If you’ve heard about the term Memcached before but you’ve been unsure of how it worked, don’t worry because we’ve got your covered. Memcached is simply the distributed caching system for all generally purposed memory in use. Read on as we dive in to all things Memcached!
Memcached is widely used for those who are interested in speeding up their databases which are utilized by websites as they cache objects and data in RAM. This is done as a means of reducing the read time taken by external data sources. Memcached has been licensed under a revised BSD license and is a fully free software that is completely open sourced. The Memcached system readily runs on any Unix type system like that of Windows, OS X and even Linux and it is fully dependent on libevent libraries.
The API within the system is quite large and the hash table has been built in such a way that it distributes across several machines at once. In the case where the table is as they say full, the system goes on to automatically remove data that hasn’t been used in quite some time. When applications utilize Memcached, requests are layered and RAM additions are done before the system falls back into a slower storage medium. However, a downside to this system is that misses are never tracked and users have to depend on third parties to provide a tracking service.
When it comes to the software’s architecture, the servers used go on to readily maintain an associative array of key-value. In essence, clients therefore populate these by key. However, keys can be at a maximum of 1 Mb or 250 bytes. And, client make use of the libraries that are client-side when they need to interface with the servers.
Memcached fully supports UDP and TCP and all clients involved know each server since servers cannot communicate with others alike. So, in the case where clients wish to read or even set values that go with a particular key, their own library firstly calculates the hash of the key in order to figure out which server system should be used. This form of action goes on to create the simplest form of sharding as well as a shared-nothing between the servers. And the server calculates an additional hash of the key which specifies where to read and store the relating value.
As we previously mentioned, when a memory table is filled, it goes on to replace those that weren’t used in a long time. As such, users of Memcached can in no way assume that old data is still on the system when they are ready to use them at a further time. So, it is highly recommended that users use some form of external saving mechanism in order to keep all their data safe. And they can go on to use the Couchbase Server or even the MemcacheDB for storage as well as perfect compatibility.
As we conclude we have just looked at what is Memcached. And we’ve also given quite the info about how the system works. Don’t forget that old data is removed and you won’t be able to find them if they aren’t stored in an external way!