Add time tracking to http status agent (#1517)

* Add time tracking to http status agent

* Replace time tracking to monotonic

* Add tests for time tracker

app/models/agents/http_status_agent.rb

@@ -14,7 +14,7 @@ class HttpStatusAgent < Agent
     form_configurable :disable_redirect_follow, type: :array, values: ['true', 'false']
 
     description <<-MD
-      The HttpStatusAgent will check a url and emit the resulting HTTP status code.
+      The HttpStatusAgent will check a url and emit the resulting HTTP status code with the time that it waited for a reply.
 
       Specify a `Url` and the Http Status Agent will produce an event with the http status code.
 
@@ -27,6 +27,7 @@ class HttpStatusAgent < Agent
           {
             "url": "...",
             "status": "..."
+            "elapsed_time": "..."
           }
     MD
 
@@ -60,11 +61,12 @@ def receive(incoming_events)
     private
 
     def check_this_url(url)
-      if result = ping(url)
-        create_event payload: { 'url' => url, 'status' => result.status.to_s, 'response_received' => true }
-        memory['last_status'] = result.status.to_s
+      measured_result = TimeTracker.track { ping(url) }
+      if measured_result.result
+        create_event payload: { 'url' => url, 'status' => measured_result.status.to_s, 'response_received' => true, 'elapsed_time' => measured_result.elapsed_time }
+        memory['last_status'] = measured_result.status.to_s
       else
-        create_event payload: { 'url' => url, 'response_received' => false }
+        create_event payload: { 'url' => url, 'response_received' => false, 'elapsed_time' => measured_result.elapsed_time }
         memory['last_status'] = nil
       end
     end
@@ -75,7 +77,6 @@ def ping(url)
     rescue
       nil
     end
-
   end
 
 end

lib/time_tracker.rb

@@ -0,0 +1,22 @@
+class TimeTracker
+  attr_accessor :elapsed_time, :result
+
+  def self.track
+    start = Process.clock_gettime(Process::CLOCK_MONOTONIC)
+    result = yield
+    new(Process.clock_gettime(Process::CLOCK_MONOTONIC) - start, result)
+  end
+
+  def initialize(elapsed_time, result)
+    @elapsed_time = elapsed_time
+    @result = result
+  end
+
+  def method_missing(method_sym, *arguments, &block)
+    if @result.respond_to?(method_sym)
+      @result.send(method_sym, *arguments, &block)
+    else
+      super
+    end
+  end
+end

spec/controllers/http_status_agent_spec.rb

@@ -133,6 +133,11 @@ def agent.checked_url
         expect(agent.memory['last_status']).to eq('200')
       end
 
+      it "should record the time spent waiting for the reply" do
+        agent.receive events
+        expect(agent.the_created_events[0][:payload]['elapsed_time']).not_to be_nil
+      end
+
       describe "but the status code is not 200" do
         let(:status_code) { 500 }
 
@@ -236,6 +241,12 @@ def agent.checked_url
           expect(agent.the_created_events[1][:payload]['url']).to eq(failing_url)
         end
 
+        it "should record the time spent waiting for the reply" do
+          agent.receive events
+          expect(agent.the_created_events[0][:payload]['elapsed_time']).not_to be_nil
+          expect(agent.the_created_events[1][:payload]['elapsed_time']).not_to be_nil
+        end
+
       end
 
     end

spec/lib/time_tracker_spec.rb

@@ -0,0 +1,21 @@
+require 'rails_helper'
+
+describe TimeTracker do
+  describe "#track" do
+    it "tracks execution time" do
+      tracked_result = TimeTracker.track { sleep(0.01) }
+      expect(tracked_result.elapsed_time).to satisfy {|v| v > 0.01 && v < 0.1}
+    end
+
+    it "returns the proc return value" do
+      tracked_result = TimeTracker.track { 42 }
+      expect(tracked_result.result).to eq(42)
+    end
+
+    it "returns an object that behaves like the proc result" do
+      tracked_result = TimeTracker.track { 42 }
+      expect(tracked_result.to_i).to eq(42)
+      expect(tracked_result + 1).to eq(43)
+    end
+  end
+end