org.apache.hadoop.hbase.regionserver.wal

Class SequenceIdAccounting

java.lang.Object

org.apache.hadoop.hbase.regionserver.wal.SequenceIdAccounting

@InterfaceAudience.Private
class SequenceIdAccounting
extends Object

Accounting of sequence ids per region and then by column family. So we can our accounting current, call startCacheFlush and then finishedCacheFlush or abortCacheFlush so this instance can keep abreast of the state of sequence id persistence. Also call update per append.

For the implementation, we assume that all the encodedRegionName passed in is gotten by RegionInfo.getEncodedNameAsBytes(). So it is safe to use it as a hash key. And for family name, we use ImmutableByteArray as key. This is because hash based map is much faster than RBTree or CSLM and here we are on the critical write path. See HBASE-16278 for more details.

Field Summary

Fields

Modifier and Type	Field and Description
private Map<byte[],Map<ImmutableByteArray,Long>>	flushingSequenceIds Map of encoded region names and family names to their lowest or OLDEST sequence/edit id currently being flushed out to hfiles.
private Map<byte[],Long>	highestSequenceIds Map of region encoded names to the latest/highest region sequence id.
private static org.slf4j.Logger	LOG
private ConcurrentMap<byte[],ConcurrentMap<ImmutableByteArray,Long>>	lowestUnflushedSequenceIds Map of encoded region names and family names to their OLDEST -- i.e.
private Object	tieLock This lock ties all operations on flushingSequenceIds and lowestUnflushedSequenceIds Maps.

Constructor Summary

Constructors

Constructor and Description
SequenceIdAccounting()

Method Summary

Modifier and Type	Method and Description
(package private) void	abortCacheFlush(byte[] encodedRegionName)
(package private) boolean	areAllLower(Map<byte[],Long> sequenceids) See if passed sequenceids are lower -- i.e.
(package private) void	completeCacheFlush(byte[] encodedRegionName)
(package private) byte[][]	findLower(Map<byte[],Long> sequenceids) Iterates over the given Map and compares sequence ids with corresponding entries in lowestUnflushedSequenceIds.
private <T extends Map<?,Long>> Map<byte[],Long>	flattenToLowestSequenceId(Map<byte[],T> src)
(package private) long	getLowestSequenceId(byte[] encodedRegionName) Returns the lowest unflushed sequence id for the region.
(package private) long	getLowestSequenceId(byte[] encodedRegionName, byte[] familyName)
private static long	getLowestSequenceId(Map<?,Long> sequenceids)
(package private) ConcurrentMap<ImmutableByteArray,Long>	getOrCreateLowestSequenceIds(byte[] encodedRegionName)
(package private) Map<byte[],Long>	resetHighest() Reset the accounting of highest sequenceid by regionname.
(package private) Long	startCacheFlush(byte[] encodedRegionName, Map<byte[],Long> familyToSeq)
(package private) Long	startCacheFlush(byte[] encodedRegionName, Set<byte[]> families)
(package private) void	update(byte[] encodedRegionName, Set<byte[]> families, long sequenceid, boolean lowest) We've been passed a new sequenceid for the region.
(package private) void	updateStore(byte[] encodedRegionName, byte[] familyName, Long sequenceId, boolean onlyIfGreater) Update the store sequence id, e.g., upon executing in-memory compaction

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

LOG

private static final org.slf4j.Logger LOG

tieLock

private final Object tieLock

This lock ties all operations on flushingSequenceIds and lowestUnflushedSequenceIds Maps. lowestUnflushedSequenceIds has the lowest outstanding sequence ids EXCEPT when flushing. When we flush, the current lowest set for the region/column family are moved (atomically because of this lock) to flushingSequenceIds.

The two Maps are tied by this locking object EXCEPT when we go to update the lowest entry; see lowestUnflushedSequenceIds. In here is a putIfAbsent call on lowestUnflushedSequenceIds. In this latter case, we will add this lowest sequence id if we find that there is no entry for the current column family. There will be no entry only if we just came up OR we have moved aside current set of lowest sequence ids because the current set are being flushed (by putting them into flushingSequenceIds). This is how we pick up the next 'lowest' sequence id per region per column family to be used figuring what is in the next flush.

lowestUnflushedSequenceIds

private final ConcurrentMap<byte[],ConcurrentMap<ImmutableByteArray,Long>> lowestUnflushedSequenceIds

Map of encoded region names and family names to their OLDEST -- i.e. their first, the longest-lived, their 'earliest', the 'lowest' -- sequence id.

When we flush, the current lowest sequence ids get cleared and added to flushingSequenceIds. The next append that comes in, is then added here to lowestUnflushedSequenceIds as the next lowest sequenceid.

