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PHP日期对应的二十四节气显示

作者: Joyber
时间: 2022-07-13
分类: 默认分类
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/**
     *
     *  二十四节气通用的新算法
     *
     *
     *
     *
     * */
 
 
    function solar_term($years,$mon,$mday)
    {
        $solar_term = array(
            0=>array(621, 419, 621, 521, 622, 622, 823, 824, 824, 924, 823, 822), //1901
            1=>array(621, 519, 621, 621, 622, 722, 824, 824, 824, 924, 823, 823), //1902
            2=>array(621, 520, 722, 621, 722, 722, 824, 924, 924, 924, 823, 823), //1903
            3=>array(721, 520, 621, 520, 621, 622, 723, 823, 823, 824, 823, 722), //1904
            4=>array(621, 419, 621, 521, 622, 622, 823, 824, 824, 924, 823, 822), //1905
            5=>array(621, 519, 621, 621, 622, 622, 824, 824, 824, 924, 823, 823), //1906
            6=>array(621, 520, 722, 621, 722, 722, 824, 924, 924, 924, 823, 823), //1907
            7=>array(721, 520, 621, 520, 621, 622, 723, 823, 823, 924, 823, 722), //1908
            8=>array(621, 419, 621, 521, 622, 622, 823, 824, 824, 924, 823, 822), //1909
            9=>array(621, 519, 621, 621, 622, 622, 824, 824, 824, 924, 823, 823), //1910
            10=>array(621, 520, 722, 621, 722, 722, 824, 924, 924, 924, 823, 823), //1911
            11=>array(721, 520, 621, 520, 621, 622, 723, 823, 823, 924, 823, 722), //1912
            12=>array(620, 419, 621, 521, 622, 622, 823, 824, 824, 924, 823, 822), //1913
            13=>array(621, 419, 621, 521, 622, 622, 824, 824, 824, 924, 823, 823), //1914
            14=>array(621, 520, 622, 621, 622, 722, 824, 824, 924, 924, 823, 823), //1915
            15=>array(621, 520, 621, 520, 621, 622, 723, 823, 823, 824, 822, 722), //1916
            16=>array(620, 419, 621, 521, 621, 622, 823, 824, 823, 924, 823, 722), //1917
            17=>array(621, 419, 621, 521, 622, 622, 824, 824, 824, 924, 823, 822), //1918
            18=>array(621, 520, 622, 621, 622, 722, 824, 824, 924, 924, 823, 823), //1919
            19=>array(621, 520, 621, 520, 621, 622, 723, 823, 823, 824, 822, 722), //1920
            20=>array(620, 419, 621, 520, 621, 622, 823, 824, 823, 924, 823, 722), //1921
            21=>array(621, 419, 621, 521, 622, 622, 824, 824, 824, 924, 823, 822), //1922
            22=>array(621, 519, 621, 621, 622, 722, 824, 824, 924, 924, 823, 823), //1923
            23=>array(621, 520, 621, 520, 621, 622, 723, 823, 823, 824, 822, 722), //1924
            24=>array(620, 419, 621, 520, 621, 622, 823, 824, 823, 924, 823, 722), //1925
            25=>array(621, 419, 621, 521, 622, 622, 823, 824, 824, 924, 823, 822), //1926
            26=>array(621, 519, 621, 621, 622, 722, 824, 824, 824, 924, 823, 823), //1927
            27=>array(621, 520, 621, 520, 621, 621, 723, 823, 823, 823, 722, 722), //1928
            28=>array(620, 419, 621, 520, 621, 622, 723, 823, 823, 824, 822, 722), //1929
            29=>array(621, 419, 621, 521, 622, 622, 823, 824, 824, 924, 823, 822), //1930
            30=>array(621, 519, 621, 621, 622, 722, 824, 824, 824, 924, 823, 823), //1931
            31=>array(621, 520, 621, 520, 621, 621, 723, 823, 823, 823, 722, 722), //1932
            32=>array(620, 419, 621, 520, 621, 622, 723, 823, 823, 924, 823, 722), //1933
            33=>array(621, 419, 621, 521, 622, 622, 823, 824, 824, 924, 823, 822), //1934
            34=>array(621, 519, 621, 621, 622, 622, 824, 824, 824, 924, 823, 823), //1935
            35=>array(621, 520, 621, 520, 621, 621, 723, 823, 823, 823, 722, 722), //1936
