Circuit breaker usage

heartbeat.cs

using System;
using System.Collections.Generic;
using CityIQ.HealthMonitor.Notifiers;
using CityIQ.HealthMonitor.Testers;

namespace CityIQ.HealthMonitor
{
    /// <summary>
    /// Implementation that can make requests of services and optionally notify
    /// interested parties of the results.
    /// </summary>
    public class HeartbeatMonitor : IHeartbeatMonitor
    {
        private readonly IEnumerable<INotifier> _notifiers;

        public HeartbeatMonitor()
        {
            _notifiers = new List<INotifier>();
        }

        /// <summary>
        /// Ctor that can take some notification providers
        /// </summary>
        /// <param name="notifiers"></param>
        public HeartbeatMonitor(IEnumerable<INotifier> notifiers)
        {
            _notifiers = notifiers;
        }

        #region IHeartbeatMonitor Members

        public void CheckResource(IResourceTester resource, ICircuitBreaker circuitBreaker)
        {
            try
            {
                circuitBreaker.ExecuteCall(resource, r => r.IsAlive());
                bool alive = resource.IsAlive();

                if (!alive)
                {
                    Notify(Importance.Minor, resource.Name, string.Format("Failed to call the resource {0}", resource.Name));
                }
            }
            catch (OpenCircuitException oce)
            {
                // This indicates that the service has been repeatedly unavailable
                // and we should let someone know about it. Until the timeout period
                // has passed we'll keep throwing these until the circuit is reset to half open
                Notify(Importance.Critical, resource.Name, oce.ToString());
            }
            catch (Exception e)
            {
                // The operation failed but not didn't happen enough to trip the circuit breaker.
                // So this is the exception that caused the problem.
                Notify(Importance.Important, resource.Name, e.ToString());
            }
        }

        #endregion

        private void Notify(Importance severity, string resourceName, string message)
        {
            foreach (INotifier notifier in _notifiers)
            {
                notifier.Notify(severity, resourceName, message);
            }
        }
    }
}

tests.cs

using System;
using CityIQ.HealthMonitor;
using CityIQ.HealthMonitor.Testers;
using NUnit.Framework;
using StructureMap;

namespace CityIQ.MonitorTests
{
    [TestFixture]
    public class When_testing_web_sites
    {
        [SetUp]
        public void Before_any_test()
        {
            IoC.Bootstrap();
        }

        [Test]
        public void Valid_website_causes_no_failures()
        {
            var tester = new WebSite("Google","http://www.google.com",TimeSpan.FromSeconds(5d));
            var hb = new HeartbeatMonitor();
            var cb = ObjectFactory.GetInstance<ICircuitBreaker>();
            Assert.AreEqual(cb.Failures, 0);
            hb.CheckResource(tester, cb);
            Assert.AreEqual(cb.Failures, 0);
        }

        [Test]
        public void Inaccessible_website_causes_1_failure()
        {
            var tester = new WebSite("Boom", "http://www.google.com/c", TimeSpan.FromSeconds(5));
            var hb = new HeartbeatMonitor();
            var cb = ObjectFactory.GetInstance<ICircuitBreaker>();
            Assert.AreEqual(cb.Failures, 0);
            hb.CheckResource(tester, cb);
            Assert.AreEqual(cb.Failures, 1);
        }
    }
}