MyRocks in the Wild Wild West! - percona.com · Percona tools generally work with MyRocks PMM...

© 2019 Percona 1

AlkinTezuysal

MyRocksintheWildWildWest!AlternateStorageEngineforMySQL

Sr.TechnicalManagerFOSDEM–Feb1st2020

© 2019 Percona 2

Whoarewe?

@ask_dba-AlkinTezuysalBorntoSail,ForcedtoWork❖  OpenSourceDatabaseEvangelist❖  GlobalDatabaseOperationsExpert❖  StoryTeller❖  InspiringTechnicalandStrategicLeader❖  CreativeTeamBuilder❖  Speaker,Mentor,andCoach

© 2019 Percona 3

Agenda

•  Introandbasics•  Advancedinternalsandlimitations•  Benchmarks•  Tuningsuggestions•  Conclusion

© 2019 Percona 4

OverviewofMyRocks

❖  What’sMyRocks?●  StorageengineforMySQL●  BasedonRocksDB,aforkofLevelDB●  Persistentkey-valuestore●  ImplementedatFacebookandintroducedin2016●  UsedbyFBinproduction●  Wasonlyavailableassourcecodeatfirst

© 2019 Percona 5

OverviewofMyRocks

❖  What’sMyRocks?●  PerconaServer:○  AnnouncedforQ12017○  Fullysupported:5.7.20,8.0

●  MariaDB:○  Pluginalphasince10.2.5○  Stablesince10.3.7/10.2.16

●  Gettingmoremature●  Notwidelyused

© 2019 Percona 6

OverviewofMyRocks

❖  BasedonLSMtree❖  Optimizedforwrites❖  Space-efficient❖  Fastdataload(withcorrectsetup)❖  Fastread-freereplication❖  Noforeignkeys,noserializable❖  NoFullTextorSpatialkeys❖  MyRockshasTTLfordata

© 2019 Percona 7

LSMvsB-tree

Imagecredit:b+treelsmhttp://www.benstopford.com/2015/02/14/log-structured-merge-trees/

© 2019 Percona 8

LSMvsB-tree

LSM: write-optimized B-tree: read-optimized

Sequential writes first In-place

Compaction in background Live tree re-balancing

Fast access only to leaves in the fast levels: memory, L0

Fast access to all leaves

© 2019 Percona 9

InnodbvsMyRocks

❖  MyRocks:betterwrites❖  MyRocks:2-5xlesssizethanInnoDB❖  InnoDBsupportsFKsandSerializable❖  InnoDBsupportsXA❖  Handlelockingdifferently

© 2019 Percona 10

InnodbvsMyRocks

❖  InnoDBcanbeusedwithadvancedreplication:Galera,PerconaXtradbCluster,GroupReplication

❖  InnoDBsupportsSTATEMENTandMIXEDbinlogformat❖  MyRocksdoesn’tsupporttransactionslargerthan

availablememory

© 2019 Percona 11

WhyuseMyRocksengine?

❖  Largedatasets➢  Largerthanmemoryavailable

■  100Gisnotthatlarge➢ Multipleindexes

❖  Write-intensiveload❖  Mostlypointselects*(it’scomplicated)❖  NoFKs/Serializable/XArequired

© 2019 Percona 13


❖  Costs➢  Cloudcostsspecifically➢ GoodforFlash➢  Resourceutilization

https://www.percona.com/blog/2019/07/19/assessing-mysql-performance-amongst-aws-options-part-two/

© 2019 Percona 14

InstallationandConfiguration

❖  EasilyinstalledforPerconaServerwithpercona-release.#yuminstallPercona-Server-server-57.x86_64#yuminstallPercona-Server-rocksdb-57.x86_64#ps-admin--enable-rocksdbmysql>SHOWENGINES;ROCKSDB|YES|RocksDBstorageenginemysql>createtabletest(idintprimarykey)engine=ROCKSDB;QueryOK,0rowsaffected(0.03sec)❖  Nodowntimerequired

© 2019 Percona 15


❖  Configurationoptionscanbereviewedmysql>SHOWVARIABLESLIKE'rocksdb%';rocksdb_block_cache_size:536870912rocksdb_default_cf_options:compression=kLZ4Compression;bottommost_compression=kLZ4Compression

❖  PerconaServer8.0bringsalotofimprovementstodefaults

© 2019 Percona 16


❖  SomethingsareconfigurablepercolumnfamilyCREATETABLEt1(aINT,bINT,PRIMARYKEY(a)COMMENT'cfname=cf1’,KEYkb(b)COMMENT'cfname=cf2’)rocksdb_override_cf_options='cf1={compression=kNoCompression};cf2={compression=kZSTD}'

© 2019 Percona 17

Differencesbetweendistributions

❖  Compression➢  Facebook:none,dependsonwhatyoucompilewith➢  PerconaServer:Zlib,ZSTD,LZ4,LZ4HC➢ MariaDB:Snappy,Zlib(+LZ4,LZ4HConUbuntu)