            36=>array(620, 419, 621, 520, 621, 622, 723, 823, 823, 924, 823, 722), //1937
            37=>array(621, 419, 621, 521, 622, 622, 823, 824, 824, 924, 823, 822), //1938
            38=>array(621, 519, 621, 621, 622, 622, 824, 824, 824, 924, 823, 823), //1939
            39=>array(621, 520, 621, 520, 621, 621, 723, 823, 823, 823, 722, 722), //1940
            40=>array(620, 419, 621, 520, 621, 622, 723, 823, 823, 924, 823, 722), //1941
            41=>array(621, 419, 621, 521, 622, 622, 823, 824, 824, 924, 823, 822), //1942
            42=>array(621, 519, 621, 621, 622, 622, 824, 824, 824, 924, 823, 823), //1943
            43=>array(621, 520, 621, 520, 521, 621, 723, 823, 823, 823, 722, 722), //1944
            44=>array(620, 419, 621, 520, 621, 622, 723, 823, 823, 824, 822, 722), //1945
            45=>array(620, 419, 621, 521, 622, 622, 823, 824, 823, 924, 823, 822), //1946
            46=>array(621, 419, 621, 521, 622, 622, 824, 824, 824, 924, 823, 823), //1947
            47=>array(621, 520, 521, 520, 521, 621, 723, 723, 823, 823, 722, 722), //1948
            48=>array(520, 419, 621, 520, 621, 622, 723, 824, 823, 824, 822, 722), //1949
            49=>array(620, 419, 621, 520, 621, 622, 823, 824, 823, 924, 823, 822), //1950
            50=>array(621, 419, 621, 521, 622, 622, 824, 824, 824, 924, 823, 823), //1951
            51=>array(621, 520, 521, 520, 521, 621, 723, 723, 823, 823, 722, 722), //1952
            52=>array(520, 419, 621, 520, 621, 622, 723, 823, 823, 824, 822, 722), //1953
            53=>array(620, 419, 621, 520, 621, 622, 823, 824, 823, 923, 823, 722), //1954
            54=>array(621, 419, 621, 521, 622, 622, 823, 824, 824, 924, 823, 822), //1955
            55=>array(621, 520, 520, 520, 521, 621, 723, 723, 823, 823, 722, 722), //1956
            56=>array(520, 419, 621, 520, 621, 622, 723, 823, 823, 824, 822, 722), //1957
            57=>array(620, 419, 621, 520, 621, 622, 723, 823, 823, 924, 823, 722), //1958
            58=>array(621, 419, 621, 521, 622, 622, 823, 824, 824, 924, 823, 822), //1958
            59=>array(621, 519, 520, 520, 521, 621, 723, 723, 723, 823, 722, 722), //1960
            60=>array(520, 419, 621, 520, 621, 621, 723, 823, 823, 823, 722, 722), //1961
            61=>array(621, 419, 621, 520, 621, 622, 723, 823, 823, 924, 823, 722), //1962
            62=>array(621, 419, 621, 521, 622, 622, 823, 824, 824, 924, 823, 822), //1963
            63=>array(621, 519, 520, 520, 521, 621, 723, 723, 723, 823, 722, 722), //1964
            64=>array(520, 419, 621, 520, 621, 621, 723, 823, 823, 823, 722, 722), //1965
            65=>array(620, 419, 621, 520, 621, 622, 723, 823, 823, 924, 823, 722), //1966
            66=>array(621, 419, 621, 521, 622, 622, 823, 824, 824, 924, 823, 822), //1967
            67=>array(621, 519, 520, 520, 521, 521, 723, 723, 723, 823, 722, 722), //1968
            68=>array(520, 419, 621, 520, 621, 621, 723, 823, 823, 823, 722, 722), //1969
            69=>array(620, 419, 621, 520, 621, 622, 723, 823, 823, 924, 823, 722), //1970
            70=>array(621, 419, 621, 521, 622, 622, 823, 824, 824, 924, 823, 822), //1971
            71=>array(621, 519, 520, 520, 521, 521, 723, 723, 723, 823, 722, 722), //1972
            72=>array(520, 420, 621, 520, 521, 621, 723, 823, 823, 823, 722, 722), //1973
            73=>array(620, 419, 621, 520, 621, 622, 723, 823, 823, 924, 823, 722), //1974
            74=>array(621, 419, 621, 521, 622, 622, 823, 824, 823, 924, 823, 822), //1975
