Introducing super basic health check for cart service (GoogleCloudPlatform#44)

* Introducing super basic health check for cart service
  - Generated C# proto implementation for grpc health check
  - Moved all C# protos to a dedicated folder
  - Implemented basic health checking to ping CartStore (which is Redis in default implementation)
  - Base plumbing for health checks

* Introducing super basic health check for cart service

- Generated C# proto implementation for grpc health check
- Moved all C# protos to a dedicated folder
- Implemented basic health checking to ping CartStore (which is Redis in default implementation)
- Base plumbing for health checks

* Changing Ping health probe to call Redis Cache Ping method

Author: Simon Zeltser

src/cartservice/HealthImpl.cs

@@ -0,0 +1,22 @@
+using System;
+using cartservice.interfaces;
+using Grpc.Health.V1;
+using StackExchange.Redis;
+using static Grpc.Health.V1.Health;
+
+namespace cartservice {
+    internal class HealthImpl : HealthBase {
+        private ICartStore dependency { get; }
+        public HealthImpl (ICartStore dependency) {
+            this.dependency = dependency;
+        }
+
+        public HealthCheckResponse Check (HealthCheckRequest request) {
+            Console.WriteLine ("Checking CartService Health");
+
+            return new HealthCheckResponse {
+                Status = dependency.Ping() ? HealthCheckResponse.Types.ServingStatus.Serving : HealthCheckResponse.Types.ServingStatus.NotServing
+            };
+        }
+    }
+}

src/cartservice/Program.cs

@@ -56,7 +56,14 @@ static object StartServer(string host, int port, ICartStore cartStore)
                     Console.WriteLine($"Trying to start a grpc server at  {host}:{port}");
                     Server server = new Server
                     {
-                        Services = { Hipstershop.CartService.BindService(new CartServiceImpl(cartStore)) },
+                        Services = 
+                        {
+                            // Cart Service Endpoint
+                             Hipstershop.CartService.BindService(new CartServiceImpl(cartStore)),
+
+                             // Health Endpoint
+                             Grpc.Health.V1.Health.BindService(new HealthImpl(cartStore))
+                        },
                         Ports = { new ServerPort(host, port, ServerCredentials.Insecure) }
                     };
 

src/cartservice/cartservice.csproj

@@ -7,9 +7,10 @@
 
   <ItemGroup>
     <PackageReference Include="CommandLineParser" Version="2.2.1" />
-    <PackageReference Include="Google.Protobuf" Version="3.5.1" />
+    <PackageReference Include="Google.Protobuf" Version="3.6.1" />
     <PackageReference Include="Google.Protobuf.Tools" Version="3.5.1" />
     <PackageReference Include="grpc" Version="1.12.0" />
+    <PackageReference Include="Grpc.HealthCheck" Version="1.15.0" />
     <PackageReference Include="grpc.tools" Version="1.12.0" />
     <PackageReference Include="Microsoft.Extensions.Configuration" Version="2.1.1" />
     <PackageReference Include="Microsoft.Extensions.Configuration.Json" Version="2.1.1" />

src/cartservice/cartstore/LocalCartStore.cs

@@ -82,5 +82,10 @@ public Task EmptyCartAsync(string userId)
 
             return Task.FromResult(cart);
         }
+
+        public bool Ping()
+        {
+            return true;
+        }
     }
 }

src/cartservice/cartstore/RedisCartStore.cs

@@ -197,5 +197,20 @@ public async Task EmptyCartAsync(string userId)
                 throw new RpcException(new Status(StatusCode.FailedPrecondition, $"Can't access cart storage. {ex}"));
             }
         }
+
+        public bool Ping()
+        {
+            try
+            {
+                var redis = ConnectionMultiplexer.Connect(redisConnectionOptions);
+                var cache = redis.GetDatabase();
+                var res = cache.Ping();
+                return res != TimeSpan.Zero;
+            }
+            catch (Exception)
+            {
+                return false;
+            }
+        }
     }
 }

src/cartservice/generate_protos.bat

@@ -22,6 +22,6 @@ cd /d %~dp0
 set NUGET_PATH=%UserProfile%\.nuget\packages
 set TOOLS_PATH=%NUGET_PATH%\Grpc.Tools\1.12.0\tools\windows_x64
 
-%TOOLS_PATH%\protoc.exe -I%~dp0/../../pb;%NUGET_PATH%\google.protobuf.tools\3.5.1\tools\ --csharp_out %~dp0 %~dp0\..\..\pb\demo.proto --grpc_out %~dp0 --plugin=protoc-gen-grpc=%TOOLS_PATH%\grpc_csharp_plugin.exe
+%TOOLS_PATH%\protoc.exe -I%~dp0/../../pb;%NUGET_PATH%\google.protobuf.tools\3.5.1\tools\ --csharp_out %~dp0\grpc_generated %~dp0\..\..\pb\demo.proto --grpc_out %~dp0\grpc_generated --plugin=protoc-gen-grpc=%TOOLS_PATH%\grpc_csharp_plugin.exe
 
 endlocal

src/cartservice/Demo.cs renamed to src/cartservice/grpc_generated/Demo.cs

@@ -24,5 +24,7 @@ internal interface ICartStore
         Task EmptyCartAsync(string userId);
 
         Task<Hipstershop.Cart> GetCartAsync(string userId);
+
+        bool Ping();
     }
 }