats;
@@ -89,9 +90,10 @@ public class HostRegexTableLoadBalancerReconfigurationTest
     this.balance(Collections.unmodifiableSortedMap(allTabletServers), migrations, migrationsOut);
     assertEquals(0, migrationsOut.size());
     // Change property, simulate call by TableConfWatcher
-    DEFAULT_TABLE_PROPERTIES
-        .put(HostRegexTableLoadBalancer.HOST_BALANCER_PREFIX + BAR.getTableName(), "r01.*");
-    this.propertiesChanged();
+
+    ((ConfigurationCopy) factory.getSystemConfiguration())
+        .set(HostRegexTableLoadBalancer.HOST_BALANCER_PREFIX + BAR.getTableName(), "r01.*");
+
     // Wait to trigger the out of bounds check and the repool check
     UtilWaitThread.sleep(10000);
     this.balance(Collections.unmodifiableSortedMap(allTabletServers), migrations, migrationsOut);
diff --git a/server/base/src/test/java/org/apache/accumulo/server/master/balancer/HostRegexTableLoadBalancerTest.java b/server/base/src/test/java/org/apache/accumulo/server/master/balancer/HostRegexTableLoadBalancerTest.java
index ab9cad7..7d3dd41 100644
--- a/server/base/src/test/java/org/apache/accumulo/server/master/balancer/HostRegexTableLoadBalancerTest.java
+++ b/server/base/src/test/java/org/apache/accumulo/server/master/balancer/HostRegexTableLoadBalancerTest.java
@@ -33,14 +33,10 @@ import java.util.Map;
 import java.util.Map.Entry;
 import java.util.Set;
 import java.util.SortedMap;
-import java.util.function.Predicate;
 import java.util.regex.Pattern;
 
-import org.apache.accumulo.core.clientImpl.Namespace;
 import org.apache.accumulo.core.conf.AccumuloConfiguration;
 import org.apache.accumulo.core.conf.ConfigurationCopy;
-import org.apache.accumulo.core.conf.DefaultConfiguration;
-import org.apache.accumulo.core.conf.Property;
 import org.apache.accumulo.core.data.TableId;
 import org.apache.accumulo.core.dataImpl.KeyExtent;
 import org.apache.accumulo.core.dataImpl.thrift.TKeyExtent;
@@ -48,9 +44,7 @@ import org.apache.accumulo.core.master.thrift.TabletServerStatus;
 import org.apache.accumulo.core.tabletserver.thrift.TabletStats;
 import org.apache.accumulo.fate.util.UtilWaitThread;
 import org.apache.accumulo.server.ServerContext;
-import org.apache.accumulo.server.conf.NamespaceConfiguration;
 import org.apache.accumulo.server.conf.ServerConfigurationFactory;
-import org.apache.accumulo.server.conf.TableConfiguration;
 import org.apache.accumulo.server.master.state.TServerInstance;
 import org.apache.accumulo.server.master.state.TabletMigration;
 import org.junit.Test;
@@ -84,15 +78,6 @@ public class HostRegexTableLoadBalancerTest extends BaseHostRegexTableLoadBalanc
     assertEquals(Pattern.compile("r01.*").pattern(), patterns.get(FOO.getTableName()).pattern());
     assertTrue(patterns.containsKey(BAR.getTableName()));
     assertEquals(Pattern.compile("r02.*").pattern(), patterns.get(BAR.getTableName()).pattern());
-    Map<TableId,String> tids = this.getTableIdToTableName();
-    assertEquals(3, tids.size());
-    assertTrue(tids.containsKey(FOO.getId()));
-    assertEquals(FOO.getTableName(), tids.get(FOO.getId()));
-    assertTrue(tids.containsKey(BAR.getId()));
-    assertEquals(BAR.getTableName(), tids.get(BAR.getId()));
-    assertTrue(tids.containsKey(BAZ.getId()));
-    assertEquals(BAZ.getTableName(), tids.get(BAZ.getId()));
-    assertFalse(this.isIpBasedRegex());
   }
 
