Nginx 502 and 504 wrong solutions

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 how is the value of "Max_children" calculated? 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:

<value name= "Max_children" >32</value>

<value name= "Request_terminate_timeout" >30s</value>

2, adjust the relevant settings of nginx.conf:

    Server_tokens off;
    sendfile        on;
    tcp_nopush     on;
    server_names_hash_bucket_size 256;
    client_header_buffer_size 256k;
    large_client_header_buffers 4 256k;
    client_body_buffer_size 256k;
    client_header_timeout     3m;
    client_body_timeout 3m;
    send_timeout              3m;
    client_max_body_size 50m;
    keepalive_timeout ;

#fastcgi_connect_timeout 300;
#fastcgi_send_timeout 300;
#fastcgi_read_timeout 300;
#fastcgi_buffer_size 64k;
#fastcgi_buffers 4 64k;
#fastcgi_busy_buffers_size 128k;
#fastcgi_temp_file_write_size 128k;

Fastcgi_intercept_errors on;
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, Solution:
A, crontab write php-fpm Smooth restart command
B, appropriately increase the children value, reduce the max_requests value.
     recommends General cloud host children in 5-10,max_requests at 1000-2000, specifically self tuning. &NBSP
    , reducing the number of max_requests can shorten the cycle of php-cgi restart
     Accidental high memory operations can cause problems that affect time.