Support registering apps with nil tags

If an app is registered without providing tags, the droplet will be
saved successfully, but when the app is looked up, ULS will generate
a response nginx cannot deal with, which leads to an internal error.

This change makes ULS tolerant of register message without tags.

Change-Id: I053f98c76d5454a4022094828c1d33d64afa33be

lib/router/router.rb

@@ -171,6 +171,8 @@ def lookup_droplet(url)
     def register_droplet(url, host, port, tags, app_id)
       return unless host && port
       url.downcase!
+      tags ||= {}
+
       droplets = @droplets[url] || []
       # Skip the ones we already know about..
       droplets.each { |droplet|
@@ -180,7 +182,7 @@ def register_droplet(url, host, port, tags, app_id)
           return
         end
       }
-      tags.delete_if { |key, value| key.nil? || value.nil? } if tags
+      tags.delete_if { |key, value| key.nil? || value.nil? }
       droplet = {
         :app => app_id,
         :host => host,
@@ -191,7 +193,7 @@ def register_droplet(url, host, port, tags, app_id)
         :requests => 0,
         :tags => tags
       }
-      add_tag_metrics(tags) if tags
+      add_tag_metrics(tags)
       droplets << droplet
       @droplets[url] = droplets
       VCAP::Component.varz[:urls] = @droplets.size

lib/router/router_uls_server.rb

@@ -50,7 +50,7 @@ class ParserError < StandardError; end
       # Get session cookie for droplet
       new_sticky = Router.get_session_cookie(droplet)
 
-      uls_req_tags = Base64.encode64(Marshal.dump(droplet[:tags])).strip if droplet[:tags]
+      uls_req_tags = Base64.encode64(Marshal.dump(droplet[:tags])).strip
       uls_response = {
         ULS_STICKY_SESSION => new_sticky,
         ULS_BACKEND_ADDR   => "#{droplet[:host]}:#{droplet[:port]}",

spec/unit/router_spec.rb

@@ -36,6 +36,17 @@ def setup
       VCAP::Component.varz[:urls].should == 1
     end
 
+    it 'should register a droplet with nil tags' do
+      Router.register_droplet('foo.vcap.me', '10.0.1.22', 2222, nil, 123)
+      VCAP::Component.varz[:droplets].should == 1
+      VCAP::Component.varz[:urls].should == 1
+
+      droplets = Router.lookup_droplet('foo.vcap.me')
+      droplet = droplets.first
+      droplet.should have_key :tags
+      droplet[:tags].should == {}
+    end
+
     it 'should allow proper lookup' do
       Router.register_droplet('foo.vcap.me', '10.0.1.22', 2222, {}, 123)
       droplets = Router.lookup_droplet('foo.vcap.me')
@@ -49,11 +60,13 @@ def setup
       droplet.should have_key :host
       droplet.should have_key :port
       droplet.should have_key :clients
+      droplet.should have_key :tags
       droplet[:requests].should == 0
       droplet[:url].should == 'foo.vcap.me'
       droplet[:host].should == '10.0.1.22'
       droplet[:port].should == 2222
       droplet[:clients].should == {}
+      droplet[:tags].should == {}
     end
 
     it 'should allow looking up uppercase uri' do