From efe38ffadbd86157f5a241c1c602de171ff9626e Mon Sep 17 00:00:00 2001
From: Josh Kleinpeter <josh.kleinpeter@bigcommerce.com>
Date: Thu, 21 Nov 2024 08:44:35 -0600
Subject: [PATCH 1/3] PoC migrating from thign to puma

---
 bc-prometheus-ruby.gemspec                    |  3 ++-
 lib/bigcommerce/prometheus.rb                 | 19 ++++++++++---------
 lib/bigcommerce/prometheus/server.rb          |  2 +-
 .../controllers/base_controller.rb            |  6 +++---
 .../controllers/error_controller.rb           |  2 +-
 .../controllers/metrics_controller.rb         |  2 +-
 .../controllers/not_found_controller.rb       |  2 +-
 .../controllers/send_metrics_controller.rb    |  2 +-
 .../servers/{thin => puma}/rack_app.rb        | 14 +++++++-------
 .../servers/{thin => puma}/server.rb          | 14 +++++++-------
 .../servers/{thin => puma}/server_metrics.rb  |  2 +-
 .../controllers/metrics_controller_spec.rb    |  4 ++--
 .../send_metrics_controller_spec.rb           |  4 ++--
 .../servers/{thin => puma}/server_spec.rb     | 10 +++++-----
 14 files changed, 44 insertions(+), 42 deletions(-)
 rename lib/bigcommerce/prometheus/servers/{thin => puma}/controllers/base_controller.rb (94%)
 rename lib/bigcommerce/prometheus/servers/{thin => puma}/controllers/error_controller.rb (98%)
 rename lib/bigcommerce/prometheus/servers/{thin => puma}/controllers/metrics_controller.rb (99%)
 rename lib/bigcommerce/prometheus/servers/{thin => puma}/controllers/not_found_controller.rb (98%)
 rename lib/bigcommerce/prometheus/servers/{thin => puma}/controllers/send_metrics_controller.rb (99%)
 rename lib/bigcommerce/prometheus/servers/{thin => puma}/rack_app.rb (89%)
 rename lib/bigcommerce/prometheus/servers/{thin => puma}/server.rb (85%)
 rename lib/bigcommerce/prometheus/servers/{thin => puma}/server_metrics.rb (99%)
 rename spec/bigcommerce/prometheus/servers/{thin => puma}/controllers/metrics_controller_spec.rb (95%)
 rename spec/bigcommerce/prometheus/servers/{thin => puma}/controllers/send_metrics_controller_spec.rb (95%)
 rename spec/bigcommerce/prometheus/servers/{thin => puma}/server_spec.rb (63%)

diff --git a/bc-prometheus-ruby.gemspec b/bc-prometheus-ruby.gemspec
index 5ed645d..daff97a 100644
--- a/bc-prometheus-ruby.gemspec
+++ b/bc-prometheus-ruby.gemspec
@@ -35,6 +35,7 @@ Gem::Specification.new do |spec|
 
   spec.add_runtime_dependency 'bigcommerce-multitrap', '~> 0.1'
   spec.add_runtime_dependency 'prometheus_exporter', '~> 0.7'
+  spec.add_runtime_dependency 'puma', '> 5'
+  spec.add_runtime_dependency 'rack', '>= 3.0'
   spec.add_runtime_dependency 'rake', '>= 10.0'
-  spec.add_runtime_dependency 'thin', '~> 1.7'
 end
diff --git a/lib/bigcommerce/prometheus.rb b/lib/bigcommerce/prometheus.rb
index 5f9e845..e1819ad 100644
--- a/lib/bigcommerce/prometheus.rb
+++ b/lib/bigcommerce/prometheus.rb
@@ -22,7 +22,8 @@
 require 'prometheus_exporter/client'
 require 'prometheus_exporter/middleware'
 require 'prometheus_exporter/instrumentation'
-require 'thin'
+require 'puma'
+require 'rack'
 
 require_relative 'prometheus/version'
 require_relative 'prometheus/loggable'
@@ -42,14 +43,14 @@
 require_relative 'prometheus/integrations/puma'
 require_relative 'prometheus/integrations/resque'
 
