Merge branch 'patch/geo-avoid-locking-itself-out' into 'master'

Geo: Avoid locking yourself out when adding a GeoNode

This is a fix to https://gitlab.com/gitlab-org/gitlab-ee/issues/374 for Geo (#76).

It was possible to lock yourself out on the primary node, as in this example:

1. My GitLab domain is example.com
2. I go to the Geo nodes admin area for the first time (no node yet registered)
3. I register a new node http://example.com but I forget to mark it as primary
4. The GitLab server is now read-only and I cannot undo my action because of that
5. Users start e-mailing me death threats because they cannot use GitLab

This should be in 8.5 too.
cc @DouweM 

See merge request !252

app/models/geo_node.rb

@@ -72,4 +72,13 @@ class GeoNode < ActiveRecord::Base
   def change_geo_node_key_title
     self.geo_node_key.title = "Geo node: #{self.url}" if self.geo_node_key
   end
+
+  def validate(record)
+    # Prevent locking yourself out
+    if record.host == Gitlab.config.gitlab.host &&
+       record.port == Gitlab.config.gitlab.port &&
+       record.relative_url_root == Gitlab.config.gitlab.relative_url_root && !record.primary
+      record.errors[:base] << 'Current node must be the primary node or you will be locking yourself out'
+    end
+  end
 end

spec/models/geo_node_spec.rb

@@ -32,6 +32,18 @@ describe GeoNode, type: :model do
     end
   end
 
+  context 'prevent locking yourself out' do
+    subject do
+      GeoNode.new(host: Gitlab.config.gitlab.host,
+                  port: Gitlab.config.gitlab.port,
+                  relative_url_root: Gitlab.config.gitlab.relative_url_root)
+    end
+
+    it 'does not accept adding a non primary node with same details as current_node' do
+      expect(subject).not_to be_valid
+    end
+  end
+
   describe '#uri' do
     context 'when all fields are filled' do
       subject { GeoNode.new(schema: 'https', host: 'localhost', port: 3000, relative_url_root: 'gitlab') }