(POOLER-160) Add Prometheus to pooler startup

This is a re-architect of the vmpooler initialisation code to:
1. Allow an API service for both manager and the api
2. Add the Prometheus endpoints to the web service.
   Needed to change the way the Rack Service is started as instantiating
   using ".New" leads to a failure to initialise the http Stats
   collection.
3. Selectively load the pooler api and/or Prometheus endpoints.
4. Rework API Spec tests for revised API loading. Needed to tidy up the
   initialisation and perform a reset! after each test to avoid "leaks"
   and dependencies between the tests.

Gemfile

@@ -8,6 +8,7 @@ gem 'rake', '~> 13.0'
 gem 'redis', '~> 4.1'
 gem 'rbvmomi', '~> 2.1'
 gem 'sinatra', '~> 2.0'
+gem 'prometheus-client', '~> 2.0'
 gem 'net-ldap', '~> 0.16'
 gem 'statsd-ruby', '~> 1.4.0', :require => 'statsd'
 gem 'connection_pool', '~> 2.2'

bin/vmpooler

@@ -25,12 +25,16 @@ end
 
 if torun.include? 'api'
   api = Thread.new do
-    thr = Vmpooler::API.new
     redis = Vmpooler.new_redis(redis_host, redis_port, redis_password)
-    thr.helpers.configure(config, redis, metrics)
-    thr.helpers.execute!
+    Vmpooler::API.execute(torun, config, redis, metrics)
   end
   torun_threads << api
+elsif metrics.respond_to?(:setup_prometheus_metrics)
+  # Run the cut down API - Prometheus Metrics only.
+  prometheus_only_api = Thread.new do
+    Vmpooler::API.execute(torun, config, nil, metrics)
+  end
+  torun_threads << prometheus_only_api
 end
 
 if torun.include? 'manager'

lib/vmpooler/api.rb

@@ -2,10 +2,24 @@
 
 module Vmpooler
   class API < Sinatra::Base
-    def initialize
-      super
+    # Load API components
+    %w[helpers dashboard reroute v1 request_logger].each do |lib|
+      require "vmpooler/api/#{lib}"
     end
+    # Load dashboard components
+    require 'vmpooler/dashboard'
 
+    def self.execute(torun, config, redis, metrics)
+      self.settings.set :config, config
+      self.settings.set :redis, redis unless redis.nil?
+      self.settings.set :metrics, metrics
+      self.settings.set :checkoutlock, Mutex.new
+
+      # Deflating in all situations
+      # https://www.schneems.com/2017/11/08/80-smaller-rails-footprint-with-rack-deflate/
+      use Rack::Deflater
+
+      # not_found clause placed here to fix rspec test issue.
       not_found do
         content_type :json
 
@@ -16,37 +30,24 @@ module Vmpooler
         JSON.pretty_generate(result)
       end
 
-    # Load dashboard components
-    begin
-      require 'dashboard'
-    rescue LoadError
-      require File.expand_path(File.join(File.dirname(__FILE__), 'dashboard'))
+      if metrics.respond_to?(:setup_prometheus_metrics)
+        # Prometheus metrics are only setup if actually specified
+        # in the config file.
+        metrics.setup_prometheus_metrics
+
+        use Prometheus::Middleware::Collector, metrics_prefix: "#{metrics.metrics_prefix}_http"
+        use Prometheus::Middleware::Exporter, path: metrics.endpoint
       end
 
+      if torun.include? 'api'
         use Vmpooler::Dashboard
-
-    # Load API components
-    %w[helpers dashboard reroute v1].each do |lib|
-      begin
-        require "api/#{lib}"
-      rescue LoadError
-        require File.expand_path(File.join(File.dirname(__FILE__), 'api', lib))
-      end
-    end
-
         use Vmpooler::API::Dashboard
         use Vmpooler::API::Reroute
         use Vmpooler::API::V1
-
-    def configure(config, redis, metrics)
-      self.settings.set :config, config
-      self.settings.set :redis, redis
-      self.settings.set :metrics, metrics
-      self.settings.set :checkoutlock, Mutex.new
       end
 