-require_relative 'prometheus/servers/thin/server'
-require_relative 'prometheus/servers/thin/rack_app'
-require_relative 'prometheus/servers/thin/server_metrics'
-require_relative 'prometheus/servers/thin/controllers/base_controller'
-require_relative 'prometheus/servers/thin/controllers/error_controller'
-require_relative 'prometheus/servers/thin/controllers/metrics_controller'
-require_relative 'prometheus/servers/thin/controllers/not_found_controller'
-require_relative 'prometheus/servers/thin/controllers/send_metrics_controller'
+require_relative 'prometheus/servers/puma/server'
+require_relative 'prometheus/servers/puma/rack_app'
+require_relative 'prometheus/servers/puma/server_metrics'
+require_relative 'prometheus/servers/puma/controllers/base_controller'
+require_relative 'prometheus/servers/puma/controllers/error_controller'
+require_relative 'prometheus/servers/puma/controllers/metrics_controller'
+require_relative 'prometheus/servers/puma/controllers/not_found_controller'
+require_relative 'prometheus/servers/puma/controllers/send_metrics_controller'
 
 module Bigcommerce
   ##
diff --git a/lib/bigcommerce/prometheus/server.rb b/lib/bigcommerce/prometheus/server.rb
index 0d70e39..ebc75a1 100644
--- a/lib/bigcommerce/prometheus/server.rb
+++ b/lib/bigcommerce/prometheus/server.rb
@@ -35,7 +35,7 @@ def initialize(host: nil, port: nil, timeout: nil, prefix: nil, logger: nil, thr
         @prefix = (prefix || ::PrometheusExporter::DEFAULT_PREFIX).to_s
         @process_name = ::Bigcommerce::Prometheus.process_name
         @logger = logger || ::Bigcommerce::Prometheus.logger
-        @server = ::Bigcommerce::Prometheus::Servers::Thin::Server.new(
+        @server = ::Bigcommerce::Prometheus::Servers::Puma::Server.new(
           port: @port,
           timeout: @timeout,
           logger: @logger,
diff --git a/lib/bigcommerce/prometheus/servers/thin/controllers/base_controller.rb b/lib/bigcommerce/prometheus/servers/puma/controllers/base_controller.rb
similarity index 94%
rename from lib/bigcommerce/prometheus/servers/thin/controllers/base_controller.rb
rename to lib/bigcommerce/prometheus/servers/puma/controllers/base_controller.rb
index 94c5fe4..1bf4fa9 100644
--- a/lib/bigcommerce/prometheus/servers/thin/controllers/base_controller.rb
+++ b/lib/bigcommerce/prometheus/servers/puma/controllers/base_controller.rb
@@ -18,16 +18,16 @@
 module Bigcommerce
   module Prometheus
     module Servers
-      module Thin
+      module Puma
         module Controllers
           ##
-          # Base thin controller for prometheus metrics
+          # Base puma controller for prometheus metrics
           #
           class BaseController
             ##
             # @param [Rack::Request] request
             # @param [Rack::Response] response
-            # @param [Bigcommerce::Prometheus::Servers::Thin::ServerMetrics]
+            # @param [Bigcommerce::Prometheus::Servers::Puma::ServerMetrics]
             # @param [PrometheusExporter::Server::Collector] collector
             # @param [Logger] logger
             #
diff --git a/lib/bigcommerce/prometheus/servers/thin/controllers/error_controller.rb b/lib/bigcommerce/prometheus/servers/puma/controllers/error_controller.rb
similarity index 98%
rename from lib/bigcommerce/prometheus/servers/thin/controllers/error_controller.rb
rename to lib/bigcommerce/prometheus/servers/puma/controllers/error_controller.rb
index 06840b8..e3ffcfc 100644
--- a/lib/bigcommerce/prometheus/servers/thin/controllers/error_controller.rb
+++ b/lib/bigcommerce/prometheus/servers/puma/controllers/error_controller.rb
@@ -18,7 +18,7 @@
 module Bigcommerce
