HBASE-18747 Introduce new example and helper classes to tell CP users how to do filtering on scanners

hbase-examples/pom.xml

@@ -183,6 +183,18 @@
       <groupId>com.google.protobuf</groupId>
       <artifactId>protobuf-java</artifactId>
     </dependency>
+    <dependency>
+      <groupId>org.apache.curator</groupId>
+      <artifactId>curator-framework</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>org.apache.curator</groupId>
+      <artifactId>curator-client</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>org.apache.curator</groupId>
+      <artifactId>curator-recipes</artifactId>
+    </dependency>
     <dependency>
       <groupId>com.github.stephenc.findbugs</groupId>
       <artifactId>findbugs-annotations</artifactId>

hbase-examples/src/main/java/org/apache/hadoop/hbase/coprocessor/example/DelegatingInternalScanner.java

@@ -0,0 +1,47 @@
+/**
+ * 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.hadoop.hbase.coprocessor.example;
+
+import java.io.IOException;
+import java.util.List;
+
+import org.apache.hadoop.hbase.Cell;
+import org.apache.hadoop.hbase.regionserver.InternalScanner;
+import org.apache.hadoop.hbase.regionserver.ScannerContext;
+
+/**
+ * A simple delegation for doing filtering on {@link InternalScanner}.
+ */
+public class DelegatingInternalScanner implements InternalScanner {
+
+  protected final InternalScanner scanner;
+
+  public DelegatingInternalScanner(InternalScanner scanner) {
+    this.scanner = scanner;
+  }
+
+  @Override
+  public boolean next(List<Cell> result, ScannerContext scannerContext) throws IOException {
+    return scanner.next(result, scannerContext);
+  }
+
+  @Override
+  public void close() throws IOException {
+    scanner.close();
+  }
+}

hbase-examples/src/main/java/org/apache/hadoop/hbase/coprocessor/example/ZooKeeperScanPolicyObserver.java

@@ -1,4 +1,4 @@
-/*
+/**
  * Copyright The Apache Software Foundation
  *
  * Licensed to the Apache Software Foundation (ASF) under one or more
@@ -20,54 +20,40 @@ package org.apache.hadoop.hbase.coprocessor.example;
 
 import java.io.IOException;
 import java.util.List;
-import java.util.NavigableSet;
 import java.util.Optional;
-import java.util.OptionalInt;
+import java.util.OptionalLong;
 
-import org.apache.commons.logging.Log;
+import org.apache.curator.framework.CuratorFramework;
-import org.apache.commons.logging.LogFactory;
+import org.apache.curator.framework.CuratorFrameworkFactory;
+import org.apache.curator.framework.recipes.cache.ChildData;
+import org.apache.curator.framework.recipes.cache.NodeCache;
+import org.apache.curator.retry.RetryForever;
+import org.apache.hadoop.hbase.Cell;
 import org.apache.hadoop.hbase.CoprocessorEnvironment;
-import org.apache.hadoop.hbase.HConstants;
-import org.apache.hadoop.hbase.client.IsolationLevel;
-import org.apache.hadoop.hbase.client.Scan;
 import org.apache.hadoop.hbase.coprocessor.ObserverContext;
 import org.apache.hadoop.hbase.coprocessor.RegionCoprocessor;
 import org.apache.hadoop.hbase.coprocessor.RegionCoprocessorEnvironment;
 import org.apache.hadoop.hbase.coprocessor.RegionObserver;
-import org.apache.hadoop.hbase.regionserver.HStore;
 import org.apache.hadoop.hbase.regionserver.InternalScanner;
-import org.apache.hadoop.hbase.regionserver.KeyValueScanner;
-import org.apache.hadoop.hbase.regionserver.ScanInfo;
 import org.apache.hadoop.hbase.regionserver.ScanType;
+import org.apache.hadoop.hbase.regionserver.ScannerContext;
 import org.apache.hadoop.hbase.regionserver.Store;
-import org.apache.hadoop.hbase.regionserver.StoreScanner;
 import org.apache.hadoop.hbase.regionserver.compactions.CompactionLifeCycleTracker;
 import org.apache.hadoop.hbase.regionserver.compactions.CompactionRequest;
 import org.apache.hadoop.hbase.util.Bytes;
-import org.apache.hadoop.hbase.util.EnvironmentEdgeManager;
-import org.apache.zookeeper.KeeperException;
-import org.apache.zookeeper.WatchedEvent;
-import org.apache.zookeeper.Watcher;
-import org.apache.zookeeper.ZooKeeper;
 