            75=>array(621, 519, 520, 420, 521, 521, 723, 724, 723, 823, 722, 722), //1976
            76=>array(520, 419, 621, 520, 621, 621, 723, 723, 823, 823, 722, 722), //1977
            77=>array(620, 419, 621, 520, 621, 622, 723, 823, 823, 824, 823, 722), //1978
            78=>array(621, 419, 621, 521, 621, 622, 823, 824, 823, 924, 823, 822), //1979
            79=>array(621, 519, 520, 420, 521, 521, 723, 723, 723, 823, 722, 722), //1980
            80=>array(520, 419, 621, 520, 521, 621, 723, 723, 823, 823, 822, 722), //1981
            81=>array(620, 419, 621, 520, 621, 622, 723, 823, 823, 824, 822, 722), //1982
            82=>array(620, 419, 621, 520, 621, 622, 823, 824, 823, 924, 823, 822), //1983
            83=>array(621, 419, 520, 420, 521, 521, 722, 723, 723, 823, 722, 722), //1984
            84=>array(520, 419, 521, 520, 521, 621, 723, 723, 823, 823, 722, 722), //1985
            85=>array(520, 419, 621, 520, 621, 622, 723, 823, 823, 824, 822, 722), //1986
            86=>array(620, 419, 621, 520, 621, 622, 723, 824, 823, 924, 823, 722), //1987
            87=>array(621, 419, 520, 420, 521, 521, 722, 723, 723, 823, 722, 721), //1988
            88=>array(520, 419, 520, 520, 521, 621, 723, 723, 723, 823, 722, 722), //1989
            89=>array(520, 419, 621, 520, 621, 621, 723, 823, 823, 824, 822, 722), //1990
            90=>array(620, 419, 621, 520, 721, 622, 723, 823, 823, 924, 823, 722), //1991
            91=>array(621, 419, 520, 420, 521, 521, 722, 723, 723, 823, 722, 721), //1992
            92=>array(520, 418, 520, 520, 521, 621, 723, 723, 723, 823, 722, 722), //1993
            93=>array(520, 419, 621, 520, 621, 621, 723, 823, 823, 823, 722, 722), //1994
            94=>array(620, 419, 621, 520, 621, 622, 723, 821, 823, 924, 823, 722), //1995
            95=>array(621, 419, 520, 420, 521, 521, 722, 723, 723, 823, 722, 721), //1996
            96=>array(520, 418, 520, 520, 521, 521, 723, 723, 723, 823, 722, 722), //1997
            97=>array(520, 419, 621, 520, 621, 621, 723, 823, 823, 823, 722, 722), //1998
            98=>array(620, 419, 621, 520, 621, 622, 723, 823, 823, 924, 823, 722), //1999
            99=>array(621, 419, 520, 420, 521, 521, 722, 723, 723, 823, 722, 721), //2000
            100=>array(520, 418, 520, 520, 521, 521, 723, 723, 723, 823, 722, 722), //2001
            101=>array(520, 419, 621, 520, 621, 621, 723, 823, 823, 823, 722, 722), //2002
            102=>array(620, 419, 621, 520, 621, 622, 723, 823, 823, 924, 823, 722), //2003
            103=>array(621, 419, 520, 420, 521, 521, 722, 723, 723, 823, 722, 721), //2004
            104=>array(520, 418, 520, 520, 521, 521, 723, 723, 723, 823, 722, 722), //2005
            105=>array(520, 419, 621, 520, 521, 621, 723, 723, 823, 823, 722, 722), //2006
            106=>array(620, 419, 621, 520, 621, 622, 723, 823, 823, 924, 823, 722), //2007
            107=>array(621, 419, 520, 420, 521, 521, 722, 723, 722, 823, 722, 721), //2008
            108=>array(520, 418, 520, 420, 521, 521, 723, 723, 723, 823, 722, 722), //2009
            109=>array(520, 419, 621, 520, 521, 621, 723, 723, 823, 823, 722, 722), //2010
            110=>array(620, 419, 621, 520, 621, 622, 723, 823, 823, 824, 823, 722), //2011
            111=>array(621, 419, 520, 420, 520, 521, 722, 723, 722, 823, 722, 721), //2012
            112=>array(520, 418, 520, 420, 521, 521, 722, 723, 723, 823, 722, 722), //2013
            113=>array(520, 419, 621, 520, 521, 621, 723, 723, 823, 823, 722, 722), //2014