❖  Datafilelocation➢  FacebookandPerconaServer:$datadir/.rocksdb➢ MariaDB:$datadir/#rocksdb

❖  Gaplockdetection➢  PerconaServerandFacebook:yes(FBoffbydefault)➢ MariaDB:no

© 2019 Percona 18

AdvancedInternalsandLimitations

❖  MemTable❖  WAL(WriteAheadLog)❖  LeveledLSMStructure❖  Compaction❖  ColumnFamily❖  …andmore

© 2019 Percona 19

MyRocksEngineArchitectureMemory

PersistentStorage

WAL

WAL

ActiveMemTable

MemTable

Switch Switch

Flush

Compaction

SSTFiles

WriteRequest

© 2019 Percona 20

HowdoesLSMhandlewrites?INSERT INTO ..

WAL/MemTable

Sort

New SST

Existing SSTs Merge & Compact

New SST

© 2019 Percona 21

MemTable(s)❖  StorewritesinMyRocks➢  Associatedwitheachcolumnfamily➢  ChangesgotoWAL➢  Limitedto64Mb

Ref:https://blog.pythian.com/exposing-myrocks-internals-via-system-variables-part-1-data-writing/

© 2019 Percona 22

WAL(WriteAheadLog)

❖  Immediatewrites❖  Actasredo-log

© 2019 Percona 23

LSMLeveledCompaction

Ref:https://www.percona.com/live/17/sites/default/files/slides/MyRocks_Tutorial.pdf

© 2019 Percona 24

Compaction

❖  LSMcompactiononRowlevelisbetter➢  AlignedtoOSsector(4Kbunit)➢  NegligibleOSpagealignmentoverhead

❖  PerconaServerLZ4asdefaultalgorithm➢  Alllevelscompressed➢  Zstdavailable➢  Columnfamiliesallowpertable/index

© 2019 Percona 25

CompressionResults

© 2019 Percona 26

ColumnFamily

❖  Providesqueryatomicitybetweendifferentkeyspaces.➢  MemTablesandSSTfiles➢  Sharedtransactionlogs

❖  Indexmappingis1toN❖  MyRocksconfigurationparametersareperCF❖  IndexCommentperCF

© 2019 Percona 27

LSMonDisk

❖  Innodb(WriteAmplificationonB+Tree)➢  LowerwritepenaltyvsReducedfragmentation➢  B+TreeFragmentationoverspace➢  Compressionissues

❖  Higherreadpenalty❖  Goodfitforwriteheavyworkloads

© 2019 Percona 28

LSMonFlash

❖  Pros➢  Smallerspacewithcompression➢  Lowerwriteamplification

❖  Cons➢  Higherreadpenalty

❖  Goodfitforwriteheavyworkloads

© 2019 Percona 29

MyRocksEngineArchitectureMemory

PersistentStorage

WAL

WAL

ActiveMemTableBloomFilter

MemTableBloomFilter

SSTFiles

ReadRequest

IndexandBloomFilterscached

BlockCache

© 2019 Percona 30

DataStructure&QueryOptimizer

❖  SupportsPrimaryandSecondaryKeys➢  PKisclustered,singlesteplookup➢  FKnotsupported

❖  Tablespacesdon’texist❖  OnlineDDLnotpossible❖  Fastonscanningforward,slowonORDERBYDESC❖  ReversecolumnfamiliescanmakeDESCscanfast

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❖  OptimizerStatistics➢  Tablestatistics(rocksdb_table_stats_sampling_pct; the default value is 10% )➢  Indexcardinality➢  Records-in-rangeestimates➢  SHOWENGINEROCKSDBSTATUS\G➢  CaseSensitiveandBinaryCollations

■  CREATETABLEmyrocksENGINE=ROCKSDBCOLLATElatin1_bin

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❖  OptimizerStatistics➢  SSTfilesstoresindexstatistics

■  Idxname,size,#ofrows,diskspace,deletes■  Distinct#ofkeys

➢  Calculatedduringflush/compaction■  AbilitytoforceusingANALYZETABLEsyntax(smalltables)

➢  MultiRangeRead(MRR)isnotsupported

© 2019 Percona 33

DataDictionary

❖  ColumnFamilyID❖  IndexID❖  GlobalIndexID:ColumnFamilyID+IndexID❖  InformationSchema

© 2019 Percona 34

Locking&IsolationLevels

❖  Rowlocking➢  Read-Committed➢  Repeatable-Read

❖  GapLock-NotSupported➢  ErroronstatementforRepeatable-Read➢  PerconaServerwilldetectanderrorout

© 2019 Percona 35

Replication

❖  RBRbinlog_format=ROW➢  Largebinlogs➢  Notriggersonslaves➢  Schemaincompatibilities

