Add a warning for Postgresql < 9.6 when show replication status

ee/app/views/admin/geo_nodes/index.html.haml

@@ -18,6 +18,9 @@
   %strong exact order
   they appear.
 
+- unless Gitlab::Database.pg_stat_wal_receiver_supported?
+  %p.alert.text-danger WARNING: Please upgrade Postgresql to version 9.6 or greater as the status of the streaming cannot be determined realiable enough in this version
+
 - if @nodes.any?
   #js-geo-nodes{ data: { primary_version: "#{Gitlab::VERSION}", primary_revision: "#{Gitlab::REVISION}", node_details_path: "#{admin_geo_nodes_path}", node_actions_allowed: "#{Gitlab::Database.read_write?}", node_edit_allowed: "#{Gitlab::Geo.license_allows?}" } }
 - else

ee/lib/gitlab/geo/health_check.rb

@@ -7,7 +7,7 @@ module Gitlab
         return '' unless Gitlab::Geo.secondary?
         return 'The Geo database configuration file is missing.' unless Gitlab::Geo.geo_database_configured?
         return 'The Geo node has a database that is not configured for streaming replication with the primary node.' unless self.database_secondary?
-        return 'The Geo node does not appear to be replicating data from the primary node.' unless self.streaming_active?
+        return 'The Geo node does not appear to be replicating data from the primary node.' if Gitlab::Database.pg_stat_wal_receiver_supported? && !self.streaming_active?
 
         database_version  = self.get_database_version.to_i
         migration_version = self.get_migration_version.to_i

ee/lib/tasks/geo.rake

@@ -219,6 +219,12 @@ namespace :geo do
     puts GeoNode.current_node_url
     puts '-----------------------------------------------------'.color(:yellow)
 
+    unless Gitlab::Database.pg_stat_wal_receiver_supported?
+      puts
+      puts 'WARNING: Please upgrade Postgresql to version 9.6 or greater as the status of the streaming cannot be determined realiable enough for this version'.color(:red)
+      puts
+    end
+
     print 'GitLab version: '.rjust(COLUMN_WIDTH)
     puts Gitlab::VERSION
 

lib/gitlab/database.rb

@@ -54,6 +54,10 @@ module Gitlab
       postgresql? && version.to_f >= 9.4
     end
 
+    def self.pg_stat_wal_receiver_supported?
+      postgresql? && version.to_f >= 9.6
+    end
+
     def self.nulls_last_order(field, direction = 'ASC')
       order = "#{field} #{direction}"
 

spec/ee/spec/lib/gitlab/geo/health_check_spec.rb

@@ -67,12 +67,21 @@ describe Gitlab::Geo::HealthCheck, :postgresql do
       expect(subject.perform_checks).to match(/Current Geo database version \([0-9]+\) does not match latest migration \([0-9]+\)/)
     end
 
-    it 'returns an error when replication lag is not present' do
+    it 'returns an error when streaming is not active and Postgresql supports pg_stat_wal_receiver' do
+      allow(Gitlab::Database).to receive(:pg_stat_wal_receiver_supported?).and_return(true)
       allow(described_class).to receive(:database_secondary?).and_return(true)
       allow(described_class).to receive(:streaming_active?).and_return(false)
 
       expect(subject.perform_checks).to match(/The Geo node does not appear to be replicating data from the primary node/)
     end
+
+    it 'returns an error when streaming is not active and Postgresql does not support pg_stat_wal_receiver' do
+      allow(Gitlab::Database).to receive(:pg_stat_wal_receiver_supported?).and_return(false)
+      allow(described_class).to receive(:database_secondary?).and_return(true)
+      allow(described_class).to receive(:streaming_active?).and_return(false)
+
+      expect(subject.perform_checks).to be_empty
+    end
   end
 
   describe 'MySQL checks' do