            114=>array(620, 419, 621, 520, 621, 622, 723, 823, 823, 824, 822, 722), //2015
            115=>array(620, 419, 520, 419, 520, 521, 722, 723, 722, 823, 722, 721), //2016
            116=>array(520, 318, 520, 420, 521, 521, 722, 723, 723, 823, 722, 722), //2017
            117=>array(520, 419, 521, 520, 521, 621, 723, 723, 823, 823, 722, 722), //2018
            118=>array(520, 419, 621, 520, 621, 621, 723, 823, 823, 824, 822, 722), //2019
            119=>array(620, 419, 520, 419, 520, 521, 622, 722, 722, 823, 722, 721), //2020
            120=>array(520, 318, 520, 420, 521, 521, 722, 723, 723, 823, 722, 721), //2021
            121=>array(520, 419, 520, 520, 521, 621, 723, 723, 723, 823, 722, 722), //2022
            122=>array(520, 419, 621, 520, 621, 621, 723, 823, 823, 824, 822, 722), //2023
            123=>array(620, 419, 520, 419, 520, 521, 622, 722, 722, 823, 722, 621), //2024
            124=>array(520, 318, 520, 420, 521, 521, 722, 723, 723, 823, 722, 721), //2025
            125=>array(520, 418, 520, 520, 521, 521, 723, 723, 723, 823, 722, 722), //2026
            126=>array(520, 419, 621, 520, 621, 621, 723, 823, 823, 823, 722, 722), //2027
            127=>array(620, 419, 520, 419, 520, 521, 622, 722, 722, 823, 722, 621), //2028
            128=>array(520, 318, 520, 420, 521, 521, 722, 723, 723, 823, 722, 721), //2029
            129=>array(520, 418, 520, 520, 521, 521, 723, 723, 723, 823, 722, 722), //2030
            130=>array(520, 419, 621, 520, 621, 621, 723, 823, 823, 823, 722, 722), //2031
            131=>array(620, 419, 520, 419, 520, 521, 622, 722, 722, 823, 722, 621), //2032
            132=>array(520, 318, 520, 420, 521, 521, 723, 723, 723, 823, 722, 721), //2033
            133=>array(520, 418, 520, 520, 521, 521, 723, 823, 723, 823, 722, 722), //2034
            134=>array(520, 419, 621, 520, 521, 621, 723, 723, 823, 823, 722, 722), //2035
            135=>array(620, 419, 520, 419, 520, 521, 622, 722, 722, 823, 722, 621), //2036
            136=>array(520, 318, 520, 420, 521, 521, 722, 723, 723, 823, 722, 721), //2037
            137=>array(520, 418, 520, 520, 521, 521, 723, 723, 723, 823, 722, 722), //2038
            138=>array(520, 419, 621, 520, 521, 621, 723, 723, 823, 823, 722, 722), //2039
            139=>array(620, 419, 520, 419, 520, 521, 622, 722, 722, 823, 722, 621), //2040
            140=>array(520, 318, 520, 420, 520, 521, 722, 723, 722, 823, 722, 721), //2041
            141=>array(520, 418, 520, 420, 521, 521, 723, 723, 723, 823, 722, 722), //2042
            142=>array(520, 419, 621, 520, 521, 621, 723, 723, 823, 823, 722, 722), //2043
            143=>array(620, 419, 520, 419, 520, 521, 622, 722, 722, 723, 722, 621), //2044
            144=>array(520, 318, 520, 419, 520, 521, 722, 723, 722, 823, 722, 721), //2045
            145=>array(520, 418, 520, 420, 521, 521, 722, 723, 723, 823, 722, 722), //2046
            146=>array(520, 419, 621, 520, 521, 621, 723, 723, 823, 823, 722, 722), //2047
            147=>array(620, 419, 520, 419, 520, 520, 622, 722, 722, 723, 721, 621), //2048
            148=>array(519, 318, 520, 520, 520, 521, 622, 722, 722, 823, 722, 721), //2049
            149=>array(520, 318, 520, 420, 521, 521, 722, 723, 823, 823, 722, 722) //2050
        );
//节气名称
        $term_name = array(
            "小寒","大寒","立春","雨水","惊蛰","春分","清明","谷雨",
            "立夏","小满","芒种","夏至","小暑","大暑","立秋","处暑",
            "白露","秋分","寒露","霜降","立冬","小雪","大雪","冬至");
 