 /**
- * This is an example showing how a RegionObserver could configured
+ * This is an example showing how a RegionObserver could configured via ZooKeeper in order to
- * via ZooKeeper in order to control a Region compaction, flush, and scan policy.
+ * control a Region compaction, flush, and scan policy. This also demonstrated the use of shared
- *
+ * {@link org.apache.hadoop.hbase.coprocessor.RegionObserver} state. See
- * This also demonstrated the use of shared
+ * {@link RegionCoprocessorEnvironment#getSharedData()}.
- * {@link org.apache.hadoop.hbase.coprocessor.RegionObserver} state.
+ * <p>
- * See {@link RegionCoprocessorEnvironment#getSharedData()}.
+ * This would be useful for an incremental backup tool, which would indicate the last time of a
- *
+ * successful backup via ZK and instruct HBase that to safely delete the data which has already been
- * This would be useful for an incremental backup tool, which would indicate the last
+ * backup.
- * time of a successful backup via ZK and instruct HBase to not delete data that was
- * inserted since (based on wall clock time).
- *
- * This implements org.apache.zookeeper.Watcher directly instead of using
- * {@link org.apache.hadoop.hbase.zookeeper.ZooKeeperWatcher},
- * because RegionObservers come and go and currently
- * listeners registered with ZooKeeperWatcher cannot be removed.
  */
 public class ZooKeeperScanPolicyObserver implements RegionCoprocessor, RegionObserver {
+
   @Override
   public Optional<RegionObserver> getRegionObserver() {
     return Optional.of(this);
@@ -78,178 +64,138 @@ public class ZooKeeperScanPolicyObserver implements RegionCoprocessor, RegionObs
   public static final String ZK_SESSION_TIMEOUT_KEY =
       "ZooKeeperScanPolicyObserver.zookeeper.session.timeout";
   public static final int ZK_SESSION_TIMEOUT_DEFAULT = 30 * 1000; // 30 secs
-  public static final String node = "/backup/example/lastbackup";
+  public static final String NODE = "/backup/example/lastbackup";
-  public static final String zkkey = "ZK";
+  private static final String ZKKEY = "ZK";
-  private static final Log LOG = LogFactory.getLog(ZooKeeperScanPolicyObserver.class);
 
-  private ZooKeeper zk = null;
+  private NodeCache cache;
 
   /**
    * Internal watcher that keep "data" up to date asynchronously.
    */
-  private static class ZKWatcher implements Watcher {
+  private static final class ZKDataHolder {
-    private byte[] data = null;
-    private ZooKeeper zk;
-    private volatile boolean needSetup = true;
-    private volatile long lastSetupTry = 0;
 
-    public ZKWatcher(ZooKeeper zk) {
+    private final String ensemble;
-      this.zk = zk;
+
-      // trigger the listening
+    private final int sessionTimeout;
-      getData();
+
+    private CuratorFramework client;
+
+    private NodeCache cache;
+
+    private int ref;
+
+    public ZKDataHolder(String ensemble, int sessionTimeout) {
+      this.ensemble = ensemble;
+      this.sessionTimeout = sessionTimeout;
     }
 