   @Test
@@ -193,40 +178,13 @@ public class HostRegexTableLoadBalancerTest extends BaseHostRegexTableLoadBalanc
     ServerContext context = createMockContext();
     replay(context);
     initFactory(new TestServerConfigurationFactory(context) {
-
       @Override
-      public TableConfiguration getTableConfiguration(TableId tableId) {
-        NamespaceConfiguration defaultConf = new NamespaceConfiguration(Namespace.DEFAULT.id(),
-            this.context, DefaultConfiguration.getInstance());
-        return new TableConfiguration(this.context, tableId, defaultConf) {
-          HashMap<String,String> tableProperties = new HashMap<>();
-          {
-            tableProperties
-                .put(HostRegexTableLoadBalancer.HOST_BALANCER_PREFIX + FOO.getTableName(), "r.*");
-            tableProperties.put(
-                HostRegexTableLoadBalancer.HOST_BALANCER_PREFIX + BAR.getTableName(),
-                "r01.*|r02.*");
-          }
-
-          @Override
-          public String get(Property property) {
-            return tableProperties.get(property.name());
-          }
-
-          @Override
-          public void getProperties(Map<String,String> props, Predicate<String> filter) {
-            for (Entry<String,String> e : tableProperties.entrySet()) {
-              if (filter.test(e.getKey())) {
-                props.put(e.getKey(), e.getValue());
-              }
-            }
-          }
-
-          @Override
-          public long getUpdateCount() {
-            return 0;
-          }
-        };
+      public synchronized AccumuloConfiguration getSystemConfiguration() {
+        HashMap<String,String> props = new HashMap<>(DEFAULT_TABLE_PROPERTIES);
+        props.put(HostRegexTableLoadBalancer.HOST_BALANCER_PREFIX + FOO.getTableName(), "r.*");
+        props.put(HostRegexTableLoadBalancer.HOST_BALANCER_PREFIX + BAR.getTableName(),
+            "r01.*|r02.*");
+        return new ConfigurationCopy(props);
       }
     });
     Map<String,SortedMap<TServerInstance,TabletServerStatus>> groups =
@@ -281,44 +239,12 @@ public class HostRegexTableLoadBalancerTest extends BaseHostRegexTableLoadBalanc
         HashMap<String,String> props = new HashMap<>();
         props.put(HostRegexTableLoadBalancer.HOST_BALANCER_OOB_CHECK_KEY, "30s");
         props.put(HostRegexTableLoadBalancer.HOST_BALANCER_REGEX_USING_IPS_KEY, "true");
+        props.put(HostRegexTableLoadBalancer.HOST_BALANCER_PREFIX + FOO.getTableName(),
+            "192\\.168\\.0\\.[1-5]");
+        props.put(HostRegexTableLoadBalancer.HOST_BALANCER_PREFIX + BAR.getTableName(),
+            "192\\.168\\.0\\.[6-9]|192\\.168\\.0\\.10");
         return new ConfigurationCopy(props);
       }
-
-      @Override
-      public TableConfiguration getTableConfiguration(TableId tableId) {
-        NamespaceConfiguration defaultConf = new NamespaceConfiguration(Namespace.DEFAULT.id(),
-            this.context, DefaultConfiguration.getInstance());
-        return new TableConfiguration(context, tableId, defaultConf) {
-          HashMap<String,String> tableProperties = new HashMap<>();
-          {
-            tableProperties.put(
-                HostRegexTableLoadBalancer.HOST_BALANCER_PREFIX + FOO.getTableName(),
-                "192\\.168\\.0\\.[1-5]");
-            tableProperties.put(
-                HostRegexTableLoadBalancer.HOST_BALANCER_PREFIX + BAR.getTableName(),
-                "192\\.168\\.0\\.[6-9]|192\\.168\\.0\\.10");
-          }
-
-          @Override
-          public String get(Property property) {
-            return tableProperties.get(property.name());
-          }
-
-          @Override
-          public void getProperties(Map<String,String> props, Predicate<String> filter) {
-            for (Entry<String,String> e : tableProperties.entrySet()) {
-              if (filter.test(e.getKey())) {
-                props.put(e.getKey(), e.getValue());
-              }
-            }
-          }
-
-          @Override
-          public long getUpdateCount() {
-            return 0;
-          }
-        };
-      }
     });
     assertTrue(isIpBasedRegex());
     Map<String,SortedMap<TServerInstance,TabletServerStatus>> groups =
diff --git a/server/tserver/src/main/java/org/apache/accumulo/tserver/TabletServer.java b/server/tserver/src/main/java/org/apache/accumulo/tserver/TabletServer.java
index 557c53c..db9623c 100644
--- a/server/tserver/src/main/java/org/apache/accumulo/tserver/TabletServer.java
+++ b/server/tserver/src/main/java/org/apache/accumulo/tserver/TabletServer.java
@@ -3145,14 +3145,6 @@ public class TabletServer extends AbstractServer {
     Runnable gcDebugTask = () -> gcLogger.logGCInfo(getConfiguration());
 
