You'll find the maintained version of plugin, called logstash-output-vespa_feed, along with its sister input plugin logstash-input-vespa at https://github.com/vespa-engine/vespa/tree/master/integration/logstash-plugins
You'll find the maintained version of plugin, called logstash-output-vespa_feed, along with its sister input plugin logstash-input-vespa at https://github.com/vespa-engine/vespa/tree/master/integration/logstash-plugins