If flush fails, currently server is aborted so no need to restore previous sequence ids.

Needs to be concurrent Maps because we use putIfAbsent updating oldest.

flushingSequenceIds

private final Map<byte[],Map<ImmutableByteArray,Long>> flushingSequenceIds

Map of encoded region names and family names to their lowest or OLDEST sequence/edit id currently being flushed out to hfiles. Entries are moved here from lowestUnflushedSequenceIds while the lock tieLock is held (so movement between the Maps is atomic).

highestSequenceIds

private Map<byte[],Long> highestSequenceIds

Map of region encoded names to the latest/highest region sequence id. Updated on each call to append.

This map uses byte[] as the key, and uses reference equality. It works in our use case as we use RegionInfo.getEncodedNameAsBytes() as keys. For a given region, it always returns the same array.

Constructor Detail

SequenceIdAccounting

SequenceIdAccounting()

Method Detail

getLowestSequenceId

long getLowestSequenceId(byte[] encodedRegionName)

Returns the lowest unflushed sequence id for the region.

Parameters:

encodedRegionName -

Returns:

Lowest outstanding unflushed sequenceid for encodedRegionName. Will return HConstants.NO_SEQNUM when none.

getLowestSequenceId

long getLowestSequenceId(byte[] encodedRegionName,
                         byte[] familyName)

Parameters:

encodedRegionName -

familyName -

Returns:

Lowest outstanding unflushed sequenceid for encodedRegionname and familyName. Returned sequenceid may be for an edit currently being flushed.

resetHighest

Map<byte[],Long> resetHighest()

Reset the accounting of highest sequenceid by regionname.

Returns:

Return the previous accounting Map of regions to the last sequence id written into each.

update

void update(byte[] encodedRegionName,
            Set<byte[]> families,
            long sequenceid,
            boolean lowest)

We've been passed a new sequenceid for the region. Set it as highest seen for this region and if we are to record oldest, or lowest sequenceids, save it as oldest seen if nothing currently older.

Parameters:

encodedRegionName -

families -

sequenceid -

lowest - Whether to keep running account of oldest sequence id.

updateStore

void updateStore(byte[] encodedRegionName,
                 byte[] familyName,
                 Long sequenceId,
                 boolean onlyIfGreater)

Update the store sequence id, e.g., upon executing in-memory compaction

getOrCreateLowestSequenceIds

ConcurrentMap<ImmutableByteArray,Long> getOrCreateLowestSequenceIds(byte[] encodedRegionName)

getLowestSequenceId

private static long getLowestSequenceId(Map<?,Long> sequenceids)

Parameters:

sequenceids - Map to search for lowest value.

Returns:

Lowest value found in sequenceids.

flattenToLowestSequenceId

private <T extends Map<?,Long>> Map<byte[],Long> flattenToLowestSequenceId(Map<byte[],T> src)

Parameters:

src -

Returns:

New Map that has same keys as src but instead of a Map for a value, it instead has found the smallest sequence id and it returns that as the value instead.

startCacheFlush

Long startCacheFlush(byte[] encodedRegionName,
                     Set<byte[]> families)

Parameters:

encodedRegionName - Region to flush.

families - Families to flush. May be a subset of all families in the region.

Returns:

Returns HConstants.NO_SEQNUM if we are flushing the whole region OR if we are flushing a subset of all families but there are no edits in those families not being flushed; in other words, this is effectively same as a flush of all of the region though we were passed a subset of regions. Otherwise, it returns the sequence id of the oldest/lowest outstanding edit.

startCacheFlush

Long startCacheFlush(byte[] encodedRegionName,
                     Map<byte[],Long> familyToSeq)

completeCacheFlush

void completeCacheFlush(byte[] encodedRegionName)

abortCacheFlush

void abortCacheFlush(byte[] encodedRegionName)

areAllLower

boolean areAllLower(Map<byte[],Long> sequenceids)

See if passed sequenceids are lower -- i.e. earlier -- than any outstanding sequenceids, sequenceids we are holding on to in this accounting instance.

Parameters:

sequenceids - Keyed by encoded region name. Cannot be null (doesn't make sense for it to be null).

Returns:

true if all sequenceids are lower, older than, the old sequenceids in this instance.

findLower

byte[][] findLower(Map<byte[],Long> sequenceids)

Iterates over the given Map and compares sequence ids with corresponding entries in lowestUnflushedSequenceIds. If a region in lowestUnflushedSequenceIds has a sequence id less than that passed in sequenceids then return it.

Parameters:

sequenceids - Sequenceids keyed by encoded region name.

Returns:

regions found in this instance with sequence ids less than those passed in.