8 Years in Beijing

8.

setlock

setlock - runs another program with a file locked.

setlock [-nNxX] fn child，简单说 setlock 会打开 fn 并加锁，然后执行 child。如果 lock 失败，可以指定 child 退出或等待：

-n: fn 被其他进程锁住，setlock 放弃执行 child
-N: fn 被其他进程锁住，setlock 会等待，直到重新加锁，并执行 child
-x: fn 打开失败或已加锁，setlock exit 0
-X: fn 打开失败或已加锁，setlock 输出错误并退出

setlock 可以和 crontab 搭配使用，比如某个任务每十分钟执行一次，如果上一次执行尚未退出，不再开启新任务:

*/10 * * * * /usr/bin/setlock -n /tmp/test.lock /home/x.sh

Stop

Stop, 是一个行程的中止。

Stop，也是一个站点，下车，上车，继续前进。

2010.6 - 2018.5.

Nginx + Websocket

upstream ws {
    server 127.0.0.1:8080;
    server 127.0.0.1:8081;
}

server {
    listen  8090;

    location / {
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "upgrade";

        proxy_pass http://ws;
    }
}

在 Nginx reload 的时候，socket 连接并不会中断。

Quote

什么都不放弃实际上是怕放弃后自己什么都没有，无所畏惧的人生要敢于放弃。

via

Linux Performance Analysis in 60s

uptime/w --------------------> load average
dmesg | tail ----------------> kernel errors
vmstat 1 --------------------> overall stats every second
mpstat -P ALL 1 -------------> CPU balance
pidstat 1 -------------------> process usage, every second
iostat -xz 1 ----------------> disk I/O
free -m ---------------------> memory usage
sar -n DEV 1 ----------------> network I/O
sar -n TCP,ETCP 1 -----------> TCP stats
top -------------------------> check overview

dmidecode

You can use dmidecode to display server physical info, for example RAM max capacity.

dmidecode -t 16

Handle 0x0032, DMI type 16, 15 bytes
Physical Memory Array
	Location: System Board Or Motherboard
	Use: System Memory
	Error Correction Type: Multi-bit ECC
	Maximum Capacity: 48 GB
	Error Information Handle: Not Provided
	Number Of Devices: 6

App Store Front Code

X-Apple-Store-Front header is needed to scrape in App Store.

CN 143465-19,29
US 143441-1,29
JP 143462-9,29
KR 143466-13,29
HK 143463-18,29
AU 143460,29
TW 143470-18,29
CA 143455-6,29

App info:

curl -H 'x-apple-store-front: 143465-19,29' 'https://itunes.apple.com/cn/app/id1318151064?mt=8'

Top Free iPhone Apps:

curl -H 'x-apple-store-front: 143465-0,9' 'https://itunes.apple.com/WebObjects/MZStore.woa/wa/topChartFragmentData?=&popId=27&pageNumbers=0&pageSize=1000'

curl -H 'x-apple-store-front: 143465-19,29' 'https://itunes.apple.com/WebObjects/MZStore.woa/wa/viewTop?id=25204&popId=27&genreId=36'

Nginx map

map $room $room_server {
    default 192.168.1.101:8080;
    1 192.168.1.101:8080;
    2 192.168.1.102:8080;
}

server {
    listen  80;

    location ~ /api/(\d+)/room {
        set $room $1;
        echo $room_server;
    }
}

Shell Notes

&& || ; in shell command:

  • cmd1 && cmd2 means cmd2 will only run while cmd1 success.
  • cmd1 || cmd2 means cmd2 will only run while fmd1 fails.
  • cmd1 ; cmd2 will run cmd2 regardless cmd1 success or not.