How can I add new fields into the access log?

Plugins
1

1. Caddy version (2.10.2):

2. The problem I am having:

Hi guys, I am currently writing a new plugin which check the POST payloads, and I want to record some certain fields in the data payload, for example, the “method“ field of the POST request. I was trying to set the wanted value in the http.context and using ‘format append’ feature to append this field to the access log.
The code is like:

caddyhttp.SetVar(r.Context(), "method", data["method"])

and my Caddyfile looks like:

log {
        level info
        output file access.log {
            roll_size 10MB
            roll_keep 5
            roll_keep_for 168h
        }

	format append {
           fields {
              method {http.vars.method}
           }
           wrap json
      }
}

However, the access.log indeed has this method field, but no matter how I tried adding values, this field is always NULL in the log.
I noticed that the caddy doc says that it supports only global placeholders (e.g. {env.*} ), as shown in the picture:

image
image1037×516 60.2 KB

So does it mean that we are unable to append such information into the access log? Is there any way that I can realize this requirement?

Thanks in advance!

2

Not sure if I fully understand your use case, but have a look at this:

3

What’s the rest of your caddyfile? How is your code like? How are you plugging your plugin?

4

Thank you so much @stbu , this is exactly what I am looking for!

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