   module Prometheus
     module Servers
-      module Thin
+      module Puma
         module Controllers
           ##
           # Handle 500s
diff --git a/lib/bigcommerce/prometheus/servers/thin/controllers/metrics_controller.rb b/lib/bigcommerce/prometheus/servers/puma/controllers/metrics_controller.rb
similarity index 99%
rename from lib/bigcommerce/prometheus/servers/thin/controllers/metrics_controller.rb
rename to lib/bigcommerce/prometheus/servers/puma/controllers/metrics_controller.rb
index e6cbeab..76aca82 100644
--- a/lib/bigcommerce/prometheus/servers/thin/controllers/metrics_controller.rb
+++ b/lib/bigcommerce/prometheus/servers/puma/controllers/metrics_controller.rb
@@ -22,7 +22,7 @@
 module Bigcommerce
   module Prometheus
     module Servers
-      module Thin
+      module Puma
         module Controllers
           ##
           # GET /metrics
diff --git a/lib/bigcommerce/prometheus/servers/thin/controllers/not_found_controller.rb b/lib/bigcommerce/prometheus/servers/puma/controllers/not_found_controller.rb
similarity index 98%
rename from lib/bigcommerce/prometheus/servers/thin/controllers/not_found_controller.rb
rename to lib/bigcommerce/prometheus/servers/puma/controllers/not_found_controller.rb
index ae09ba2..f8c70d6 100644
--- a/lib/bigcommerce/prometheus/servers/thin/controllers/not_found_controller.rb
+++ b/lib/bigcommerce/prometheus/servers/puma/controllers/not_found_controller.rb
@@ -18,7 +18,7 @@
 module Bigcommerce
   module Prometheus
     module Servers
-      module Thin
+      module Puma
         module Controllers
           ##
           # Handle invalid requests to server
diff --git a/lib/bigcommerce/prometheus/servers/thin/controllers/send_metrics_controller.rb b/lib/bigcommerce/prometheus/servers/puma/controllers/send_metrics_controller.rb
similarity index 99%
rename from lib/bigcommerce/prometheus/servers/thin/controllers/send_metrics_controller.rb
rename to lib/bigcommerce/prometheus/servers/puma/controllers/send_metrics_controller.rb
index 302e051..b2ef824 100644
--- a/lib/bigcommerce/prometheus/servers/thin/controllers/send_metrics_controller.rb
+++ b/lib/bigcommerce/prometheus/servers/puma/controllers/send_metrics_controller.rb
@@ -18,7 +18,7 @@
 module Bigcommerce
   module Prometheus
     module Servers
-      module Thin
+      module Puma
         module Controllers
           ##
           # POST /send-metrics
diff --git a/lib/bigcommerce/prometheus/servers/thin/rack_app.rb b/lib/bigcommerce/prometheus/servers/puma/rack_app.rb
similarity index 89%
rename from lib/bigcommerce/prometheus/servers/thin/rack_app.rb
rename to lib/bigcommerce/prometheus/servers/puma/rack_app.rb
index a41434c..198f891 100644
--- a/lib/bigcommerce/prometheus/servers/thin/rack_app.rb
+++ b/lib/bigcommerce/prometheus/servers/puma/rack_app.rb
@@ -18,9 +18,9 @@
 module Bigcommerce
   module Prometheus
     module Servers
-      module Thin
+      module Puma
         ##
-        # Handles metrics requests as a Rack App on the Thin server
+        # Handles metrics requests as a Rack App on the Puma server
         #
         class RackApp
           ##
@@ -29,7 +29,7 @@ def initialize(collector: nil, timeout: nil, logger: nil)
             @timeout = timeout || ::Bigcommerce::Prometheus.server_timeout
             @collector = collector || ::PrometheusExporter::Server::Collector.new
             @logger = logger || ::Bigcommerce::Prometheus.logger
-            @server_metrics = ::Bigcommerce::Prometheus::Servers::Thin::ServerMetrics.new(logger: @logger)
+            @server_metrics = ::Bigcommerce::Prometheus::Servers::Puma::ServerMetrics.new(logger: @logger)
           end
 