-    /**
+    private void create() throws Exception {
-     * Get the maintained data. In case of any ZK exceptions this will retry
+      client =
-     * establishing the connection (but not more than twice/minute).
+          CuratorFrameworkFactory.builder().connectString(ensemble).sessionTimeoutMs(sessionTimeout)
-     *
+              .retryPolicy(new RetryForever(1000)).canBeReadOnly(true).build();
-     * getData is on the critical path, so make sure it is fast unless there is
+      client.start();
-     * a problem (network partion, ZK ensemble down, etc)
+      cache = new NodeCache(client, NODE);
-     * Make sure at most one (unlucky) thread retries and other threads don't pile up
+      cache.start(true);
-     * while that threads tries to recreate the connection.
+    }
-     *
+
-     * @return the last know version of the data
+    private void close() {
-     */
+      if (cache != null) {
-    @edu.umd.cs.findbugs.annotations.SuppressWarnings(value="REC_CATCH_EXCEPTION")
-    public byte[] getData() {
-      // try at most twice/minute
-      if (needSetup && EnvironmentEdgeManager.currentTime() > lastSetupTry + 30000) {
-        synchronized (this) {
-          // make sure only one thread tries to reconnect
-          if (needSetup) {
-            needSetup = false;
-          } else {
-            return data;
-          }
-        }
-        // do this without the lock held to avoid threads piling up on this lock,
-        // as it can take a while
         try {
-          LOG.debug("Connecting to ZK");
+          cache.close();
-          // record this attempt
+        } catch (IOException e) {
-          lastSetupTry = EnvironmentEdgeManager.currentTime();
+          // should not happen
-          if (zk.exists(node, false) != null) {
+          throw new AssertionError(e);
-            data = zk.getData(node, this, null);
+        }
-            LOG.debug("Read synchronously: "+(data == null ? "null" : Bytes.toLong(data)));
+        cache = null;
-          } else {
+      }
-            zk.exists(node, this);
+      if (client != null) {
-          }
+        client.close();
-        } catch (Exception x) {
+        client = null;
-          // try again if this fails
+      }
-          needSetup = true;
+    }
+
+    public synchronized NodeCache acquire() throws Exception {
+      if (ref == 0) {
+        try {
+          create();
+        } catch (Exception e) {
+          close();
+          throw e;
         }
       }
-      return data;
+      ref++;
+      return cache;
     }
 
-    @Override
+    public synchronized void release() {
-    public void process(WatchedEvent event) {
+      ref--;
-      switch (event.getType()) {
+      if (ref == 0) {
-        case NodeDataChanged:
+        close();
-        case NodeCreated:
-          try {
-            // get data and re-watch
-            data = zk.getData(node, this, null);
-            LOG.debug("Read asynchronously: " + (data == null ? "null" : Bytes.toLong(data)));
-          } catch (InterruptedException ix) {
-          } catch (KeeperException kx) {
-            needSetup = true;
-          }
-          break;
-
-        case NodeDeleted:
-          try {
-            // just re-watch
-            zk.exists(node, this);
-            data = null;
-          } catch (InterruptedException ix) {
-          } catch (KeeperException kx) {
-            needSetup = true;
-          }
-          break;
-
-        default:
-          // ignore
       }
     }
   }
 