     SimpleTimer.getInstance(aconf).schedule(gcDebugTask, 0, TIME_BETWEEN_GC_CHECKS);
-
-    Runnable constraintTask = () -> {
-      for (Tablet tablet : getOnlineTablets().values()) {
-        tablet.checkConstraints();
-      }
-    };
-
-    SimpleTimer.getInstance(aconf).schedule(constraintTask, 0, 1000);
   }
 
   public TabletServerStatus getStats(Map<TableId,MapCounter<ScanRunState>> scanCounts) {
diff --git a/server/tserver/src/main/java/org/apache/accumulo/tserver/constraints/ConstraintChecker.java b/server/tserver/src/main/java/org/apache/accumulo/tserver/constraints/ConstraintChecker.java
index a375d12..c7762b4 100644
--- a/server/tserver/src/main/java/org/apache/accumulo/tserver/constraints/ConstraintChecker.java
+++ b/server/tserver/src/main/java/org/apache/accumulo/tserver/constraints/ConstraintChecker.java
@@ -20,8 +20,8 @@ import java.io.IOException;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Map.Entry;
-import java.util.concurrent.atomic.AtomicLong;
 
+import org.apache.accumulo.core.conf.AccumuloConfiguration;
 import org.apache.accumulo.core.conf.Property;
 import org.apache.accumulo.core.constraints.Constraint;
 import org.apache.accumulo.core.constraints.Constraint.Environment;
@@ -41,43 +41,39 @@ public class ConstraintChecker {
   private ArrayList<Constraint> constrains;
   private static final Logger log = LoggerFactory.getLogger(ConstraintChecker.class);
 
-  private ClassLoader loader;
-  private TableConfiguration conf;
-
-  private AtomicLong lastCheck = new AtomicLong(0);
-
-  public ConstraintChecker(TableConfiguration conf) {
+  public ConstraintChecker(AccumuloConfiguration conf) {
     constrains = new ArrayList<>();
 
-    this.conf = conf;
-
     try {
       String context = conf.get(Property.TABLE_CLASSPATH);
 
+      ClassLoader loader;
+
       if (context != null && !context.equals("")) {
         loader = AccumuloVFSClassLoader.getContextManager().getClassLoader(context);
       } else {
         loader = AccumuloVFSClassLoader.getClassLoader();
       }
 
-      for (Entry<String,String> entry : conf) {
+      for (Entry<String,String> entry : conf
+          .getAllPropertiesWithPrefix(Property.TABLE_CONSTRAINT_PREFIX).entrySet()) {
         if (entry.getKey().startsWith(Property.TABLE_CONSTRAINT_PREFIX.getKey())) {
           String className = entry.getValue();
           Class<? extends Constraint> clazz =
               loader.loadClass(className).asSubclass(Constraint.class);
-          log.debug("Loaded constraint {} for {}", clazz.getName(), conf.getTableId());
+
+          log.debug("Loaded constraint {} for {}", clazz.getName(),
+              ((TableConfiguration) conf).getTableId());
           constrains.add(clazz.getDeclaredConstructor().newInstance());
         }
       }
 