           def call(env)
@@ -39,7 +39,7 @@ def call(env)
             handle(controller: controller, request: request, response: response)
           rescue StandardError => e
             @logger.error "Error: #{e.message}"
-            handle(controller: ::Bigcommerce::Prometheus::Servers::Thin::Controllers::ErrorController, request: request, response: response)
+            handle(controller: ::Bigcommerce::Prometheus::Servers::Puma::Controllers::ErrorController, request: request, response: response)
           end
 
           ##
@@ -60,11 +60,11 @@ def add_type_collector(collector)
           #
           def route(request)
             if request.fullpath == '/metrics' && request.request_method.to_s.downcase == 'get'
-              Bigcommerce::Prometheus::Servers::Thin::Controllers::MetricsController
+              Bigcommerce::Prometheus::Servers::Puma::Controllers::MetricsController
             elsif request.fullpath == '/send-metrics' && request.request_method.to_s.downcase == 'post'
-              Bigcommerce::Prometheus::Servers::Thin::Controllers::SendMetricsController
+              Bigcommerce::Prometheus::Servers::Puma::Controllers::SendMetricsController
             else
-              Bigcommerce::Prometheus::Servers::Thin::Controllers::NotFoundController
+              Bigcommerce::Prometheus::Servers::Puma::Controllers::NotFoundController
             end
           end
 
diff --git a/lib/bigcommerce/prometheus/servers/thin/server.rb b/lib/bigcommerce/prometheus/servers/puma/server.rb
similarity index 85%
rename from lib/bigcommerce/prometheus/servers/thin/server.rb
rename to lib/bigcommerce/prometheus/servers/puma/server.rb
index 4a3388b..27eecdb 100644
--- a/lib/bigcommerce/prometheus/servers/thin/server.rb
+++ b/lib/bigcommerce/prometheus/servers/puma/server.rb
@@ -18,21 +18,21 @@
 module Bigcommerce
   module Prometheus
     module Servers
-      module Thin
+      module Puma
         ##
-        # Thin adapter for server
+        # Puma adapter for server
         #
-        class Server < ::Thin::Server
+        class Server < ::Puma::Server
           def initialize(port: nil, host: nil, timeout: nil, logger: nil, thread_pool_size: nil)
             @port = port || ::Bigcommerce::Prometheus.server_port
             @host = host || ::Bigcommerce::Prometheus.server_host
             @timeout = timeout || ::Bigcommerce::Prometheus.server_timeout
             @logger = logger || ::Bigcommerce::Prometheus.logger
-            @rack_app = ::Bigcommerce::Prometheus::Servers::Thin::RackApp.new(timeout: timeout, logger: logger)
-            super(@host, @port, @rack_app)
-            ::Thin::Logging.logger = @logger
+            @rack_app = ::Bigcommerce::Prometheus::Servers::Puma::RackApp.new(timeout: timeout, logger: logger)
+            thread_pool_size = (thread_pool_size || ::Bigcommerce::Prometheus.server_thread_pool_size).to_i
+            super(@app, nil, max_threads: thread_pool_size)
+            add_tcp_listener(@host, @port)
             @logger.info "[bigcommerce-prometheus] Prometheus server started on #{@host}:#{@port}"
-            self.threadpool_size = (thread_pool_size || ::Bigcommerce::Prometheus.server_thread_pool_size).to_i
           end
 
