Including new Gems to work with logstash-filter-ruby

[Smitto (Nathan Smith)]

I'm working on applying some custom filters using the logstash-filter-ruby plugin that make use of the Timezone gem at https://github.com/panthomakos/timezone. When simply adding
gem 'timezone', '~> 1.0'
to my logstash Gemfile and running bundle install, it results in the error

[!] There was an error while loading 'logstash-core-plugin-api.gemspec': No such file or directory - 
/my/path/logstash/logstash-6.5.1/logstash-core-plugin- 
api/versions-gem-copy.yml. Bundler cannot continue.

I also tried following this post, where someone used logstash-plugin update to force the installation of a new ruby gem, but it didn't work: https://github.com/elastic/logstash/issues/7016

Has anyone added custom ruby gems in their ruby filters?

[Smitto (Nathan Smith)]

Bumping this guy as I've yet to find a consensus method for using external gems in ruby filters.