php+nginx 服务发生500 502错误排查思路

概述

当线上的服务中访问中出现500或者502错误时，需要紧急处理，排查问题，该怎么做？可以通过分析一些错误日志或者跟踪php-fpm进程来进行问题定位。

nginx error_log

nginx的error_log在nginx的配置文件中定义的

server {
    listen       80;
    server_name  localhost;
    root         /var/www;

    access_log  /Users/jiao/logs/default.access.log;
    error_log /Users/jiao/logs/default.error.log;
    location / {
        index  index.html index.htm index.php;
        autoindex   on;
    }
    location = /info {
        allow   127.0.0.1;
        deny    all;
        rewrite (.*) /.info.php;
    }
    location ~ \.php$ {
        root    /var/www;
        fastcgi_pass 127.0.0.1:9000;
        fastcgi_index index.php;
        fastcgi_param SCRIPT_FILENAME /var/www$fastcgi_script_name;
        include /usr/local/etc/nginx/fastcgi_params;
    }
}

查看error_log

➜  tail /Users/jiao/logs/default.error.log
2019/07/17 11:08:18 [error] 77416#0: *76 kevent() reported about an closed connection (54: Connection reset by peer) while reading response header from upstream, client: 127.0.0.1, server: localhost, request: "GET / HTTP/1.1", upstream: "fastcgi://127.0.0.1:9000", host: "localhost"

发现出现了Connection reset by peer，连接被重置了，此时可以再查看php-fpm的error_log进一步分析问题

php-fpm error_log

php-fpm的error_log在php-fpm.conf文件中配置中定义的

; Error log file
; If it's set to "syslog", log is sent to syslogd instead of being written
; in a local file.
; Note: the default prefix is /usr/local/var
; Default Value: log/php-fpm.log
error_log = log/php-fpm.log

error_log里面的内容是这样的

➜  tail /usr/local/var/log/php-fpm.log
[17-Jul-2019 10:49:54] NOTICE: [pool www] child 81948 started
[17-Jul-2019 11:08:18] WARNING: [pool www] child 77537, script '/var/www/index.php' (request: "GET /index.php") execution timed out (3.801267 sec), terminating
[17-Jul-2019 11:08:18] WARNING: [pool www] child 77537 exited on signal 15 (SIGTERM) after 1503.113967 seconds from start
[17-Jul-2019 11:08:18] NOTICE: [pool www] child 94339 started

可以看到是请求/var/www/index.php文件出现了超时

dtruss

dtruss是动态跟踪命令，可以根据PID，name跟踪进程
mac环境下使用dtruss，linux环境可以使用strace，pstack

➜ dtruss
USAGE: dtruss [-acdefholLs] [-t syscall] { -p PID | -n name | command | -W name }

      -p PID          # examine this PID
      -n name         # examine this process name
      -t syscall      # examine this syscall only
      -W name         # wait for a process matching this name
      -a              # print all details
      -c              # print syscall counts
      -d              # print relative times (us)
      -e              # print elapsed times (us)
      -f              # follow children
      -l              # force printing pid/lwpid
      -o              # print on cpu times
      -s              # print stack backtraces
      -L              # don't print pid/lwpid
      -b bufsize      # dynamic variable buf size

eg,

   dtruss df -h       # run and examine "df -h"
   dtruss -p 1871     # examine PID 1871
   dtruss -n tar      # examine all processes called "tar"
   dtruss -f test.sh  # run test.sh and follow children
   

