About NGINX's 502's road to pretending to fight monsters, nginx502's road_PHP tutorial

About NGINX’s 502’s road to pretending to fight monsters, the road to nginx502

The reason for copying a section of nginx502 before writing a log is as follows from a certain website, but this is not It’s not the key point, the most important thing is to look at what the blogger is typing.

1. NGINX 502 error troubleshooting
The NGINX 502 Bad Gateway error is a problem with FastCGI, causing NGINX 502 errors are more likely. Combine some found online with 502 Bad Here is a list of issues and troubleshooting methods related to Gateway errors. Let’s start with FastCGI configuration:
1.Whether the FastCGI process has been started
2. Is the number of FastCGI worker processes not enough?
Run netstat -anpo | grep "php-cgi" | wc -l Determine whether it is close to the FastCGI process and close to the value set in the configuration file, indicating that the number of worker processes is set too few
3.FastCGI execution time is too long
Increase the following parameter values ​​according to actual conditions
fastcgi_connect_timeout 300;
fastcgi_send_timeout 300;
fastcgi_read_timeout 300;
4.FastCGI Buffer is not enough
nginxLike apache, it has front-end buffering restrictions and the buffering parameters can be adjusted
fastcgi_buffer_size 32k;
fastcgi_buffers 8 32k;
5.Proxy Buffer is not enough
If you use Proxying, adjust
proxy_buffer_size 16k;
proxy_buffers 4 16k;
See: http://www.server110.com
6.https forwarding configuration error
Correct configuration method
server_name www.mydomain.com;
location /myproj/repos {
set $fixed_destination $http_destination;
if ( $http_destination ~* ^https(.*)$ )
{
set $fixed_destination http$1;
}
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header Destination $fixed_destination;
proxy_pass http://subversion_hosts;
}
Of course, it also depends on what type of FastCGI you use in the backend. I have used php-fpm, and the traffic is about 400,000 PV (dynamic page) on a single machine. Now basically no 502 is encountered.

7.php script execution time is too long
Change the 0s to a time

~~~~~~~~~~~~~~~~~~~~~~~~~~~ Gorgeous dividing line~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~

The problem encountered by the blogger is because there is a parameter in the code that is passed by reference, and then directly accesses 502. When the blogger sees this information, the first time he opens display_errors directly,

Then I wondered why when the error display was turned on, there was no 502, but some E_STRICT warnings. After rounds of debugging, there was still no way to find out the reason.

After having no choice, I checked the nginx error screenshot as follows. At that time, I thought that this was not an error reported by php fastcgi. Why did it appear in the error log of nginx? This does not feel very scientific, and I thought hard

After several rounds of painful and fruitless adjustments, I still feel powerless, so I can only call it a day.

As a lucky programmer, I didn't know that the error log file was not written in the local virtual machine environment after some troubleshooting. There was no problem with the configuration, but the error log was not written. (Please don’t complain, because bloggers usually The page directly displays errors and adds xdebug, so I think it doesn't matter. It's a good idea not to write about the things that concern me. ) The blogger’s keen eye and highly intelligent brain (bloggers in this era must be a bit more assertive) felt that it should be a problem with file permissions, and then decided to do something about it. chmod 777 superb skills, restarted php-fpm, tested the error code, and the error log file was still written as expected. Now that I think back to the morning's problem, I always wonder if the error warning output will be the same as the one written in the log. Sleep Then just do it naked, tail the error log, block the display, and play with the code. It doesn’t report 502 anymore. It runs perfectly. The error log is written to the log file as scheduled. It’s unscientific. Open the nginx error log and play again. I found out that nginx was gone. mistake. All right! I feel that the problem is that the 502 error is due to a permission issue with PHP's error log. There is no way to write it, and then it is thrown directly to cgi, so nginx gets a 502. As for why it was dumped to cgi, I don’t understand that. Don’t ask me. People who understand will follow. A few moves. Ouch, not bad. This pretentious journey is over. Thank you Tvb, thank you parents, thank you Blog Park.

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