PECL/mysqlnd_ms 1.5 series

1.5.0-alpha

• Release date: 03/2013
• Motto/theme: Sharding support, improved transaction support

Note:

This is the current development series. All features are at an early stage. Changes may happen at any time without prior notice. Please, do not use this version in production environments.

The documentation may not reflect all changes yet.

Bug fixes

• Fixed #60605 PHP segmentation fault when mysqlnd_ms is enabled.

• Setting transaction stickiness disables all load balancing, including automatic failover, for the duration of a transaction. So far connection switches could have happened in the middle of a transaction in multi-master configurations and during automatic failover although transaction monitoring had detected transaction boundaries properly.

• BC break and bug fix. SQL hints enforcing the use of a specific kind of server (MYSQLND_MS_MASTER_SWITCH, MYSQLND_MS_SLAVE_SWITCH, MYSQLND_MS_LAST_USED_SWITCH) are ignored for the duration of a transaction of transaction stickiness is enabled and transaction boundaries have been detected properly.

  This is a change in behaviour. However, it is also a bug fix and a step to align behaviour. If, in previous versions, transaction stickiness, one of the above listed SQL hints and the quality of service filtering was combined it could happened that the SQL hints got ignored. In some case the SQL hints did work, in other cases they did not. The new behaviour is more consistent. SQL hints will always be ignore for the duration of a transaction, if transaction stickiness is enabled.

  Please note, transaction boundary detection continues to be based on API call monitoring. SQL commands controlling transactions are not monitored.

• BC break and bug fix. Calls to mysqlnd_ms_set_qos() will fail when done in the middle of a transaction if transaction stickiness is enabled. Connection switches are not allowed for the duration of a transaction. Changing the quality of service likely results on a different set of servers qualifying for query execution, possibly making it necessary to switch connections. Thus, the call is not allowed in during an active transaction. The quality of server can, however, be changed in between transactions.

Feature changes

• Introduced the node_group filter. The filter lets you organize servers (master and slaves) into groups. Queries can be directed to a certain group of servers by prefixing the query statement with a SQL hint/comment that contains the groups configured name. Grouping can be used for partitioning and sharding, and also to optimize for local caching. In the case of sharding, a group name can be thought of like a shard key. All queries for a given shard key will be executed on the configured shard. Note: both the client and server must support sharding for sharding to function with mysqlnd_ms.

• Extended configuration file validation during PHP startup (RINIT). An E_WARNING level error will be thrown if the configuration file can not be read (permissions), is empty, or the file (JSON) could not be parsed. Warnings may appear in log files, which depending on how PHP is configured.

  Distributions that aim to provide a pre-configured setup, including a configuration file stub, are asked to put {} into the configuration file to prevent this warning about an invalid configuration file.

  Further configuration file validation is done when parsing sections upon opening a connection. Please, note that there may still be situations when an invalid plugin configuration file does not lead to proper error messages but a failure to connect.

• As of PHP 5.5.0, improved support for transaction boundaries detection was added for mysqli. The mysqli extension has been modified to use the new C API calls of the mysqlnd library to begin, commit, and rollback a transaction or savepoint. If trx_stickiness is used to enable transaction aware load balancing, the mysqli_begin(), mysqli_commit() and mysqli_rollback() functions will now be monitered by the plugin, to go along with the mysqli_autocommit() function that was already supported. All SQL features to control transactions are also available through the improved mysqli transaction control related functions. This means that it is not required to issue SQL statements instead of using API calls. Applications using the appropriate API calls can be load balanced by PECL/mysqlnd_ms in a completely transaction-aware way.

  Please note, PDO_MySQL has not been updated yet to utilize the new mysqlnd API calls. Thus, transaction boundary detection with PDO_MySQL continues to be limited to the monitoring by passing in PDO::ATTR_AUTOCOMMIT to PDO::setAttribute().

• Introduced trx_stickiness=on. This trx_stickiness option differs from trx_stickiness=master as it tries to execute a read-only transaction on a slave, if quality of service (consistency level) allows the use of a slave. Read-only transactions were introduced in MySQL 5.6, and they offer performance gains.

• Query cache support is considered beta if used with the mysqli API. It should work fine with primary copy based clusters. For all other APIs, this feature continues to be called experimental.

• The code examples in the mysqlnd_ms source were updated.