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How to create custom Nginx log file

Published at: 12/10/2019

Nginx is one of the most widely used web server, regarded highly for its performance & simplicity. Log files are a common requirement for web server configurations. Let’s see how can we create nginx log files with customised values.

For example. let’s say we have setup a web API with Nginx. Now we need to monitor various metrics like number of API access, user-agent, response status etc. Below are the steps -

Define access & error log file: As per default nginx configuration at /etc/nginx/nginx.conf, below log files are defined
```
access_log /var/log/nginx/access.log;
error_log /var/log/nginx/error.log;
```
We can define different log files as well, in virtual blocks configuration, at /etc/nginx/sites-available/[virtual_block_file]

Create one or more custom log format: We can create log format specifications with a name

log_format myapilogformat '$remote_addr - $remote_user xxx[$time_local]xxx '
 '"$request" $status $body_bytes_sent '
 '"$http_referer" "$http_user_agent" $response_time ';

Update log file with log format: Now we have to update the access_log / error_log to work as per provided log format as below
```
access_log /var/log/nginx/access.log myapilogformat;
```
Save & test if no error present
```
nginx -t   #tests all nginx configurations
```
If error shown, check for syntax/ spelling errors etc. If no error found, restart nginx
```
sudo service nginx restart
```

Reference:

Nginx format options here

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