-    def execute!
-      self.settings.run!
+      # Get thee started O WebServer
+      self.run!
     end
   end
 end

lib/vmpooler/metrics/promstats.rb

@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+require 'prometheus/client'
+
 module Vmpooler
   class Promstats < Metrics
     attr_reader :prefix, :endpoint, :metrics_prefix

spec/integration/api/v1/config_spec.rb

@@ -8,6 +8,13 @@ describe Vmpooler::API::V1 do
     Vmpooler::API
   end
 
+  # Added to ensure no leakage in rack state from previous tests.
+  # Removes all routes, filters, middleware and extension hooks from the current class
+  # https://rubydoc.info/gems/sinatra/Sinatra/Base#reset!-class_method 
+  before(:each) do
+    app.reset!
+  end
+
   let(:config) {
     {
       config: {
@@ -32,9 +39,8 @@ describe Vmpooler::API::V1 do
     let(:current_time) { Time.now }
 
     before(:each) do
-      app.settings.set :config, config
-      app.settings.set :redis, redis
-      app.settings.set :metrics, metrics
+      expect(app).to receive(:run!).once
+      app.execute(['api'], config, redis, metrics)
       app.settings.set :config, auth: false
       create_token('abcdefghijklmnopqrstuvwxyz012345', 'jdoe', current_time)
     end

spec/integration/api/v1/ondemandvm_spec.rb

@@ -5,7 +5,14 @@ describe Vmpooler::API::V1 do
   include Rack::Test::Methods
 
   def app()
-    Vmpooler::API end
+    Vmpooler::API
+  end
+  # Added to ensure no leakage in rack state from previous tests.
+  # Removes all routes, filters, middleware and extension hooks from the current class
+  # https://rubydoc.info/gems/sinatra/Sinatra/Base#reset!-class_method 
+  before(:each) do
+    app.reset!
+  end
 
   describe '/ondemandvm' do
     let(:prefix) { '/api/v1' }
@@ -32,13 +39,11 @@ describe Vmpooler::API::V1 do
     let(:current_time) { Time.now }
     let(:vmname) { 'abcdefghijkl' }
     let(:checkoutlock) { Mutex.new }
-    let(:redis) { MockRedis.new }
     let(:uuid) { SecureRandom.uuid }
 
     before(:each) do
-      app.settings.set :config, config
-      app.settings.set :redis, redis
-      app.settings.set :metrics, metrics
+      expect(app).to receive(:run!).once
+      app.execute(['api'], config, redis, metrics)
       app.settings.set :config, auth: false
       app.settings.set :checkoutlock, checkoutlock
       create_token('abcdefghijklmnopqrstuvwxyz012345', 'jdoe', current_time)

spec/integration/api/v1/poolreset.rb

@@ -8,6 +8,10 @@ describe Vmpooler::API::V1 do
     Vmpooler::API
   end
 
+  after(:each) do
+    Vmpooler::API.reset!
+  end
+
   let(:config) {
     {
       config: {
@@ -32,9 +36,8 @@ describe Vmpooler::API::V1 do
     let(:current_time) { Time.now }
 
     before(:each) do
-      app.settings.set :config, config
-      app.settings.set :redis, redis
-      app.settings.set :metrics, metrics
+      expect(app).to receive(:run!).once
+      app.execute(['api'], config, redis, metrics)
       app.settings.set :config, auth: false
       create_token('abcdefghijklmnopqrstuvwxyz012345', 'jdoe', current_time)
     end

spec/integration/api/v1/status_spec.rb

@@ -12,6 +12,13 @@ describe Vmpooler::API::V1 do
     Vmpooler::API
   end
 
+  # Added to ensure no leakage in rack state from previous tests.
+  # Removes all routes, filters, middleware and extension hooks from the current class
+  # https://rubydoc.info/gems/sinatra/Sinatra/Base#reset!-class_method 
+  before(:each) do
+    app.reset!
+  end
+
   describe 'status and metrics endpoints' do
     let(:prefix) { '/api/v1' }
 
@@ -32,8 +39,8 @@ describe Vmpooler::API::V1 do
     let(:current_time) { Time.now }
 
     before(:each) do
-      app.settings.set :config, config
-      app.settings.set :redis, redis
+      expect(app).to receive(:run!).once
+      app.execute(['api'], config, redis, nil)
       app.settings.set :config, auth: false
       create_token('abcdefghijklmnopqrstuvwxyz012345', 'jdoe', current_time)
     end

spec/integration/api/v1/token_spec.rb

@@ -8,14 +8,21 @@ describe Vmpooler::API::V1 do
     Vmpooler::API
   end
 
+  # Added to ensure no leakage in rack state from previous tests.
+  # Removes all routes, filters, middleware and extension hooks from the current class
+  # https://rubydoc.info/gems/sinatra/Sinatra/Base#reset!-class_method 
+  before(:each) do
+    app.reset!
+  end
+
   describe '/token' do
     let(:prefix) { '/api/v1' }
     let(:current_time) { Time.now }
     let(:config) { { } }
 
