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 sizeeg,
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
