Front-end nginx cannot call back-end php: troubleshooting and solutions

When your project includes both front-end and back-end, and the problem "front-end nginx cannot call back-end php" occurs during debugging, it may give you a headache. In order to solve this problem, we need to do some troubleshooting and debugging work. This article will introduce you to troubleshooting ideas and solutions in detail.

Troubleshooting Ideas

Before troubleshooting the problem, we first need to understand the interaction process between the front-end nginx and the back-end php. When the browser requests a URL, the request first enters the front-end nginx, and nginx forwards the request to the back-end php according to the requested URL. The back-end php processes the request and returns the result, and nginx returns the result to the browser.

Therefore, during the troubleshooting process, we need to check the configuration of the front-end nginx and back-end php in order to ensure that the interaction between them is normal.

1. Check the front-end nginx configuration

First check whether the front-end nginx configuration is correct. You can proceed through the following steps:

1. Open the nginx configuration file and check whether there is a correct proxy_pass configuration in the server segment, that is, the address, port and URI of the backend PHP.
2. Make sure the php-fpm process is running and listening on the correct port.
3. Make sure that the users and groups of nginx and php-fpm are the same. This can prevent conflicts caused by permission issues.
4. Check the back-end php configuration

If the front-end nginx configuration has been confirmed correct, then we need to check whether the back-end php configuration is correct. You can proceed through the following steps:

1. Ensure that PHP has been installed and the version meets the project requirements.
2. Check the php-fpm configuration file to ensure that the listening port is consistent with the Nginx reverse proxy configuration.
3. Check the php.ini file to ensure that the correct PHP error level is set to facilitate locating problems in the future.
4. Check the log

If no problem is found in the above two checks, then we can check the error logs of Nginx and PHP to further troubleshoot the problem.

• Nginx error log path: /var/log/nginx/error.log (Ubuntu), /usr/local/var/log/nginx/error.log (macOS)
• PHP error log path:/usr/local/var/log/php-fpm.log (macOS)

In the log, you can view the specific error information, as well as the corresponding timestamp and request URL. This will help troubleshoot the source and solution of the problem.

Solution

If after investigation, we find that the problem that front-end nginx cannot call back-end php still exists, then we need to further solve this problem. The following are some possible solutions:

1. Restart the service

If the nginx or php-fpm process suddenly stops, the request may not be processed normally. At this point, we can try to restart the nginx and php-fpm processes and test the request again.

2. Check the network

If the front-end nginx and back-end php are running on different servers, then we need to ensure that the network connection is normal. You can test the network connection between servers through the ping or telnet command to further troubleshoot the problem.

3. Check the firewall

If the firewall blocks the communication between the front-end nginx and the back-end php, the request may not be processed normally. At this point, we need to check the server's firewall configuration to ensure that nginx can access the php-fpm process.

4. Check SELinux

SELinux is a security module on Linux that is used to limit the access rights of processes. If SELinux blocks communication between nginx and php-fpm, requests may not be processed properly. You can check whether SELinux is blocking communication between nginx and php-fpm by enabling SELinux logging.

Conclusion

The problem that front-end nginx cannot call back-end php may be caused by a variety of factors. During the troubleshooting process, we need to conduct inspection and debugging step by step according to the problem performance, find the source of the problem and solve it. A pile of rocks can make a mountain, and a pile of armpits can make a fur coat. As long as we persist with our heart, problems can always be solved.

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