❖  SBRcausesissueswithGapLocks➢  Canuseonslaves➢  Ifsafesetrocksdb_unsafe_for_binlog=1

© 2019 Percona 36

BackupandRecovery

❖  XtraBackup➢  Onlyin8.0withxtrabackup8.0.6+➢  OptimizedforInnodbandMyRocks➢  NopartialbackupsforMyRocks

❖  Mariabackup➢  10.2.16+,10.3.8+➢  NopartialbackupsforMyRocks

© 2019 Percona 37

BackupandRecovery

❖  myrocks_hotbackup➢  Originalbackuptool➢  Doesn’tworkwith8.0➢  CopiesRocksDBcheckpoint+WAL➢  MyRocksonly,won’tdoanythingforinnodb➢  Supportsrollingcheckpoint

■  LessWALtoapplyonrestoretillreplication

© 2019 Percona 38

BackupandRecovery

❖  mysqldump➢  Optimizationcanbeenabledforimport➢  rocksdb_bulk_load=1➢  mysqldumpinPerconaServerdetectsMyRocksautomatically

❖  Snapshots➢  Quitedifficulttodorightwhenmixingengines➢  MyRocks:checkpoint+wal

© 2019 Percona 39

Crashrecovery

❖  Corruptedimmutablefiles:notrecoverable❖  WALfile:recoverable➢  Variablerocksdb_wal_recovery_mode

■  1:Failtostart,donotrecover■  0:Ifcorruptedlastentry:truncateandstart■  2:Truncateeverythingaftercorruptedentry■  3:Truncateonlycorruptedentry(unsafe)

© 2019 Percona 40

Toolcompatibility

PerconatoolsgenerallyworkwithMyRocks

PMM Supported Built-in dashboards for MyRocks

xtrabackup Supported Since xtrabackup 8.0.6 (MySQL 8.0 only)

pt-online-schema-change Partial Only in read committed

pt-table-checksum Not supported Only ROW is supported by MyRocks

pt-table-sync Not supported Only ROW is supported by MyRocks

© 2019 Percona 43

Tuningsuggestions

❖  DirectoryStructure➢  Allfilesareunder.rocksdbdirectory➢  Nofilepertableoption(notevenperdb)➢  Logfileverbosityishigh

❖  Bewareofbulkloadisproblematic➢  Setrocksdb_bulk_load=1➢  Setrocksdb_commit_in_the_middle=1

© 2019 Percona 44

Tuningsuggestions

❖  MemoryCacheBlocks➢  rocksdb_block_cache_size-SHOWENGINEROCKSDBSTATUS

❖  DirectIO(bypassOScache)➢  rocksdb_use_direct_reads=ON➢  rocksdb_use_direct_io_for_flush_and_compaction=ON

© 2019 Percona 45

Tuningsuggestions

❖  Simulationcache➢  rocksdb_sim_cache_size■  Simulatesblockcache(forreads)■  Settolarger/smallervalue(restart)■  Costs~2%ofthatvalue■  Showenginerocksdbstatus\G

●  rocksdb.sim.block.cache.hitCOUNT:346684●  rocksdb.sim.block.cache.missCOUNT:86667

© 2019 Percona 46

Tuningsuggestions

❖  Backgroundjobs➢  rocksdb_max_background_jobs=<num_cpu_cores/4>➢  rocksdb_max_total_wal_size=4G

❖  Bettercompression➢  rocksdb_block_size=16384

© 2019 Percona 47

Tuningsuggestions

❖  Memorylimits➢  rocksdb_db_write_buffer_size

❖  UnlessusingPerconaServer8.0withoptimizeddefaults➢  rocksdb_default_cf_options■  Use8.0defaults,atleastenablebloomfilters■  block_based_table_factory= {filter_policy=bloomfilter:10:false;};

© 2019 Percona 48

Conclusion

❖  Bigdatasetsover100Gb❖  Multipleindexes❖  Write-intensiveworkloads❖  Concurrentreadswithoutrangescans❖  Cloudefficientandcheapertorun➢  LessIOPS,Memory,Storage

❖  WriteandReadimmediately

© 2019 Percona 49

SpecialThanksto...

❖  YoshinoriMatsunobu@matsunobu ❖  VadimTkachenko@VadimTk❖  SvetaSmirnova@svetsmirnova❖ MarkCallaghanfordoingtheextensive

researchanddevelopment.❖  Engineering,ExpertsandServicesTeamsat

Percona

© 2019 Percona 51

Credits&Referenceshttps://www.slideshare.net/matsunobu/myrocks-deep-divehttps://blog.pythian.com/exposing-myrocks-internals-via-system-variables-part-1-data-writing/https://www.percona.com/resources/webinars/how-rock-myrockshttps://mariadb.com/kb/en/library/optimizer-statistics-in-myrocks/http://smalldatum.blogspot.com/2017/12/myrocks-innodb-and-tokudb-summary.html

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