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varnish

Web Page Cache:

squid –> varnish
程序的运行具有局部性特征:
时间局部性:一个数据被访问过之后,可能很快会被再次访问
空间局部性:一个数据被访问时,其周边的数据也有可能被访问到

cache:命中
热区:局部性;
时效性:
缓存空间耗尽:LRU
过期:缓存清理

缓存命中率:hit/(hit+miss)
(0,1)
页面命中率:基于页面数量进行衡量
字节命中率:基于页面的体积进行衡量

缓存与否:
私有数据:private,private cache;
公共数据:public, public or private cache;

Cache-related Headers Fields
The most important caching header fields are:

Expires:过期时间;
Expires:Thu, 22 Oct 2026 06:34:30 GMT
Cache-Control:max-age=

Etag
If-None-Match

Last-Modified
If-Modified-Since

Vary
Age

缓存有效性判断机制:
过期时间:Expires
HTTP/1.0
Expires
HTTP/1.1
Cache-Control: maxage=
Cache-Control: s-maxage=
条件式请求:
Last-Modified/If-Modified-Since
Etag/If-None-Match 

Expires:Thu, 13 Aug 2026 02:05:12 GMT
Cache-Control:max-age=315360000
ETag:”1ec5-502264e2ae4c0″
Last-Modified:Wed, 03 Sep 2014 10:00:27 GMT

缓存层级:
私有缓存:用户代理附带的本地缓存机制;
公共缓存:反向代理服务器的缓存功能;

User-Agent <–> private cache <–> public cache <–> public cache 2 <–> Original Server

请求报文用于通知缓存服务如何使用缓存响应请求:
cache-request-directive = 
“no-cache”,                        
| “no-store”                         
| “max-age” “=” delta-seconds        
| “max-stale” [ “=” delta-seconds ]  
| “min-fresh” “=” delta-seconds      
| “no-transform”                    
| “only-if-cached”                  
| cache-extension                    

响应报文用于通知缓存服务器如何存储上级服务器响应的内容:
cache-response-directive =
“public”                               
| “private” [ “=” <“> 1#field-name <“> ] 
| “no-cache” [ “=” <“> 1#field-name <“> ],可缓存,但响应给客户端之前需要revalidation;
| “no-store” ,不允许存储响应内容于缓存中;                           
| “no-transform”                        
| “must-revalidate”                     
| “proxy-revalidate”                  
| “max-age” “=” delta-seconds           
| “s-maxage” “=” delta-seconds          
| cache-extension     

开源解决方案:
squid:
varnish:

varnish官方站点: http://www.varnish-cache.org/
Community
Enterprise

This is Varnish Cache, a high-performance HTTP accelerator. 

程序架构:
Manager进程
Cacher进程,包含多种类型的线程:
accept, worker, expiry, … 
shared memory log:
统计数据:计数器;
日志区域:日志记录;
varnishlog, varnishncsa, varnishstat… 

配置接口:VCL
Varnish Configuration Language, 
vcl complier –> c complier –> shared object 

varnish的程序环境:
/etc/varnish/varnish.params: 配置varnish服务进程的工作特性,例如监听的地址和端口,缓存机制;
/etc/varnish/default.vcl:配置各Child/Cache线程的缓存工作属性;
主程序:
/usr/sbin/varnishd
CLI interface:
/usr/bin/varnishadm
Shared Memory Log交互工具:
/usr/bin/varnishhist
/usr/bin/varnishlog
/usr/bin/varnishncsa
/usr/bin/varnishstat
/usr/bin/varnishtop
测试工具程序:
/usr/bin/varnishtest
VCL配置文件重载程序:
/usr/sbin/varnish_reload_vcl
Systemd Unit File:
/usr/lib/systemd/system/varnish.service
varnish服务
/usr/lib/systemd/system/varnishlog.service
/usr/lib/systemd/system/varnishncsa.service
日志持久的服务;

varnish的缓存存储机制( Storage Types):
-s [name=]type[,options]

