hbase-server/src/main/java/org/apache/hadoop/hbase/wal/WALEdit.java

/*
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 * 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
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package org.apache.hadoop.hbase.wal;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.TreeSet;
import org.apache.hadoop.hbase.Cell;
import org.apache.hadoop.hbase.CellUtil;
import org.apache.hadoop.hbase.HBaseInterfaceAudience;
import org.apache.hadoop.hbase.KeyValue;
import org.apache.hadoop.hbase.PrivateCellUtil;
import org.apache.hadoop.hbase.client.RegionInfo;
import org.apache.hadoop.hbase.codec.Codec;
import org.apache.hadoop.hbase.io.HeapSize;
import org.apache.hadoop.hbase.util.Bytes;
import org.apache.hadoop.hbase.util.ClassSize;
import org.apache.hadoop.hbase.util.EnvironmentEdgeManager;
import org.apache.yetus.audience.InterfaceAudience;

import org.apache.hadoop.hbase.shaded.protobuf.generated.WALProtos;
import org.apache.hadoop.hbase.shaded.protobuf.generated.WALProtos.CompactionDescriptor;
import org.apache.hadoop.hbase.shaded.protobuf.generated.WALProtos.FlushDescriptor;
import org.apache.hadoop.hbase.shaded.protobuf.generated.WALProtos.RegionEventDescriptor;

/**
 * Used in HBase's transaction log (WAL) to represent a collection of edits (Cell/KeyValue objects)
 * that came in as a single transaction. All the edits for a given transaction are written out as a
 * single record, in PB format, followed (optionally) by Cells written via the WALCellEncoder.
 * <p>This class is LimitedPrivate for CPs to read-only. The {@link #add} methods are
 * classified as private methods, not for use by CPs.</p>
 *
 * <p>A particular WALEdit 'type' is the 'meta' type used to mark key operational
 * events in the WAL such as compaction, flush, or region open. These meta types do not traverse
 * hbase memstores. They are edits made by the hbase system rather than edit data submitted by
 * clients. They only show in the WAL. These 'Meta' types have not been formally specified
 * (or made into an explicit class type). They evolved organically. HBASE-8457 suggests codifying
 * a WALEdit 'type' by adding a type field to WALEdit that gets serialized into the WAL. TODO.
 * Would have to work on the consumption-side. Reading WALs on replay we seem to consume
 * a Cell-at-a-time rather than by WALEdit. We are already in the below going out of our
 * way to figure particular types --  e.g. if a compaction, replay, or close meta Marker -- during
 * normal processing so would make sense to do this. Current system is an awkward marking of Cell
 * columnfamily as {@link #METAFAMILY} and then setting qualifier based off meta edit type. For
 * replay-time where we read Cell-at-a-time, there are utility methods below for figuring
 * meta type. See also
 * {@link #createBulkLoadEvent(RegionInfo, WALProtos.BulkLoadDescriptor)}, etc., for where we
 * create meta WALEdit instances.</p>
 *
 * <p>WALEdit will accumulate a Set of all column family names referenced by the Cells
 * {@link #add(Cell)}'d. This is an optimization. Usually when loading a WALEdit, we have the
 * column family name to-hand.. just shove it into the WALEdit if available. Doing this, we can
 * save on a parse of each Cell to figure column family down the line when we go to add the
 * WALEdit to the WAL file. See the hand-off in FSWALEntry Constructor.
 * @see WALKey
 */
// TODO: Do not expose this class to Coprocessors. It has set methods. A CP might meddle.
@InterfaceAudience.LimitedPrivate({ HBaseInterfaceAudience.REPLICATION,
    HBaseInterfaceAudience.COPROC })
public class WALEdit implements HeapSize {
  // Below defines are for writing WALEdit 'meta' Cells..
  // TODO: Get rid of this system of special 'meta' Cells. See HBASE-8457. It suggests
  // adding a type to WALEdit itself for use denoting meta Edits and their types.
  public static final byte [] METAFAMILY = Bytes.toBytes("METAFAMILY");

  /**
   * @deprecated Since 2.3.0. Not used.
   */
  @Deprecated
  public static final byte [] METAROW = Bytes.toBytes("METAROW");

  /**
   * @deprecated Since 2.3.0. Make it protected, internal-use only. Use
   *   {@link #isCompactionMarker(Cell)}
   */
  @Deprecated
  @InterfaceAudience.Private
  public static final byte[] COMPACTION = Bytes.toBytes("HBASE::COMPACTION");

