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<h4 class="subsection">4.6.1 Database Specification</h4>
<p>Buildbot requires a connection to a database to maintain certain state
information, such as tracking pending build requests. By default this is
stored in a sqlite file called 'state.sqlite' in the base directory of your
master. This can be overridden with the <code>db_url</code> parameter.
<p>The format of this parameter is completely documetned at
<a href="http://www.sqlalchemy.org/docs/dialects/">http://www.sqlalchemy.org/docs/dialects/</a>, but is generally of the form:
<pre class="example"> driver://[username:password@]host:port/database[?args]
</pre>
<p>For sqlite databases, since there is no host and port, relative paths are
specified with <code>sqlite:///</code> and absolute paths with <code>sqlite:////</code>.
Examples:
<p>Notes for particular database backends:
<h3 class="heading">SQLite</h3>
<pre class="example"> c['db_url'] = "sqlite:///state.sqlite"
</pre>
<p>No special configuration is required to use SQLite.
<h3 class="heading">MySQL</h3>
<pre class="example"> c['db_url'] = "mysql://user:pass@somehost.com/database_name?max_idle=300"
</pre>
<p>The <code>max_idle</code> argument for MySQL connections is unique to Buildbot, and
should be set to something less than the wait_timeout configured for your
server. This controls the SQLAlchemy <code>pool_recycle</code> parameter, which
defaults to no timeout. Setting this parameter ensures that connections are
closed and re-opened after the configured amount of idle time. If you see
errors such as <code>_mysql_exceptions.OperationalError: (2006, 'MySQL server
has gone away')</code>, this means your <code>max_idle</code> setting is probably too high.
<code>show global variables like 'wait_timeout';</code> will show what the currently
configured <code>wait_timeout</code> is on your MySQL server.
<p>Buildbot requires <code>use_unique=True</code> and <code>charset=utf8</code>, and will add
them automatically, so they do not need to be specified in <code>db_url</code>.
<p>MySQL defaults to the MyISAM storage engine, but this can be overridden with
the <code>storage_engine</code> URL argument. Note that, because of InnoDB's
extremely short key length limitations, it cannot be used to run Buildbot. See
<a href="http://bugs.mysql.com/bug.php?id=4541">http://bugs.mysql.com/bug.php?id=4541</a> for more information.
<p>Buildbot uses temporary tables internally to manage large transactions. MySQL
has trouble doing replication with temporary tables, so if you are using a
replicated MySQL installation, you may need to handle this situation carefully.
The MySQL documentation
(<a href="http://dev.mysql.com/doc/refman/5.5/en/replication-features-temptables.html">http://dev.mysql.com/doc/refman/5.5/en/replication-features-temptables.html</a>)
recommends using <code>--replicate-wild-ignore-table</code> to ignore temporary
tables that should not be replicated. All Buildbot temporary tables begin with
<code>bbtmp_</code>, so an option such as
<code>--replicate-wild-ignore-table=bbtmp_.*</code> may help.
<h3 class="heading">Postgres</h3>
<pre class="example"> c['db_url'] = "postgresql://username@hostname/dbname"
</pre>
<p>No special configuration is required to use Postgres.
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