From 483340f21e38e9730ba516b14d7813f87829569b Mon Sep 17 00:00:00 2001
From: Steve Smith <steve@kentsmiths.com>
Date: Fri, 18 Jan 2019 11:48:26 -0500
Subject: [PATCH] Adding API Health Check (#191)

---
 src/Web/HealthChecks/ApiHealthCheck.cs      | 40 +++++++++++++++++++++
 src/Web/HealthChecks/HomePageHealthCheck.cs |  4 ++-
 src/Web/Properties/launchSettings.json      |  2 +-
 src/Web/Startup.cs                          | 28 +++++++++++++--
 4 files changed, 70 insertions(+), 4 deletions(-)
 create mode 100644 src/Web/HealthChecks/ApiHealthCheck.cs

diff --git a/src/Web/HealthChecks/ApiHealthCheck.cs b/src/Web/HealthChecks/ApiHealthCheck.cs
new file mode 100644
index 0000000..989fe99
--- /dev/null
+++ b/src/Web/HealthChecks/ApiHealthCheck.cs
@@ -0,0 +1,40 @@
+using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Routing;
+using Microsoft.Extensions.Diagnostics.HealthChecks;
+using System.Net.Http;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace Microsoft.eShopWeb.Web.HealthChecks
+{
+    public class ApiHealthCheck : IHealthCheck
+    {
+        private readonly IHttpContextAccessor _httpContextAccessor;
+        private readonly LinkGenerator _linkGenerator;
+
+        public ApiHealthCheck(IHttpContextAccessor httpContextAccessor, LinkGenerator linkGenerator)
+        {
+            _httpContextAccessor = httpContextAccessor;
+            _linkGenerator = linkGenerator;
+        }
+
+        public async Task<HealthCheckResult> CheckHealthAsync(
+            HealthCheckContext context,
+            CancellationToken cancellationToken = default(CancellationToken))
+        {
+            var request = _httpContextAccessor.HttpContext.Request;
+
+            string apiLink = _linkGenerator.GetPathByAction("List", "Catalog");
+            string myUrl = request.Scheme + "://" + request.Host.ToString() + apiLink;
+            var client = new HttpClient();
+            var response = await client.GetAsync(myUrl);
+            var pageContents = await response.Content.ReadAsStringAsync();
+            if (pageContents.Contains(".NET Bot Black Sweatshirt"))
+            {
+                return HealthCheckResult.Healthy("The check indicates a healthy result.");
+            }
+
+            return HealthCheckResult.Unhealthy("The check indicates an unhealthy result.");
+        }
+    }
+}
diff --git a/src/Web/HealthChecks/HomePageHealthCheck.cs b/src/Web/HealthChecks/HomePageHealthCheck.cs
index a8f322a..f858a55 100644
--- a/src/Web/HealthChecks/HomePageHealthCheck.cs
+++ b/src/Web/HealthChecks/HomePageHealthCheck.cs
@@ -19,7 +19,9 @@ namespace Microsoft.eShopWeb.Web.HealthChecks
             HealthCheckContext context,
             CancellationToken cancellationToken = default(CancellationToken))
         {
-            string myUrl = _httpContextAccessor.HttpContext.Request.Host.ToString();
+            var request = _httpContextAccessor.HttpContext.Request;
+            string myUrl = request.Scheme + "://" + request.Host.ToString();
+
             var client = new HttpClient();
             var response = await client.GetAsync(myUrl);
             var pageContents = await response.Content.ReadAsStringAsync();
diff --git a/src/Web/Properties/launchSettings.json b/src/Web/Properties/launchSettings.json
index b1b4320..652d021 100644
--- a/src/Web/Properties/launchSettings.json
+++ b/src/Web/Properties/launchSettings.json
@@ -1,4 +1,4 @@
-{
+{
   "iisSettings": {
     "windowsAuthentication": false,
     "anonymousAuthentication": true,
diff --git a/src/Web/Startup.cs b/src/Web/Startup.cs
index 2e34f80..e66d563 100644
--- a/src/Web/Startup.cs
+++ b/src/Web/Startup.cs
@@ -1,4 +1,5 @@
 using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.Diagnostics.HealthChecks;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Identity;
@@ -18,8 +19,12 @@ using Microsoft.eShopWeb.Web.Interfaces;
 using Microsoft.eShopWeb.Web.Services;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Diagnostics.HealthChecks;
+using Newtonsoft.Json;
 using Swashbuckle.AspNetCore.Swagger;
 using System;
+using System.Linq;
+using System.Net.Mime;
 using System.Text;
 
 namespace Microsoft.eShopWeb.Web
@@ -121,7 +126,8 @@ namespace Microsoft.eShopWeb.Web
             });
 
             services.AddHealthChecks()
-                .AddCheck<HomePageHealthCheck>("home_page_health_check");
+                .AddCheck<HomePageHealthCheck>("home_page_health_check")
+                .AddCheck<ApiHealthCheck>("api_health_check");
 
             _services = services; // used to debug registered services
         }
@@ -151,7 +157,25 @@ namespace Microsoft.eShopWeb.Web
         public void Configure(IApplicationBuilder app, IHostingEnvironment env, LinkGenerator linkGenerator)
         {
             //app.UseDeveloperExceptionPage();
-            app.UseHealthChecks("/health");
+            app.UseHealthChecks("/health",
+                new HealthCheckOptions
+                {
+                    ResponseWriter = async (context, report) =>
+                    {
+                        var result = JsonConvert.SerializeObject(
+                            new
+                            {
+                                status = report.Status.ToString(),
+                                errors = report.Entries.Select(e => new
+                                {
+                                    key = e.Key,
+                                    value = Enum.GetName(typeof(HealthStatus), e.Value.Status)
+                                })
+                            });
+                        context.Response.ContentType = MediaTypeNames.Application.Json;
+                        await context.Response.WriteAsync(result);
+                    }
+                });
             if (env.IsDevelopment())
             {
                 app.UseDeveloperExceptionPage();