avoid checking all tablet file in bulk import conditional mutation (apache#5159)

After the changes in apache#5104 bulk import would read a tablets files,
examine the files, and then require the set of files to be the same to
update the tablet.  The code only cared that the count of files was
below a specified limit. Requiring the set of files not to change was
causing the conditional mutation to fail on a busy tablet.  This change
modifies the condition to check the count of file which avoids
contention on a busy tablet where the set of files is constantly
changing.

Author: keith-turner

core/src/main/java/org/apache/accumulo/core/metadata/schema/Ample.java

@@ -520,6 +520,11 @@ ConditionalTabletMutator requireSame(TabletMetadata tabletMetadata, ColumnType t
      */
     ConditionalTabletMutator requireFiles(Set<StoredTabletFile> files);
 
+    /**
+     * Require that a tablet have less than or equals the specified number of files.
+     */
+    ConditionalTabletMutator requireLessOrEqualsFiles(long limit);
+
     /**
      * <p>
      * Ample provides the following features on top of the conditional writer to help automate

server/base/src/main/java/org/apache/accumulo/server/metadata/ConditionalTabletMutatorImpl.java

@@ -64,6 +64,7 @@
 import org.apache.accumulo.core.tabletserver.log.LogEntry;
 import org.apache.accumulo.core.util.Pair;
 import org.apache.accumulo.server.ServerContext;
+import org.apache.accumulo.server.metadata.iterators.ColumnFamilySizeLimitIterator;
 import org.apache.accumulo.server.metadata.iterators.PresentIterator;
 import org.apache.accumulo.server.metadata.iterators.SetEncodingIterator;
 import org.apache.accumulo.server.metadata.iterators.TabletExistsIterator;
@@ -344,6 +345,14 @@ public ConditionalTabletMutator requireFiles(Set<StoredTabletFile> files) {
     return this;
   }
 
+  @Override
+  public ConditionalTabletMutator requireLessOrEqualsFiles(long limit) {
+    Preconditions.checkState(updatesEnabled, "Cannot make updates after calling mutate.");
+    Condition c = ColumnFamilySizeLimitIterator.createCondition(DataFileColumnFamily.NAME, limit);
+    mutation.addCondition(c);
+    return this;
+  }
+
   @Override
   public void submit(Ample.RejectionHandler rejectionCheck) {
     Preconditions.checkState(updatesEnabled, "Cannot make updates after calling mutate.");

server/base/src/main/java/org/apache/accumulo/server/metadata/iterators/ColumnFamilySizeLimitIterator.java

@@ -0,0 +1,145 @@
+/*
+ * 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
+ *
+ *   https://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.metadata.iterators;
+
+import static org.apache.accumulo.server.metadata.iterators.SetEncodingIterator.getTabletRow;
+
+import java.io.IOException;
+import java.util.Collection;
+import java.util.Map;
+import java.util.NoSuchElementException;
+import java.util.Set;
+
+import org.apache.accumulo.core.client.IteratorSetting;
+import org.apache.accumulo.core.data.ByteSequence;
+import org.apache.accumulo.core.data.Condition;
+import org.apache.accumulo.core.data.Key;
+import org.apache.accumulo.core.data.PartialKey;
+import org.apache.accumulo.core.data.Range;
+import org.apache.accumulo.core.data.Value;
+import org.apache.accumulo.core.iterators.IteratorEnvironment;
+import org.apache.accumulo.core.iterators.SortedKeyValueIterator;
+import org.apache.accumulo.core.iterators.WrappingIterator;
+import org.apache.accumulo.server.metadata.ConditionalTabletMutatorImpl;
+import org.apache.hadoop.io.Text;
+
+import com.google.common.base.Preconditions;
+
+/**
+ * Iterator that checks if a column family size is less than or equal a limit as part of a
+ * conditional mutation.
+ */
+public class ColumnFamilySizeLimitIterator extends WrappingIterator {
+
+  private static final String LIMIT_OPT = "limit";
+  private static final Text EMPTY = new Text();
+
+  private Long limit;
+
+  private Key startKey = null;
+  private Value topValue = null;
+
+  @Override
+  public void init(SortedKeyValueIterator<Key,Value> source, Map<String,String> options,
+      IteratorEnvironment env) throws IOException {
+    super.init(source, options, env);
+    limit = Long.parseLong(options.get(LIMIT_OPT));
+    Preconditions.checkState(limit >= 0);
+  }
+
+  @Override
+  public void seek(Range range, Collection<ByteSequence> columnFamilies, boolean inclusive)
+      throws IOException {
+    Text tabletRow = getTabletRow(range);
+    Text family = range.getStartKey().getColumnFamily();
+
+    Preconditions.checkArgument(
+        family.getLength() > 0 && range.getStartKey().getColumnQualifier().getLength() == 0);
+
+    startKey = new Key(tabletRow, family);
+    Key endKey = startKey.followingKey(PartialKey.ROW_COLFAM);
+
+    Range r = new Range(startKey, true, endKey, false);
+
+    var source = getSource();
+    source.seek(r, Set.of(startKey.getColumnFamilyData()), true);
+
+    long count = 0;
+    while (source.hasTop()) {
+      source.next();
+      count++;
+    }
+
+    if (count <= limit) {
+      topValue = new Value("1");
+    } else {
+      topValue = null;
+    }
+  }
+
+  @Override
+  public boolean hasTop() {
+    if (startKey == null) {
+      throw new IllegalStateException("never been seeked");
+    }
+    return topValue != null;
+  }
+
+  @Override
+  public void next() throws IOException {
+    if (startKey == null) {
+      throw new IllegalStateException("never been seeked");
+    }
+    topValue = null;
+  }
+
+  @Override
+  public Key getTopKey() {
+    if (startKey == null) {
+      throw new IllegalStateException("never been seeked");
+    }
+    if (topValue == null) {
+      throw new NoSuchElementException();
+    }
+
+    return startKey;
+  }
+
+  @Override
+  public Value getTopValue() {
+    if (startKey == null) {
+      throw new IllegalStateException("never been seeked");
+    }
+    if (topValue == null) {
+      throw new NoSuchElementException();
+    }
+    return topValue;
+  }
+
+  /**
+   * Create a condition that checks if the specified column family's size is less than or equal to
+   * the given limit.
+   */
+  public static Condition createCondition(Text family, long limit) {
+    IteratorSetting is = new IteratorSetting(ConditionalTabletMutatorImpl.INITIAL_ITERATOR_PRIO,
+        ColumnFamilySizeLimitIterator.class);
+    is.addOption(LIMIT_OPT, limit + "");
+    return new Condition(family, EMPTY).setValue("1").setIterators(is);
+  }
+}