-    before do
-      app.settings.set :config, config
-      app.settings.set :redis, redis
+    before(:each) do
+      expect(app).to receive(:run!).once
+      app.execute(['api'], config, redis, nil)
     end
 
     describe 'GET /token' do
@@ -97,7 +104,9 @@ describe Vmpooler::API::V1 do
     let(:prefix) { '/api/v1' }
     let(:current_time) { Time.now }
 
-    before do
+    before(:each) do
+      expect(app).to receive(:run!).once
+      app.execute(['api'], config, redis, nil)
       app.settings.set :config, config
       app.settings.set :redis, redis
     end

spec/integration/api/v1/vm_hostname_spec.rb

@@ -12,8 +12,16 @@ describe Vmpooler::API::V1 do
     Vmpooler::API
   end
 
+  # Added to ensure no leakage in rack state from previous tests.
+  # Removes all routes, filters, middleware and extension hooks from the current class
+  # https://rubydoc.info/gems/sinatra/Sinatra/Base#reset!-class_method 
+  before(:each) do
+    app.reset!
+  end
+
   describe '/vm/:hostname' do
     let(:prefix) { '/api/v1' }
+    let(:metrics) { Vmpooler::DummyStatsd.new }
 
     let(:config) {
       {
@@ -33,11 +41,9 @@ describe Vmpooler::API::V1 do
 
     let(:current_time) { Time.now }
 
-    let(:redis) { MockRedis.new }
-
     before(:each) do
-      app.settings.set :config, config
-      app.settings.set :redis, redis
+      expect(app).to receive(:run!).once
+      app.execute(['api'], config, redis, metrics)
       create_token('abcdefghijklmnopqrstuvwxyz012345', 'jdoe', current_time)
     end
 
@@ -81,9 +87,9 @@ describe Vmpooler::API::V1 do
       end
 
       context '(tagfilter configured)' do
-        let(:config) { {
-          tagfilter: { 'url' => '(.*)\/' },
-        } }
+        before(:each) do
+          app.settings.set :config, tagfilter: { 'url' => '(.*)\/' }
+        end
 
         it 'correctly filters tags' do
           create_vm('testhost', redis)
@@ -104,7 +110,9 @@ describe Vmpooler::API::V1 do
       end
 
       context '(auth not configured)' do
-        let(:config) { { auth: false } }
+        before(:each) do
+          app.settings.set :config, auth: false
+        end
 
         it 'allows VM lifetime to be modified without a token' do
           create_vm('testhost', redis)

spec/integration/api/v1/vm_spec.rb

@@ -8,6 +8,13 @@ describe Vmpooler::API::V1 do
     Vmpooler::API
   end
 
+  # Added to ensure no leakage in rack state from previous tests.
+  # Removes all routes, filters, middleware and extension hooks from the current class
+  # https://rubydoc.info/gems/sinatra/Sinatra/Base#reset!-class_method 
+  before(:each) do
+    app.reset!
+  end
+
   describe '/vm' do
     let(:prefix) { '/api/v1' }
     let(:metrics) { Vmpooler::DummyStatsd.new }
@@ -32,9 +39,8 @@ describe Vmpooler::API::V1 do
     let(:checkoutlock) { Mutex.new }
 
     before(:each) do
-      app.settings.set :config, config
-      app.settings.set :redis, redis
-      app.settings.set :metrics, metrics
+      expect(app).to receive(:run!).once
+      app.execute(['api'], config, redis, metrics)
       app.settings.set :config, auth: false
       app.settings.set :checkoutlock, checkoutlock
       create_token('abcdefghijklmnopqrstuvwxyz012345', 'jdoe', current_time)
@@ -104,8 +110,8 @@ describe Vmpooler::API::V1 do
       end
 
       it 'returns 503 for empty pool when aliases are not defined' do
-        Vmpooler::API.settings.config.delete(:alias)
-        Vmpooler::API.settings.config[:pool_names] = ['pool1', 'pool2']
+        app.settings.config.delete(:alias)
+        app.settings.config[:pool_names] = ['pool1', 'pool2']
 
         create_ready_vm 'pool1', vmname, redis
         post "#{prefix}/vm/pool1"

spec/integration/api/v1/vm_template_spec.rb

@@ -8,6 +8,13 @@ describe Vmpooler::API::V1 do
     Vmpooler::API
   end
 
+  # Added to ensure no leakage in rack state from previous tests.
+  # Removes all routes, filters, middleware and extension hooks from the current class
+  # https://rubydoc.info/gems/sinatra/Sinatra/Base#reset!-class_method 
+  before(:each) do
+    app.reset!
+  end
+
   describe '/vm/:template' do
     let(:prefix) { '/api/v1' }
     let(:metrics) { Vmpooler::DummyStatsd.new }
@@ -33,9 +40,8 @@ describe Vmpooler::API::V1 do
     let(:checkoutlock) { Mutex.new }
 