   @Override
-  public void start(CoprocessorEnvironment e) throws IOException {
+  public void start(CoprocessorEnvironment env) throws IOException {
-    RegionCoprocessorEnvironment re = (RegionCoprocessorEnvironment) e;
+    RegionCoprocessorEnvironment renv = (RegionCoprocessorEnvironment) env;
-    if (!re.getSharedData().containsKey(zkkey)) {
+    try {
-      // there is a short race here
+      this.cache = ((ZKDataHolder) renv.getSharedData().computeIfAbsent(ZKKEY, k -> {
-      // in the worst case we create a watcher that will be notified once
+        String ensemble = renv.getConfiguration().get(ZK_ENSEMBLE_KEY);
-      String ensemble = re.getConfiguration().get(ZK_ENSEMBLE_KEY);
+        int sessionTimeout =
-      int sessionTimeout = re.getConfiguration().getInt(ZK_SESSION_TIMEOUT_KEY,
+            renv.getConfiguration().getInt(ZK_SESSION_TIMEOUT_KEY, ZK_SESSION_TIMEOUT_DEFAULT);
-          ZK_SESSION_TIMEOUT_DEFAULT);
+        return new ZKDataHolder(ensemble, sessionTimeout);
-      this.zk = new ZooKeeper(ensemble, sessionTimeout, null);
+      })).acquire();
-      re.getSharedData().putIfAbsent(zkkey, new ZKWatcher(zk));
+    } catch (Exception e) {
+      throw new IOException(e);
     }
   }
 
   @Override
   public void stop(CoprocessorEnvironment env) throws IOException {
-    if (this.zk != null) {
+    RegionCoprocessorEnvironment renv = (RegionCoprocessorEnvironment) env;
-      try {
+    this.cache = null;
-        this.zk.close();
+    ((ZKDataHolder) renv.getSharedData().get(ZKKEY)).release();
-      } catch (InterruptedException e) {
-        LOG.error("Excepion while closing the ZK connection!", e);
-      }
-    }
   }
 
-  protected ScanInfo getScanInfo(Store store, RegionCoprocessorEnvironment e) {
+  private OptionalLong getExpireBefore() {
-    byte[] data = ((ZKWatcher) e.getSharedData().get(zkkey)).getData();
+    ChildData data = cache.getCurrentData();
     if (data == null) {
-      return null;
+      return OptionalLong.empty();
     }
-    ScanInfo oldSI = ((HStore) store).getScanInfo();
+    byte[] bytes = data.getData();
-    if (oldSI.getTtl() == Long.MAX_VALUE) {
+    if (bytes == null || bytes.length != Long.BYTES) {
-      return null;
+      return OptionalLong.empty();
     }
-    long ttl = Math.max(EnvironmentEdgeManager.currentTime() - Bytes.toLong(data), oldSI.getTtl());
+    return OptionalLong.of(Bytes.toLong(bytes));
-    return new ScanInfo(oldSI.getConfiguration(), store.getColumnFamilyDescriptor(), ttl,
+  }
-        oldSI.getTimeToPurgeDeletes(), oldSI.getComparator());
+
+  private InternalScanner wrap(InternalScanner scanner) {
+    OptionalLong optExpireBefore = getExpireBefore();
+    if (!optExpireBefore.isPresent()) {
+      return scanner;
+    }
+    long expireBefore = optExpireBefore.getAsLong();
+    return new DelegatingInternalScanner(scanner) {
+
+      @Override
+      public boolean next(List<Cell> result, ScannerContext scannerContext) throws IOException {
+        boolean moreRows = scanner.next(result, scannerContext);
+        result.removeIf(c -> c.getTimestamp() < expireBefore);
+        return moreRows;
+      }
+    };
   }
 
   @Override
-  public InternalScanner preFlushScannerOpen(ObserverContext<RegionCoprocessorEnvironment> c,
+  public InternalScanner preFlush(ObserverContext<RegionCoprocessorEnvironment> c, Store store,
-      Store store, List<KeyValueScanner> scanners, InternalScanner s, long readPoint)
+      InternalScanner scanner) throws IOException {
-      throws IOException {
+    return wrap(scanner);
-    ScanInfo scanInfo = getScanInfo(store, c.getEnvironment());
-    if (scanInfo == null) {
-      // take default action
-      return null;
-    }
-    return new StoreScanner((HStore) store, scanInfo, OptionalInt.empty(), scanners,
-        ScanType.COMPACT_RETAIN_DELETES, store.getSmallestReadPoint(), HConstants.OLDEST_TIMESTAMP);
   }
 