server/base/src/main/java/org/apache/accumulo/server/metadata/iterators/SetEncodingIterator.java

@@ -93,11 +93,11 @@ public void seek(Range range, Collection<ByteSequence> columnFamilies, boolean i
         family.getLength() > 0 && range.getStartKey().getColumnQualifier().getLength() == 0);
 
     startKey = new Key(tabletRow, family);
-    Key endKey = new Key(tabletRow, family).followingKey(PartialKey.ROW_COLFAM);
+    Key endKey = startKey.followingKey(PartialKey.ROW_COLFAM);
 
     Range r = new Range(startKey, true, endKey, false);
 
-    source.seek(r, Set.of(), false);
+    source.seek(r, Set.of(startKey.getColumnFamilyData()), true);
 
     try (ByteArrayOutputStream baos = new ByteArrayOutputStream();
         DataOutputStream dos = new DataOutputStream(baos)) {

server/manager/src/main/java/org/apache/accumulo/manager/tableOps/bulkVer2/LoadFiles.java

@@ -178,9 +178,6 @@ void load(List<TabletMetadata> tablets, Files files) {
       if (setTime) {
         rsc.add(TIME);
       }
-      if (pauseLimit > 0) {
-        rsc.add(FILES);
-      }
 
       ColumnType[] requireSameCols = rsc.toArray(new ColumnType[0]);
 
@@ -237,6 +234,10 @@ void load(List<TabletMetadata> tablets, Files files) {
         var tabletMutator = conditionalMutator.mutateTablet(tablet.getExtent())
             .requireAbsentOperation().requireSame(tablet, LOADED, requireSameCols);
 
+        if (pauseLimit > 0) {
+          tabletMutator.requireLessOrEqualsFiles(pauseLimit);
+        }
+
         filesToLoad.forEach((f, v) -> {
           tabletMutator.putBulkFile(f, fateId);
           tabletMutator.putFile(f, v);

test/src/main/java/org/apache/accumulo/test/functional/AmpleConditionalWriterIT.java

@@ -1788,7 +1788,7 @@ public void testRequiresFiles() {
     assertEquals(time2, context.getAmple().readTablet(e1).getTime());
 
