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覺得累就是進步的開始!

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= NTD$1813

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Shell script syntax

Bourne shell (sh) syntax samples

test:
[ number -lt|-le|-eq|-ne|-ge|-gt number ]
[ string = != string ]

if [ test ]
then
   commands
elif [ test ]
   commands
else
   commands
fi

for var in item1 item2 item3
do
  commands
done

while test
do
  commands
done

case expression in
  case1)         commands ;;
  case2|case3)   commands ;;
  *)             default-commands ;;
esac

# How to read an input file into shell variables:
while read variable1 variable2
do
  ...
done < $input_file

# How to redirect stdout/stderr
echo something 1>&2
echo something 2>&1

# How to throw out stdout and stderr
some_command > /dev/null 2>&1

# Shell functions:
func () {
	echo $1 $2 $3
}
func a b c

C shell (csh) syntax samples

test:
( expression ==|!=|>>|<< expression )

if ( test ) command

if ( test ) then
   commands
else if ( test ) then
   commands
else
   commands
end if

foreach var ( list list list )
  commands
end

while condition
   commands
end

# How to throw out stdout and stderr
some_command >& /dev/null

另一個

#!/bin/sh
count=0
while [ $count -lt 5 ]
do
  count=`expr $count + 1`
  echo $count
done

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net.ipv4.ip_local_port_range = 1024 65536
net.core.rmem_max=16777216
net.core.wmem_max=16777216
net.ipv4.tcp_rmem=4096 87380 16777216
net.ipv4.tcp_wmem=4096 65536 16777216
net.ipv4.tcp_fin_timeout = 3
net.ipv4.tcp_tw_recycle = 1
net.core.netdev_max_backlog = 30000
net.ipv4.tcp_no_metrics_save=1
net.core.somaxconn = 262144
net.ipv4.tcp_syncookies = 0
net.ipv4.tcp_max_orphans = 262144
net.ipv4.tcp_max_syn_backlog = 262144
net.ipv4.tcp_synack_retries = 2
net.ipv4.tcp_syn_retries = 2

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據說用 3台 varnish 可以抵 12台 squid 來用 , 有時間要來玩一下.

http://varnish.projects.linpro.no/

Varnish is a state-of-the-art, high-performance HTTP accelerator. It uses the advanced features in Linux 2.6, FreeBSD 6/7 and Solaris 10 to achieve its high performance.

Some of the features include

• A modern design
• VCL – a very flexible configuration language
• Load balancing with health checking of backends
• Partial support for ESI
• URL rewriting
• Graceful handling of "dead" backends
• more features…

Varnish is free software and is licenced under a modified BSD licence. Please read the introduction to get started with Varnish.

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這是簡單版的架構, http flow:

其實, 裝起來並沒有想像中複雜, 只是準備一個測試環境比較麻煩些罷了–> vmware 又幫了我不少忙

參考他的 online document:
http://haproxy.1wt.eu/download/1.3/doc/haproxy-en.txt

及架構圖
http://haproxy.1wt.eu/download/1.3/doc/architecture.txt

略翻完這兩個文件就可以來測試了 , 首先準備三台 web server : webA 到 webC , 然後還要一台 server 當 haproxy server 這台不用跑 apache , 安裝 haproxy 很簡單, 在 gentoo 就是 emerge –av haproxy , 設定檔要自己建 (放到 /etc/ )

我的 /etc/haproxy.cnf

listen webfarm 172.30.0.235:80
monitor-uri /haproxy_status
stats uri /stats
stats auth admin:admin
mode http
balance roundrobin
cookie SERVERID insert indirect
option httpchk HEAD /index.php HTTP/1.0
server webA 172.30.0.206:80 cookie A check
server webB 172.30.0.227:80 cookie B check
server webC 172.30.0.228:80 cookie C check

第一次連上後, haproxy 如他的 menual 寫的 , 會丟一個 cookie 給 client , 作為下次要連的實體 server 的依據 , 我把那台 apache 停掉, 果然就連到別去了 , 然後 phpinfo 中值得紀錄的是:

SERVER_NAME 就是 haproxy.cfg 中寫的 listen 的 IP , 然後 , SERVER_ADDR 就是實體連到的 apache 的 IP , haproxy 會不停的丟 HTTP/1.0 的 HEAD 取得 apache 是否還活著.

