普遍缓存技术
数据缓存：这里所说的数据缓存是指数据库查询缓存，每次访问页面的时候,都会先检测相应的缓存数据是否存在，如果不存在，就连接数据库，得到数据， 并把查询结果序列化后保存到文件中，以后同样的查询结果就直接从缓存表或文件中获得。
用的最广的例子看Discuz的搜索功能，把结果ID缓存到一个表中，下次搜索相同关键字时先搜索缓存表。
举个常用的方法，多表关联的时候，把附表中的内容生成数组保存到主表的一个字段中，需要的时候数组分解一下，这样的好处是只读一个表，坏处就是两个 数据同步会多不少步骤，数据库永远是瓶颈，用硬盘换速度，是这个的关键点。
页面缓存：
每次访问页面的时候，都会先检测相应的缓存页面文件是否存在，如果不存在，就连接数据库，得到数据，显示页面并同时生成缓存页面文件，这样下次访问 的时候页面文件就发挥作用了。(模板引擎和网上常见的一些缓存类通常有此功能)
时间触发缓存：
检查文件是否存在并且时间戳小于设置的过期时间,如果文件修改的时间戳比当前时间戳减去过期时间戳大，那么就用缓存，否则更新缓存。
内容触发缓存：
当插入数据或更新数据时，强制更新缓存。
静态缓存：
这里所说的静态缓存是指静态化，直接生成HTML或xml等文本文件，有更新的时候重生成一次，适合于不太变化的页面，这就不说了。
以上内容是代码级的解决方案，我直接CP别的框架，也懒得改，内容都差不多，很容易就做到，而且会几种方式一起用，但下面的内容是服务器端的缓存方 案，非代码级的，要有多方的合作才能做到
内存缓存:
Memcached是高性能的，分布式的内存对象缓存系统，用于在动态应用中减少数据库负载，提升访问速度。
这里说下Memcached的例子：
<ol class="dp-c"> <li class="alt"><span><span><?php </span></span></span></li> <li> <span class="vars">$memcache</span><span> = </span><span class="keyword">new</span><span> Memcache; </span> </li> <li class="alt"> <span class="vars">$memcache</span><span>->connect(‘localhost’, 11211) </span><span class="keyword">or</span><span> </span><span class="keyword">die</span><span> (“Could not connect”); </span> </li> <li> <span class="vars">$version</span><span> = </span><span class="vars">$memcache</span><span>->getVersion(); </span> </li> <li class="alt"> <span class="func">echo</span><span> “Server’s version: “.</span><span class="vars">$version</span><span>.”n”; </span> </li> <li> <span class="vars">$tmp_object</span><span> = </span><span class="keyword">new</span><span> stdClass; </span> </li> <li class="alt"> <span class="vars">$tmp_object</span><span>->str_attr = ‘test’; </span> </li> <li> <span class="vars">$tmp_object</span><span>->int_attr = 123; </span> </li> <li class="alt"> <span class="vars">$memcache</span><span>->set(‘key’, </span><span class="vars">$tmp_object</span><span>, false, 10) </span><span class="keyword">or</span><span> </span><span class="keyword">die</span><span> (“Failed to save data at the server”); </span> </li> <li> <span class="func">echo</span><span> “Store data in the cache (data will expire in 10 seconds)n”; </span> </li> <li class="alt"> <span class="vars">$get_result</span><span> = </span><span class="vars">$memcache</span><span>->get(‘key’); </span> </li> <li> <span class="func">echo</span><span> “Data from the cache:n”; </span> </li> <li class="alt"> <span>var_dump(</span><span class="vars">$get_result</span><span>); </span> </li> <li><span>?> </span></li> </ol>
读库的例子：
<ol class="dp-c">
<li class="alt"><span><span><?php </span></span></span></li>
<li>
<span class="vars">$sql</span><span> = ‘SELECT * FROM users’; </span>
</li>
<li class="alt">
<span class="vars">$key</span><span> = md5(</span><span class="vars">$sql</span><span>); </span><span class="comment">//memcached 对象标识符 </span><span> </span>
</li>
<li>
<span class="keyword">if</span><span> ( !(</span><span class="vars">$datas</span><span> = </span><span class="vars">$mc</span><span>->get(</span><span class="vars">$key</span><span>)) ) { </span>
</li>
<li class="alt">
<span class="comment">// 在 memcached 中未获取到缓存数据，则使用数据库查询获取记录集。 </span><span> </span>
</li>
<li>
<span class="func">echo</span><span> “n”.</span><span class="func">str_pad</span><span>(‘Read datas from MySQL.’, 60, ‘_’).”n”; </span>
</li>
<li class="alt">
<span class="vars">$conn</span><span> = mysql_connect(‘localhost’, ‘test’, ‘test’); </span>
</li>
<li><span>mysql_select_db(‘test’); </span></li>
<li class="alt">
<span class="vars">$result</span><span> = mysql_query(</span><span class="vars">$sql</span><span>); </span>
</li>
<li>
<span class="keyword">while</span><span> (</span><span class="vars">$row</span><span> = mysql_fetch_object(</span><span class="vars">$result</span><span>)) </span>