  /**
   * @deprecated Since 2.3.0. Make it protected, internal-use only.
   */
  @Deprecated
  @InterfaceAudience.Private
  public static final byte [] FLUSH = Bytes.toBytes("HBASE::FLUSH");

  /**
   * Qualifier for region event meta 'Marker' WALEdits start with the
   * {@link #REGION_EVENT_PREFIX} prefix ('HBASE::REGION_EVENT::'). After the prefix,
   * we note the type of the event which we get from the RegionEventDescriptor protobuf
   * instance type (A RegionEventDescriptor protobuf instance is written as the meta Marker
   * Cell value). Adding a type suffix means we do not have to deserialize the protobuf to
   * figure out what type of event this is.. .just read the qualifier suffix. For example,
   * a close region event descriptor will have a qualifier of HBASE::REGION_EVENT::REGION_CLOSE.
   * See WAL.proto and the EventType in RegionEventDescriptor protos for all possible
   * event types.
   */
  private static final String REGION_EVENT_STR = "HBASE::REGION_EVENT";
  private static final String REGION_EVENT_PREFIX_STR = REGION_EVENT_STR + "::";
  private static final byte [] REGION_EVENT_PREFIX = Bytes.toBytes(REGION_EVENT_PREFIX_STR);

  /**
   * @deprecated Since 2.3.0. Remove. Not for external use. Not used.
   */
  @Deprecated
  public static final byte [] REGION_EVENT = Bytes.toBytes(REGION_EVENT_STR);

  /**
   * We use this define figuring if we are carrying a close event.
   */
  private static final byte [] REGION_EVENT_CLOSE =
      createRegionEventDescriptorQualifier(RegionEventDescriptor.EventType.REGION_CLOSE);

  @InterfaceAudience.Private
  public static final byte [] BULK_LOAD = Bytes.toBytes("HBASE::BULK_LOAD");

  private final transient boolean replay;

  private ArrayList<Cell> cells;

  /**
   * All the Cell families in <code>cells</code>. Updated by {@link #add(Cell)} and
   * {@link #add(Map)}. This Set is passed to the FSWALEntry so it does not have
   * to recalculate the Set of families in a transaction; makes for a bunch of CPU savings.
   */
  private Set<byte []> families = null;

  public WALEdit() {
    this(1, false);
  }

  /**
   * @deprecated since 2.0.1 and will be removed in 4.0.0. Use {@link #WALEdit(int, boolean)}
   *   instead.
   * @see #WALEdit(int, boolean)
   * @see <a href="https://issues.apache.org/jira/browse/HBASE-20781">HBASE-20781</a>
   */
  @Deprecated
  public WALEdit(boolean replay) {
    this(1, replay);
  }

  /**
   * @deprecated since 2.0.1 and will be removed in 4.0.0. Use {@link #WALEdit(int, boolean)}
   *   instead.
   * @see #WALEdit(int, boolean)
   * @see <a href="https://issues.apache.org/jira/browse/HBASE-20781">HBASE-20781</a>
   */
  @Deprecated
  public WALEdit(int cellCount) {
    this(cellCount, false);
  }

  /**
   * @param cellCount Pass so can pre-size the WALEdit. Optimization.
   */
  public WALEdit(int cellCount, boolean isReplay) {
    this.replay = isReplay;
    cells = new ArrayList<>(cellCount);
  }

  private Set<byte[]> getOrCreateFamilies() {
    if (this.families == null) {
      this.families = new TreeSet<>(Bytes.BYTES_COMPARATOR);
    }
    return this.families;
  }

  /**
   * For use by FSWALEntry ONLY. An optimization.
   * @return All families in {@link #getCells()}; may be null.
   */
  public Set<byte []> getFamilies() {
    return this.families;
  }

  /**
   * @return True is <code>f</code> is {@link #METAFAMILY}
   * @deprecated Since 2.3.0. Do not expose. Make protected.
   */
  @Deprecated
  public static boolean isMetaEditFamily(final byte [] f) {
    return Bytes.equals(METAFAMILY, f);
  }

  /**
   * Replaying WALs can read Cell-at-a-time so need this method in those cases.
   */
  public static boolean isMetaEditFamily(Cell cell) {
    return CellUtil.matchingFamily(cell, METAFAMILY);
  }

  /**
   * @return True if this is a meta edit; has one edit only and its columnfamily
   *   is {@link #METAFAMILY}.
   */
  public boolean isMetaEdit() {
    return this.families != null && this.families.size() == 1 && this.families.contains(METAFAMILY);
  }

  /**
   * @return True when current WALEdit is created by log replay. Replication skips WALEdits from
   *         replay.
   */
  public boolean isReplay() {
    return this.replay;
  }