           ##
diff --git a/lib/bigcommerce/prometheus/servers/thin/server_metrics.rb b/lib/bigcommerce/prometheus/servers/puma/server_metrics.rb
similarity index 99%
rename from lib/bigcommerce/prometheus/servers/thin/server_metrics.rb
rename to lib/bigcommerce/prometheus/servers/puma/server_metrics.rb
index 31d55b3..76df096 100644
--- a/lib/bigcommerce/prometheus/servers/thin/server_metrics.rb
+++ b/lib/bigcommerce/prometheus/servers/puma/server_metrics.rb
@@ -22,7 +22,7 @@
 module Bigcommerce
   module Prometheus
     module Servers
-      module Thin
+      module Puma
         ##
         # Server metrics for the collector
         #
diff --git a/spec/bigcommerce/prometheus/servers/thin/controllers/metrics_controller_spec.rb b/spec/bigcommerce/prometheus/servers/puma/controllers/metrics_controller_spec.rb
similarity index 95%
rename from spec/bigcommerce/prometheus/servers/thin/controllers/metrics_controller_spec.rb
rename to spec/bigcommerce/prometheus/servers/puma/controllers/metrics_controller_spec.rb
index 443c80a..e0980e6 100644
--- a/spec/bigcommerce/prometheus/servers/thin/controllers/metrics_controller_spec.rb
+++ b/spec/bigcommerce/prometheus/servers/puma/controllers/metrics_controller_spec.rb
@@ -15,7 +15,7 @@
 #
 require 'spec_helper'
 
-describe Bigcommerce::Prometheus::Servers::Thin::Controllers::MetricsController do
+describe Bigcommerce::Prometheus::Servers::Puma::Controllers::MetricsController do
   let(:request_method) { 'GET' }
   let(:env) do
     {
@@ -27,7 +27,7 @@
   let(:request) { Rack::Request.new(env) }
   let(:response) { Rack::Response.new }
   let(:collector) { PrometheusExporter::Server::Collector.new }
-  let(:server_metrics) { Bigcommerce::Prometheus::Servers::Thin::ServerMetrics.new }
+  let(:server_metrics) { Bigcommerce::Prometheus::Servers::Puma::ServerMetrics.new }
   let(:controller) { described_class.new(request: request, response: response, server_metrics: server_metrics, collector: collector, logger: logger) }
 
   let(:metrics) { ['ruby_collector_metrics_total 19', 'ruby_collector_sessions_total 19'].join("\n") }
diff --git a/spec/bigcommerce/prometheus/servers/thin/controllers/send_metrics_controller_spec.rb b/spec/bigcommerce/prometheus/servers/puma/controllers/send_metrics_controller_spec.rb
similarity index 95%
rename from spec/bigcommerce/prometheus/servers/thin/controllers/send_metrics_controller_spec.rb
rename to spec/bigcommerce/prometheus/servers/puma/controllers/send_metrics_controller_spec.rb
index 3eac8f2..ef547bb 100644
--- a/spec/bigcommerce/prometheus/servers/thin/controllers/send_metrics_controller_spec.rb
+++ b/spec/bigcommerce/prometheus/servers/puma/controllers/send_metrics_controller_spec.rb
@@ -15,7 +15,7 @@
 #
 require 'spec_helper'
 
-describe Bigcommerce::Prometheus::Servers::Thin::Controllers::SendMetricsController do
+describe Bigcommerce::Prometheus::Servers::Puma::Controllers::SendMetricsController do
   let(:request_method) { 'POST' }
   let(:env) do
     {
@@ -27,7 +27,7 @@
   let(:request) { Rack::Request.new(env) }
   let(:response) { Rack::Response.new }
   let(:collector) { PrometheusExporter::Server::Collector.new }
-  let(:server_metrics) { Bigcommerce::Prometheus::Servers::Thin::ServerMetrics.new }
+  let(:server_metrics) { Bigcommerce::Prometheus::Servers::Puma::ServerMetrics.new }
   let(:controller) { described_class.new(request: request, response: response, server_metrics: server_metrics, collector: collector, logger: logger) }
 
