Workaround changed behavior in Protobuf's Message#to_h (#4401)

The behavior of 'to_h' for Protobuf objects changed [1]; unset and
default values are now being omitted. Thus the update of Protobuf
libraries [2] led to an incompatible change as the Cloud Controller
returned "null" instead of "0" for the external and internal ports as
part of the process stats endpoint.

With this change the hash is created manually by accessing all fields in
the Protobuf object(s) directly.

[1] protocolbuffers/protobuf#15234
[2] #4359

Author: philippthun

lib/cloud_controller/diego/reporters/instances_stats_reporter.rb

@@ -78,7 +78,7 @@ def build_info(state, actual_lrp, process, stats, quota_stats, log_cache_errors)
             host: actual_lrp.actual_lrp_net_info.address,
             instance_guid: actual_lrp.actual_lrp_instance_key.instance_guid,
             port: get_default_port(actual_lrp.actual_lrp_net_info),
-            net_info: actual_lrp.actual_lrp_net_info.to_h,
+            net_info: actual_lrp_net_info_to_hash(actual_lrp.actual_lrp_net_info),
             uptime: nanoseconds_to_seconds((Time.now.to_f * 1e9) - actual_lrp.since),
             fds_quota: process.file_descriptors
           }.merge(metrics_data_for_instance(stats, quota_stats, log_cache_errors, Time.now.to_datetime.rfc3339, actual_lrp.actual_lrp_key.index))
@@ -198,6 +198,22 @@ def get_default_port(net_info)
 
         0
       end
+
+      def actual_lrp_net_info_to_hash(net_info)
+        %i[address instance_address ports preferred_address].index_with do |field_name|
+          if field_name == :ports
+            net_info.ports.map(&method(:port_mapping_to_hash))
+          else
+            net_info.send(field_name)
+          end
+        end
+      end
+
+      def port_mapping_to_hash(port_mapping)
+        %i[container_port container_tls_proxy_port host_port host_tls_proxy_port].index_with do |field_name|
+          port_mapping.send(field_name)
+        end
+      end
     end
   end
 end

spec/unit/lib/cloud_controller/diego/reporters/instances_stats_reporter_spec.rb

@@ -78,6 +78,17 @@ def make_actual_lrp(instance_guid:, index:, state:, error:, since:)
           [container_metric_batch]
         end
 
+        let(:expected_lrp_1_net_info) do
+          {
+            address: 'lrp-host',
+            instance_address: '',
+            ports: [
+              { container_port: DEFAULT_APP_PORT, container_tls_proxy_port: 0, host_port: 2222, host_tls_proxy_port: 0 },
+              { container_port: 1111, container_tls_proxy_port: 0, host_port: 0, host_tls_proxy_port: 0 }
+            ],
+            preferred_address: :UNKNOWN
+          }
+        end
         let(:expected_stats_response) do
           {
             0 => {
@@ -90,7 +101,7 @@ def make_actual_lrp(instance_guid:, index:, state:, error:, since:)
                 host: 'lrp-host',
                 instance_guid: 'instance-a',
                 port: 2222,
-                net_info: lrp_1_net_info.to_h,
+                net_info: expected_lrp_1_net_info,
                 uptime: two_days_in_seconds,
                 mem_quota: 1234,
                 disk_quota: 10_234,
@@ -217,7 +228,7 @@ def make_actual_lrp(instance_guid:, index:, state:, error:, since:)
                   host: 'lrp-host',
                   instance_guid: 'instance-a',
                   port: 2222,
-                  net_info: lrp_1_net_info.to_h,
+                  net_info: expected_lrp_1_net_info,
                   uptime: two_days_in_seconds,
                   mem_quota: nil,
                   disk_quota: nil,
@@ -272,7 +283,7 @@ def make_actual_lrp(instance_guid:, index:, state:, error:, since:)
                     host: 'lrp-host',
                     instance_guid: 'instance-a',
                     port: 2222,
-                    net_info: lrp_1_net_info.to_h,
+                    net_info: expected_lrp_1_net_info,
                     uptime: two_days_in_seconds,
                     mem_quota: nil,
                     disk_quota: nil,
@@ -519,7 +530,7 @@ def make_actual_lrp(instance_guid:, index:, state:, error:, since:)
                   host: 'lrp-host',
                   instance_guid: 'instance-a',
                   port: 2222,
-                  net_info: lrp_1_net_info.to_h,
+                  net_info: expected_lrp_1_net_info,
                   uptime: two_days_in_seconds,
                   mem_quota: nil,
                   disk_quota: nil,
@@ -653,7 +664,7 @@ def make_actual_lrp(instance_guid:, index:, state:, error:, since:)
                   host: 'lrp-host',
                   instance_guid: 'instance-a',
                   port: 2222,
-                  net_info: lrp_1_net_info.to_h,
+                  net_info: expected_lrp_1_net_info,
                   uptime: two_days_in_seconds,
                   mem_quota: nil,
                   disk_quota: nil,