     before(:each) do
-      app.settings.set :config, config
-      app.settings.set :redis, redis
-      app.settings.set :metrics, metrics
+      expect(app).to receive(:run!).once
+      app.execute(['api'], config, redis, metrics)
       app.settings.set :config, auth: false
       app.settings.set :checkoutlock, checkoutlock
       create_token('abcdefghijklmnopqrstuvwxyz012345', 'jdoe', current_time)
@@ -84,8 +90,8 @@ describe Vmpooler::API::V1 do
       end
 
       it 'returns 503 for empty pool when aliases are not defined' do
-        Vmpooler::API.settings.config.delete(:alias)
-        Vmpooler::API.settings.config[:pool_names] = ['pool1', 'pool2']
+        app.settings.config.delete(:alias)
+        app.settings.config[:pool_names] = ['pool1', 'pool2']
 
         create_ready_vm 'pool1', 'abcdefghijklmnop', redis
         post "#{prefix}/vm/pool1"

spec/integration/dashboard_spec.rb

@@ -5,13 +5,35 @@ describe Vmpooler::API do
   include Rack::Test::Methods
 
   def app()
-    described_class
+    Vmpooler::API
+  end
+
+  # Added to ensure no leakage in rack state from previous tests.
+  # Removes all routes, filters, middleware and extension hooks from the current class
+  # https://rubydoc.info/gems/sinatra/Sinatra/Base#reset!-class_method 
+  before(:each) do
+    app.reset!
   end
 
   describe 'Dashboard' do
 
+    let(:config) { {
+      pools: [
+          {'name' => 'pool1', 'size' => 5}
+      ],
+      graphite: {}
+    } }
+
+    before(:each) do
+      expect(app).to receive(:run!)
+      app.execute(['api'], config, redis, nil)
+      app.settings.set :config, auth: false
+    end
+
     context '/' do
-      before { get '/' }
+      before(:each) do
+        get '/'
+      end
 
       it { expect(last_response.status).to eq(302) }
       it { expect(last_response.location).to eq('http://example.org/dashboard/') }
@@ -21,7 +43,7 @@ describe Vmpooler::API do
       ENV['SITE_NAME'] = 'test pooler'
       ENV['VMPOOLER_CONFIG'] = 'thing'
 
-      before do
+      before(:each) do
         get '/dashboard/'
       end
 
@@ -31,10 +53,12 @@ describe Vmpooler::API do
     end
 
     context 'unknown route' do
-      before { get '/doesnotexist' }
+      before(:each) do
+        get '/doesnotexist'
+      end
 
-      it { expect(last_response.status).to eq(404) }
       it { expect(last_response.header['Content-Type']).to eq('application/json') }
+      it { expect(last_response.status).to eq(404) }
       it { expect(last_response.body).to eq(JSON.pretty_generate({ok: false})) }
     end
 
@@ -47,10 +71,8 @@ describe Vmpooler::API do
           graphite: {}
       } }
 
-      before do
-        $config = config
+      before(:each) do
         app.settings.set :config, config
-        app.settings.set :redis, redis
         app.settings.set :environment, :test
       end
 
@@ -120,10 +142,8 @@ describe Vmpooler::API do
           graphite: {}
       } }
 
-      before do
-        $config = config
+      before(:each) do
         app.settings.set :config, config
-        app.settings.set :redis, redis
         app.settings.set :environment, :test
       end
 

spec/unit/pool_manager_spec.rb

@@ -27,7 +27,6 @@ describe 'Pool Manager' do
     timeout: 5
   ) { MockRedis.new }
   }
-  let(:redis) { MockRedis.new }
 
   let(:provider) { Vmpooler::PoolManager::Provider::Base.new(config, logger, metrics, redis_connection_pool, 'mock_provider', provider_options) }
 

vmpooler.gemspec

@@ -24,6 +24,7 @@ Gem::Specification.new do |s|
   s.add_dependency 'redis', '~> 4.1'
   s.add_dependency 'rbvmomi', '~> 2.1'
   s.add_dependency 'sinatra', '~> 2.0'
+  s.add_dependency 'prometheus-client', '~> 2.0'
   s.add_dependency 'net-ldap', '~> 0.16'
   s.add_dependency 'statsd-ruby', '~> 1.4'
   s.add_dependency 'connection_pool', '~> 2.2'