prevent from running multiple same cron jobs (#846)

app/controllers/crons_controller.rb

@@ -4,18 +4,6 @@ class CronsController < ApplicationController
   SCRIPT_PATH = Rails.root.join('cron')
   CRON_DEFINITIONS = Rails.root.join('cron.yaml')
 
-  def configured_job_names
-    YAML.load_file(CRON_DEFINITIONS)['cron'].map { |d| d['name'] }
-  end
-
-  def runnable?
-    request.local? && configured_job_names.include?(taskname)
-  end
-
-  def taskname
-    request.headers['X-Aws-Sqsd-Taskname']
-  end
-
   def create
     return head(:forbidden) unless runnable?
 
@@ -27,4 +15,31 @@ def create
       render(plain: "Unable to run #{taskname}", status: 500)
     end
   end
+
+  private
+
+  def runnable?
+    request.local? && configured_job_names.include?(taskname) && !running_same_job?
+  end
+
+  def configured_job_names
+    YAML.load_file(CRON_DEFINITIONS)['cron'].map { |d| d['name'] }
+  end
+
+  def taskname
+    @taskname ||= request.headers['X-Aws-Sqsd-Taskname']
+  end
+
+  def running_same_job?
+    res = false
+    IO.popen('ps ax') do |io|
+      io.each_line do |line|
+        if line.chomp.split.last.end_with?(taskname)
+          res = true
+          break
+        end
+      end
+    end
+    res
+  end
 end

spec/controllers/crons_controller_spec.rb

@@ -0,0 +1,47 @@
+# frozen_string_literal: true
+
+# frozen_string_literals: true
+
+require 'spec_helper'
+
+RSpec.describe CronsController, type: :controller do
+  describe 'GET #create' do
+    before do
+      @request.env['REMOTE_ADDR'] = '127.0.0.1'
+      allow(IO).to receive(:popen)
+        .with('ps ax')
+        .and_yield(
+          StringIO.new(<<~STRING)
+            PID TTY          TIME CMD
+            1 ?        S      0:00 bash ./dump_measurements
+          STRING
+        )
+      allow(controller).to receive(:system) # Not to run cron jobs
+      allow($?).to receive(:success?).and_return(true) # rubocop:disable Style/SpecialGlobalVars
+    end
+
+    describe 'when task exists' do
+      before do
+        allow(controller).to receive(:taskname).and_return('dump_clean')
+      end
+
+      it 'returns HTTP 200 OK' do
+        get :create
+
+        expect(response).to have_http_status(200)
+      end
+    end
+
+    describe 'when task exists but try to run same job' do
+      before do
+        allow(controller).to receive(:taskname).and_return('dump_measurements')
+      end
+
+      it 'returns HTTP 403 Forbidden' do
+        get :create
+
+        expect(response).to have_http_status(403)
+      end
+    end
+  end
+end