   describe '#call' do
diff --git a/spec/bigcommerce/prometheus/servers/thin/server_spec.rb b/spec/bigcommerce/prometheus/servers/puma/server_spec.rb
similarity index 63%
rename from spec/bigcommerce/prometheus/servers/thin/server_spec.rb
rename to spec/bigcommerce/prometheus/servers/puma/server_spec.rb
index f482699..07344fc 100644
--- a/spec/bigcommerce/prometheus/servers/thin/server_spec.rb
+++ b/spec/bigcommerce/prometheus/servers/puma/server_spec.rb
@@ -1,7 +1,7 @@
 require 'spec_helper'
 
-describe Bigcommerce::Prometheus::Servers::Thin::Server do
-  let(:server) { described_class.new }
+describe Bigcommerce::Prometheus::Servers::Puma::Server do
+  let(:server) { described_class.new(port: 9800+rand(100)) }
 
   before do
     Bigcommerce::Prometheus.reset
@@ -9,8 +9,8 @@
 
   context 'when the thread pool size is not configured' do
     it 'falls back to the default configuration' do
-      expect(server.threadpool_size).to eq ::Bigcommerce::Prometheus.server_thread_pool_size
-      expect(server.threadpool_size).to eq 3
+      expect(server.max_threads).to eq ::Bigcommerce::Prometheus.server_thread_pool_size
+      expect(server.max_threads).to eq 3
     end
   end
 
@@ -24,7 +24,7 @@
     end
 
     it 'allows you to set the thread pool size through the configuration block' do
-      expect(server.threadpool_size).to eq server_thread_pool_size
+      expect(server.max_threads).to eq server_thread_pool_size
     end
   end
 end

From 4b5703a28f3b914bb5b3a6909c0d4139c0d95a58 Mon Sep 17 00:00:00 2001
From: Josh Kleinpeter <josh.kleinpeter@bigcommerce.com>
Date: Thu, 5 Dec 2024 10:35:50 -0600
Subject: [PATCH 2/3] Fix implementation bugs for methods not on Puma::Server

---
 lib/bigcommerce/prometheus/server.rb              | 8 +++-----
 lib/bigcommerce/prometheus/servers/puma/server.rb | 2 +-
 2 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/lib/bigcommerce/prometheus/server.rb b/lib/bigcommerce/prometheus/server.rb
index ebc75a1..7a5600e 100644
--- a/lib/bigcommerce/prometheus/server.rb
+++ b/lib/bigcommerce/prometheus/server.rb
@@ -52,12 +52,10 @@ def initialize(host: nil, port: nil, timeout: nil, prefix: nil, logger: nil, thr
       def start
         @logger.info "[bigcommerce-prometheus][#{@process_name}] Starting prometheus exporter on port #{@host}:#{@port}"
 
-        @run_thread = ::Thread.start do
-          @server.start
-        end
+        @run_thread = @server.run
         @running = true
 
-        @logger.info "[bigcommerce-prometheus][#{@process_name}] Prometheus exporter started on #{@host}:#{@port} with #{@server.threadpool_size} threads"
+        @logger.info "[bigcommerce-prometheus][#{@process_name}] Prometheus exporter started on #{@host}:#{@port} with #{@server.pool_capacity} threads"
 