  @InterfaceAudience.Private
  public WALEdit add(Cell cell, byte [] family) {
    getOrCreateFamilies().add(family);
    return addCell(cell);
  }

  @InterfaceAudience.Private
  public WALEdit add(Cell cell) {
    // We clone Family each time we add a Cell. Expensive but safe. For CPU savings, use
    // add(Map) or add(Cell, family).
    return add(cell, CellUtil.cloneFamily(cell));
  }

  public boolean isEmpty() {
    return cells.isEmpty();
  }

  public int size() {
    return cells.size();
  }

  public ArrayList<Cell> getCells() {
    return cells;
  }

  /**
   * This is not thread safe.
   * This will change the WALEdit and shouldn't be used unless you are sure that nothing
   * else depends on the contents being immutable.
   *
   * @param cells the list of cells that this WALEdit now contains.
   */
  @InterfaceAudience.Private
  // Used by replay.
  public void setCells(ArrayList<Cell> cells) {
    this.cells = cells;
    this.families = null;
  }

  /**
   * Reads WALEdit from cells.
   * @param cellDecoder Cell decoder.
   * @param expectedCount Expected cell count.
   * @return Number of KVs read.
   */
  public int readFromCells(Codec.Decoder cellDecoder, int expectedCount) throws IOException {
    cells.clear();
    cells.ensureCapacity(expectedCount);
    while (cells.size() < expectedCount && cellDecoder.advance()) {
      add(cellDecoder.current());
    }
    return cells.size();
  }

  @Override
  public long heapSize() {
    long ret = ClassSize.ARRAYLIST;
    for (Cell cell : cells) {
      ret += cell.heapSize();
    }
    return ret;
  }

  public long estimatedSerializedSizeOf() {
    long ret = 0;
    for (Cell cell: cells) {
      ret += PrivateCellUtil.estimatedSerializedSizeOf(cell);
    }
    return ret;
  }

  @Override
  public String toString() {
    StringBuilder sb = new StringBuilder();

    sb.append("[#edits: ").append(cells.size()).append(" = <");
    for (Cell cell : cells) {
      sb.append(cell);
      sb.append("; ");
    }
    sb.append(">]");
    return sb.toString();
  }

  public static WALEdit createFlushWALEdit(RegionInfo hri, FlushDescriptor f) {
    KeyValue kv = new KeyValue(getRowForRegion(hri), METAFAMILY, FLUSH,
      EnvironmentEdgeManager.currentTime(), f.toByteArray());
    return new WALEdit().add(kv, METAFAMILY);
  }

  public static FlushDescriptor getFlushDescriptor(Cell cell) throws IOException {
    return CellUtil.matchingColumn(cell, METAFAMILY, FLUSH)?
        FlushDescriptor.parseFrom(CellUtil.cloneValue(cell)): null;
  }

  /**
   * @return A meta Marker WALEdit that has a single Cell whose value is the passed in
   *   <code>regionEventDesc</code> serialized and whose row is this region,
   *   columnfamily is {@link #METAFAMILY} and qualifier is
   *   {@link #REGION_EVENT_PREFIX} + {@link RegionEventDescriptor#getEventType()};
   *   for example HBASE::REGION_EVENT::REGION_CLOSE.
   */
  public static WALEdit createRegionEventWALEdit(RegionInfo hri,
      RegionEventDescriptor regionEventDesc) {
    return createRegionEventWALEdit(getRowForRegion(hri), regionEventDesc);
  }

  @InterfaceAudience.Private
  public static WALEdit createRegionEventWALEdit(byte [] rowForRegion,
      RegionEventDescriptor regionEventDesc) {
    KeyValue kv = new KeyValue(rowForRegion, METAFAMILY,
        createRegionEventDescriptorQualifier(regionEventDesc.getEventType()),
        EnvironmentEdgeManager.currentTime(), regionEventDesc.toByteArray());
    return new WALEdit().add(kv, METAFAMILY);
  }

  /**
   * @return Cell qualifier for the passed in RegionEventDescriptor Type; e.g. we'll
   *   return something like a byte array with HBASE::REGION_EVENT::REGION_OPEN in it.
   */
  @InterfaceAudience.Private
  public static byte [] createRegionEventDescriptorQualifier(RegionEventDescriptor.EventType t) {
    return Bytes.toBytes(REGION_EVENT_PREFIX_STR + t.toString());
  }

