Configurable outage response handling (department-of-veterans-affairs#5)

* configurable outage response handling

* bump version

Author: aub

README.md

@@ -154,6 +154,15 @@ service.end_forced_outage!
 Unlike with outages detected by the middleware, forced outages are not periodically tested to see if they have completed and must be
 manually ended with a call to `end_forced_outage!`.
 
+### Changing the Outage Response
+
+By default, if you make a request against a service that is experiencing an outage a Breakers::OutageException will be raised. If you would
+prefer to receive a response with a certain status code instead, you can change that with:
+
+```ruby
+Breakers.outage_response = { type: :status_code, status_code: 503 }
+```
+
 ### Redis Data Structure
 
 Data is stored in Redis with the following structure:

lib/breakers.rb

@@ -1,5 +1,6 @@
 require 'breakers/client'
 require 'breakers/outage'
+require 'breakers/outage_exception'
 require 'breakers/service'
 require 'breakers/uptime_middleware'
 require 'breakers/version'
@@ -40,4 +41,21 @@ def self.redis_prefix=(prefix)
   def self.redis_prefix
     @redis_prefix || ''
   end
+
+  # Configure the middleware's handling of outages. The default is to raise a Breakers::OutageException
+  # but you can also request that the response comes back with a configurable status code.
+  #
+  # @param [Hash] opts A hash of options
+  # @option opts [Symbol] :type Pass :exception to raise a Breakers::OutageException when an error occurs. Pass :status_code to respond.
+  # @option opts [Integer] :status_code If the type is :status_code, configure which code to return.
+  def self.outage_response=(opts)
+    @outage_response = { type: :exception }.merge(opts)
+  end
+
+  # Query for the outage response configuration
+  #
+  # @return [Hash] configuration for the outage response, as defined in outage_response=
+  def self.outage_response
+    @outage_response || { type: :exception }
+  end
 end

lib/breakers/outage_exception.rb

@@ -0,0 +1,17 @@
+module Breakers
+  # The error that is raised when a request is made against a service that is
+  # experiencing an outage
+  class OutageException < StandardError
+    attr_reader :outage
+    attr_reader :service
+
+    def initialize(outage, service)
+      @outage = outage
+      @service = service
+    end
+
+    def message
+      "Outage detected on #{@service.name} beginning at #{@outage.start_time.to_i}"
+    end
+  end
+end

lib/breakers/uptime_middleware.rb

@@ -31,12 +31,16 @@ def call(request_env)
     protected
 
     def outage_response(outage:, service:)
-      Faraday::Response.new.tap do |response|
-        response.finish(
-          status: 503,
-          body: "Outage detected on #{service.name} beginning at #{outage.start_time.to_i}",
-          response_headers: {}
-        )
+      if Breakers.outage_response[:type] == :status_code
+        Faraday::Response.new.tap do |response|
+          response.finish(
+            status: Breakers.outage_response[:status_code],
+            body: "Outage detected on #{service.name} beginning at #{outage.start_time.to_i}",
+            response_headers: {}
+          )
+        end
+      else
+        raise Breakers::OutageException.new(outage, service)
       end
     end
 
@@ -60,13 +64,15 @@ def handle_request(service:, request_env:, current_outage: nil)
         end
       end
     rescue => e
-      handle_error(
-        service: service,
-        request_env: request_env,
-        response_env: nil,
-        error: "#{e.class.name} - #{e.message}",
-        current_outage: current_outage
-      )
+      unless e.is_a?(Breakers::OutageException)
+        handle_error(
+          service: service,
+          request_env: request_env,
+          response_env: nil,
+          error: "#{e.class.name} - #{e.message}",
+          current_outage: current_outage
+        )
+      end
       raise
     end
 

lib/breakers/version.rb

@@ -1,3 +1,3 @@
 module Breakers
-  VERSION = '0.1.1'.freeze
+  VERSION = '0.2.0'.freeze
 end

spec/integration_spec.rb

@@ -29,6 +29,7 @@
   end
 
   before do
+    Breakers.outage_response = { type: :status_code, status_code: 503 }
     Breakers.client = client
   end
 
@@ -399,4 +400,21 @@
       end
     end
   end
+
+  context 'configured to raise exceptions' do
+    let(:start_time) { Time.now.utc - 30 }
+    let(:now) { Time.now.utc }
+    before do
+      Timecop.freeze(now)
+      redis.zadd('VA-outages', start_time.to_i, MultiJson.dump(start_time: start_time.to_i))
+    end
+
+    before do
+      Breakers.outage_response = { type: :exception }
+    end
+
+    it 'raises the exception' do
+      expect { connection.get '/' }.to raise_error(Breakers::OutageException)
+    end
+  end
 end