</li>
<li class="alt">
<span class="vars">$datas</span><span>[] = </span><span class="vars">$row</span><span>; </span>
</li>
<li>
<span class="comment">// 将数据库中获取到的结果集数据保存到 memcached 中，以供下次访问时使用。 </span><span> </span>
</li>
<li class="alt">
<span class="vars">$mc</span><span>->add(</span><span class="vars">$key</span><span>, </span><span class="vars">$datas</span><span>); </span>
</li>
<li>
<span>} </span><span class="keyword">else</span><span> { </span>
</li>
<li class="alt">
<span class="func">echo</span><span> “n”.</span><span class="func">str_pad</span><span>(‘Read datas from memcached.’, 60, ‘_’).”n”; </span>
</li>
<li><span>} </span></li>
<li class="alt">
<span>var_dump(</span><span class="vars">$datas</span><span>); </span>
</li>
<li><span>?> </span></li>
</ol>PHP的缓冲器：
有eaccelerator， apc， PHPa，xcache，这个这个就不说了吧，搜索一堆一堆的，自己看啦，知道有这玩意就OK
MYSQL缓存：
这也算非代码级的，经典的数据库就是用的这种方式，看下面的运行时间，0.09xxx之类的
我贴段根据蓝色那家伙修改后部分my.ini 吧，2G的MYISAM表可以在0.05S左右，据说他前后改了有快一年
<ol class="dp-c"> <li class="alt"><span><span>[client] </span></span></li> <li><span>…… </span></li> <li class="alt"> <span class="keyword">default</span><span>-character-set=gbk </span> </li> <li> <span class="keyword">default</span><span>-storage-engine=MYISAM </span> </li> <li class="alt"><span>max_connections=600 </span></li> <li><span>max_connect_errors=500 </span></li> <li class="alt"><span>back_log=200 </span></li> <li><span>interactive_timeout=7200 </span></li> <li class="alt"><span>query_cache_size=64M </span></li> <li><span>…… </span></li> <li class="alt"><span>table_cache=512 </span></li> <li><span>…… </span></li> <li class="alt"><span>myisam_max_sort_file_size=100G </span></li> <li><span>myisam_max_extra_sort_file_size=100G </span></li> <li class="alt"><span>myisam_sort_buffer_size=128M </span></li> <li><span>key_buffer_size=1024M </span></li> <li class="alt"><span>read_buffer_size=512M </span></li> <li><span>…… </span></li> <li class="alt"><span>thread_concurrency=8 </span></li> </ol>
基于反向代理的Web缓存:
如Nginx，SQUID，mod_PRoxy(apache2以上又分为mod_proxy和mod_cache)
NGINX的例子
<ol class="dp-c">
<li class="alt"><span><span><nginx.conf> </nginx.conf></span></span></li>
<li><span>#user nobody; </span></li>
<li class="alt"><span>worker_processes 4; </span></li>
<li>
<span class="func">error_log</span><span> logs/error.log crit; </span>
</li>
<li class="alt"><span>pid logs/nginx.pid; </span></li>
<li><span>worker_rlimit_nofile 10240; </span></li>
<li class="alt"><span>events { </span></li>
<li>
<span class="keyword">use</span><span> epoll; </span>
</li>
<li class="alt"><span>worker_connections 51200; </span></li>
<li><span>} </span></li>
<li class="alt"><span>http { </span></li>
<li>
<span class="keyword">include</span><span> mime.types; </span>
</li>
<li class="alt"><span>default_type application/octet-stream; </span></li>
<li><span>sendfile on; </span></li>
<li class="alt"><span>keepalive_timeout 65; </span></li>
<li><span>tcp_nodelay on; </span></li>
<li class="alt"><span># server pool </span></li>
<li><span>upstream bspfrontsvr { </span></li>
<li class="alt"><span>server 10.10.10.224:80 weight=1; </span></li>
<li><span>server 10.10.10.221:80 weight=1; </span></li>
<li class="alt"><span>} </span></li>
<li><span> </span></li>
<li class="alt"><span>upstream bspimgsvr { </span></li>
<li><span>server 10.10.10.201:80 weight=1; </span></li>
<li class="alt"><span>} </span></li>
<li><span> </span></li>
<li class="alt"><span>upstream bspstylesvr { </span></li>
<li><span>server 10.10.10.202:80 weight=1; </span></li>
<li class="alt"><span>} </span></li>
<li><span> </span></li>
<li class="alt"><span>upstream bsphelpsvr { </span></li>