-      lastCheck.set(System.currentTimeMillis());
-
     } catch (Throwable e) {
       constrains.clear();
-      loader = null;
       constrains.add(new UnsatisfiableConstraint((short) -1,
           "Failed to load constraints, not accepting mutations."));
-      log.error("Failed to load constraints " + conf.getTableId() + " " + e, e);
+      log.error("Failed to load constraints " + ((TableConfiguration) conf).getTableId() + " " + e,
+          e);
     }
   }
 
@@ -86,29 +82,6 @@ public class ConstraintChecker {
     return constrains;
   }
 
-  public boolean classLoaderChanged() {
-
-    if (constrains.size() == 0)
-      return false;
-
-    try {
-      String context = conf.get(Property.TABLE_CLASSPATH);
-
-      ClassLoader currentLoader;
-
-      if (context != null && !context.equals("")) {
-        currentLoader = AccumuloVFSClassLoader.getContextManager().getClassLoader(context);
-      } else {
-        currentLoader = AccumuloVFSClassLoader.getClassLoader();
-      }
-
-      return currentLoader != loader;
-    } catch (Exception e) {
-      log.debug("Failed to check {}", e.getMessage());
-      return true;
-    }
-  }
-
   private static Violations addViolation(Violations violations, ConstraintViolationSummary cvs) {
     if (violations == null) {
       violations = new Violations();
diff --git a/server/tserver/src/main/java/org/apache/accumulo/tserver/tablet/Tablet.java b/server/tserver/src/main/java/org/apache/accumulo/tserver/tablet/Tablet.java
index 1f17cef..68eb79f 100644
--- a/server/tserver/src/main/java/org/apache/accumulo/tserver/tablet/Tablet.java
+++ b/server/tserver/src/main/java/org/apache/accumulo/tserver/tablet/Tablet.java
@@ -42,7 +42,6 @@ import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicLong;
-import java.util.concurrent.atomic.AtomicReference;
 import java.util.concurrent.locks.ReentrantLock;
 
 import org.apache.accumulo.core.Constants;
@@ -53,8 +52,8 @@ import org.apache.accumulo.core.client.sample.SamplerConfiguration;
 import org.apache.accumulo.core.clientImpl.DurabilityImpl;
 import org.apache.accumulo.core.clientImpl.Tables;
 import org.apache.accumulo.core.conf.AccumuloConfiguration;
+import org.apache.accumulo.core.conf.AccumuloConfiguration.Deriver;
 import org.apache.accumulo.core.conf.ConfigurationCopy;
-import org.apache.accumulo.core.conf.ConfigurationObserver;
 import org.apache.accumulo.core.conf.Property;
 import org.apache.accumulo.core.constraints.Violations;
 import org.apache.accumulo.core.data.ByteSequence;
@@ -151,7 +150,6 @@ import org.apache.zookeeper.KeeperException.NoNodeException;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Preconditions;
 import com.google.common.cache.Cache;
 import com.google.common.cache.CacheBuilder;
@@ -166,6 +164,8 @@ import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
 public class Tablet {
   private static final Logger log = LoggerFactory.getLogger(Tablet.class);
 
+  private static final byte[] EMPTY_BYTES = new byte[0];
+
   private final TabletServer tabletServer;
   private final ServerContext context;
   private final KeyExtent extent;
@@ -222,7 +222,7 @@ public class Tablet {
   private final Set<MajorCompactionReason> majorCompactionQueued =
       Collections.synchronizedSet(EnumSet.noneOf(MajorCompactionReason.class));
 
-  private final AtomicReference<ConstraintChecker> constraintChecker = new AtomicReference<>();
+  private final Deriver<ConstraintChecker> constraintChecker;
 
   private int writesInProgress = 0;
 
@@ -240,7 +240,7 @@ public class Tablet {
   private final Rate ingestByteRate = new Rate(0.95);
   private long ingestBytes = 0;
 
-  private byte[] defaultSecurityLabel = new byte[0];
+  private final Deriver<byte[]> defaultSecurityLabel;
 
   private long lastMinorCompactionFinishTime = 0;
   private long lastMapFileImportTime = 0;
@@ -251,8 +251,6 @@ public class Tablet {
   private final Rate scannedRate = new Rate(0.95);
   private final AtomicLong scannedCount = new AtomicLong(0);
 
