Nginx Tip 502 and 504 Error Final Solution

First, the error hint Description:

Nginx 502 Bad Gateway means that the requested php-cgi has been executed, but the php-cgi process is terminated for some reason (typically a problem reading the resource) is not completed.

The implication of Nginx 504 Gateway time-out is that the requested gateway is not requested, simply that there is no request to the php-cgi that can be executed.

Second, the cause of error analysis:

To solve these two problems is a need for comprehensive thinking, in general Nginx 502 Bad Gateway and php-fpm.conf settings,

and the Nginx 504 Gateway time-out is related to the nginx.conf setting.

Php-fpm.conf has two critical parameters, one is "Max_children" and the other is "request_terminate_timeout", but the value is not universal, but it needs to be calculated by itself.

The method of calculation is as follows:

If your server performance is good enough and your broadband resources are sufficient, PHP scripts do not have loops or bugs, you can set the "request_terminate_timeout" to 0s directly. The meaning of 0s is to allow php-cgi to carry on without any time limit. And if you can't do this, which means that your php-cgi may be a bug, or that your broadband is not enough or that other reasons cause your php-cgi to be suspended, then it's recommended that you assign a value to "Request_terminate_timeout", This value can be set according to the performance of your server. Generally the better performance you can set the higher, 20 minutes-30 minutes can be. Because my server PHP script needs to run for a long time, and some may be more than 10 minutes so I set 900 seconds, so that will not cause php-cgi to die and appear 502 Bad Gateway this error.

and "Max_children" This value is how to calculate out of it. This value is in principle the bigger the better, the php-cgi process will be processed more quickly, the queue of requests will be very little. Set "Max_children" also need to set according to the performance of the server, generally a server under normal circumstances of each php-cgi memory consumed in about 20M, so my "Max_children" I set to 40, 20m*40= 800M means that at peak time all php-cgi are consumed within 800M, less than my valid memory 1Gb. And if my "max_children" set smaller, such as 5-10, then php-cgi will be "very tired", processing speed is also very slow, waiting for a long time. If a long time did not get processing requests will appear 504 Gateway time-out this error, and is processing a very tired of those php-cgi if encountered problems will appear 502 bad Gateway this error.

III. Interim Solutions:

To sum up, the Nginx tips for 502 and 504 errors in the interim solution are:

1, adjust the relevant settings of php-fpm.conf:

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505

2, adjust the relevant settings of nginx.conf:

Fastcgi_connect_timeout 600;
Fastcgi_send_timeout 600;
Fastcgi_read_timeout 600;
Fastcgi_buffer_size 256k;
Fastcgi_buffers 256k;
Fastcgi_busy_buffers_size 512k;
Fastcgi_temp_file_write_size 512k;

Iv. End-Level solutions:

The solution shown in heading 3 can only temporarily solve the problem, and if the site's access is really very large, and nginx+fastcgi can only deal with instantaneous or short time high concurrency has a good effect, so the only ultimate solution is: Timed smooth restart php-cgi.

The specific configuration is as follows:

1. Write a very simple script:

#vi/home/www/scripts/php-fpm.sh

The contents are as follows:

#!/bin/bash
# This script run at */1
/USR/LOCAL/PHP/SBIN/PHP-FPM Reload

2, add the script to the scheduled task:

#crontab-E

The contents are as follows:

*/1 * * * */home/www/scripts/php-fpm.sh

Note: For the sake of convenience, you can write the PHP-FPM smooth restart command directly in the crontab without writing a script.