跟踪php-fpm：sudo dtruss -a -n php-fpm
此时访问web页面，就可以看到跟踪内容

21416/0x3479b6:      1559      63      3 getrusage(0x0, 0x7FFEE1EC0760, 0x0)         = 0 0
21416/0x3479b6:      1561       4      0 getrusage(0xFFFFFFFFFFFFFFFF, 0x7FFEE1EC0760, 0x0)         = 0 0
21416/0x3479b6:      1627      77     17 poll(0x7FFEE1EC08C0, 0x1, 0x1388)         = 1 0
dtrace: error on enabled probe ID 2174 (ID 159: syscall::read:return): invalid kernel access in action #13 at DIF offset 68
dtrace: error on enabled probe ID 2174 (ID 159: syscall::read:return): invalid kernel access in action #13 at DIF offset 68
dtrace: error on enabled probe ID 2174 (ID 159: syscall::read:return): invalid kernel access in action #13 at DIF offset 68
dtrace: error on enabled probe ID 2174 (ID 159: syscall::read:return): invalid kernel access in action #13 at DIF offset 68
dtrace: error on enabled probe ID 2174 (ID 159: syscall::read:return): invalid kernel access in action #13 at DIF offset 68
21416/0x3479b6:      1872      29     24 lstat64("/var/www/index.php\0", 0x7FFEE1ECFF38, 0x0)         = 0 0
21416/0x3479b6:      1884       9      6 lstat64("/var/www\0", 0x7FFEE1ECFDF8, 0x0)         = 0 0
21416/0x3479b6:      1889       6      3 lstat64("/var\0", 0x7FFEE1ECFCB8, 0x0)         = 0 0
21416/0x3479b6:      1899      12      8 readlink("/var\0", 0x7FFEE1ED0090, 0x400)         = 11 0
21416/0x3479b6:      1905       6      4 lstat64("/private/var\0", 0x7FFEE1ECFB78, 0x0)         = 0 0
21416/0x3479b6:      1917       6      3 lstat64("/private\0", 0x7FFEE1ECFA38, 0x0)         = 0 0
21416/0x3479b6:      2178      18     14 stat64("/var/www/.user.ini\0", 0x7FFEE1ED0240, 0x0)         = -1 Err#2
21416/0x3479b6:      2217       5      1 setitimer(0x2, 0x7FFEE1ED07E0, 0x0)         = 0 0
21416/0x3479b6:      2225       4      0 sigaction(0x1B, 0x7FFEE1ED0788, 0x7FFEE1ED07B0)         = 0 0
21416/0x3479b6:      2237       5      1 sigprocmask(0x2, 0x7FFEE1ED0804, 0x0)         = 0x0 0
21416/0x3479b6:      3643      48     40 open_nocancel(".\0", 0x0, 0x1)         = 5 0
21416/0x3479b6:      3648       7      3 fstat64(0x5, 0x7FFEE1ED0110, 0x0)         = 0 0
21416/0x3479b6:      3653       7      2 fcntl_nocancel(0x5, 0x32, 0x10F252158)         = 0 0
21416/0x3479b6:      3661      12      7 close_nocancel(0x5)         = 0 0
21416/0x3479b6:      3670      10      7 stat64("/usr/local/var\0", 0x7FFEE1ED0080, 0x0)         = 0 0
21416/0x3479b6:      3681      11      8 chdir("/var/www\0", 0x0, 0x0)         = 0 0
21416/0x3479b6:      3698       4      0 setitimer(0x2, 0x7FFEE1ED02D0, 0x0)         = 0 0
21416/0x3479b6:      3710       6      3 fcntl(0x3, 0x8, 0x10F3FD858)         = 0 0
21416/0x3479b6:      3733       9      6 stat64("/private/var/www/index.php\0", 0x7FFEE1ECFF10, 0x0)         = 0 0
74904/0x332630:    723125 1073381     19 kevent(0x9, 0x0, 0x0)         = 0 0
74902/0x332629:    770666 1073387     17 kevent(0x8, 0x0, 0x0)         = 0 0
74904/0x332630:    723165 1061954     20 kevent(0x9, 0x0, 0x0)         = 0 0
74902/0x332629:    770709 1061954     20 kevent(0x8, 0x0, 0x0)         = 0 0
74904/0x332630:    723201 1074786     16 kevent(0x9, 0x0, 0x0)         = 0 0