-  private final ConfigurationObserver configObserver;
-
   // Files that are currently in the process of bulk importing. Access to this is protected by the
   // tablet lock.
   private final Set<FileRef> bulkImporting = new HashSet<>();
@@ -302,30 +300,6 @@ public class Tablet {
     }
   }
 
-  /**
-   * Only visible for testing
-   */
-  @VisibleForTesting
-  protected Tablet(TabletTime tabletTime, String tabletDirectory, int logId, Path location,
-      DatafileManager datafileManager, TabletServer tabletServer,
-      TabletResourceManager tabletResources, TabletMemory tabletMemory,
-      TableConfiguration tableConfiguration, KeyExtent extent,
-      ConfigurationObserver configObserver) {
-    this.tabletTime = tabletTime;
-    this.tabletDirectory = tabletDirectory;
-    this.logId = logId;
-    this.location = location;
-    this.datafileManager = datafileManager;
-    this.tabletServer = tabletServer;
-    this.context = tabletServer.getContext();
-    this.tabletResources = tabletResources;
-    this.tabletMemory = tabletMemory;
-    this.tableConfiguration = tableConfiguration;
-    this.extent = extent;
-    this.configObserver = configObserver;
-    this.splitCreationTime = 0;
-  }
-
   public Tablet(final TabletServer tabletServer, final KeyExtent extent,
       final TabletResourceManager trm, TabletData data) throws IOException {
 
@@ -372,56 +346,23 @@ public class Tablet {
     for (Entry<Long,List<FileRef>> entry : data.getBulkImported().entrySet()) {
       this.bulkImported.put(entry.getKey(), new CopyOnWriteArrayList<>(entry.getValue()));
     }
-    setupDefaultSecurityLabels(extent);
 
     final List<LogEntry> logEntries = tabletPaths.logEntries;
     final SortedMap<FileRef,DataFileValue> datafiles = tabletPaths.datafiles;
 
-    tableConfiguration.addObserver(configObserver = new ConfigurationObserver() {
-
-      private void reloadConstraints() {
-        log.debug("Reloading constraints for extent: " + extent);
-        constraintChecker.set(new ConstraintChecker(tableConfiguration));
-      }
-
-      @Override
-      public void propertiesChanged() {
-        reloadConstraints();
-
-        try {
-          setupDefaultSecurityLabels(extent);
-        } catch (Exception e) {
-          log.error("Failed to reload default security labels for extent: {}", extent);
-        }
-      }
-
-      @Override
-      public void propertyChanged(String prop) {
-        if (prop.startsWith(Property.TABLE_CONSTRAINT_PREFIX.getKey())) {
-          reloadConstraints();
-        } else if (prop.equals(Property.TABLE_DEFAULT_SCANTIME_VISIBILITY.getKey())) {
-          try {
-            log.info("Default security labels changed for extent: {}", extent);
-            setupDefaultSecurityLabels(extent);
-          } catch (Exception e) {
-            log.error("Failed to reload default security labels for extent: {}", extent);
-          }
-        }
-
-      }
-
-      @Override
-      public void sessionExpired() {
-        log.trace("Session expired, no longer updating per table props...");
-      }
+    constraintChecker = tableConfiguration.newDeriver(conf -> new ConstraintChecker(conf));
 
-    });
+    if (extent.isMeta()) {
+      defaultSecurityLabel = () -> EMPTY_BYTES;
+    } else {
+      defaultSecurityLabel = tableConfiguration.newDeriver(conf -> {
+        return new ColumnVisibility(conf.get(Property.TABLE_DEFAULT_SCANTIME_VISIBILITY))
+            .getExpression();
+      });
+    }
 
-    tableConfiguration.getNamespaceConfiguration().addObserver(configObserver);
     tabletMemory = new TabletMemory(this);
 
