15th chapter (attached) distributed cache-memcached

First, the concept

Memcached is a set of distributed memory object caching systems developed by danga.com (the technical team of operations LiveJournal) to reduce database load and improve performance in dynamic systems.

Second, the application of the occasion

1. Distributed applications. Because the memcached itself is based on a distributed system, it is particularly suitable for large distributed systems.

2. Database front-section cache. Database is often the bottleneck of the website system. Large concurrent access to the database often results in Web site memory overflow. Of course we can also use Hibernate's caching mechanism. But Memcached is based on distributed, and can be independent of the website application itself, so it is more suitable for large-scale web site for the application of the split.

3. Data sharing between servers. For example, we will be the site's login system, query system split into two applications, placed on different servers, and cluster, that time when the user logged on, how to log on the login information from the system server synchronization to the query system server? At this time, we can use memcached, login system to cache the login information, the query system can get login information, like to obtain local information.

Third, not applicable occasions

Those that do not need to be "distributed", do not need to be shared, or simply scale to a single server, memcached does not bring any benefit, and instead slows down system efficiency because network connectivity also requires resources

15th chapter (attached) distributed cache-memcached