JQuery Post - random 502 bad gateway error - NGINX - php

Question

I am noticing strange behavior with my code. ( PHP 7.4 ).
I am using Jquery (jquery-3.6.0.min.js).
I am using JQuery post to retrieve the data from the server, but randomly ( sometimes on every 4th attempt ), I do get for the same request 502 Bad Gateway - with no errors in NGINX.
The jquery code is:
$.post(IBE_URL+"/assets/ajax/tour-addons.php",
payload,
function(data, status){
$("#addon_canvas_body").html(data);
});
The current nginx configuration is:
## For a live site, handling more connections, uncomment, then start WinNMP.exe --phpCgiServers=25:
#worker_processes auto;
#worker_rlimit_nofile 100000;
events {
## For a live site, uncomment:
#worker_connections 8096;
}
http {
server_tokens off;
sendfile on;
tcp_nopush on;
tcp_nodelay on;
ssi off;
server_names_hash_bucket_size 64;
## Timeouts ##
##############
client_body_timeout 5;
client_header_timeout 5;
keepalive_timeout 25 25;
send_timeout 15s;
resolver_timeout 3s;
# Timeout period for connection with FastCGI-server. It should be noted that this value can't exceed 75 seconds.
fastcgi_connect_timeout 5s;
# Amount of time for upstream to wait for a fastcgi process to send data.
# Change this directive if you have long running fastcgi processes that do not produce output until they have finished processing.
# If you are seeing an upstream timed out error in the error log, then increase this parameter to something more appropriate.
fastcgi_read_timeout 40s;
# Request timeout to the server. The timeout is calculated between two write operations, not for the whole request.
# If no data have been written during this period then serve closes the connection.
fastcgi_send_timeout 15s;
## Buffers ##
#############
fastcgi_temp_file_write_size 10m;
#fastcgi_busy_buffers_size 512k;
fastcgi_buffer_size 512k;
fastcgi_buffers 16 512k;
open_file_cache off;
# php max upload limit cannot be larger than this
client_max_body_size 50m;
####client_body_buffer_size 1K;
client_header_buffer_size 8k;
large_client_header_buffers 8 16k;
types_hash_max_size 2048;
include nginx.mimetypes.conf;
default_type text/html;
## Logging ##
#############
access_log "c:/winnmp/log/nginx_access.log";
error_log "c:/winnmp/log/nginx_error.log" warn; #debug or warn
log_not_found on; #enables or disables messages in error_log about files not found on disk.
rewrite_log off;
fastcgi_intercept_errors off; # Do Not Change (off) !
gzip off;
index index.php index.htm index.html;
server {
# NEVER ALLOW PUBLIC ACCESS TO THIS SERVER !!!
# Instead, create projects using WinNMP Manager, and allow public access only to those projects!
# How to allow access from LAN and Internet to your local project:
# http://WinNMP.wtriple.com/howtos.php#How-to-allow-access-from-LAN-and-Internet-to-your-local-project
listen 127.0.0.1:80 default_server; # Do Not Change ! Security Risk !
#listen [::1]:80 ipv6only=on; # Do Not Change ! Security Risk !
server_name localhost; # Do Not Change ! Security Risk !
# This directive is modified automatically by WinNMP.exe for portability.
root "c:/winnmp/www";
autoindex on;
allow 127.0.0.1; # Do Not Change ! Security Risk !
allow ::1; # Do Not Change ! Security Risk !
deny all; # Do Not Change ! Security Risk !
## deny access to .htaccess files, if Apache's document root concurs with nginx's one
location ~ /\.ht {
deny all;
}
location = /favicon.ico {
log_not_found off;
}
location = /robots.txt {
log_not_found off;
}
## Tools are now served from include/tools/
location ~ ^/tools/.*\.php$ {
root "c:/winnmp/include";
try_files $uri =404;
include nginx.fastcgi.conf;
fastcgi_pass php_farm;
allow 127.0.0.1; # Do Not Change ! Security Risk !
allow ::1; # Do Not Change ! Security Risk !
deny all; # Do Not Change ! Security Risk !
}
location ~ ^/tools/ {
root "c:/winnmp/include";
allow 127.0.0.1; # Do Not Change ! Security Risk !
allow ::1; # Do Not Change ! Security Risk !
deny all; # Do Not Change ! Security Risk !
}
## How to add phpMyAdmin
## Copy phpMyAdmin files to c:/winnmp/include/phpMyAdmin then uncomment:
#location ~ ^/phpMyAdmin/.*\.php$ {
# root "c:/winnmp/include";
# try_files $uri =404;
# include nginx.fastcgi.conf;
# fastcgi_pass php_farm;
# allow 127.0.0.1;
# allow ::1;
# deny all;
#}
#location ~ ^/phpMyAdmin/ {
# root "c:/winnmp/include";
#}
## Notice that the root directive lacks /phpMyAdmin because Nginx adds the URL path /phpMyAdmin to the root path, so the resulting directory is c:/winnmp/include/phpMyAdmin
## PHP for localhost ##
#######################
location ~ \.php$ {
try_files $uri =404;
include nginx.fastcgi.conf;
include nginx.redis.conf;
fastcgi_pass php_farm;
allow 127.0.0.1; # Do Not Change ! Security Risk !
allow ::1; # Do Not Change ! Security Risk !
deny all; # Do Not Change ! Security Risk !
}
# How to allow access from LAN and Internet to your local project:
# http://WinNMP.wtriple.com/howtos.php#How-to-allow-access-from-LAN-and-Internet-to-your-local-project
}
include domains.d/*.conf;
include nginx.phpfarm.conf;
}
Considering I'm on windows machine, I'm using WinNMP to run NGINX.
The things that I believe that are important, that I have checked are:
The payload is an array containing 2 short strings ( up to 5 characters ) with no strange characters
I have re-worked the tour-addons.php script to only return a string "ok" and 200 HTTP code, to make sure the the amount of data going over a network is not an issue - still the same behavior
Following the online responses, I have updated my fastcgi parameters and have restarted NGINX, but still the same result.
I have also tried to make the intervals between the requests to be longer ( up to 10-15 seconds ) to make sure that I am not sending too many requests in short amount of time, but still with the same result. Even with 30 seconds in between the requests, for the SAME request, every 4th fails.
If I use postman to send the requests, the same behavior is repeated with 502 bad gateway having the error: The server was acting as a gateway or proxy and received an invalid response from the upstream server.
Thank you in advance!