Use registry as singleton object

Signed-off-by: Ahmad Tolba <tolpa1@gmail.com>

lib/prometheus/client.rb

@@ -8,7 +8,7 @@ module Prometheus
   module Client
     # Returns a default registry object
     def self.registry
-      @registry ||= Registry.new
+      Registry.instance
     end
 
     def self.config

lib/prometheus/client/registry.rb

@@ -5,13 +5,16 @@
 require 'prometheus/client/gauge'
 require 'prometheus/client/histogram'
 require 'concurrent'
+require 'singleton'
 
 module Prometheus
   module Client
     # Registry
     class Registry
       class AlreadyRegisteredError < StandardError; end
 
+      include Singleton
+
       def initialize
         @metrics = {}
         @lock    = Concurrent::ReentrantReadWriteLock.new

spec/prometheus/client/formats/text_spec.rb

@@ -10,7 +10,7 @@
     Prometheus::Client.config.data_store = Prometheus::Client::DataStores::Synchronized.new
   end
 
-  let(:registry) { Prometheus::Client::Registry.new }
+  let(:registry) { Prometheus::Client::Registry.instance }
 
   before do
     foo = registry.counter(:foo,

spec/prometheus/client/registry_spec.rb

@@ -4,7 +4,7 @@
 require 'prometheus/client/registry'
 
 describe Prometheus::Client::Registry do
-  let(:registry) { Prometheus::Client::Registry.new }
+  let(:registry) { Prometheus::Client::Registry.instance }
 
   describe '.new' do
     it 'returns a new registry instance' do
@@ -13,6 +13,8 @@
   end
 
   describe '#register' do
+    let(:registry) { Prometheus::Client::Registry.clone.instance }
+
     it 'registers a new metric container and returns it' do
       metric = double(name: :test)
 
@@ -89,6 +91,8 @@ def registry.exist?(*args)
   end
 
   describe '#exist?' do
+    let(:registry) { Prometheus::Client::Registry.clone.instance }
+
     it 'returns true if a metric name has been registered' do
       registry.register(double(name: :test))
 
@@ -101,6 +105,8 @@ def registry.exist?(*args)
   end
 
   describe '#get' do
+    let(:registry) { Prometheus::Client::Registry.clone.instance }
+
     it 'returns a previously registered metric container' do
       registry.register(double(name: :test))
 

spec/prometheus/middleware/collector_spec.rb

@@ -12,7 +12,7 @@
   end
 
   let(:registry) do
-    Prometheus::Client::Registry.new
+    Prometheus::Client::Registry.instance
   end
 
   let(:original_app) do
@@ -41,18 +41,22 @@
     expect(last_response).to be_ok
   end
 
-  it 'traces request information' do
-    expect(Benchmark).to receive(:realtime).and_yield.and_return(0.2)
+  context 'trace' do
+    let(:registry) { Prometheus::Client::Registry.clone.instance }
 
-    get '/foo'
+    it 'traces request information' do
+      expect(Benchmark).to receive(:realtime).and_yield.and_return(0.2)
 
-    metric = :http_server_requests_total
-    labels = { method: 'get', path: '/foo', code: '200' }
-    expect(registry.get(metric).get(labels: labels)).to eql(1.0)
+      get '/foo'
 
-    metric = :http_server_request_duration_seconds
-    labels = { method: 'get', path: '/foo' }
-    expect(registry.get(metric).get(labels: labels)).to include("0.1" => 0, "0.25" => 1)
+      metric = :http_server_requests_total
+      labels = { method: 'get', path: '/foo', code: '200' }
+      expect(registry.get(metric).get(labels: labels)).to eql(1.0)
+
+      metric = :http_server_request_duration_seconds
+      labels = { method: 'get', path: '/foo' }
+      expect(registry.get(metric).get(labels: labels)).to include("0.1" => 0, "0.25" => 1)
+    end
   end
 
   it 'normalizes paths containing numeric IDs by default' do
@@ -113,6 +117,7 @@
         metrics_prefix: 'lolrus',
       )
     end
+    let(:registry) { Prometheus::Client::Registry.clone.instance }
 
     it 'provides alternate metric names' do
       expect(

spec/prometheus/middleware/exporter_spec.rb

@@ -7,7 +7,7 @@
   include Rack::Test::Methods
 
   let(:registry) do
-    Prometheus::Client::Registry.new
+    Prometheus::Client::Registry.instance
   end
 
   let(:app) do