Implement Lambda warmer

AWSServerless1/APIGatewayProxyFunction.cs

@@ -0,0 +1,43 @@
+using Amazon.Lambda;
+using Amazon.Lambda.APIGatewayEvents;
+using Amazon.Lambda.Core;
+using Newtonsoft.Json;
+using System;
+using System.Threading.Tasks;
+
+namespace AWSServerless1
+{
+    public abstract class APIGatewayProxyFunction : Amazon.Lambda.AspNetCoreServer.APIGatewayProxyFunction
+    {
+        public override async Task<APIGatewayProxyResponse> FunctionHandlerAsync(APIGatewayProxyRequest request,
+            ILambdaContext lambdaContext)
+        {
+            Console.WriteLine("In overridden FunctionHandlerAsync...");
+
+            if (request.Resource == "WarmingLambda")
+            {
+                int.TryParse(request.Body, out var concurrencyCount);
+
+                if (concurrencyCount > 1)
+                {
+                    Console.WriteLine($"Warming instance {concurrencyCount}.");
+                    var client = new AmazonLambdaClient();
+                    await client.InvokeAsync(new Amazon.Lambda.Model.InvokeRequest
+                    {
+                        FunctionName = lambdaContext.FunctionName,
+                        InvocationType = InvocationType.RequestResponse,
+                        Payload = JsonConvert.SerializeObject(new APIGatewayProxyRequest
+                        {
+                            Resource = request.Resource,
+                            Body = (concurrencyCount - 1).ToString()
+                        })
+                    });
+                }
+
+                return new APIGatewayProxyResponse { };
+            }
+
+            return await base.FunctionHandlerAsync(request, lambdaContext);
+        }
+    }
+}

AWSServerless1/AWSServerless1.csproj

@@ -12,6 +12,7 @@
     <ItemGroup>
         <PackageReference Include="Microsoft.AspNetCore.App" />
         <PackageReference Include="Amazon.Lambda.AspNetCoreServer" Version="3.0.3" />
+        <PackageReference Include="AWSSDK.Lambda" Version="3.3.101" />
         <PackageReference Include="Amazon.Lambda.RuntimeSupport" Version="1.0.0" />
         <PackageReference Include="AWSSDK.Extensions.NETCore.Setup" Version="3.3.100.1" />
     </ItemGroup>

AWSServerless1/serverless.template

@@ -29,7 +29,14 @@
 							"Path": "/",
 							"Method": "ANY"
 						}
-					}
+					},
+                    "APIWarmingSchedule": {
+                        "Type": "Schedule",
+                        "Properties": {
+                            "Schedule": "rate(5 minutes)",
+                            "Input": "{ \"Resource\": \"WarmingLambda\", \"Body\": \"5\" }"
+                        }
+                    }
 				}
 			}
 		}