Merge branch '2911-shuffle-es-urls' into 'master'

Spread load across all nodes in an elasticsearch cluster

Closes #2911

See merge request !2625

changelogs/unreleased-ee/2911-shuffle-es-urls.yml

+---
+title:  Spread load across all nodes in an elasticsearch cluster
+merge_request: 2625
+author:

lib/gitlab/elastic/client.rb

@@ -10,7 +10,11 @@ module Gitlab
       # Takes a hash as returned by `ApplicationSetting#elasticsearch_config`,
       # and configures itself based on those parameters
       def self.build(config)
-        base_config = { urls: config[:url], retry_on_failure: true }
+        base_config = {
+          urls: config[:url],
+          randomize_hosts: true,
+          retry_on_failure: true
+        }
 
         if config[:aws]
           creds = resolve_aws_credentials(config)