Nginx allows to override the default access_logs format via the log_format directive. We are using this feature to get Nginx logs in a JSON format.
However, as noted in kong.log docs, plugin logs are reported to the Nginx error_log directive. AFAIK, there is no option to set error_log format.
Is there any workaround we can use to get plugins output in a JSON format?
Hi, there is indeed no built-in way to customize the error_log format. I have seen some options but I don’t take this as a recommendation, as I haven’t tried them myself:
Thanks for answering
I’m not sure how we can use those options for plugins logs:
- You could try generating one access log entry per error, but that is a hack: logging - Is it possible to specify custom error log format on Nginx? - Stack Overflow
We are logging info in the plugins, not only errors. So we actually don’t have a status code to work with…
- You could try to parse the error_log and generate a json log from it. Here’s some info about the log format: logging - NGINX error log format documentation - Stack Overflow
Do you mean to alter the log files themselves after they are generated? It is doable but really complicates the whole logging process 
Right. You can’t use the “error code escape” then.
I was not proposing modifying the log files. The exact solution will depend on your sytem. You could do a very simple demon which translates every new line on the logs to a JSON line in a different, separate file, and then use that to feed your system. Or you could batch the json requests, aggregate them in memory, and periodically send your aggregator a POST request, if it accepts that.