<li><span>server 10.10.10.204:80 weight=1; </span></li>
<li class="alt"><span>} </span></li>
<li><span> </span></li>
<li class="alt"><span>upstream bspwsisvr { </span></li>
<li><span>server 10.10.10.203:80 weight=1; </span></li>
<li class="alt"><span>} </span></li>
<li><span> </span></li>
<li class="alt"><span>upstream bspadminsvr { </span></li>
<li><span>server 10.10.10.222:80 weight=1; </span></li>
<li class="alt"><span>} </span></li>
<li><span> </span></li>
<li class="alt"><span>upstream bspbuyersvr { </span></li>
<li><span>server 10.10.10.223:80 weight=1; </span></li>
<li class="alt"><span>} </span></li>
<li><span> </span></li>
<li class="alt"><span>upstream bspsellersvr { </span></li>
<li><span>server 10.10.10.225:80 weight=1; </span></li>
<li class="alt"><span>} </span></li>
<li><span>upstream bsploginsvr { </span></li>
<li class="alt"><span>server 10.10.10.220:443 weight=1; </span></li>
<li><span>} </span></li>
<li class="alt"><span>upstream bspregistersvr { </span></li>
<li><span>server 10.10.10.220:80 weight=1; </span></li>
<li class="alt"><span>} </span></li>
<li>
<span>log_format test_com ‘</span><span class="vars">$remote_addr</span><span> – </span><span class="vars">$remote_user</span><span> [</span><span class="vars">$time_local</span><span>] “</span><span class="vars">$request</span><span>” ‘ </span>
</li>
<li class="alt">
<span>‘</span><span class="vars">$status</span><span> </span><span class="vars">$body_bytes_sent</span><span> “</span><span class="vars">$http_referer</span><span>” “</span><span class="vars">$http_user_agent</span><span>” ‘; </span>
</li>
<li><span>#——————————————————————– </span></li>
<li class="alt"><span>#img.test.com </span></li>
<li><span>server { </span></li>
<li class="alt"><span>listen 10.10.10.230:80; </span></li>
<li><span>server_name img.test.com; </span></li>
<li class="alt"><span>location / { </span></li>
<li>
<span>proxy_pass http:</span><span class="comment">//bspimgsvr; </span><span> </span>
</li>
<li class="alt">
<span class="keyword">include</span><span> proxy_setting.conf; </span>
</li>
<li><span>} </span></li>
<li class="alt"><span>access_log logs/img.log test_com; </span></li>
<li><span>} </span></li>
<li class="alt"><span> </span></li>
<li><span>#style.test.com </span></li>
<li class="alt"><span>server { </span></li>
<li><span>listen 10.10.10.230:80; </span></li>
<li class="alt"><span>server_name style.test.com; </span></li>
<li><span>location / { </span></li>
<li class="alt">
<span>proxy_pass http:</span><span class="comment">//bspstylesvr; </span><span> </span>
</li>
<li>
<span class="keyword">include</span><span> proxy_setting.conf; </span>
</li>
<li class="alt"><span>} </span></li>
<li><span>access_log logs/style.log test_com; </span></li>
<li class="alt"><span>} </span></li>
<li><span> </span></li>
<li class="alt"><span>#help.test.com </span></li>
<li><span>server { </span></li>
<li class="alt"><span>listen 10.10.10.230:80; </span></li>
<li><span>server_name help.test.com; </span></li>
<li class="alt"><span>location / { </span></li>
<li>
<span>proxy_pass http:</span><span class="comment">//bsphelpsvr; </span><span> </span>
</li>
<li class="alt">
<span class="keyword">include</span><span> proxy_setting.conf; </span>
</li>
<li><span>} </span></li>
<li class="alt"><span>access_log logs/help.log test_com; </span></li>
<li><span>} </span></li>
<li class="alt"><span> </span></li>
<li><span>#admin.test.com </span></li>
<li class="alt"><span>server { </span></li>
<li><span>listen 10.10.10.230:80; </span></li>
<li class="alt"><span>server_name admin.test.com; </span></li>
<li><span>location / { </span></li>
<li class="alt">
