Remember to troubleshoot the 502 bad gateway error when nginx deploys the yii2 project

I had nothing to do on Saturday, so I tried to install and deploy yii2. There was no problem during the installation process, but when I deployed it to nginx, I encountered a 502 bad gateway problem. It took me a long time to fix it. This problem is something I have not encountered before when deploying yii2, so I note it here for reference.

1. Installation and deployment environment

Operating system: macOS, php version: 5.6, nginx version: 1.10.1, yii2 version: 2.0.

2, installation of yii2

The installation of yii2 is very simple, just refer to the manual on the official website. What I installed here is yii2-app-advanced (Yii 2 Advanced Project Template). The project address is on github. Just follow the installation instructions in the README step by step. I won’t go into details about this.

3, yii2 deployment on nginx

In fact, the README of the yii2-app-advanced project has made it very clear on how to deploy on nginx. There should be no problems if you follow the steps. But I was lazy during deployment and directly used the nginx deployment parameters in the README, which resulted in a 502 bad gateway error.

The response codes starting with 5 in the HTTP status code are all caused by the server side, so take a look at the nginx log:

error log:

When I saw upstream: "fastcgi: //127.0.0.1:9090", the port seemed wrong, so I checked the configuration of the virtual host:

Let’s take a look at the configuration of php-fpm:

Sure enough, the FastCGI server listening port specified by the nginx virtual host is wrong, which will cause nginx to not get a response from the FastCGI server. So when the browser makes a request, nginx returns a 502 status code to the browser, telling the browser that the upstream FastCGI server has not responded.

4, solved

In the nginx virtual host, modify the port specified by fastcgi_pass correctly, and this error will be solved.

5, summary

(1) Errors starting with HTTP status code 5 are caused by the server side. 502 bad gateway is caused by the server (web server) working as a gateway or proxy trying to execute a request. It receives an invalid message from the upstream server (fastcgi server). the response to.

(2) fastcgi_pass is a configuration directive of the ngx_http_fastcgi_module module. It specifies the address of the fastcgi server. Its description in the nginx document is as follows:

<span style="color: #008080;"> 1</span> <span style="color: #000000;">Syntax:    fastcgi_pass address;
</span><span style="color: #008080;"> 2</span> <span style="color: #0000ff;">Default</span><span style="color: #000000;">:    —
</span><span style="color: #008080;"> 3</span> Context:    location, <span style="color: #0000ff;">if</span> <span style="color: #0000ff;">in</span><span style="color: #000000;"> location
</span><span style="color: #008080;"> 4</span> 
<span style="color: #008080;"> 5</span> <span style="color: #000000;">Sets the address of a FastCGI server. The address can be specified as a domain name or IP address, and a port:
</span><span style="color: #008080;"> 6</span> fastcgi_pass localhost:9000<span style="color: #000000;">;
</span><span style="color: #008080;"> 7</span> 
<span style="color: #008080;"> 8</span> or as a UNIX-<span style="color: #000000;">domain socket path:
</span><span style="color: #008080;"> 9</span> fastcgi_pass unix:/tmp/<span style="color: #000000;">fastcgi.socket;
</span><span style="color: #008080;">10</span> 
<span style="color: #008080;">11</span> <span style="color: #0000ff;">If</span> a domain name resolves to several addresses, all of them will be used <span style="color: #0000ff;">in</span> a round-robin fashion. <span style="color: #0000ff;">In</span> addition, an address can be specified as a server group.

Reference:

HTTP status code

fastcgi_pass

Syntax:	<strong>fastcgi_pass</strong> <code><em>address</em>;
Default:	—
Context:	location, if in location