· malloc[,size]
内存存储,[,size]用于定义空间大小;重启后所有缓存项失效;
· file[,path[,size[,granularity]]]
文件存储,黑盒;重启后所有缓存项失效;
· persistent,path,size
文件存储,黑盒;重启后所有缓存项有效;实验;

varnish程序的选项:
程序选项:/etc/varnish/varnish.params文件
-a address[:port][,address[:port][…],默认为6081端口; 
-T address[:port],默认为6082端口;
-s [name=]type[,options],定义缓存存储机制;
-u user
-g group
-f config:VCL配置文件;
-F:运行于前台;

运行时参数:/etc/varnish/varnish.params文件, DEAMON_OPTS
DAEMON_OPTS=”-p thread_pool_min=5 -p thread_pool_max=500 -p thread_pool_timeout=300″

-p param=value:设定运行参数及其值; 可重复使用多次;
-r param[,param…]: 设定指定的参数为只读状态; 

重载vcl配置文件:
~ ]# varnish_reload_vcl

varnishadm
-S /etc/varnish/secret -T [ADDRESS:]PORT 
      
help [<command>]
ping [<timestamp>]
auth <response>
quit
banner
status
start
stop
vcl.load <configname> <filename>
vcl.inline <configname> <quoted_VCLstring>
vcl.use <configname>
vcl.discard <configname>
vcl.list
param.show [-l] [<param>]
param.set <param> <value>
panic.show
panic.clear
storage.list
vcl.show [-v] <configname>
backend.list [<backend_expression>]
backend.set_health <backend_expression> <state>
ban <field> <operator> <arg> [&& <field> <oper> <arg>]…
ban.list

配置文件相关:
vcl.list 
vcl.load:装载,加载并编译;
vcl.use:激活;
vcl.discard:删除;
vcl.show [-v] <configname>:查看指定的配置文件的详细信息;

运行时参数:
param.show -l:显示列表;
param.show <PARAM>
param.set <PARAM> <VALUE>

缓存存储:
storage.list

后端服务器:
backend.list 

VCL:
”域“专有类型的配置语言;

state engine:状态引擎;

VCL有多个状态引擎,状态之间存在相关性,但状态引擎彼此间互相隔离;每个状态引擎可使用return(x)指明关联至哪个下一级引擎;每个状态引擎对应于vcl文件中的一个配置段,即为subroutine

vcl_hash –> return(hit) –> vcl_hit

Client Side:
vcl_recv, vcl_pass, vcl_hit, vcl_miss, vcl_pipe, vcl_purge, vcl_synth, vcl_deliver

vcl_recv:
hash:vcl_hash
pass: vcl_pass 
pipe: vcl_pipe
synth: vcl_synth
purge: vcl_hash –> vcl_purge

vcl_hash:
lookup:
hit: vcl_hit
miss: vcl_miss
pass, hit_for_pass: vcl_pass
purge: vcl_purge

Backend Side:
vcl_backend_fetch, vcl_backend_response, vcl_backend_error

两个特殊的引擎:
vcl_init:在处理任何请求之前要执行的vcl代码:主要用于初始化VMODs;
vcl_fini:所有的请求都已经结束,在vcl配置被丢弃时调用;主要用于清理VMODs;

vcl的语法格式:
(1) VCL files start with vcl 4.0;
(2) //, # and /* foo / for comments;
(3) Subroutines are declared with the sub keyword; 例如sub vcl_recv { …};
(4) No loops, state-limited variables(受限于引擎的内建变量);
(5) Terminating statements with a keyword for next action as argument of the return() function, i.e.: return(action);用于实现状态引擎转换; 
(6) Domain-specific;

The VCL Finite State Machine
(1) Each request is processed separately;
(2) Each request is independent from others at any given time;
(3) States are related, but isolated;
(4) return(action); exits one state and instructs Varnish to proceed to the next state;
(5) Built-in VCL code is always present and appended below your own VCL;

三类主要语法:
sub subroutine {

}

if CONDITION {

} else {

}

return(), hash_data()

VCL Built-in Functions and Keywords
函数:
regsub(str, regex, sub)
regsuball(str, regex, sub)
ban(boolean expression)
hash_data(input)
synthetic(str)