//获取当前日期及其年月日
//        $today = getdate();
        $this_year = $years;
        $this_month = $mon;
        $this_day = $mday;
 
//算取在数组中的位置
        $line = $this_year-1901;
        $row = $this_month-1;
 
//获取数组中的两个日期
        $term_one =substr($solar_term[$line][$row], 0, 1);
        $term_two =substr($solar_term[$line][$row], 1, 2);
 
//获取在节气表中的位置
        $t_name_1 = ($this_month-1)*2;
        $t_name_2 = ($this_month-1)*2+1;
 
//显示相应的节气
        if ($this_day==$term_one)
        {
            $this_term = $term_name[$t_name_1];
        }
        else if($this_day==$term_two)
        {
            $this_term = $term_name[$t_name_2];
        }
        else
        {
            $this_term = NULL;
        }
        return $this_term;
    }

压测工具作个笔记 wrk

作者: Joyber
时间: 2022-07-12
分类: 默认分类
评论

项目地址：https://github.com/wg/wrk

git clone https://github.com/wg/wrk.git 或从github上直接下载zip包、
进入项目目录后直接执行make，你就可以得到一个可执行文件wrk 。

xindoo大大：“我用单机(40 cores)压90台机器的集群，压到了31w的QPS，最后压不上去不是因为这台机器抗不住了，而是因为我们服务扛不住了。一个有复杂业务逻辑的服务和一个毫无逻辑的压测相比有失公允，但在压测过程中我也干垮了4台机器的nginx集群（这里nginx也只是个方向代理而已），这足见wrk性能之高。依赖lua脚本，wrk也可以完成复杂http请求的压测”

官方使用说明：

Basic Usage
wrk -t12 -c400 -d30s http://127.0.0.1:8080/index.html
This runs a benchmark for 30 seconds, using 12 threads, and keeping 400 HTTP connections open.

Output:

Running 30s test @ http://127.0.0.1:8080/index.html
  12 threads and 400 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency   635.91us    0.89ms  12.92ms   93.69%
    Req/Sec    56.20k     8.07k   62.00k    86.54%
  22464657 requests in 30.00s, 17.76GB read
Requests/sec: 748868.53
Transfer/sec:    606.33MB
Command Line Options
-c, --connections: total number of HTTP connections to keep open with
                   each thread handling N = connections/threads

-d, --duration:    duration of the test, e.g. 2s, 2m, 2h

-t, --threads:     total number of threads to use

-s, --script:      LuaJIT script, see SCRIPTING

-H, --header:      HTTP header to add to request, e.g. "User-Agent: wrk"

    --latency:     print detailed latency statistics

    --timeout:     record a timeout if a response is not received within
                   this amount of time.

