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Karol Bucek edited this page · 6 revisions

Profiling SQL

  adapter: mysql
  database: borg
  host: localhost
  properties: # specific for MySQL
    profileSQL: true # will profile/explain each SQL operation
    #autoSlowLog: true # alternatively (less logging) use this

NOTE: logging won't use ActiveRecord::Base.logger but should instead print to Java's System.err by default.


Sample configuration (properties) to start with :

  adapter: mysql
  database: borg
    dumpQueriesOnException: true
    includeThreadDumpInDeadlockExceptions: true # on exceptions a system thread-dump will be taken
    #includeInnodbStatusInDeadlockExceptions: true # automatically "innodb status" on potential locks
    #includeThreadNamesAsStatementComment: true # Java thread names will be visible with "innodb status"
    #useUsageAdvisor: true # lots off output

Reference for all supported properties:


Configuring SSL is a bit different than on MRI, since we're not using the "native" MySQL client library. Usually, instead one sets up the JVM with the desired key/trust stores, preferably using the JVM's native key-store format. Please read the official documentation:

Another (older) guide of a MySQL Connector/J setup with Tomcat


Since AR-JDBC relies on JDBC we inherit whatsoever the driver shoots at us, for the official MySQL Connector/J among others it's fail-over support (multi-host connections). This might turn out useful for a number of high-availability scenarios. The support is very simple and you can use it any-time you use the MySQL adapter, just specify multiple hosts e.g. :

  adapter: mysql
  database: zoo
  username: mia
    # autoReconnect: false
    failOverReadOnly: true # default value
    secondsBeforeRetryMaster: 30 # default

Whenever the first (master) host goes down the following hosts will be used (in read-only mode by default) for queries. Please consult the official documentation for how fail-over behaves and what are its costs (only fails-over during connection initialization as long as the autoReconnect property is not set to true)

NOTE: Please be aware that these features are available using the official (jdbc-mysql) driver, since we also support MariaDB's (jdbc-mariadb) driver.

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