Debug message causes Fatal error

[defensivedepth]

I have a very simple pipeline using the following http filter, but I continue to get errors (see here: https://gist.github.com/defensivedepth/7b8d22aeec6dedac6438d8adeaed4b1d 1)

I have tried different sites, different settings, but always come back to this error. Logstash 6.6.1

Appears to be a bug - https://discuss.elastic.co/t/http-filter-undefined-local-variable-or-method-parameters-sprintfed/169905?

---

input {
file {
path => "/input*.json"
codec => json
}

}

filter {
http {
url => "https://site.com/%{identifier}"
}

}

output {
stdout {}
}

[michaelhyatt]

Same with Logstash 6.7.0

[ttimasdf]

the parameter_sprintfed is not defined elsewhere

logstash-filter-http/lib/logstash/filters/http.rb

Line 54 in 9d9a837

@logger.debug? && @logger.debug('processing request', :url => url_for_event, :headers => headers_sprintfed, :parameters => parameters_sprintfed)