Memcached is a free, open source, high-performance, distributed memory object caching system, aimed at speeding up dynamic web applications by alleviating database load.

As the saying goes, the palest ink is better than the best memory.
This document is what I use to record some experiences during the process of reading Memcached source code, as well as analyzing some internal working mechanisms of memcached.
I hope it can also bring convenience to everyone.

PDF Table of Contents

1. Background …………………………………………………………………………………………………………………. 3
2. Memcached Installation …………………………………………………………………………………………….. 4
3. Memcached Configuration …………………………………………………………………………………………….. 5
4. Memcached Usage …………………………………………………………………………………………….. 6
4.1. Storage Commands ……………………………………………………………………………………………… 7
4.2. Retrieval Commands ……………………………………………………………………………………………… 8
4.3. Deletion Commands ……………………………………………………………………………………………… 8
4.4. Advanced Commands ……………………………………………………………………………………………… 9
4.5. Other Commands ……………………………………………………………………………………………. 10
5. Memcached Internal Working Mechanism ………………………………………………………………………………… 11
5.1. Memcached Basic Data Structures ……………………………………………………………….. 11
5.2. Basic Design Concepts and Processing Flow …………………………………………………………………… 12
5.3. Internal Hash Mechanism …………………………………………………………………………………… 15
5.3.1. Hash Function and Collision Resolution ………………………………………………………………….. 15
5.3.2. HashTable Main Functions …………………………………………………………………….. 15
5.4. Slab Memory Handling Mechanism ………………………………………………………………………………. 17
5.4.1. Slab Main Functions ………………………………………………………………………………. 17
5.4.2. LRU Algorithm Used in Slab Mechanism ……………………………………………………. 19
5.5. Various Functions for Controlling Items …………………………………………………………………………….. 20
5.6. Daemon Process Mechanism …………………………………………………………………………………….. 22
5.7. Socket Handling Mechanism …………………………………………………………………………………. 23
5.7.1. Unix Domain Protocol …………………………………………………………………………………. 23
5.7.2. TCP/UDP Protocol …………………………………………………………………………….. 24
5.8. Multi-threading Handling Mechanism …………………………………………………………………………………. 25
5.9. Event Handling Mechanism …………………………………………………………………………………….. 25
6. Unfinished Aspects ……………………………………………………………………………………………………… 27
7. References …………………………………………………………………………………………………………. 28

My abilities are limited, everyone is welcome to criticize!
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References

[1].Masahiro Nagano[JP] & charlee(translator).Comprehensive Analysis of memcached .2008-7-2

[2].W.Richard Stevens & Yang Jizhang(translator).UNIX Network Programming (Third Edition).2004

[3]. W.Richard Stevens.Advanced Programming in the UNIX Environment (Second Edition).2005

[4]. dsallings.Memcached FAQ .2009-9

[5]. bachmozart .Memcached Source Code Analysis (Thread Model) .

[6]. Love Writing Development Blog.Enabling Memcached Support for Wordpress on Linux .

Original Chinese version: http://www.cppblog.com/xguru/archive/2010/01/23/106265.html