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https://github.com/sigmasternchen/php-doc-en
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git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@335811 c90b9560-bf6c-de11-be94-00142212c4b1
179 lines
6.7 KiB
XML
179 lines
6.7 KiB
XML
<?xml version="1.0" encoding="utf-8"?>
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<!-- $Revision$ -->
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<refentry xml:id="function.mysqlnd-ms-xa-begin" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
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<refnamediv>
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<refname>mysqlnd_ms_xa_begin</refname>
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<refpurpose>Starts a distributed/XA transaction among MySQL servers</refpurpose>
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</refnamediv>
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<refsect1 role="description">
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&reftitle.description;
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<methodsynopsis>
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<type>int</type>
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<methodname>mysqlnd_ms_xa_begin</methodname>
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<methodparam><type>mixed</type><parameter>connection</parameter></methodparam>
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<methodparam><type>string</type><parameter>gtrid</parameter></methodparam>
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<methodparam choice="opt"><type>int</type><parameter>timeout</parameter></methodparam>
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</methodsynopsis>
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<para>
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Starts a XA transaction among MySQL servers. PECL/mysqlnd_ms acts as a transaction
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coordinator the distributed transaction.
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</para>
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<para>
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Once a global transaction has been started, the plugin injects appropriate
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<literal>XA BEGIN</literal> SQL statements on all MySQL servers used in the following.
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The global transaction is either ended by calling <function>mysqlnd_ms_xa_commit</function>,
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<function>mysqlnd_ms_xa_rollback</function> or by an implicit rollback in case
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of an error.
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</para>
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<para>
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During a global transaction, the plugin tracks all server switches,
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for example, when switching from one MySQL shard to another MySQL shard.
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Immediately before a query is run on a server that has not been participating
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in the global transaction yet, <literal>XA BEGIN</literal> is executed on
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the server. From a users perspective the injection happens during a call to a
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query execution function such as <function>mysqli_query</function>. Should
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the injection fail an error is reported to the caller of the query execution
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function. The failing server does not become a participant in the global
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transaction. The user may retry executing a query on the server and hereby retry
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injecting <literal>XA BEGIN</literal>, abort the global transaction because
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not all required servers can participate, or ignore and continue the global without
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the failed server.
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</para>
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<para>
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Reasons to fail executing <literal>XA BEGIN</literal> include but are not limited to
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a server being unreachable or the server having an open, concurrent
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XA transaction using the same xid.
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</para>
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<para>
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Please note, global and local transactions
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are mutually exclusive. You cannot start a XA transaction when you have a local
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transaction open. The local transaction must be ended first. The plugin tries
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to detect this conflict as early as possible. It monitors API calls for controlling
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local transactions to learn about the current state. However, if using
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SQL statements for local transactions such as <literal>BEGIN</literal>, the
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plugin may not know the current state and the conflict is not detected
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before <literal>XA BEGIN</literal> is injected and executed.
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</para>
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<para>
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The use of other XA resources but MySQL servers is not supported by
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the function. To carry out a global transaction among, for example,
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a MySQL server and another vendors database system, you should issue
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the systems SQL commands yourself.
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</para>
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<note>
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<title>Experimental</title>
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<para>
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The feature is currently under development. There may be issues and/or
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feature limitations. Do not use in production environments.
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</para>
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</note>
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</refsect1>
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<refsect1 role="parameters">
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&reftitle.parameters;
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<variablelist>
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<varlistentry>
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<term><parameter>connection</parameter></term>
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<listitem>
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<para>
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A MySQL connection handle obtained from any of the
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connect functions of the <link linkend="ref.mysqli">mysqli</link>,
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<link linkend="ref.mysql">mysql</link> or
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<link linkend="ref.pdo-mysql">PDO_MYSQL</link> extensions.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>gtrid</parameter></term>
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<listitem>
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<para>
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Global transaction identifier (gtrid). The gtrid is a binary string
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up to 64 bytes long. Please note, depending on your character set settings,
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64 characters may require more than 64 bytes to store.
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</para>
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<para>
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In accordance with the MySQL SQL syntax,
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XA transactions use identifiers made of three parts. An xid consists of a
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global transaction identifier (gtrid), a branch qualifier (bqual) and a
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format identifier (formatID). Only the global transaction identifier can
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and needs to be set.
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</para>
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<para>
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The branch qualifier and format identifier are set automatically. The details
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should be considered implementation dependent, which may change without
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prior notice. In version 1.6 the branch qualifier is consecutive number
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which is incremented whenever a participant joins the global transaction.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>timeout</parameter></term>
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<listitem>
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<para>
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Timeout in seconds. The default value is 60 seconds.
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</para>
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<para>
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The timeout is a hint to the garbage collection. If a transaction is recorded
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to take longer than expected, the garbage collection begins checking the
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transactions status.
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</para>
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<para>
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Setting a low value may make the garbage collection check the progress
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too often. Please note, checking the status of a global transaction may
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involve connecting to all recorded participants and possibly issuing
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queries on the servers.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1 role="returnvalues">
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&reftitle.returnvalues;
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<para>
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Returns &true; if there is no open local or global transaction and a new global
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transaction can be started. Otherwise, returns &false;
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</para>
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</refsect1>
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<refsect1 role="seealso">
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&reftitle.seealso;
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<para>
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<simplelist>
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<member>
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<link linkend="mysqlnd-ms.quickstart.xa_transactions">Quickstart XA/Distributed transactions</link>
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</member>
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<member>
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<link linkend="mysqlnd-ms.configuration">Runtime configuration</link>
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</member>
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<member>
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<function>mysqlnd_ms_get_stats</function>
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</member>
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</simplelist>
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</para>
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</refsect1>
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</refentry>
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<!-- Keep this comment at the end of the file
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Local variables:
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mode: sgml
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sgml-omittag:t
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sgml-shorttag:t
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sgml-minimize-attributes:nil
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sgml-always-quote-attributes:t
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sgml-indent-step:1
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sgml-indent-data:t
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indent-tabs-mode:nil
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sgml-parent-document:nil
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sgml-default-dtd-file:"~/.phpdoc/manual.ced"
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sgml-exposed-tags:nil
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sgml-local-catalogs:nil
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sgml-local-ecat-files:nil
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End:
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vim600: syn=xml fen fdm=syntax fdl=2 si
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vim: et tw=78 syn=sgml
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vi: ts=1 sw=1
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-->
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