缓存框架Ehcache 2.7.5

显示全部楼层 · 2014-2-19 11:55:14

本帖最后由 jieforest 于 2013-10-26 08:51 编辑
Ehcache 2.7.5 发布了，官方没有提及该版本的改进内容。下载地址：
http://sourceforge.net/projects/ehcache/files/ehcache/ehcache-2.7.5/
EhCache 是一个纯Java的进程内缓存框架，具有快速、精干等特点，是Hibernate中默认的CacheProvider。
下图是 Ehcache 在应用程序中的位置：

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千问 · 2014-2-19 11:55:14

官网：http://ehcache.org/
Ehcache: Java's Most Widely-Used Cache
Ehcache is an open source, standards-based cache for boosting performance, offloading your database, and simplifying scalability. It's the most widely-used Java-based cache because it's robust, proven, and full-featured. Ehcache scales from in-process, with one or more nodes, all the way to mixed in-process/out-of-process configurations with terabyte-sized caches.
Terracotta actively develops, maintains, and supports Ehcache as a professional open source project available under an Apache 2 license. In addition to the open source Ehcache edition, Terracotta offers BigMemory for enterprise-grade in-memory data management with high availability, worldwide 24x7 professional support, consulting, and training services.
For applications requiring a coherent distributed cache, use Terracotta BigMemory Max, which is available in both free and full versions. (Terracotta no longer actively updates the open-source version of Terracotta Server Array, also known as Terracotta. However, you can still download the latest open-source version of Terrcotta Server Array.)

千问 · 2014-2-19 11:55:14

BigMemory for Ehcache
All Your Data in Memory—Without Garbage Collection Pauses
Ready to create very large in-memory data stores—without worrying about garbage collection performance hits or time-consuming tuning? BigMemory extends Ehcache's' capabilities with an off-heap store that frees you from GC’s constraints. BigMemory uses the Ehcache API for reading and writing, so it's a snap to add to any Ehcache deployment. You also get a search API, advanced in-memory monitoring and management tools, disk-backed, fast restartability, and much more.
BigMemory Go—with 32GB free
For in-memory data management on a standalone JVM, download BigMemory Go, with 32GB free!
BigMemory Max
For in-memory data management across a server arrary, with data consistency guarantees, full fault-tolerance, and more, download the free 30-day trial of BigMemory Max.
With BigMemory, take full advantage of ALL the memory on ALL your machines to achieve predictable, extremely low latency at massive scale.

千问 · 2014-2-19 11:55:14

Introduction
Ehcache is a cache library introduced in October 2003 with the key goal of improving performance by reducing the load on underlying resources. Ehcache is not just for general-purpose caching, however, but also for caching Hibernate (second-level cache), data access objects, security credentials, web pages. It can also be used for SOAP and RESTful server caching, application persistence, and distributed caching.
Definitions
cache: Wiktionary defines a cache as "a store of things that will be required in future, and can be retrieved rapidly." That is the nub of it. In computer science terms, a cache is a collection of temporary data which either duplicates data located elsewhere or is the result of a computation. Once in the cache, the data can be repeatedly accessed inexpensively.
cache-hit: When a data element is requested of the cache and the element exists for the given key, it is referrred to as a cache hit (or simply 'hit').
cache-miss: When a data element is requested of the cache and the element does not exist for the given key, it is referred to as a cache miss (or simply 'miss').
system-of-record: The core premise of caching assumes that there is a source of truth for the data. This is often referred to as a system-of-record (SOR). The cache acts as a local copy of data retrieved from or stored to the system-of-record. This is often a traditional database, although it may be a specialized file system or some other reliable long-term storage. For the purposes of using Ehcache, the SOR is assumed to be a database.
SOR: See system-of-record.

千问 · 2014-2-19 11:55:14

Why caching works
Locality of Reference
While Ehcache concerns itself with Java objects, caching is used throughout computing, from CPU caches to the DNS system. Why? Because many computer systems exhibit "locality of reference". Data that is near other data or has just been used is more likely to be used again.

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The Long Tail
Chris Anderson, of Wired Magazine, coined the term "The Long Tail" to refer to Ecommerce systems. The idea that a small number of items may make up the bulk of sales, a small number of blogs might get the most hits and so on. While there is a small list of popular items, there is a long tail of less popular ones.
Ehcache Image
The Long Tail
The Long Tail is itself a vernacular term for a Power Law probability distribution. They don't just appear in ecommerce, but throughout nature. One form of a Power Law distribution is the Pareto distribution, commonly know as the 80:20 rule. This phenomenon is useful for caching. If 20% of objects are used 80% of the time and a way can be found to reduce the cost of obtaining that 20%, then the system performance will improve.