   @Override
-  public InternalScanner preCompactScannerOpen(ObserverContext<RegionCoprocessorEnvironment> c,
+  public InternalScanner preCompact(ObserverContext<RegionCoprocessorEnvironment> c, Store store,
-      Store store, List<? extends KeyValueScanner> scanners, ScanType scanType, long earliestPutTs,
+      InternalScanner scanner, ScanType scanType, CompactionLifeCycleTracker tracker,
-      InternalScanner s, CompactionLifeCycleTracker tracker, CompactionRequest request,
+      CompactionRequest request) throws IOException {
-      long readPoint) throws IOException {
+    return wrap(scanner);
-    ScanInfo scanInfo = getScanInfo(store, c.getEnvironment());
-    if (scanInfo == null) {
-      // take default action
-      return null;
-    }
-    return new StoreScanner((HStore) store, scanInfo, OptionalInt.empty(), scanners, scanType,
-        store.getSmallestReadPoint(), earliestPutTs);
-  }
-
-  @Override
-  public KeyValueScanner preStoreScannerOpen(ObserverContext<RegionCoprocessorEnvironment> c,
-      Store store, Scan scan, NavigableSet<byte[]> targetCols, KeyValueScanner s, long readPoint)
-      throws IOException {
-    ScanInfo scanInfo = getScanInfo(store, c.getEnvironment());
-    if (scanInfo == null) {
-      // take default action
-      return null;
-    }
-    return new StoreScanner((HStore) store, scanInfo, scan, targetCols,
-        ((HStore) store).getHRegion().getReadPoint(IsolationLevel.READ_COMMITTED));
   }
 }

hbase-examples/src/test/java/org/apache/hadoop/hbase/coprocessor/example/TestZooKeeperScanPolicyObserver.java