Keywords:
call subroutine, return(action),new,set,unset 

操作符:
==, !=, ~, >, >=, <, <=
逻辑操作符:&&, ||, !
变量赋值:=

举例:obj.hits
if (obj.hits>0) {
set resp.http.X-Cache = “HIT via ” + server.ip;
} else {
set resp.http.X-Cache = “MISS via ” + server.ip;
}

变量类型:
内建变量:
req.
:request,表示由客户端发来的请求报文相关;
req.http.
req.http.User-Agent, req.http.Referer, …
bereq.
:由varnish发往BE主机的httpd请求相关;
bereq.http.
beresp.
:由BE主机响应给varnish的响应报文相关;
beresp.http.
resp.
:由varnish响应给client相关;
obj.:存储在缓存空间中的缓存对象的属性;只读;

常用变量:
bereq.
, req.
bereq.http.HEADERS
bereq.request:请求方法;
bereq.url:请求的url;
bereq.proto:请求的协议版本;
bereq.backend:指明要调用的后端主机;

req.http.Cookie:客户端的请求报文中Cookie首部的值; 
req.http.User-Agent ~ “chrome”

beresp., resp.
beresp.http.HEADERS
beresp.status:响应的状态码;
reresp.proto:协议版本;
beresp.backend.name:BE主机的主机名;
beresp.ttl:BE主机响应的内容的余下的可缓存时长;

obj.
obj.hits:此对象从缓存中命中的次数;
obj.ttl:对象的ttl值

server.
server.ip
server.hostname
client.

client.ip

用户自定义:
set 
unset 

示例1:强制对某类资源的请求不检查缓存:
vcl_recv {
if (req.url ~ “(?i)^/(login|admin)”) {
return(pass);
}
}

示例2:对于特定类型的资源,例如公开的图片等,取消其私有标识,并强行设定其可以由varnish缓存的时长; 
if (beresp.http.cache-control !~ “s-maxage”) {
if (bereq.url ~ “(?i).(jpg|jpeg|png|gif|css|js)$”) {
unset beresp.http.Set-Cookie;
set beresp.ttl = 3600s;
}
}

示例3:
if (req.restarts == 0) {
if (req.http.X-Fowarded-For) {
set req.http.X-Forwarded-For = req.http.X-Forwarded-For + “,” + client.ip;
} else {
set req.http.X-Forwarded-For = client.ip;
}
}

缓存对象的修剪:purge, ban 
(1) 能执行purge操作
sub vcl_purge {
return (synth(200,”Purged”));
}

(2) 何时执行purge操作
sub vcl_recv {
if (req.method == “PURGE”) {
return(purge);
}

}

添加此类请求的访问控制法则:
acl purgers {
“127.0.0.0”/8;
“10.1.0.0”/16;
}

sub vcl_recv {
if (req.method == “PURGE”) {
if (!client.ip ~ purgers) {
return(synth(405,”Purging not allowed for ” + client.ip));
}
return(purge);
}

}

如何设定使用多个后端主机:
backend default {
.host = “172.16.100.6”;
.port = “80”;
}

backend appsrv {
.host = “172.16.100.7”;
.port = “80”;
}

sub vcl_recv {
if (req.url ~ “(?i).php$”) {
set req.backend_hint = appsrv;
} else {
set req.backend_hint = default;
}


}

Director:
varnish module; 
使用前需要导入:
import directors;

示例:
import directors;    # load the directors

backend server1 {
.host = 
.port = 
}
backend server2 {
.host = 
.port = 
}

sub vcl_init {
new GROUP_NAME = directors.round_robin();
GROUP_NAME.add_backend(server1);
GROUP_NAME.add_backend(server2);
}

sub vcl_recv {

send all traffic to the bar director:

set req.backend_hint = GROUP_NAME.backend();
}

BE Health Check:
backend BE_NAME {
.host =  
.port = 
.probe = {
.url= 
.timeout= 
.interval= 
.window=
.threshold=
}
}