  /**
   * Public so can be accessed from regionserver.wal package.
   * @return True if this is a Marker Edit and it is a RegionClose type.
   */
  public boolean isRegionCloseMarker() {
    return isMetaEdit() && PrivateCellUtil.matchingQualifier(this.cells.get(0),
        REGION_EVENT_CLOSE, 0, REGION_EVENT_CLOSE.length);
  }

  /**
   * @return Returns a RegionEventDescriptor made by deserializing the content of the
   *   passed in <code>cell</code>, IFF the <code>cell</code> is a RegionEventDescriptor
   *   type WALEdit.
   */
  public static RegionEventDescriptor getRegionEventDescriptor(Cell cell) throws IOException {
    return CellUtil.matchingColumnFamilyAndQualifierPrefix(cell, METAFAMILY, REGION_EVENT_PREFIX)?
      RegionEventDescriptor.parseFrom(CellUtil.cloneValue(cell)): null;
  }

  /**
   * @return A Marker WALEdit that has <code>c</code> serialized as its value
   */
  public static WALEdit createCompaction(final RegionInfo hri, final CompactionDescriptor c) {
    byte [] pbbytes = c.toByteArray();
    KeyValue kv = new KeyValue(getRowForRegion(hri), METAFAMILY, COMPACTION,
      EnvironmentEdgeManager.currentTime(), pbbytes);
    return new WALEdit().add(kv, METAFAMILY); //replication scope null so this won't be replicated
  }

  public static byte[] getRowForRegion(RegionInfo hri) {
    byte[] startKey = hri.getStartKey();
    if (startKey.length == 0) {
      // empty row key is not allowed in mutations because it is both the start key and the end key
      // we return the smallest byte[] that is bigger (in lex comparison) than byte[0].
      return new byte[] {0};
    }
    return startKey;
  }

  /**
   * Deserialized and returns a CompactionDescriptor is the KeyValue contains one.
   * @param kv the key value
   * @return deserialized CompactionDescriptor or null.
   */
  public static CompactionDescriptor getCompaction(Cell kv) throws IOException {
    return isCompactionMarker(kv)? CompactionDescriptor.parseFrom(CellUtil.cloneValue(kv)): null;
  }

  /**
   * Returns true if the given cell is a serialized {@link CompactionDescriptor}
   *
   * @see #getCompaction(Cell)
   */
  public static boolean isCompactionMarker(Cell cell) {
    return CellUtil.matchingColumn(cell, METAFAMILY, COMPACTION);
  }

  /**
   * Create a bulk loader WALEdit
   *
   * @param hri                The RegionInfo for the region in which we are bulk loading
   * @param bulkLoadDescriptor The descriptor for the Bulk Loader
   * @return The WALEdit for the BulkLoad
   */
  public static WALEdit createBulkLoadEvent(RegionInfo hri,
      WALProtos.BulkLoadDescriptor bulkLoadDescriptor) {
    KeyValue kv = new KeyValue(getRowForRegion(hri), METAFAMILY, BULK_LOAD,
        EnvironmentEdgeManager.currentTime(), bulkLoadDescriptor.toByteArray());
    return new WALEdit().add(kv, METAFAMILY);
  }

  /**
   * Deserialized and returns a BulkLoadDescriptor from the passed in Cell
   * @param cell the key value
   * @return deserialized BulkLoadDescriptor or null.
   */
  public static WALProtos.BulkLoadDescriptor getBulkLoadDescriptor(Cell cell) throws IOException {
    return CellUtil.matchingColumn(cell, METAFAMILY, BULK_LOAD)?
      WALProtos.BulkLoadDescriptor.parseFrom(CellUtil.cloneValue(cell)):  null;
  }

  /**
   * Append the given map of family->edits to a WALEdit data structure.
   * This does not write to the WAL itself.
   * Note that as an optimization, we will stamp the Set of column families into the WALEdit
   * to save on our having to calculate column families subsequently down in the actual WAL
   * writing.
   *
   * @param familyMap map of family->edits
   */
  public void add(Map<byte[], List<Cell>> familyMap) {
    for (Map.Entry<byte [], List<Cell>> e: familyMap.entrySet()) {
      // 'foreach' loop NOT used. See HBASE-12023 "...creates too many iterator objects."
      int listSize = e.getValue().size();
      // Add all Cells first and then at end, add the family rather than call {@link #add(Cell)}
      // and have it clone family each time. Optimization!
      for (int i = 0; i < listSize; i++) {
        addCell(e.getValue().get(i));
      }
      addFamily(e.getKey());
    }
  }

  private void addFamily(byte [] family) {
    getOrCreateFamilies().add(family);
  }

  private WALEdit addCell(Cell cell) {
    this.cells.add(cell);
    return this;
  }
}