The Google Compute Engine Discovery plugin uses the GCE API for unicast discovery.
This plugin can be installed using the plugin manager:
sudo bin/elasticsearch-plugin install discovery-gce
The plugin must be installed on every node in the cluster, and each node must be restarted after installation.
This plugin can be downloaded for offline install from https://artifacts.elastic.co/downloads/elasticsearch-plugins/discovery-gce/discovery-gce-5.6.3.zip.
The plugin can be removed with the following command:
sudo bin/elasticsearch-plugin remove discovery-gce
The node must be stopped before removing the plugin.