在 webA-C 的 aapache access log 中若 沒特別改的話, 就是紀錄 haproxy server 的 IP address

….

好了! 實驗完成了!

結論, HAProxy 在他的官網寫說他:

“ 提供一個免費/快速的 HA / LOAD BALANCE 方案 , 可是我覺得他僅能夠說 HA / BALANCE (並沒有很徹底的偵測 server loading) , 並且在 SPF 方面也並沒有很好的解決辦法.

不過呢, 至少 HAProxy 比 DNS roundrobin 還好.

各種 LOAD BALANCE 方案 評估表

過了一個晚上想了想 , 即使 Citrix / Alteon / Foundry 這些 SLB hardware device 也沒有做到真正的 loading detective , 所以就一個免費又高容量的 HAProxy 來說, 算是很好的 SLB 解決方案了.

ㄎㄎ 有做過 HAProxy 實驗的都會貼這一張:

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雖然我已經會了 ,  但是看到這個Vi-vim Cheat Sheet 還是蠻好奇的把它收錄下來

完整的請看原網站 , from : http://www.viemu.com/a_vi_vim_graphical_cheat_sheet_tutorial.html

發覺一般人只要會 1/3 , 就算上手了 , 可以拿 vi 衝了 . . .

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[youtube]http://www.youtube.com/watch?v=udivD0kzWUI[/youtube] (more…)

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FILE* fp = fopen(path, "r");
if (fp) {
    // file exists
    fclose(fp);
} else {
    // file doesn't exist
}

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起因是不想要動到舊的程式碼 , 若用 mysql-proxy 把讀寫分離出來 , 那舊的程式連接資料庫的 connect 段就不用改了 , 而且 mysql-proxy 官網還寫了不少好處:

- load balancing
- failover
- query analysis
- query filtering and modification
and many more.

好早就想要試看看了! 首先要先建制一個 master/slave 的 mysql 架構 – 設定 mysql 成 master / slave 架構

在 gentoo 中 , 用 emerge –av mysql-proxy 把 目前版本 0.61 裝進來 , 然後 /etc/conf.d/mysql-proxy 的設定如下

# /etc/conf.d/mysql-proxy: config file for /etc/init.d/mysql-proxy

# location auf pidfile
PIDFILE="/var/run/mysql-proxy.pid"

# general options for mysql-proxy
OPTS="--proxy-lua-script=/root/tutorial-keepalive.lua
--proxy-backend-addresses=172.30.0.182:3306
--proxy-read-only-backend-addresses=172.30.0.183:3306
"
#OPTS="/root/mysql-proxy.lua"

# if you want mysql-proxy to depend on mysql, enable this:
#RC_NEED="mysql"

這邊的 tutorial-keepalive.lua 可以到 http://svn.mysql.com/svnpublic/mysql-proxy/trunk/examples/tutorial-keepalive.lua下載

參考 http://jan.kneschke.de/2007/8/1/mysql-proxy-learns-r-w-splitting

O’Reilly 有一些 lua 的 sample : http://www.oreillynet.com/pub/a/databases/2007/07/12/getting-started-with-mysql-proxy.html?page=4

MySQL 官網的 FAQ : http://dev.mysql.com/doc/refman/5.0/en/mysql-proxy-faq.html

http://dev.mysql.com/doc/refman/5.0/en/mysql-proxy.html

在 January 30th, 2009 , MySQL Proxy 有新版了  from 0.6.1 to 0.7.0

http://jan.kneschke.de/2009/1/30/mysql-proxy-from-0-6-1-to-0-7-0

另外 Lua 是一種簡單/快速的 script language , mysql proxy snippets

最後看到有個問題 : “SPoF” , Sigle Point of Failure , 我看如果要用 mysql proxy 還是有得搞了 … 暫時打住吧!

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