@@ -0,0 +1,133 @@
+/**
+ * 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.hadoop.hbase.coprocessor.example;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+
+import java.io.IOException;
+
+import org.apache.hadoop.hbase.HBaseTestingUtility;
+import org.apache.hadoop.hbase.TableName;
+import org.apache.hadoop.hbase.client.ColumnFamilyDescriptorBuilder;
+import org.apache.hadoop.hbase.client.Get;
+import org.apache.hadoop.hbase.client.Put;
+import org.apache.hadoop.hbase.client.Table;
+import org.apache.hadoop.hbase.client.TableDescriptorBuilder;
+import org.apache.hadoop.hbase.testclassification.CoprocessorTests;
+import org.apache.hadoop.hbase.testclassification.MediumTests;
+import org.apache.hadoop.hbase.util.Bytes;
+import org.apache.zookeeper.CreateMode;
+import org.apache.zookeeper.KeeperException;
+import org.apache.zookeeper.ZooDefs;
+import org.apache.zookeeper.ZooKeeper;
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import org.junit.experimental.categories.Category;
+
+@Category({ CoprocessorTests.class, MediumTests.class })
+public class TestZooKeeperScanPolicyObserver {
+
+  private static final HBaseTestingUtility UTIL = new HBaseTestingUtility();
+
+  private static TableName NAME = TableName.valueOf("TestCP");
+
+  private static byte[] FAMILY = Bytes.toBytes("cf");
+
+  private static byte[] QUALIFIER = Bytes.toBytes("cq");
+
+  private static Table TABLE;
+
+  @BeforeClass
+  public static void setUp() throws Exception {
+    UTIL.startMiniCluster(3);
+    UTIL.getAdmin()
+        .createTable(TableDescriptorBuilder.newBuilder(NAME)
+            .addCoprocessor(ZooKeeperScanPolicyObserver.class.getName())
+            .setValue(ZooKeeperScanPolicyObserver.ZK_ENSEMBLE_KEY,
+              "localhost:" + UTIL.getZkCluster().getClientPort())
+            .setValue(ZooKeeperScanPolicyObserver.ZK_SESSION_TIMEOUT_KEY, "2000")
+            .addColumnFamily(ColumnFamilyDescriptorBuilder.newBuilder(FAMILY).build()).build());
+    TABLE = UTIL.getConnection().getTable(NAME);
+  }
+
+  @AfterClass
+  public static void tearDown() throws Exception {
+    if (TABLE != null) {
+      TABLE.close();
+    }
+    UTIL.shutdownMiniCluster();
+  }
+
+  private void setExpireBefore(long time)
+      throws KeeperException, InterruptedException, IOException {
+    ZooKeeper zk = UTIL.getZooKeeperWatcher().getRecoverableZooKeeper().getZooKeeper();
+    if (zk.exists(ZooKeeperScanPolicyObserver.NODE, false) == null) {
+      zk.create(ZooKeeperScanPolicyObserver.NODE, Bytes.toBytes(time), ZooDefs.Ids.OPEN_ACL_UNSAFE,
+        CreateMode.PERSISTENT);
+    } else {
+      zk.setData(ZooKeeperScanPolicyObserver.NODE, Bytes.toBytes(time), -1);
+    }
+  }
+
+  private void assertValueEquals(int start, int end) throws IOException {
+    for (int i = start; i < end; i++) {
+      assertEquals(i,
+        Bytes.toInt(TABLE.get(new Get(Bytes.toBytes(i))).getValue(FAMILY, QUALIFIER)));
+    }
+  }
+
+  private void assertNotExists(int start, int end) throws IOException {
+    for (int i = start; i < end; i++) {
+      assertFalse(TABLE.exists(new Get(Bytes.toBytes(i))));
+    }
+  }
+
+  private void put(int start, int end, long ts) throws IOException {
+    for (int i = start; i < end; i++) {
+      TABLE.put(new Put(Bytes.toBytes(i)).addColumn(FAMILY, QUALIFIER, ts, Bytes.toBytes(i)));
+    }
+  }
+
+  @Test
+  public void test() throws IOException, KeeperException, InterruptedException {
+    long now = System.currentTimeMillis();
+    put(0, 100, now - 10000);
+    assertValueEquals(0, 100);
+
+    setExpireBefore(now - 5000);
+    Thread.sleep(5000);
+    UTIL.getAdmin().flush(NAME);
+    assertNotExists(0, 100);
+
+    put(0, 50, now - 1000);
+    UTIL.getAdmin().flush(NAME);
+    put(50, 100, now - 100);
+    UTIL.getAdmin().flush(NAME);
+    assertValueEquals(0, 100);
+
+    setExpireBefore(now - 500);
+    Thread.sleep(5000);
+    UTIL.getAdmin().majorCompact(NAME);
+    UTIL.waitFor(30000, () -> UTIL.getHBaseCluster().getRegions(NAME).iterator().next()
+        .getStore(FAMILY).getStorefilesCount() == 1);
+    assertNotExists(0, 50);
+    assertValueEquals(50, 100);
+  }
+}

hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/InternalScanner.java

@@ -46,11 +46,13 @@ import org.apache.yetus.audience.InterfaceStability;
 public interface InternalScanner extends Closeable {
   /**
    * Grab the next row's worth of values.
-   * @param results return output array
+   * @param result return output array
    * @return true if more rows exist after this one, false if scanner is done
    * @throws IOException e
    */
-  boolean next(List<Cell> results) throws IOException;
+  default boolean next(List<Cell> result) throws IOException {
+    return next(result, NoLimitScannerContext.getInstance());
+  }
 
   /**
    * Grab the next row's worth of values.

hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/KeyValueHeap.java

@@ -140,14 +140,8 @@ public class KeyValueHeap extends NonReversedNonLazyKeyValueScanner
    * <p>
    * This can ONLY be called when you are using Scanners that implement InternalScanner as well as
    * KeyValueScanner (a {@link StoreScanner}).
-   * @param result
    * @return true if more rows exist after this one, false if scanner is done
    */
-  @Override
-  public boolean next(List<Cell> result) throws IOException {
-    return next(result, NoLimitScannerContext.getInstance());
-  }
-
   @Override
   public boolean next(List<Cell> result, ScannerContext scannerContext) throws IOException {
     if (this.current == null) {

hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/StoreScanner.java

@@ -503,11 +503,6 @@ public class StoreScanner extends NonReversedNonLazyKeyValueScanner
     return this.heap.seek(key);
   }
 
-  @Override
-  public boolean next(List<Cell> outResult) throws IOException {
-    return next(outResult, NoLimitScannerContext.getInstance());
-  }
-
   /**
    * Get the next row of values from this Store.
    * @param outResult

hbase-server/src/test/java/org/apache/hadoop/hbase/coprocessor/TestRegionObserverInterface.java

@@ -427,10 +427,6 @@ public class TestRegionObserverInterface {
         InternalScanner scanner, ScanType scanType, CompactionLifeCycleTracker tracker,
         CompactionRequest request) {
       return new InternalScanner() {
-        @Override
-        public boolean next(List<Cell> results) throws IOException {
-          return next(results, NoLimitScannerContext.getInstance());
-        }
 
         @Override
         public boolean next(List<Cell> results, ScannerContext scannerContext) throws IOException {

hbase-server/src/test/java/org/apache/hadoop/hbase/coprocessor/TestRegionObserverScannerOpenHook.java

@@ -139,11 +139,6 @@ public class TestRegionObserverScannerOpenHook {
       return false;
     }
 
-    @Override
-    public boolean next(List<Cell> results) throws IOException {
-      return false;
-    }
-
     @Override
     public void close() throws IOException {}
   };

hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/compactions/TestCompactor.java

@@ -192,16 +192,11 @@ public class TestCompactor {
       this.kvs = new ArrayList<>(Arrays.asList(kvs));
     }
 
-    @Override
-    public boolean next(List<Cell> results) throws IOException {
-      if (kvs.isEmpty()) return false;
-      results.add(kvs.remove(0));
-      return !kvs.isEmpty();
-    }
-
     @Override
     public boolean next(List<Cell> result, ScannerContext scannerContext) throws IOException {
-      return next(result);
+      if (kvs.isEmpty()) return false;
+      result.add(kvs.remove(0));
+      return !kvs.isEmpty();
     }
 
     @Override

hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/compactions/TestStripeCompactionPolicy.java

@@ -808,17 +808,12 @@ public class TestStripeCompactionPolicy {
       this.kvs = new ArrayList<>(Arrays.asList(kvs));
     }
 
-    @Override
-    public boolean next(List<Cell> results) throws IOException {
-      if (kvs.isEmpty()) return false;
-      results.add(kvs.remove(0));
-      return !kvs.isEmpty();
-    }
-
     @Override
     public boolean next(List<Cell> result, ScannerContext scannerContext)
         throws IOException {
-      return next(result);
+      if (kvs.isEmpty()) return false;
+      result.add(kvs.remove(0));
+      return !kvs.isEmpty();
     }
 
     @Override

pom.xml

@@ -2094,6 +2094,21 @@
           </exclusion>
         </exclusions>
       </dependency>
+      <dependency>
+        <groupId>org.apache.curator</groupId>
+        <artifactId>curator-recipes</artifactId>
+        <version>${curator.version}</version>
+        <exclusions>
+          <exclusion>
+            <groupId>com.google.guava</groupId>
+            <artifactId>guava</artifactId>
+          </exclusion>
+          <exclusion>
+            <groupId>org.apache.zookeeper</groupId>
+            <artifactId>zookeeper</artifactId>
+          </exclusion>
+        </exclusions>
+      </dependency>
       <dependency>
         <groupId>org.apache.yetus</groupId>
         <artifactId>audience-annotations</artifactId>