74902/0x332629:    770747 1074783     16 kevent(0x8, 0x0, 0x0)         = 0 0
74904/0x332630:    723229 1069141     13 kevent(0x9, 0x0, 0x0)         = 0 0
74902/0x332629:    770777 1069145     11 kevent(0x8, 0x0, 0x0)         = 0 0
21416/0x3479b6:      3942 3902233      7 __semwait_signal(0x703, 0x0, 0x1)         = -1 Err#4
74902/0x332629:    770814     103     25 kill(21416, 15)         = 0 0
dtrace: error on enabled probe ID 2172 (ID 161: syscall::write:return): invalid kernel access in action #13 at DIF offset 68
dtrace: error on enabled probe ID 2172 (ID 161: syscall::write:return): invalid kernel access in action #13 at DIF offset 68
74902/0x332629:    771325       7      2 sigreturn(0x7FFEE1ECFC40, 0x1E, 0xC1A4B78E0404663A)         = 0 Err#-2
74902/0x332629:    771336       7      3 kevent(0x8, 0x0, 0x0)         = 1 0
dtrace: error on enabled probe ID 2174 (ID 159: syscall::read:return): invalid kernel access in action #13 at DIF offset 68
74902/0x332629:    771352      11      7 wait4(0xFFFFFFFFFFFFFFFF, 0x7FFEE1ED0748, 0x3)         = 21416 0
dtrace: error on enabled probe ID 2172 (ID 161: syscall::write:return): invalid kernel access in action #13 at DIF offset 68
74902/0x332629:    773511    1957   1899 fork()         = 28060 0
28060/0x3754c5:       125:        0:       0 fork()         = 0 0
28060/0x3754c5:       128       9      2 bsdthread_register(0x7FFF6774C418, 0x7FFF6774C408, 0x2000)         = -1 Err#22
dtrace: error on enabled probe ID 2172 (ID 161: syscall::write:return): invalid kernel access in action #13 at DIF offset 68
74902/0x332629:    773737       4      1 wait4(0xFFFFFFFFFFFFFFFF, 0x7FFEE1ED0748, 0x3)         = 0 0
74902/0x332629:    773742       6      3 read(0x5, "\0", 0x1)         = -1 Err#35
28060/0x3754c5:       320       4      0 getpid(0x0, 0x0, 0x0)         = 28060 0
28060/0x3754c5:       328       7      2 __mac_syscall(0x7FFF67758A17, 0x4, 0x7FFEE1ED0208)         = -1 Err#45
28060/0x3754c5:       332       5      2 csops(0x6D9C, 0xB, 0x7FFEE1ED0248)         = -1 Err#22
28060/0x3754c5:       755      14     11 dup2(0x1, 0x2, 0x0)         = 2 0
28060/0x3754c5:       797      89     22 close(0x4)         = 0 0
28060/0x3754c5:       806      11      6 dup2(0x7, 0x0, 0x0)         = 0 0
28060/0x3754c5:       817       4      0 geteuid(0x0, 0x0, 0x0)         = 501 0
28060/0x3754c5:       820       3      0 close(0x5)         = 0 0
28060/0x3754c5:       821       3      0 close(0x6)         = 0 0
28060/0x3754c5:       824       5      1 sigaction(0xF, 0x7FFEE1ED0688, 0x0)         = 0 0
28060/0x3754c5:       825       3      0 sigaction(0x2, 0x7FFEE1ED0688, 0x0)         = 0 0
28060/0x3754c5:       827       3      0 sigaction(0x1E, 0x7FFEE1ED0688, 0x0)         = 0 0
28060/0x3754c5:       828       3      0 sigaction(0x1F, 0x7FFEE1ED0688, 0x0)         = 0 0
28060/0x3754c5:       829       3      0 sigaction(0x14, 0x7FFEE1ED0688, 0x0)         = 0 0
28060/0x3754c5:       830       3      0 sigaction(0x3, 0x7FFEE1ED0688, 0x0)         = 0 0
28060/0x3754c5:      1043       3      0 close(0x7)         = 0 0

可以看到系统底层执行的函数，如lstat64获取文件内容信息，kill(21416, 15)kill掉php-fpm进程，fork()出新的php-fpm进程，有兴趣可以深入研究每个指令的作用

参考

https://www.cnblogs.com/leezh...