一个不错的nginx日志文件分析软件，命令行工具goaccess

作者: Joyber
时间: 2022-07-10
分类: 默认分类
评论

官网下载地址：https://goaccess.io/download

用法（配置）参考：https://blog.csdn.net/weixin_43860781/article/details/104668332

使用命令：

goaccess tell520_20220709.log

使用这个命令，后会显示一个配置窗口，一般选择第一个格式就好了，如果有自己修改过日志格式，简单修改一下log-format格式即可

使用docker镜像分析日志文件

#单/多个文件
cat www.log | docker run --rm -i -e LANG=zh_CN -e TZ="Asia/Shanghai" allinurl/goaccess -a -o html --log-format '%^: %h %^[%d:%t %^] "%r" %s %b "%R" "%u"' --date-format '%d/%b/%Y' --time-format '%H:%M:%S' - > ngx.html

#实时数据流
tail -F access.log | docker run -p 7890:7890 --rm -i -e LANG=zh_CN -e TZ="Asia/Shanghai" allinurl/goaccess -a -o html --log-format '%^: %h %^[%d:%t %^] "%r" %s %b "%R" "%u"' --date-format '%d/%b/%Y' --time-format '%H:%M:%S' --real-time-html - > ngx.html

当前最新版本：1.6.1

#编译安装
$ wget https://tar.goaccess.io/goaccess-1.6.1.tar.gz
$ tar -xzvf goaccess-1.6.1.tar.gz
$ cd goaccess-1.6.1/
$ ./configure --enable-utf8 --enable-geoip=mmdb
$ make
# make install

#通过软件包管理工具安装
Fedora
# yum install goaccess

Arch Linux
# pacman -S goaccess

Gentoo
# emerge net-analyzer/goaccess

OS X / Homebrew
# brew install goaccess

#Note: If GeoIP is needed, append --with-libmaxminddb to the command above. You will need to download the City/Country database from MaxMind and use the option --geoip-database to specify the database.


FreeBSD
# pkg install sysutils/goaccess

OpenBSD
# pkg_add goaccess

OpenSUSE
# zypper ar -f obs://server:http http
# zypper in goaccess
pkgsrc (NetBSD, Solaris, SmartOS, ...)
# pkgin install goaccess
Slackware
# curl https://slackbuilds.org/slackbuilds/14.1/system/goaccess.tar.gz | tar xvz
# cd goaccess/
# GEOIP=yes ./goaccess.SlackBuild

参数配置说明：
GoAccess 中文站：https://www.goaccess.cc/?mod=man
GoAccess 官方：https://goaccess.io/man

一个不错的IP查询网站，有API

作者: Joyber
时间: 2022-07-10
分类: 默认分类
评论

网页查询：https://db-ip.com/123.6.49.38
API查询：

~$ curl http://api.db-ip.com/v2/free/123.6.49.38
{
    "ipAddress": "123.6.49.38",
    "continentCode": "AS",
    "continentName": "Asia",
    "countryCode": "CN",
    "countryName": "China",
    "stateProv": "\u6cb3\u5357",
    "city": "\u90d1\u5dde",
}

~$ curl http://api.db-ip.com/v2/free/123.6.49.38/countryName
China

Sentinel 流量控制系统

作者: Joyber
时间: 2022-07-08
分类: 默认分类
评论

Sentinel ： https://sentinelguard.io/zh-cn/docs/introduction.html

Sentinel 介绍
随着微服务的流行，服务和服务之间的稳定性变得越来越重要。Sentinel 是面向分布式、多语言异构化服务架构的流量治理组件，主要以流量为切入点，从流量路由、流量控制、流量整形、熔断降级、系统自适应过载保护、热点流量防护等多个维度来帮助开发者保障微服务的稳定性。

Sentinel 的历史
2012 年，Sentinel 诞生，主要功能为入口流量控制。
2013-2017 年，Sentinel 在阿里巴巴集团内部迅速发展，成为基础技术模块，覆盖了所有的核心场景。Sentinel 也因此积累了大量的流量归整场景以及生产实践。
2018 年，Sentinel 开源，并持续演进。
2019 年，Sentinel 朝着多语言扩展的方向不断探索，推出 C++ 原生版本，同时针对 Service Mesh 场景也推出了 Envoy 集群流量控制支持，以解决 Service Mesh 架构下多语言限流的问题。
2020 年，推出 Sentinel Go 版本，继续朝着云原生方向演进。
2021 年，Sentinel 正在朝着 2.0 云原生高可用决策中心组件进行演进；同时推出了 Sentinel Rust 原生版本。同时我们也在 Rust 社区进行了 Envoy WASM extension 及 eBPF extension 等场景探索。
2022 年，Sentinel 品牌升级为流量治理，领域涵盖流量路由/调度、流量染色、流控降级、过载保护/实例摘除等；同时社区将流量治理相关标准抽出到 OpenSergo 标准中，Sentinel 作为流量治理标准实现。

