Detailed explanation of PHP+nginx service 500 502 error troubleshooting ideas

Detailed explanation of PHP+nginx service 500 502 error troubleshooting ideas

Overview

When a 500 or 502 error occurs during access to an online service, emergency processing and troubleshooting are required. What should I do? You can locate the problem by analyzing some error logs or tracking the php-fpm process.

nginx error_log

nginx error_log is defined in the nginx configuration file

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;
 }
}

View 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"

It is found that Connection reset by peer appears. The connection is reset. At this time, you can check the error_log of php-fpm to further analyze the problem.

php-fpm error_log

php-fpm's error_log is defined in the configuration of the php-fpm.conf file

; 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

The content of error_log is as follows

➜ 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

You can see that the request for the /var/www/index.php file has timed out.

dtruss

dtruss is a dynamic tracking command that can track processes based on PID and name

Use dtruss in Mac environment, and strace and pstack in Linux environment

➜ 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

For example,

 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

Trace php-fpm: sudo dtruss -a -n php-fpm

At this time, visit the web page and you can see the tracking content

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

You can see the functions executed at the bottom of the system, such as lstat64 to obtain file content information, kill(21416, 15) to kill the php-fpm process, and fork() to create a new php-fpm process. If you are interested, you can study the role of each instruction in depth.

refer to

https://www.jb51.net/article/165773.htm

The above is the full content of this article. I hope it will be helpful for everyone’s study. I also hope that everyone will support 123WORDPRESS.COM.

You may also be interested in:
  • Nginx 502 Bad Gateway Error Causes and Solutions
  • In-depth analysis of nginx+php-fpm service HTTP status code 502
  • Detailed explanation of solutions to common 502 errors in Nginx in Linux
  • Detailed explanation of Nginx 502 error solution
  • PHP script monitors Nginx 502 errors and automatically restarts php-fpm
  • 4 Common Causes and Solutions for Nginx 502 Bad Gateway Error
  • Nginx 502 error when upgrading PHP from 5.3.28 to 5.3.29
  • Troubleshooting the cause of 502 bad gateway error on nginx server

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