-    // Force a load of any per-table properties
-    configObserver.propertiesChanged();
     if (!logEntries.isEmpty()) {
       log.info("Starting Write-Ahead Log recovery for {}", this.extent);
       final AtomicLong entriesUsedOnTablet = new AtomicLong(0);
@@ -556,21 +497,6 @@ public class Tablet {
     }
   }
 
-  private void setupDefaultSecurityLabels(KeyExtent extent) {
-    if (extent.isMeta()) {
-      defaultSecurityLabel = new byte[0];
-    } else {
-      try {
-        ColumnVisibility cv = new ColumnVisibility(
-            tableConfiguration.get(Property.TABLE_DEFAULT_SCANTIME_VISIBILITY));
-        this.defaultSecurityLabel = cv.getExpression();
-      } catch (Exception e) {
-        log.error("Error setting up default security label {}", e.getMessage(), e);
-        this.defaultSecurityLabel = new byte[0];
-      }
-    }
-  }
-
   private LookupResult lookup(SortedKeyValueIterator<Key,Value> mmfi, List<Range> ranges,
       HashSet<Column> columnSet, List<KVEntry> results, long maxResultsSize, long batchTimeOut)
       throws IOException {
@@ -722,7 +648,7 @@ public class Tablet {
       AtomicBoolean iFlag) throws IOException {
 
     ScanDataSource dataSource =
-        new ScanDataSource(this, authorizations, this.defaultSecurityLabel, iFlag);
+        new ScanDataSource(this, authorizations, this.defaultSecurityLabel.derive(), iFlag);
 
     try {
       SortedKeyValueIterator<Key,Value> iter = new SourceSwitchingIterator(dataSource);
@@ -759,8 +685,9 @@ public class Tablet {
       tabletRange.clip(range);
     }
 
-    ScanDataSource dataSource = new ScanDataSource(this, authorizations, this.defaultSecurityLabel,
-        columns, ssiList, ssio, interruptFlag, samplerConfig, batchTimeOut, classLoaderContext);
+    ScanDataSource dataSource =
+        new ScanDataSource(this, authorizations, this.defaultSecurityLabel.derive(), columns,
+            ssiList, ssio, interruptFlag, samplerConfig, batchTimeOut, classLoaderContext);
 
     LookupResult result = null;
 
@@ -894,8 +821,9 @@ public class Tablet {
     // then clip will throw an exception
     extent.toDataRange().clip(range);
 
-    ScanOptions opts = new ScanOptions(num, authorizations, this.defaultSecurityLabel, columns,
-        ssiList, ssio, interruptFlag, isolated, samplerConfig, batchTimeOut, classLoaderContext);
+    ScanOptions opts =
+        new ScanOptions(num, authorizations, this.defaultSecurityLabel.derive(), columns, ssiList,
+            ssio, interruptFlag, isolated, samplerConfig, batchTimeOut, classLoaderContext);
     return new Scanner(this, range, opts);
   }
 
@@ -1201,19 +1129,10 @@ public class Tablet {
     return commitSession;
   }
 
-  public void checkConstraints() {
-    ConstraintChecker cc = constraintChecker.get();
-
-    if (cc.classLoaderChanged()) {
-      ConstraintChecker ncc = new ConstraintChecker(tableConfiguration);
-      constraintChecker.compareAndSet(cc, ncc);
-    }
-  }
-
   public CommitSession prepareMutationsForCommit(TservConstraintEnv cenv, List<Mutation> mutations)
       throws TConstraintViolationException {
 
-    ConstraintChecker cc = constraintChecker.get();
+    ConstraintChecker cc = constraintChecker.derive();
 
     List<Mutation> violators = null;
     Violations violations = new Violations();
@@ -1483,9 +1402,6 @@ public class Tablet {
 
     log.debug("TABLET_HIST {} closed", extent);
 
-    tableConfiguration.getNamespaceConfiguration().removeObserver(configObserver);
-    tableConfiguration.removeObserver(configObserver);
-
     if (completeClose) {
       closeState = CloseState.COMPLETE;
     }
@@ -2005,7 +1921,7 @@ public class Tablet {
             getNextMapFilename((filesToCompact.size() == 0 && !propogateDeletes) ? "A" : "C");
         FileRef compactTmpName = new FileRef(fileName.path() + "_tmp");
 