<span>proxy_pass http:</span><span class="comment">//bspadminsvr; </span><span> </span>
</li>
<li>
<span class="keyword">include</span><span> proxy_setting.conf; </span>
</li>
<li class="alt"><span>} </span></li>
<li><span>access_log logs/admin.log test_com; </span></li>
<li class="alt"><span>} </span></li>
<li><span> </span></li>
<li class="alt"><span>#buyer.test.com </span></li>
<li><span>server { </span></li>
<li class="alt"><span>listen 10.10.10.230:80; </span></li>
<li><span>server_name buyer.test.com; </span></li>
<li class="alt"><span>location / { </span></li>
<li>
<span>proxy_pass http:</span><span class="comment">//bspbuyersvr; </span><span> </span>
</li>
<li class="alt">
<span class="keyword">include</span><span> proxy_setting.conf; </span>
</li>
<li><span>} </span></li>
<li class="alt"><span>access_log logs/buyer.log test_com; </span></li>
<li><span>} </span></li>
<li class="alt"><span> </span></li>
<li><span>#seller.test.com </span></li>
<li class="alt"><span>server { </span></li>
<li><span>listen 10.10.10.230:80; </span></li>
<li class="alt"><span>server_name seller.test.com; </span></li>
<li><span>location / { </span></li>
<li class="alt">
<span>proxy_pass http:</span><span class="comment">//bspsellersvr; </span><span> </span>
</li>
<li>
<span class="keyword">include</span><span> proxy_setting.conf; </span>
</li>
<li class="alt"><span>} </span></li>
<li><span>access_log logs/seller.log test_com; </span></li>
<li class="alt"><span>} </span></li>
<li><span>#wsi.test.com </span></li>
<li class="alt"><span>server { </span></li>
<li><span>listen 10.10.10.230:80; </span></li>
<li class="alt"><span>server_name wsi.test.com; </span></li>
<li><span>location / { </span></li>
<li class="alt">
<span>proxy_pass http:</span><span class="comment">//bspwsisvr; </span><span> </span>
</li>
<li>
<span class="keyword">include</span><span> proxy_setting.conf; </span>
</li>
<li class="alt"><span>} </span></li>
<li><span>access_log logs/wsi.log test_com; </span></li>
<li class="alt"><span>} </span></li>
<li><span>#www.test.com </span></li>
<li class="alt"><span>server { </span></li>
<li><span>listen 10.10.10.230:80; </span></li>
<li class="alt"><span>server_name www.test.com *.test.com; </span></li>
<li><span>location ~ ^/NginxStatus/ { </span></li>
<li class="alt"><span>stub_status on; </span></li>
<li><span>access_log off; </span></li>
<li class="alt"><span>} </span></li>
<li><span>location / { </span></li>
<li class="alt">
<span>proxy_pass http:</span><span class="comment">//bspfrontsvr; </span><span> </span>
</li>
<li>
<span class="keyword">include</span><span> proxy_setting.conf; </span>
</li>
<li class="alt"><span>} </span></li>
<li><span>access_log logs/www.log test_com; </span></li>
<li class="alt"><span>error_page 500 502 503 504 /50x.html; </span></li>
<li><span>location = /50x.html { </span></li>
<li class="alt"><span>root html; </span></li>
<li><span>} </span></li>
<li class="alt"><span>} </span></li>
<li><span>#login.test.com </span></li>
<li class="alt"><span>server { </span></li>
<li><span>listen 10.10.10.230:443; </span></li>
<li class="alt"><span>server_name login.test.com; </span></li>
<li><span>ssl on; </span></li>
<li class="alt"><span>ssl_certificate cert.pem; </span></li>
<li><span>ssl_certificate_key cert.key; </span></li>
<li class="alt"><span>ssl_session_timeout 5m; </span></li>
<li><span>ssl_protocols SSLv2 SSLv3 TLSv1; </span></li>
<li class="alt">
<span>ssl_ciphers ALL:!ADH:!EXPORT56:RC4+RSA:+HIGH:+MEDIUM:+LOW:+SSLv2:+</span><span class="func">EXP</span><span>; </span>
</li>
<li><span>ssl_prefer_server_ciphers on; </span></li>
<li class="alt"><span>location / { </span></li>
<li>
