NameError when using fallback timestamp logic

[ericdahl]

I'm observing that some events are not processed correctly due to a log statement issue.

Given an event like:

{
  "timestamp": "10/Aug/2021:22:48:47 +0000",
  "access": "GET / HTTP/1.1 200",
  "type": "access"
}

(that is, not using the "normal timestamp processing" but instead the secondary/backup parsing)

The result is an error such as:

2021-08-10 22:48:52 +0000 [warn]: #0 dump an error event: error_class=NameError error="undefined local variable or method `field' for #<Fluent::Plugin::ElasticsearchTimestampCheckFilter:0x00007f1780cc19a8>\nDid you mean?  yield" location="/usr/local/bundle/gems/fluent-plugin-elasticsearch-timestamp-check-0.3.0/lib/fluent/plugin/filter_elasticsearch_timestamp_check.rb:62:in `rescue in block in filter'" tag="docker.var.lib.docker.containers.83e55d29166ac414218614dda4e51e0409d9844e0629d50128edbb5e3bc6c9d7.83e55d29166ac414218614dda4e51e0409d9844e0629d50128edbb5e3bc6c9d7-json.log" time=2021-08-10 

22:48:52.731255982 +0000 record={"timestamp"=>"10/Aug/2021:22:48:47 +0000", "access"=>"GET / HTTP/1.1 200"}

It seems like the issue is that field is out of scope at this line (but I don't know Ruby..):

fluent-plugin-elasticsearch-timestamp-check/lib/fluent/plugin/filter_elasticsearch_timestamp_check.rb

Line 62 in 98862cf

$log.debug("#{field} (#{timestamp}) failed to parse, trying next")