-        AccumuloConfiguration tableConf = createTableConfiguration(tableConfiguration, plan);
+        AccumuloConfiguration tableConf = createCompactionConfiguration(tableConfiguration, plan);
 
         try (TraceScope span = Trace.startSpan("compactFiles")) {
           CompactionEnv cenv = new CompactionEnv() {
@@ -2082,7 +1998,7 @@ public class Tablet {
     }
   }
 
-  protected AccumuloConfiguration createTableConfiguration(TableConfiguration base,
+  protected static AccumuloConfiguration createCompactionConfiguration(TableConfiguration base,
       CompactionPlan plan) {
     if (plan == null || plan.writeParameters == null) {
       return base;
diff --git a/server/tserver/src/test/java/org/apache/accumulo/tserver/tablet/TabletTest.java b/server/tserver/src/test/java/org/apache/accumulo/tserver/tablet/TabletTest.java
index ea9c9ff..2adc9a1 100644
--- a/server/tserver/src/test/java/org/apache/accumulo/tserver/tablet/TabletTest.java
+++ b/server/tserver/src/test/java/org/apache/accumulo/tserver/tablet/TabletTest.java
@@ -21,16 +21,10 @@ import static org.junit.Assert.assertEquals;
 import java.util.Collections;
 
 import org.apache.accumulo.core.conf.AccumuloConfiguration;
-import org.apache.accumulo.core.conf.ConfigurationObserver;
 import org.apache.accumulo.core.conf.Property;
-import org.apache.accumulo.core.dataImpl.KeyExtent;
 import org.apache.accumulo.server.conf.TableConfiguration;
-import org.apache.accumulo.server.tablets.TabletTime;
-import org.apache.accumulo.tserver.TabletServer;
-import org.apache.accumulo.tserver.TabletServerResourceManager.TabletResourceManager;
 import org.apache.accumulo.tserver.compaction.CompactionPlan;
 import org.apache.accumulo.tserver.compaction.WriteParameters;
-import org.apache.hadoop.fs.Path;
 import org.easymock.EasyMock;
 import org.junit.Test;
 
@@ -42,16 +36,6 @@ public class TabletTest {
     CompactionPlan plan = EasyMock.createMock(CompactionPlan.class);
     WriteParameters writeParams = EasyMock.createMock(WriteParameters.class);
     plan.writeParameters = writeParams;
-    DatafileManager dfm = EasyMock.createMock(DatafileManager.class);
-    TabletTime time = EasyMock.createMock(TabletTime.class);
-    TabletServer tserver = EasyMock.createMock(TabletServer.class);
-    TabletResourceManager tserverResourceManager = EasyMock.createMock(TabletResourceManager.class);
-    TabletMemory tabletMemory = EasyMock.createMock(TabletMemory.class);
-    KeyExtent extent = EasyMock.createMock(KeyExtent.class);
-    ConfigurationObserver obs = EasyMock.createMock(ConfigurationObserver.class);
-
-    Tablet tablet = new Tablet(time, "", 0, new Path("/foo"), dfm, tserver, tserverResourceManager,
-        tabletMemory, tableConf, extent, obs);
 
     long hdfsBlockSize = 10000L, blockSize = 5000L, indexBlockSize = 500L;
     int replication = 5;
@@ -66,7 +50,7 @@ public class TabletTest {
 
     EasyMock.replay(tableConf, plan, writeParams);
 
-    AccumuloConfiguration aConf = tablet.createTableConfiguration(tableConf, plan);
+    AccumuloConfiguration aConf = Tablet.createCompactionConfiguration(tableConf, plan);
 
     EasyMock.verify(tableConf, plan, writeParams);
 
@@ -77,5 +61,4 @@ public class TabletTest {
     assertEquals(compressType, aConf.get(Property.TABLE_FILE_COMPRESSION_TYPE));
     assertEquals(replication, Integer.parseInt(aConf.get(Property.TABLE_FILE_REPLICATION)));
   }
-
 }


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