Sentinel 功能和设计理念
流量控制
流量控制在网络传输中是一个常用的概念，它用于调整网络包的发送数据。然而，从系统稳定性角度考虑，在处理请求的速度上，也有非常多的讲究。任意时间到来的请求往往是随机不可控的，而系统的处理能力是有限的。我们需要根据系统的处理能力对流量进行控制。Sentinel 作为一个调配器，可以根据需要把随机的请求调整成合适的形状，如下图所示：

arch

流量控制有以下几个角度:

资源的调用关系，例如资源的调用链路，资源和资源之间的关系；
运行指标，例如 QPS、线程池、系统负载等；
控制的效果，例如直接限流、冷启动、排队等。
Sentinel 的设计理念是让您自由选择控制的角度，并进行灵活组合，从而达到想要的效果。

熔断降级
什么是熔断降级
除了流量控制以外，降低调用链路中的不稳定资源也是 Sentinel 的使命之一。由于调用关系的复杂性，如果调用链路中的某个资源出现了不稳定，最终会导致请求发生堆积。这个问题和 Hystrix 里面描述的问题是一样的。

image

Sentinel 和 Hystrix 的原则是一致的: 当调用链路中某个资源出现不稳定，例如，表现为 timeout，异常比例升高的时候，则对这个资源的调用进行限制，并让请求快速失败，避免影响到其它的资源，最终产生雪崩的效果。

熔断降级设计理念
在限制的手段上，Sentinel 和 Hystrix 采取了完全不一样的方法。

Hystrix 通过线程池的方式，来对依赖(在我们的概念中对应资源)进行了隔离。这样做的好处是资源和资源之间做到了最彻底的隔离。缺点是除了增加了线程切换的成本，还需要预先给各个资源做线程池大小的分配。

Sentinel 对这个问题采取了两种手段:

通过并发线程数进行限制
和资源池隔离的方法不同，Sentinel 通过限制资源并发线程的数量，来减少不稳定资源对其它资源的影响。这样不但没有线程切换的损耗，也不需要您预先分配线程池的大小。当某个资源出现不稳定的情况下，例如响应时间变长，对资源的直接影响就是会造成线程数的逐步堆积。当线程数在特定资源上堆积到一定的数量之后，对该资源的新请求就会被拒绝。堆积的线程完成任务后才开始继续接收请求。

通过响应时间对资源进行降级
除了对并发线程数进行控制以外，Sentinel 还可以通过响应时间来快速降级不稳定的资源。当依赖的资源出现响应时间过长后，所有对该资源的访问都会被直接拒绝，直到过了指定的时间窗口之后才重新恢复。

系统负载保护
Sentinel 同时提供系统维度的自适应保护能力。防止雪崩，是系统防护中重要的一环。当系统负载较高的时候，如果还持续让请求进入，可能会导致系统崩溃，无法响应。在集群环境下，网络负载均衡会把本应这台机器承载的流量转发到其它的机器上去。如果这个时候其它的机器也处在一个边缘状态的时候，这个增加的流量就会导致这台机器也崩溃，最后导致整个集群不可用。

针对这个情况，Sentinel 提供了对应的保护机制，让系统的入口流量和系统的负载达到一个平衡，保证系统在能力范围之内处理最多的请求。

Sentinel 是如何工作的
Sentinel 的主要工作机制如下：

对主流框架提供适配或者显示的 API，来定义需要保护的资源，并提供设施对资源进行实时统计和调用链路分析。
根据预设的规则，结合对资源的实时统计信息，对流量进行控制。同时，Sentinel 提供开放的接口，方便您定义及改变规则。
Sentinel 提供实时的监控系统，方便您快速了解目前系统的状态。