What if MySQL had an HTTP interface and would reply JSON? What if MySQL had server-side JavaScript? What if you could store JSON documents in MySQL? And, what if there was Map and Reduce built-in to MySQL? Make it happen, today. A proof of concept MySQL 5.6 daemon plugin presented at IPC Spring 2012.

HTTP, JSON, JavaScript, Map&Reduce built-in to MySQL
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Eye-opening community contributions

Mycached (2009, Cybozu) was a ground breaking achievement. A …

Users of MySQL Replication sometimes throttle client requests to give slaves time to catch up to the master. PECL/mysqlnd_ms 1.4, the current development version, features some throttling through the quality-of-service filter and global transaction identifier (GTID). Both the plugins client-side GTID emulation and the MySQL 5.6 built-in GTID feature can be used to slow down PHP MySQL requests, if wanted.

How its done

The replication plugin has a neat feature called quality-of-service filter. If, for example, the quality of service you need from a MySQL Replication cluster is "read your writes", you call …

Tweaking is the motto - what an easy release PECL/mysqlnd_ms 1.4 will be! The first tweak for the next stable version of the mysqlnd replication and load balancing plugin solves pitfalls around charsets. String escaping now works on lazy connection handles (default) prior to establishing a connection to MySQL. A new server_charset setting has been introduced for this. The way it works also prevents you from the risk of using a different charset for escaping than used later on for your connection.

Lazy connections and server_charset

PECL/mysqlnd_ms is a load balancer. A users connection handle can point to different nodes of a replication cluster over time. For example, if using MySQL Replication, the connection handle may point to the master for running writes and, later on, to one of the slaves for reads. At the very moment a user opens a …

Why do we have to bother about built-in GTID support in MySQL 5.6 at all? Sure, it is a tremendous step forward for a lazy primary copy system like MySQL Replication. Period. GTIDs make server-side failover easier (slides). And, load balancer, including PECL/mysqlnd_ms as an example of a driver integrated load balancer, can use them to provide session consistency. Please, see the slides. But…

MySQL 5.6 Global Transaction IDs - Use case: (session) consistency
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MySQL 5.6 Global Transaction Identifier - Use case: Failover
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The long lasting MySQL replication failover issue is cured. MySQL 5.6 makes master failover easy, PECL/mysqlnd_ms assists with the client/connection failover. Compared to the past this is a significant step towards improving MySQL replication cluster availability, eleminating the need to use 3rd party tools in many cases. The slides illustrate the basic idea, as blogged about before.

There is not much to say …

MySQL Replication is sometimes critizied for being asynchronous and having slaves that lag behind. True! However, sometimes slaves can be used safely and reliably for read-your-writes. Its easy for PHP MySQL users. All the magic is in the driver. As of yesterday, the development version of PECL/mysqlnd_ms 1.3.0-alpha supports not only a client-side global transaction ID emulation but also the global transaction identifier feature of MySQL 5.6.4-m8.

Read-your-writes (session consistency) with MySQL Replication

A global transaction identifier can be understood as a sequence number for a transaction. The sequence number is incremented whenever a write transaction is performed on a MySQL replication master. Slaves replicate the transaction ID. After a client has executed a write on the master he can obtain a global …

Cache all queries which match a schema pattern is one of the few visible feature additions to PECL/mysqlnd_qc 1.1, the client-side query cache plugin for the mysqlnd library. As usual, this client-side cache is mostly transparent, works with all PHP MySQL APIs (mysql, mysqli, PDO_MySQL) and, of course, supports various storage backends including Memcache, process memory, SQLite, user-defined and more. Please, find details in the quickstart.

Setting a cache condition

Caching only selected queries is something that could be done in 1.0 already, for example, using a callback. What’s new is that filtering is built-in to 1.1. The new feature is straigth forward to use.

mysqlnd_qc_set_cache_condition( …

Why read stale data from an asynchronous MySQL replica (slave)? Fetch it from a local cache instead! Good for the clusters overall load, good for your applications performance. And, possible with PECL/mysqlnd_ms 1.3, the replication and load balancing plugin for PHP MySQL users.

The idea is simple

Any application using asynchronous MySQL replication must be capable of handling stale results read from a slave (replica) that is lagging behind the master. The quality of service that the application needs from the database cluster is low. If an application explicitly states the minimum service quality it needs, the underlying systems can adopt to it. That’s a cool thing, because the underlying systems don’t need to do more work than necessary. In the case of a PHP MySQL user, the first underlying system is the database driver library, which is mysqlnd.

Tell mysqlnd …

Is it worth the efforts to cache the results of a MySQL query at the client? In most cases the answer is: try it, measure it! Install the development version of the mysqlnd query cache plugin, which can be used with PDO_MySQL, mysqli and mysql. Set three PHP directives and find the answer in a log file.

While updating the query cache plugin to support PHP 5.4, the latest versions of APC and Memcached for cache storage, I virtually stumbled upon an undocumented feature I had long forgotten. The plugin can periodically dump statistics into a log file. The plugin collects tons of statistics and …

New in the PHP manual: a quickstart for the mysqlnd query cache plugin. PECL/mysqlnd_qc, the mysqlnd query cache plugin, is transparent and ease to use. But, how? Some pointers have been given in assorted presentations, here on my blog and in some, few examples from the manual. Fixed. You can now browse a quickstart to gain a quick overview.

• Architecture and Concepts
• Setup
• Setting the TTL
• …