<span>proxy_pass https:</span><span class="comment">//bsploginsvr; </span><span> </span>
</li>
<li class="alt">
<span class="keyword">include</span><span> proxy_setting.conf; </span>
</li>
<li><span>} </span></li>
<li class="alt"><span>access_log logs/login.log test_com; </span></li>
<li><span>} </span></li>
<li class="alt">
<span>#login.test.com </span><span class="keyword">for</span><span> register </span>
</li>
<li><span>server { </span></li>
<li class="alt"><span>listen 10.10.10.230:80; </span></li>
<li><span>server_name login.test.com; </span></li>
<li class="alt"><span>location / { </span></li>
<li>
<span>proxy_pass http:</span><span class="comment">//bspregistersvr; </span><span> </span>
</li>
<li class="alt">
<span class="keyword">include</span><span> proxy_setting.conf; </span>
</li>
<li><span>} </span></li>
<li class="alt"><span>access_log logs/register.log test_com; </span></li>
<li><span>} </span></li>
<li class="alt"><span> </span></li>
<li><span>} </span></li>
<li class="alt"><span><conf> </conf></span></li>
<li><span>proxy_redirect off; </span></li>
<li class="alt">
<span>proxy_set_header Host </span><span class="vars">$host</span><span>; </span>
</li>
<li>
<span>proxy_set_header X-Real-IP </span><span class="vars">$remote_addr</span><span>; </span>
</li>
<li class="alt">
<span>proxy_set_header X-Forwarded-For </span><span class="vars">$proxy_add_x_forwarded_for</span><span>; </span>
</li>
<li><span>client_max_body_size 10m; </span></li>
<li class="alt"><span>client_body_buffer_size 128k; </span></li>
<li><span>proxy_connect_timeout 90; </span></li>
<li class="alt"><span>proxy_send_timeout 90; </span></li>
<li><span>proxy_read_timeout 90; </span></li>
<li class="alt"><span>proxy_buffer_size 4k; </span></li>
<li><span>proxy_buffers 4 32k; </span></li>
<li class="alt"><span>proxy_busy_buffers_size 64k; </span></li>
<li><span>proxy_temp_file_write_size 64k; </span></li>
<li class="alt"><span>mod_proxy的例子： </span></li>
<li><span> </span></li>
<li class="alt"><span><virtualhost> </virtualhost></span></li>
<li><span>ServerName www.zxsv.com </span></li>
<li class="alt"><span>ServerAdmin admin@zxsv.com </span></li>
<li><span># reverse proxy setting </span></li>
<li class="alt">
<span>ProxyPass / http:</span><span class="comment">//www.zxsv.com:8080/ </span><span> </span>
</li>
<li>
<span>ProxyPassReverse / http:</span><span class="comment">//www.zxsv.com:8080/ </span><span> </span>
</li>
<li class="alt"><span># cache dir root </span></li>
<li>
<span>CacheRoot “/</span><span class="keyword">var</span><span>/www/proxy” </span>
</li>
<li class="alt"><span># max cache storage </span></li>
<li><span>CacheSize 50000000 </span></li>
<li class="alt"><span># hour: every 4 hour </span></li>
<li><span>CacheGcInterval 4 </span></li>
<li class="alt"><span># max page expire time: hour </span></li>
<li><span>CacheMaxExpire 240 </span></li>
<li class="alt"><span># Expire time = (now – last_modified) * CacheLastModifiedFactor </span></li>
<li><span>CacheLastModifiedFactor 0.1 </span></li>
<li class="alt"><span># defalt expire tag: hour </span></li>
<li><span>CacheDefaultExpire 1 </span></li>
<li class="alt"><span># force complete after precent of content retrived: 60-90% </span></li>
<li><span>CacheForceCompletion 80 </span></li>
<li class="alt"><span>CustomLog /usr/local/apache/logs/dev_access_log combined </span></li>
<li><span> </span></li>
</ol>而SQUID的例子我就不说明了，这方面网上有写的太多，大家自己搜索一下
DNS轮询：
BIND是一款开放源码的DNS服务器软件，这个要说起来就大了，自己搜索去，大家知道有这个东西就行了。
我知道的有chinacache 等大站就是这样做的，说简单点就是多服务器啦，把同一个页面或文件缓存到不同的服务器上，按南北自动解析到相关的服务器中。
http://www.cnblogs.com/cnblogs20112011/archive/2011/01/27/1946286.html
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