Not reuse persistent connection for healthchecks

There is a large number of EOFError's due to the persistent connections being
inactive. For the healthcheck there is no real benefit to try to use a
persistent connection so this changes it to use a new connection.

app/services/healthcheck/pvb_api_check.rb

@@ -4,8 +4,18 @@ class PvbApiCheck
 
     def initialize(description)
       build_report(description) do
-        { ok: PrisonVisits::Api.instance.healthy? }
+        { ok: healthy_pvb_connection }
       end
     end
+
+  private
+
+    def healthy_pvb_connection
+      client.healthcheck.status == 200
+    end
+
+    def client
+      PrisonVisits::Client.new(Rails.configuration.api_host, persistent: false)
+    end
   end
 end

app/services/prison_visits/api.rb

@@ -11,10 +11,6 @@ def initialize
       end
     end
 
-    def healthy?
-      pool.with { |client| client.healthcheck.status == 200 }
-    end
-
     def get_prisons
       result = pool.with { |client| client.get('/prisons') }
 

app/services/prison_visits/client.rb

@@ -8,10 +8,10 @@ class Client
     TIMEOUT = 3 # seconds
     EXCON_INSTRUMENT_NAME = 'pvb_api'.freeze
 
-    def initialize(host)
+    def initialize(host, persistent: true)
       @host = host
       @connection = Excon.new(
-        host, persistent: true, connect_timeout: TIMEOUT,
+        host, persistent: persistent, connect_timeout: TIMEOUT,
               read_timeout: TIMEOUT, write_timeout: TIMEOUT, retry_limit: 3,
               instrumentor: ActiveSupport::Notifications,
               instrumentor_name: EXCON_INSTRUMENT_NAME
@@ -31,10 +31,7 @@ def delete(route, params: {}, idempotent: true)
     end
 
     def healthcheck
-      @connection.head(
-        path: 'healthcheck',
-        persistent: false
-      )
+      @connection.head(path: 'healthcheck')
     end
 
   private

spec/controllers/healthcheck_controller_spec.rb

@@ -9,8 +9,9 @@
 
   context 'when everything is OK' do
     before do
-      allow_any_instance_of(PrisonVisits::Api).
-        to receive(:healthy?).and_return(true)
+      allow_any_instance_of(PrisonVisits::Client).
+        to receive(:healthcheck).
+        and_return(double(status: 200))
     end
 
     it { is_expected.to be_success }
@@ -30,8 +31,9 @@
 
   context 'when the healthcheck is not OK' do
     before do
-      allow_any_instance_of(PrisonVisits::Api).
-        to receive(:healthy?).and_return(false)
+      allow_any_instance_of(PrisonVisits::Client).
+        to receive(:healthcheck).
+        and_return(double(status: 502))
     end
 
     it { is_expected.to have_http_status(:bad_gateway) }

spec/services/healthcheck/pvb_api_check_spec.rb

@@ -5,9 +5,9 @@
 
   context 'with a healthy API' do
     before do
-      allow(PrisonVisits::Api.instance).
-        to receive(:healthy?).
-        and_return(true)
+      allow_any_instance_of(PrisonVisits::Client).
+        to receive(:healthcheck).
+        and_return(double(status: 200))
     end
 
     it { is_expected.to be_ok }
@@ -23,8 +23,8 @@
   context 'with an unhealthy API' do
     context 'that raises an error' do
       before do
-        allow(PrisonVisits::Api.instance).
-          to receive(:healthy?).
+        allow_any_instance_of(PrisonVisits::Client).
+          to receive(:healthcheck).
           and_raise(StandardError, 'some other exception')
       end
 
@@ -41,9 +41,9 @@
 
     context 'that reports the status' do
       before do
-        allow(PrisonVisits::Api.instance).
-          to receive(:healthy?).
-          and_return(false)
+        allow_any_instance_of(PrisonVisits::Client).
+          to receive(:healthcheck).
+          and_return(double(status: 500))
       end
 
       it { is_expected.to_not be_ok }

spec/services/prison_visits/api_spec.rb

@@ -84,17 +84,6 @@
     end
   end
 
-  describe 'healthy?', vcr: { cassette_name: 'healthy' } do
-    subject { super().healthy? }
-
-    it 'makes a request to the healtcheck endpoint' do
-      is_expected.to eq(true)
-
-      expect(WebMock).
-        to have_requested(:head, /healthcheck/)
-    end
-  end
-
   describe 'get_prisons', vcr: { cassette_name: 'get_prisons' } do
     subject { super().get_prisons }
 

spec/services/prison_visits/client_spec.rb

@@ -14,6 +14,12 @@
     RequestStore.store[:request_id] = '5cd2ef1a-4b7e-11e7-a919-92ebcb67fe33'
   end
 
+  describe '#healthcheck' do
+    it 'calls the healthcheck endpoint', vcr: { cassette_name: 'healthcheck' } do
+      expect(subject.healthcheck.status). to eq(200)
+    end
+  end
+
   describe 'error handling' do
     it 'parses returned JSON errors', vcr: { cassette_name: 'client_json_error' } do
       expect {