Added support for custom providers.

README.md

@@ -75,6 +75,28 @@ The currently supported settings are:
 
 * `latency`: the latency (in seconds) of a queue (now - when the oldest job was enqueued) which is considered unhealthy (the default is 30 seconds, but larger processing queue should have a larger latency value).
 
+### Adding a custom provider
+It's also possible to add custom health check providers suited for your needs (of course, it's highly appreciated and encouraged if you'd contribute useful providers to the project).
+
+In order to add a custom provider, you'd need to:
+
+* Implement the `HealthMonitor::Providers::Base` class and its `check!` method (a check is considered as failed if it raises an exception):
+
+```ruby
+class CustomProvider < HealthMonitor::Providers::Base
+  def check!
+    raise 'Oh oh!'
+  end
+end
+```
+* Add its class to the configuration:
+
+```ruby
+HealthMonitor.configure do |config|
+  config.add_custom_provider(CustomProvider)
+end
+```
+
 ### Adding a custom error callback
 If you need to perform any additional error handling (for example, for additional error reporting), you can configure a custom error callback:
 

lib/health_monitor/configuration.rb

@@ -9,14 +9,28 @@ def initialize
       database
     end
 
-    PROVIDERS.each do |provider|
-      define_method provider do |&block|
-        require "health_monitor/providers/#{provider}"
+    PROVIDERS.each do |provider_name|
+      define_method provider_name do |&block|
+        require "health_monitor/providers/#{provider_name}"
 
-        (@providers ||= Set.new) << provider
+        add_provider("HealthMonitor::Providers::#{provider_name.capitalize}".constantize)
+      end
+    end
 
-        "HealthMonitor::Providers::#{provider.capitalize}".constantize
+    def add_custom_provider(custom_provider_class)
+      unless custom_provider_class < HealthMonitor::Providers::Base
+        raise ArgumentError.new('custom provider class must implement HealthMonitor::Providers::Base')
       end
+
+      add_provider(custom_provider_class)
+    end
+
+    private
+
+    def add_provider(provider_class)
+      (@providers ||= Set.new) << provider_class
+
+      provider_class
     end
   end
 end

lib/health_monitor/monitor.rb

@@ -13,7 +13,7 @@ def configure
 
   def check!(request: nil)
     configuration.providers.each do |provider|
-      monitor = "HealthMonitor::Providers::#{provider.capitalize}".constantize.new(request: request)
+      monitor = provider.new(request: request)
       monitor.check!
     end
   rescue Exception => e

lib/health_monitor/version.rb

@@ -1,3 +1,3 @@
 module HealthMonitor
-  VERSION = '2.0.2'.freeze
+  VERSION = '2.1.0'.freeze
 end

spec/lib/health_monitor/configuration_spec.rb

@@ -2,31 +2,63 @@
 
 describe HealthMonitor::Configuration do
   describe 'defaults' do
-    it { expect(subject.providers).to eq(Set.new([:database])) }
+    it { expect(subject.providers).to eq(Set.new([HealthMonitor::Providers::Database])) }
     it { expect(subject.error_callback).to be_nil }
     it { expect(subject.basic_auth_credentials).to be_nil }
   end
 
   describe 'providers' do
-    HealthMonitor::Configuration::PROVIDERS.each do |provider|
+    HealthMonitor::Configuration::PROVIDERS.each do |provider_name|
       before do
         subject.instance_variable_set('@providers', Set.new)
 
-        stub_const("HealthMonitor::Providers::#{provider.capitalize}", Class.new)
+        stub_const("HealthMonitor::Providers::#{provider_name.capitalize}", Class.new)
       end
 
-      it "responds to #{provider}" do
-        expect(subject).to respond_to(provider)
+      it "responds to #{provider_name}" do
+        expect(subject).to respond_to(provider_name)
       end
 
-      it "configures #{provider}" do
+      it "configures #{provider_name}" do
         expect {
-          subject.send(provider)
-        }.to change { subject.providers }.to(Set.new([provider]))
+          subject.send(provider_name)
+        }.to change { subject.providers }.to(Set.new(["HealthMonitor::Providers::#{provider_name.capitalize}".constantize]))
       end
 
-      it "returns #{provider}'s class" do
-        expect(subject.send(provider)).to eq("HealthMonitor::Providers::#{provider.capitalize}".constantize)
+      it "returns #{provider_name}'s class" do
+        expect(subject.send(provider_name)).to eq("HealthMonitor::Providers::#{provider_name.capitalize}".constantize)
+      end
+    end
+  end
+
+  describe '#add_custom_provider' do
+    before do
+      subject.instance_variable_set('@providers', Set.new)
+    end
+
+    context 'inherits' do
+      class CustomProvider < HealthMonitor::Providers::Base
+      end
+
+      it 'accepts' do
+        expect {
+          subject.add_custom_provider(CustomProvider)
+        }.to change { subject.providers }.to(Set.new([CustomProvider]))
+      end
+
+      it "returns CustomProvider class" do
+        expect(subject.add_custom_provider(CustomProvider)).to eq(CustomProvider)
+      end
+    end
+
+    context 'does not inherit' do
+      class TestClass
+      end
+
+      it 'does not accept' do
+        expect {
+          subject.add_custom_provider(TestClass)
+        }.to raise_error(ArgumentError)
       end
     end
   end

spec/lib/health_monitor/monitor_spec.rb

@@ -14,7 +14,8 @@
           subject.configure do |config|
             config.redis
           end
-        }.to change { HealthMonitor.configuration.providers }.to(Set.new([:database, :redis]))
+        }.to change { HealthMonitor.configuration.providers }.
+          to(Set.new([HealthMonitor::Providers::Database, HealthMonitor::Providers::Redis]))
       end
 
       it 'configures a multiple providers' do
@@ -23,15 +24,18 @@
             config.redis
             config.sidekiq
           end
-        }.to change { HealthMonitor.configuration.providers }.to(Set.new([:database, :redis, :sidekiq]))
+        }.to change { HealthMonitor.configuration.providers }.
+          to(Set.new([HealthMonitor::Providers::Database, HealthMonitor::Providers::Redis,
+            HealthMonitor::Providers::Sidekiq]))
       end
 
       it 'appends new providers' do
         expect {
           subject.configure do |config|
             config.resque
           end
-        }.to change { HealthMonitor.configuration.providers }.to(Set.new([:database, :resque]))
+        }.to change { HealthMonitor.configuration.providers }.
+          to(Set.new([HealthMonitor::Providers::Database, HealthMonitor::Providers::Resque]))
       end
     end