.probe:定义健康状态检测方法;
.url:检测时请求的URL,默认为”/”; 
.request:发出的具体请求;
.request = 
“GET /.healthtest.html HTTP/1.1”
“Host: www.magedu.com”
“Connection: close”
.window:基于最近的多少次检查来判断其健康状态; 
.threshhold:最近.window中定义的这么次检查中至有.threshhold定义的次数是成功的;
.interval:检测频度; 
.timeout:超时时长;
.expected_response:期望的响应码,默认为200;

健康状态检测的配置方式:
(1) probe PB_NAME = { }
    backend NAME = {
.probe = PB_NAME;

    }
    
(2) backend NAME  {
.probe = {

}
}

示例:
probe check {
.url = “/.healthcheck.html”;
.window = 5;
.threshold = 4;
.interval = 2s;
.timeout = 1s;
}

backend default {
.host = “10.1.0.68”;
.port = “80”;
.probe = check;
}

backend appsrv {
.host = “10.1.0.69”;
.port = “80”;
.probe = check;
}

varnish的运行时参数:
线程模型:
cache-worker
cache-main
ban lurker
acceptor:
epoll/kqueue:

线程相关的参数:
在线程池内部,其每一个请求由一个线程来处理; 其worker线程的最大数决定了varnish的并发响应能力;

thread_pools:Number of worker thread pools. 最好小于或等于CPU核心数量; 
thread_pool_max:The maximum number of worker threads in each pool. 每线程池的最大线程数;
thread_pool_min:The minimum number of worker threads in each pool. 额外意义为“最大空闲线程数”;

最大并发连接数=thread_pools  * thread_pool_max

thread_pool_timeout:Thread idle threshold.  Threads in excess of thread_pool_min, which have been idle for at least this long, will be destroyed.
thread_pool_add_delay:Wait at least this long after creating a thread.
thread_pool_destroy_delay:Wait this long after destroying a thread.

设置方式:
vcl.param 
param.set

永久有效的方法:
varnish.params
DEAMON_OPTS=”-p PARAM1=VALUE -p PARAM2=VALUE”

varnish日志区域:
shared memory log 
计数器
日志信息

1、varnishstat – Varnish Cache statistics
-1
-1 -f FILED_NAME 
-l:可用于-f选项指定的字段名称列表;

MAIN.cache_hit 
MAIN.cache_miss

varnishstat -1 -f MAIN.cache_hit -f MAIN.cache_miss

varnishstat -l -f MAIN -f MEMPOOL

2、varnishtop – Varnish log entry ranking
-1     Instead of a continously updated display, print the statistics once and exit.
-i taglist,可以同时使用多个-i选项,也可以一个选项跟上多个标签;
-I <[taglist:]regex>
-x taglist:排除列表
-X  <[taglist:]regex>

3、varnishlog – Display Varnish logs

4、 varnishncsa – Display Varnish logs in Apache / NCSA combined log format

内建函数:
hash_data():指明哈希计算的数据;减少差异,以提升命中率;
regsub(str,regex,sub):把str中被regex第一次匹配到字符串替换为sub;主要用于URL Rewrite
regsuball(str,regex,sub):把str中被regex每一次匹配到字符串均替换为sub;
return():
ban(expression) 
ban_url(regex):Bans所有的其URL可以被此处的regex匹配到的缓存对象;
synth(status,”STRING”):purge操作;

总结:
varnish: state engine, vcl 
varnish 4.0:
vcl_init 
vcl_recv
vcl_hash 
vcl_hit 
vcl_pass
vcl_miss 
vcl_pipe 
vcl_waiting
vcl_purge 
vcl_deliver
vcl_synth
vcl_fini

vcl_backend_fetch
vcl_backend_response
vcl_backend_error 

sub VCL_STATE_ENGINE {

}
backend BE_NAME {} 
probe PB_NAME {}
acl ACL_NAME {}

博客作业:以上所有内容; 
实战项目:两个lamp部署wordpress,用Nginx反代,做压测;nginx后部署varnish缓存,调整vcl,多次压测;
课外实践:(1) zabbix监控varnish业务指标;
 (2) ansible实现varnish快速部署; 

 
ab, http_load, webbench, seige, jmeter, loadrunner,…

 

原创文章,作者:shewei,如若转载,请注明出处:/76700

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