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How to define quality of service in the plugins config file.
git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@321271 c90b9560-bf6c-de11-be94-00142212c4b1
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Ulf Wendel
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2 changed files with 72 additions and 11 deletions
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@ -814,7 +814,7 @@ version = 5.6.2-m5-log
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load balancing policies. The 'round robin' load balancing can be configured
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through the <literal>roundrobin</literal> filter. Setting a 'user defined
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callback' for server selection is possible with the <literal>user</literal>
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filter. The <literal>qos</literal> (quality-of-service) filter finds cluster
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filter. The <literal>quality_of_service</literal> filter finds cluster
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nodes capable of delivering a certain service, for example, read-your-writes or,
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not lagging more seconds behind the master than allowed.
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</para>
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@ -880,7 +880,7 @@ version = 5.6.2-m5-log
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</para>
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<para>
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A second type of filter exists: multi filter. A multi filter emits zero, one or multiple
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servers after processing. The <literal>qos</literal> (quality-of-service) filter
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servers after processing. The <literal>quality_of_service</literal> filter
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is an example. If the service quality requested sets an upper limit for the slave
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lag and more than one slave is lagging behind less than the allowed number of seconds,
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the filter returns more than one cluster node. A multi filter must be followed by other
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@ -888,7 +888,7 @@ version = 5.6.2-m5-log
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is found.
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</para>
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<para>
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A filter sequence with the <literal>qos</literal> (quality-of-service)
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A filter sequence with the <literal>quality_of_service</literal>
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multi filter followed by a load balancing filter.
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<itemizedlist>
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<listitem>
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@ -907,7 +907,7 @@ version = 5.6.2-m5-log
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</listitem>
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<listitem>
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<simpara>
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Filter: <literal>qos</literal>, rule set: read-your-writes
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Filter: <literal>quality_of_service</literal>, rule set: session_consistency (read-your-writes)
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Output: <literal>master_0</literal>
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</simpara>
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</listitem>
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@ -1119,19 +1119,19 @@ User has connected to 'myapp'...
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</varlistentry>
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<varlistentry xml:id="ini.mysqlnd-ms-plugin-config-v2.filter_qos">
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<term>
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Filter: <parameter>qos</parameter>
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Filter: <parameter>quality_of_service</parameter>
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<type>object</type>
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</term>
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<listitem>
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<para>
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The quality-of-service (qos) filter identifies cluster nodes
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The <literal>quality_of_service</literal> identifies cluster nodes
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capable of delivering a certain quality of service. It is a multi filter
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which returns zero, one or multiple of its input servers. Thus, it
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must be followed by other filters to reduce the number of candidates
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down to one for statement execution.
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</para>
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<para>
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The <literal>qos</literal> filter has been introduced in 1.2.0-alpha.
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The <literal>quality_of_service</literal> filter has been introduced in 1.2.0-alpha.
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In the 1.2 series the filters focus is on the consistency aspect of
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service quality. Different types of clusters offer different
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default data consistencies. For example, an asynchronous MySQL
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@ -1140,15 +1140,25 @@ User has connected to 'myapp'...
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it may serve stale database because its lagging behind or it may serve
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current information. Often, this is acceptable. In some cases
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higher consistency levels are needed for the application to work correct.
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In those cases, the <literal>qos</literal> can filter out cluster nodes
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In those cases, the <literal>quality_of_service</literal> can filter out cluster nodes
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which cannot deliver the necessary quality of service.
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</para>
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<para>
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The <literal>qos</literal> filter can be replaced
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The <literal>quality_of_service</literal> filter can be replaced or created
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at runtime. A successful call to
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<link linkend="function.mysqlnd-ms-set-qos"><function>mysqlnd_ms_set_qos</function></link>
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removes all existing <literal>qos</literal> filter entries from the
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filter list and installs a new one at the very beginning.
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filter list and installs a new one at the very beginning. All settings
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that can be made through
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<link linkend="function.mysqlnd-ms-set-qos"><function>mysqlnd_ms_set_qos</function></link>
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can also be in the plugins configuration file. However, use of the function
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is by far the most common use case. Instead of setting session consistency and
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strong consistency service levels in the plugins configuration file it is
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recommended to define only masters and no slaves. Both service levels will
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force the use of masters only. Using an empty slave list shortens the
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configuration file, thus improving readability. The only service level for which
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there is a case of defining in the plugins configuration file is the combination
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of eventual consistency and maximum slave lag.
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</para>
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<informaltable>
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<tgroup cols="3">
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@ -1172,6 +1182,57 @@ User has connected to 'myapp'...
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Request eventual consistency. Allows the use of all
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master and slave servers. Data returned may or may not be current.
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</para>
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<para>
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Eventual consistency accepts an optional <literal>age</literal>
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parameter. If <literal>age</literal> is given the plugin considers
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only slaves for reading for which MySQL replication reports
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a slave lag less or equal to <literal>age</literal>.
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The repliation lag is measure using <literal>SHOW SLAVE STATUS</literal>.
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If the plugin fails to fetch the replication lag, the slave tested
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is skipped. Implementation details and tipps are given in the
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<link linkend="mysqlnd-ms.qos_consistency">quality of service concepts section</link>.
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</para>
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<para>
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Please note, if a filter chain
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generates an empty slave list and the PHP configuration directive
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<literal>mysqlnd_ms.multi_master=0</literal> is used, the plugin may
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emit a warning.
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</para>
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<para>
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<example>
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<title>Global limit on slave lag</title>
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<programlisting role="ini">
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<![CDATA[
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{
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"myapp": {
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"master": {
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"master_0": {
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"host": "localhost"
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}
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},
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"slave": {
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"slave_0": {
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"host": "192.168.2.27",
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"port": "3306"
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},
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"slave_1": {
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"host": "192.168.78.136",
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"port": "3306"
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}
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},
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"filters": {
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"quality_of_service": {
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"eventual_consistency": {
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"age":123
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}
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}
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}
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}
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}
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]]>
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</programlisting>
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</example>
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</para>
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</entry>
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<entry>Since 1.2.0.</entry>
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</row>
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@ -1376,7 +1437,7 @@ User has connected to 'myapp'...
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</example>
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</para>
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<para>
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Please, note the <literal>qos</literal> (quality of service) filter introduced
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Please, note the <literal>quality_of_service</literal> filter introduced
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in version 1.2.0-alpha. It gives finer control, for example, for achieving read-your-writes
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and, it offers additional functionality introducing
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<link linkend="mysqlnd-ms.qos_consistency">service levels</link>.
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