         @server
       rescue ::StandardError => e
@@ -81,7 +79,7 @@ def start_until_stopped
       # Stop the server
       #
       def stop
-        @server.stop!
+        @server.stop
         @run_thread.kill
         @running = false
         $stdout.puts "[bigcommerce-prometheus][#{@process_name}] Prometheus exporter cleanly shut down"
diff --git a/lib/bigcommerce/prometheus/servers/puma/server.rb b/lib/bigcommerce/prometheus/servers/puma/server.rb
index 27eecdb..6e84030 100644
--- a/lib/bigcommerce/prometheus/servers/puma/server.rb
+++ b/lib/bigcommerce/prometheus/servers/puma/server.rb
@@ -30,7 +30,7 @@ def initialize(port: nil, host: nil, timeout: nil, logger: nil, thread_pool_size
             @logger = logger || ::Bigcommerce::Prometheus.logger
             @rack_app = ::Bigcommerce::Prometheus::Servers::Puma::RackApp.new(timeout: timeout, logger: logger)
             thread_pool_size = (thread_pool_size || ::Bigcommerce::Prometheus.server_thread_pool_size).to_i
-            super(@app, nil, max_threads: thread_pool_size)
+            super(@rack_app, nil, max_threads: thread_pool_size)
             add_tcp_listener(@host, @port)
             @logger.info "[bigcommerce-prometheus] Prometheus server started on #{@host}:#{@port}"
           end

From 8915ffd56435a27757138b2b543c50464f70b4fb Mon Sep 17 00:00:00 2001
From: Josh Kleinpeter <josh.kleinpeter@bigcommerce.com>
Date: Thu, 5 Dec 2024 11:31:11 -0600
Subject: [PATCH 3/3] Add extra tests

---
 lib/bigcommerce/prometheus/server.rb          |  2 +-
 .../prometheus/servers/puma/server_spec.rb    | 25 +++++++++++++++++--
 2 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/lib/bigcommerce/prometheus/server.rb b/lib/bigcommerce/prometheus/server.rb
index 7a5600e..3d2e3b6 100644
--- a/lib/bigcommerce/prometheus/server.rb
+++ b/lib/bigcommerce/prometheus/server.rb
@@ -55,7 +55,7 @@ def start
         @run_thread = @server.run
         @running = true
 
-        @logger.info "[bigcommerce-prometheus][#{@process_name}] Prometheus exporter started on #{@host}:#{@port} with #{@server.pool_capacity} threads"
+        @logger.info "[bigcommerce-prometheus][#{@process_name}] Prometheus exporter started on #{@host}:#{@port} with #{@server.max_threads} threads"
 
         @server
       rescue ::StandardError => e
diff --git a/spec/bigcommerce/prometheus/servers/puma/server_spec.rb b/spec/bigcommerce/prometheus/servers/puma/server_spec.rb
index 07344fc..9363e45 100644
--- a/spec/bigcommerce/prometheus/servers/puma/server_spec.rb
+++ b/spec/bigcommerce/prometheus/servers/puma/server_spec.rb
@@ -1,12 +1,18 @@
 require 'spec_helper'
 
 describe Bigcommerce::Prometheus::Servers::Puma::Server do
-  let(:server) { described_class.new(port: 9800+rand(100)) }
-
+  let(:server) { described_class.new(port: default_port) }
+  let(:default_port) { 9800 + rand(100) }
   before do
     Bigcommerce::Prometheus.reset
   end
 
+  context 'when the server is initialized' do
+    it 'has a valid rack app' do
+      expect(server.app).to be_a(Bigcommerce::Prometheus::Servers::Puma::RackApp)
+    end
+  end
+
   context 'when the thread pool size is not configured' do
     it 'falls back to the default configuration' do
       expect(server.max_threads).to eq ::Bigcommerce::Prometheus.server_thread_pool_size
@@ -27,4 +33,19 @@
       expect(server.max_threads).to eq server_thread_pool_size
     end
   end
+
+  context 'when the default port is configured' do
+    let(:server_port) { 9000 + rand(100) }
+    let(:default_port) { nil }
+
+    before do
+      Bigcommerce::Prometheus.configure do |c|
+        c.server_port = server_port
+      end
+    end
+
+    it 'allows you to set the port through the configuration block' do
+      expect(server.connected_ports).to include server_port
+    end
+  end
 end