Hide unavailable loggregator endpoints from / response

Use a nil-when-blank helper for the logging, log_cache, and log_stream
links in the root controller, matching the existing pattern used by
credhub_link and routing_link. The link entry becomes nil when the
underlying URL is not configured, instead of advertising an empty href.

Author: philippthun

app/controllers/runtime/root_controller.rb

@@ -41,17 +41,11 @@ def read
           credhub: credhub_link,
           routing: routing_link,
 
-          logging: {
-            href: config.get(:doppler, :url)
-          },
+          logging: logging_link,
 
-          log_cache: {
-            href: config.get(:log_cache, :url)
-          },
+          log_cache: log_cache_link,
 
-          log_stream: {
-            href: config.get(:log_stream, :url)
-          },
+          log_stream: log_stream_link,
 
           app_ssh: {
             href: config.get(:info, :app_ssh_endpoint),
@@ -88,6 +82,24 @@ def routing_link
       { href: config.get(:routing_api, :url) }
     end
 
+    def logging_link
+      return if config.get(:doppler, :url).blank?
+
+      { href: config.get(:doppler, :url) }
+    end
+
+    def log_cache_link
+      return if config.get(:log_cache, :url).blank?
+
+      { href: config.get(:log_cache, :url) }
+    end
+
+    def log_stream_link
+      return if config.get(:log_stream, :url).blank?
+
+      { href: config.get(:log_stream, :url) }
+    end
+
     def cloud_controller_v2(api_url_builder)
       {
         cloud_controller_v2:

spec/unit/controllers/runtime/root_controller_spec.rb

@@ -127,29 +127,91 @@ module VCAP::CloudController
         expect(hash['links']['network_policy_v1']['href']).to eq(expected_uri)
       end
 
-      it 'returns a link to the logging API' do
-        expected_uri = 'wss://doppler.my-super-cool-cf.com:1234'
-        TestConfig.override(doppler: { url: expected_uri })
+      describe 'logging link' do
+        context 'doppler url is configured' do
+          it 'returns a link to the logging API' do
+            expected_uri = 'wss://doppler.my-super-cool-cf.com:1234'
+            TestConfig.override(doppler: { url: expected_uri })
 
-        get '/'
-        hash = Oj.load(last_response.body)
-        expect(hash['links']['logging']['href']).to eq(expected_uri)
+            get '/'
+            hash = Oj.load(last_response.body)
+            expect(hash['links']['logging']['href']).to eq(expected_uri)
+          end
+        end
+
+        context 'doppler url is blank' do
+          before do
+            TestConfig.override(doppler: { url: '' })
+          end
+
+          it 'does not return a link' do
+            get '/'
+            hash = Oj.load(last_response.body)
+            expect(hash['links']['logging']).to be_nil
+          end
+        end
       end
 
-      it 'returns a link to the log cache API' do
-        expected_uri = 'https://log-cache.example.com'
+      describe 'log_cache link' do
+        context 'log_cache url is configured' do
+          it 'returns a link to the log cache API' do
+            expected_uri = 'https://log-cache.example.com'
 
-        get '/'
-        hash = Oj.load(last_response.body)
-        expect(hash['links']['log_cache']['href']).to eq(expected_uri)
+            get '/'
+            hash = Oj.load(last_response.body)
+            expect(hash['links']['log_cache']['href']).to eq(expected_uri)
+          end
+        end
+
+        context 'log_cache url is blank' do
+          before do
+            TestConfig.override(log_cache: { url: '' })
+          end
+
+          it 'does not return a link' do
+            get '/'
+            hash = Oj.load(last_response.body)
+            expect(hash['links']['log_cache']).to be_nil
+          end
+        end
       end
 
-      it 'returns a link to the v2 logging API' do
-        expected_uri = 'https://log-stream.example.com'
+      describe 'log_stream link' do
+        context 'log_stream url is configured' do
+          it 'returns a link to the v2 logging API' do
+            expected_uri = 'https://log-stream.example.com'
 
-        get '/'
-        hash = Oj.load(last_response.body)
-        expect(hash['links']['log_stream']['href']).to eq(expected_uri)
+            get '/'
+            hash = Oj.load(last_response.body)
+            expect(hash['links']['log_stream']['href']).to eq(expected_uri)
+          end
+        end
+
+        context 'log_stream url is blank' do
+          before do
+            TestConfig.override(log_stream: { url: '' })
+          end
+
+          it 'does not return a link' do
+            get '/'
+            hash = Oj.load(last_response.body)
+            expect(hash['links']['log_stream']).to be_nil
+          end
+        end
+      end
+
+      context 'all loggregator urls are blank' do
+        before do
+          TestConfig.override(doppler: { url: '' }, log_cache: { url: '' }, log_stream: { url: '' })
+        end
+
+        it 'returns nil for all three loggregator links' do
+          get '/'
+          hash = Oj.load(last_response.body)
+          expect(hash['links']['logging']).to be_nil
+          expect(hash['links']['log_cache']).to be_nil
+          expect(hash['links']['log_stream']).to be_nil
+        end
       end
 
       it 'returns a link for app_ssh with metadata' do