     // Test mutation is rejected when a file is given that the tablet does not have
-    var time3 = MetadataTime.parse("L60");
+    var time3 = MetadataTime.parse("L70");
     try (var ctmi = new ConditionalTabletsMutatorImpl(context)) {
       ctmi.mutateTablet(e1).requireAbsentOperation().requireFiles(Set.of(stf1, stf4)).putTime(time3)
           .submit(tm -> false);
@@ -1797,4 +1797,81 @@ public void testRequiresFiles() {
     // Should be previous time still as the mutation was rejected
     assertEquals(time2, context.getAmple().readTablet(e1).getTime());
   }
+
+  @Test
+  public void testFilesLimit() {
+    var context = cluster.getServerContext();
+
+    var stf1 = StoredTabletFile
+        .of(new Path("hdfs://localhost:8020/accumulo/tables/2a/default_tablet/F0000070.rf"));
+    var stf2 = StoredTabletFile
+        .of(new Path("hdfs://localhost:8020/accumulo/tables/2a/default_tablet/F0000071.rf"));
+    var stf3 = StoredTabletFile
+        .of(new Path("hdfs://localhost:8020/accumulo/tables/2a/default_tablet/F0000072.rf"));
+    var stf4 = StoredTabletFile
+        .of(new Path("hdfs://localhost:8020/accumulo/tables/2a/default_tablet/C0000073.rf"));
+    var dfv = new DataFileValue(100, 100);
+
+    // Add 3 of the files, skip the 4th file
+    try (var ctmi = new ConditionalTabletsMutatorImpl(context)) {
+      ctmi.mutateTablet(e1).requireAbsentOperation().putFile(stf1, dfv).putFile(stf2, dfv)
+          .putFile(stf3, dfv).submit(tm -> false);
+      assertEquals(Status.ACCEPTED, ctmi.process().get(e1).getStatus());
+    }
+    assertEquals(Set.of(stf1, stf2, stf3), context.getAmple().readTablet(e1).getFiles());
+
+    // Test mutation is accepted when # files in tablet equals limit
+    var time1 = MetadataTime.parse("L50");
+    try (var ctmi = new ConditionalTabletsMutatorImpl(context)) {
+      ctmi.mutateTablet(e1).requireAbsentOperation().requireLessOrEqualsFiles(3).putTime(time1)
+          .submit(tm -> false);
+      assertEquals(Status.ACCEPTED, ctmi.process().get(e1).getStatus());
+    }
+    assertEquals(time1, context.getAmple().readTablet(e1).getTime());
+
+    // Test mutation is accepted when # files in tablet is less than limit
+    var time2 = MetadataTime.parse("L60");
+    try (var ctmi = new ConditionalTabletsMutatorImpl(context)) {
+      ctmi.mutateTablet(e1).requireAbsentOperation().requireLessOrEqualsFiles(4).putTime(time2)
+          .submit(tm -> false);
+      assertEquals(Status.ACCEPTED, ctmi.process().get(e1).getStatus());
+    }
+    assertEquals(time2, context.getAmple().readTablet(e1).getTime());
+
+    // Test mutation is rejected when # files in tablet is greater than limit
+    var time3 = MetadataTime.parse("L70");
+    try (var ctmi = new ConditionalTabletsMutatorImpl(context)) {
+      ctmi.mutateTablet(e1).requireAbsentOperation().requireLessOrEqualsFiles(2).putTime(time3)
+          .submit(tm -> false);
+      assertEquals(Status.REJECTED, ctmi.process().get(e1).getStatus());
+    }
+    // Should be previous time still as the mutation was rejected
+    assertEquals(time2, context.getAmple().readTablet(e1).getTime());
+
+    // add fourth file
+    try (var ctmi = new ConditionalTabletsMutatorImpl(context)) {
+      ctmi.mutateTablet(e1).requireAbsentOperation().putFile(stf4, dfv).submit(tm -> false);
+      assertEquals(Status.ACCEPTED, ctmi.process().get(e1).getStatus());
+    }
+    assertEquals(Set.of(stf1, stf2, stf3, stf4), context.getAmple().readTablet(e1).getFiles());
+
+    // Test mutation is rejected when # files in tablet is greater than limit
+    try (var ctmi = new ConditionalTabletsMutatorImpl(context)) {
+      ctmi.mutateTablet(e1).requireAbsentOperation().requireLessOrEqualsFiles(3).putTime(time3)
+          .submit(tm -> false);
+      assertEquals(Status.REJECTED, ctmi.process().get(e1).getStatus());
+    }
+    // Should be previous time still as the mutation was rejected
+    assertEquals(time2, context.getAmple().readTablet(e1).getTime());
+
+    // Test mutation is accepted when # files in tablet equals limit
+    var time4 = MetadataTime.parse("L80");
+    try (var ctmi = new ConditionalTabletsMutatorImpl(context)) {
+      ctmi.mutateTablet(e1).requireAbsentOperation().requireLessOrEqualsFiles(4).putTime(time4)
+          .submit(tm -> false);
+      assertEquals(Status.ACCEPTED, ctmi.process().get(e1).getStatus());
+    }
+    assertEquals(time4, context.getAmple().readTablet(e1).getTime());
+
+  }
 }