1 files changed, 78 insertions, 0 deletions
diff --git a/lib/gitlab/consul/internal.rb b/lib/gitlab/consul/internal.rb
new file mode 100644
index 00000000000..3afc24ddab9
--- /dev/null
+++ b/lib/gitlab/consul/internal.rb
@@ -0,0 +1,78 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module Consul
+    class Internal
+      Error = Class.new(StandardError)
+      UnexpectedResponseError = Class.new(Gitlab::Consul::Internal::Error)
+      SocketError = Class.new(Gitlab::Consul::Internal::Error)
+      SSLError = Class.new(Gitlab::Consul::Internal::Error)
+      ECONNREFUSED = Class.new(Gitlab::Consul::Internal::Error)
+
+      class << self
+        def api_url
+          Gitlab.config.consul.api_url.to_s.presence if Gitlab.config.consul
+        rescue Settingslogic::MissingSetting
+          Gitlab::AppLogger.error('Consul api_url is not present in config/gitlab.yml')
+
+          nil
+        end
+
+        def discover_service(service_name:)
+          return unless service_name.present? && api_url
+
+          api_path = URI.join(api_url, '/v1/catalog/service/', URI.encode_www_form_component(service_name)).to_s
+          services = json_get(api_path, allow_local_requests: true, open_timeout: 5, read_timeout: 10)
+
+          # Use the first service definition
+          service = services&.first
+
+          return unless service
+
+          service_address = service['ServiceAddress'] || service['Address']
+          service_port = service['ServicePort']
+
+          [service_address, service_port]
+        end
+
+        def discover_prometheus_server_address
+          service_address, service_port = discover_service(service_name: 'prometheus')
+
+          return unless service_address && service_port
+
+          "#{service_address}:#{service_port}"
+        end
+
+        private
+
+        def json_get(path, options)
+          response = get(path, options)
+          code = response.try(:code)
+          body = response.try(:body)
+
+          raise Consul::Internal::UnexpectedResponseError unless code == 200 && body
+
+          parse_response_body(body)
+        end
+
+        def parse_response_body(body)
+          Gitlab::Json.parse(body)
+        rescue
+          raise Consul::Internal::UnexpectedResponseError
+        end
+
+        def get(path, options)
+          Gitlab::HTTP.get(path, options)
+        rescue ::SocketError
+          raise Consul::Internal::SocketError
+        rescue OpenSSL::SSL::SSLError
+          raise Consul::Internal::SSLError
+        rescue Errno::ECONNREFUSED
+          raise Consul::Internal::ECONNREFUSED
+        rescue
+          raise Consul::Internal::UnexpectedResponseError
+        end
+      end
+    end
+  end
+end