While preparing for an ElasticSearch upgrade I checked the Upgrade assistant.
One (critical) issue was mentioned: Discovery configuration is required in production mode
Let’s have a look what the documentation has to mention:
Production deployments of Elasticsearch now require at least one of the following settings to be specified in the
elasticsearch.ymlconfiguration file:
discovery.seed_hosts
discovery.seed_providers
cluster.initial_master_nodes
discovery.zen.ping.unicast.hosts
discovery.zen.hosts_providerThe first three settings in this list are only available in versions 7.0 and above. If you are preparing to upgrade from an earlier version, you must set
discovery.zen.ping.unicast.hostsordiscovery.zen.hosts_provider.
In our case we don’t want to form a multiple-node cluster. So we ignore the documentation above and instead change the discovery.type to single-node.
For more information about when you might use this setting, see Single-node discovery.