Совсем недавно компания Skype выложила в открытое пользование под лицензией BSD ряд своих наработок, анонсированных прошлым летом на конференции, посвященной 10-летию PostgreSQL. Эти решения позволяют полностью решить проблемы масштабирования и резервирования OLTP систем, а также организовать необходимую синхронизацию с OLAP базами данных, решив таким образом 2 самых основных проблемы, с которыми сталкиваются разработчики баз данных при построении высоконагруженных систем. В пресс-релизы об этом событии вошли лишь краткие описания продуктов от Skype, поэтому возникла необходимость описать более подробно те возможности, которые появились у разработчиков и администраторов баз данных PostgreSQL.
Redis is a key-value database. It is similar to memcached but the dataset is not volatile, and values can be strings, exactly like in memcached, but also lists and sets with atomic operations to push/pop elements. In order to be very fast but at the same time persistent the whole dataset is taken in memory and from time to time and/or when a number of changes to the dataset are performed it is written asynchronously on disk. You may lost the last few queries that is acceptable in many applications but it is as fast as an in memory DB (Redis supports non-blocking master-slave replication in order to solve this problem by redundancy). Compression and other interesting features are a work in progress. Redis is written in ANSI C and works in most POSIX systems like Linux, *BSD, Mac OS X, and so on. Redis is free software released under the very liberal BSD license.
The DBacesslayer aka DBSlayer aka Släyer (as we like to call it when we're feeling ironically heavy metal) is a lightweight database abstraction layer suitable for high-load websites where you need the scalable advantages of connection pooling. Written in C for speed, DBSlayer talks to clients via JSON over HTTP, meaning it's simple to monitor and can swiftly interoperate with any web framework you choose.
MemcacheDB is a distributed key-value storage system designed for persistent. It is NOT a cache solution, but a persistent storage engine for fast and reliable key-value based object storage and retrieval. It conforms to memcache protocol(not completed, see below), so any memcached client can have connectivity with it. MemcacheDB uses Berkeley DB as a storing backend, so lots of features including transaction and replication are supported.
Q4M (Queue for MySQL) is a message queue licensed under GPL that works as a pluggable storage engine of MySQL 5.1, designed to be robust, fast, flexible. It is already in production quality, and is used by several web services (see Users of Q4M).
