Logstash talking to rubygems.org during running?

Is there a scenario under which AFTER the configuration files have been checked and plugins are downloaded, logstash would try to talk to rubygems.org?

I have logstash version logstash 2.1.0. I have checked the configuration files with --configtest option and it checks out okay ..

/opt/logstash/bin/logstash --configtest -f logstash
DEBUG: exec /opt/logstash/vendor/jruby/bin/jruby --1.9 -J-XX:+UseParNewGC -J-XX:+UseConcMarkSweepGC -J-Djava.awt.headless=true -J-XX:CMSInitiatingOccupancyFraction=75 -J-XX:+UseCMSInitiatingOccupancyOnly -J-XX:+HeapDumpOnOutOfMemoryError -J-XX:HeapDumpPath=/opt/logstash/heapdump.hprof -J-Xmx1g /opt/logstash/lib/bootstrap/environment.rb logstash/runner.rb agent --configtest -f logstash
Configuration OK

However once logstash is started, it exits saying this

DEBUG: exec /opt/logstash/vendor/jruby/bin/jruby --1.9 -J-XX:+UseParNewGC -J-XX:+UseConcMarkSweepGC -J-Djava.awt.headless=true -J-XX:CMSInitiatingOccupancyFraction=75 -J-XX:+UseCMSInitiatingOccupancyOnly -J-XX:+HeapDumpOnOutOfMemoryError -J-XX:HeapDumpPath=/opt/logstash/heapdump.hprof -J-Xmx1g /opt/logstash/lib/bootstrap/environment.rb logstash/runner.rb agent -f /opt/logstash
The error reported is:
  initialize: name or service not known

The plugins that I am using in the configuration are installed (as verified by plugin list) - In case it helps, I am using logstash-input-sqs, logstash-output-sns, logstash-output-tcp, logstash-filter-mutate. They are all installed

I understand the error "initialize: name or service not known" has to do with connectivity from my docker container to rubygems.org. That's cool - except if all the preconditions above are satisfied, it should NOT talk to rubygems.

Is there a dependency that is obvious and I am missing it?

Thanks for any new ideas on what to look at.

Edit: I just verified, connectivity to rubygems.org is broken (my entire docker container is having connectivity issues). I fully intend to fix the underlying problem of connectivity - but curious to understand why logstash would be trying to talk to rubygems.org during running...

How do you know it's rubygems, did you do any packet sniffing to see or is it just a guess?

I'd suggest that it's probably something in your config that cannot resolve the network address in there.

Brilliant thinking! It was a guess. It was one of the other things in my configuration - which happened to have hosts for ES, some TCP hosts, and a bunch of other things. The problem was network connectivity, it just was NOT to rubygems.org ..

@Mark - thanks! Appreciate your suggestion, which helped me trace the problem!