innodb usage and diagnostics
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innodb usage and diagnostics

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InnoDB is the most similar storage engine for an Oracle developer. Understanding specifics such as the clustered primary key, secondary indexes sizes, page fill factor options and TEXT/BLOB management ...

InnoDB is the most similar storage engine for an Oracle developer. Understanding specifics such as the clustered primary key, secondary indexes sizes, page fill factor options and TEXT/BLOB management are important design needs developers need to know. Being able to monitor and analyze the available instrumentation and learn specifics for example auto-inc or gap locking contention, thread concurrency management options and data/log I/O options are also key in mastering InnoDB diagnostics.

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  • table creation information in .frmMySQL’s core table locking is disabled (politely)transactions do not behave quite the same in innodb – autocommit on by default. transaction isolation == repeatable readdeadlock detection
  • b-tree primary key ++ record in index (not pointer)instead of moving ½ the records, data is added to the tablespaces and indexes in natural orderpage directory uses binary searching in sparse array fill factors are auto managed – and at my last check was still an open questionindex-organized table
  • since innodb buffers both key and data there are cases where O_DIRECT can help a lot. the idea being to avoid double cachingthere will be an arbitrary useless key that is assigned if you don’t set one!
  • secondary indexes point to clustered. no data. extra callSecondary index records must always fit on a single B-tree pageIn a clustered index, BLOB, VARCHAR and TEXT columns that are not part of the primary key may be stored on separately allocated (“overflow”) pages. We call these “off-page columns” whose values are stored on singly-linked lists of overflow pages. ERROR HY000: Too big row. InnoDB requires that each B-tree page can accommodate at least two records.
  • Much performance pain come into play with lock contentionglobal counter which held the last value for the auto-incrementing column. A lock would be placed on this counter for the duration of the SQL statement which did the inserting. until MySQL 5.1.22new server variable, innodb_autoinc_lock_mode -- limits how often global locking is used and still defaults to that if not able to preserve derterministicnessA type of gap lock called an insertion intention gap lock is set by INSERT operations prior to row insertion.next key locks combo of record lock and gap lock.
  • Much performance pain come into play with lock contentionNames changed to protect the innocent
  • can’t reprise or due justice to this talk.DomasMituzas – FB go watch it.oreilly’smysql conference 2010
  • not enough knobs, must benchmark.innodb_thread_concurrency
  • LVM and slaves give easy opportunities for creating clones for testinginnodbhotbackupxtra backup
  • You might see these graphs spike during times of high concurrency or contention. These graphs basically indicate different types of activity involved in obtaining row locks or mutexes, both of which are causes of poor scaling in standard InnoDBXtraDB, the InnoDBplugin, and the Percona-patched MySQL are improved.
  • different types of activity involved in obtaining row locks or mutexesadditionally, can see what’s going on in individual transactions.
  • watching how the i/o threads are behaving.

innodb usage and diagnostics innodb usage and diagnostics Presentation Transcript

  • InnoDB usage and diagonstics
    sarah novotny – sarah@bluegecko.net
    MySQL and LAMP services
    www.BlueGecko.net
  • innodb architecture
    indexing curiosities
    scaling issues
    ops concerns
    3p tools
    www.BlueGecko.net
  • InnoDB Architecture
    MVCC
    row level locking
    transactions
    foreign keys
    tablespaces
    undo logs
    redo logs
    www.BlueGecko.net
  • the special sauce!
    clustered indexing
    natural order
    page directory
    www.BlueGecko.net
  • two short operational diversions
    innodb_flush_method = O_DIRECT
    is worth benchmarking on your system.
    choose smart primary keys
    www.BlueGecko.net
  • indexing curiosities
    secondary indexes point to the clustered index
    BLOB, VARCHAR,
    TEXT can be stored
    in overflow pages
    ERROR HY000:
    Too big row.
    www.BlueGecko.net
  • scaling issues
    when it’s time to
    go big,where are
    the bottlenecks?
    www.BlueGecko.net
  • innodb locking
    auto- increment
    gap locking
    www.BlueGecko.net
  • a view of locking in innotop
    www.BlueGecko.net
  • concurrency
    google: domas concurrency
    and click “I feel lucky!”
    http://bit.ly/domas_inno_concurrency
    www.BlueGecko.net
  • InnoDB thread concurrency
    www.BlueGecko.net
  • balance between i/o capabilities and mutex contention
    innodb_thread_concurrency
    multi cores, faster disk work to be done
    www.BlueGecko.net
  • operational concerns
    www.BlueGecko.net
  • operational concerns
    mysql> show innodbstatus;
    this gives you snapshot information
    trending gives you framework to see when things are going wrong
    http://code.google.com/p/mysql-cacti-templates
    www.BlueGecko.net
  • indirect measures to see what is happening
    www.BlueGecko.net
  • operational concerns
    the combination of historical data with current status from the host is invaluable in determining cause
    www.BlueGecko.net
  • operational concerns
    www.BlueGecko.net
  • free tools
    Innotop
    MySQL proxy/
    tcpdump
    mysql-cacti-templates
    gdb
    (poormansprofiler.org)
    www.BlueGecko.net
  • additional resources
    irc.freenode.org
    #mysql
    #maatkit
    mysql.com
    HPM2e -Baron Schwartz, Peter Zaitsev, Vadim Tkachenko, and Jeremy Zawodny
    www.BlueGecko.net
  • credits
    flickr
    hk architecture – davelau
    special sauce – fotoosvanrobin
    yellow pages - f-r-a-n-k
    Bell Labs - sodapop81
    lock - darwinbell
    License plate - severud
    voodoo - heungsub
    clones - adactio
    tools – meanestindian
    console - hermzz
    www.BlueGecko.net
  • Blue Gecko and contact info
    sarah@bluegecko.net
    sarah.novotny@gmail.com
    @sarahnovotny
    @bluegecko
    senk on #mysql
    Blue Gecko provides Remote DBA services for companies around the world
    7x24x365 support including monitoring, performance analysis, proactive maintenance and architectural guidance for small and large datasets.
    www.BlueGecko.net