This sample shows how to configure an ASP.NET Core 3.0 project to use the Amazon.Lambda.RuntimeSupport NuGet package and deploy to Lambda using Lambda's custom runtime feature.
Note: This sample was writen with .NET Core 3.0 preview 6
Amazon.Lambda.AspNetCoreServer is the NuGet package that has allowed ASP.NET Core application to run as Lambda function since the release of .NET Core Lambda support.
ASP.NET Core 3.0 has breaking changes that require a new version of Amazon.Lambda.AspNetCoreServer. Since .NET Core 3.0 is in preview the changes to Amazon.Lambda.AspNetCoreServer have not shipped. A preview version has been checked in to the nuget-cache directory of this project. A nuget.config file was also added to add the nuget-cache directory as a NuGet feed.
If the project doesn't already contain a LambdaEntryPoint class then you need to add it. The is same file as that is created by the existing ASP.NET Core Lambda templates.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Hosting;
using System.IO;
namespace CustomRuntimeAspNetCore30
{
/// <summary>
/// This class extends from APIGatewayProxyFunction which contains the method FunctionHandlerAsync which is the
/// actual Lambda function entry point.
/// </summary>
public class LambdaEntryPoint :
// When using an ELB's Application Load Balancer as the event source change
// the base class to Amazon.Lambda.AspNetCoreServer.ApplicationLoadBalancerFunction
Amazon.Lambda.AspNetCoreServer.APIGatewayProxyFunction
{
/// <summary>
/// The builder has configuration, logging and Amazon API Gateway already configured. The startup class
/// needs to be configured in this method using the UseStartup<>() method.
/// </summary>
/// <param name="builder"></param>
protected override void Init(IWebHostBuilder builder)
{
builder
.UseStartup<Startup>();
}
}
}Lambda needs an executable file called bootstrap when using the custom runtime feature. This can be done by adding a text file called bootstrap to the project. Be sure to set your project name in the bootstrap file.
#!/bin/sh
# This is the script that the Lambda host calls to start the custom runtime.
/var/task/<project-name>Updates to the project file:
- Make sure the
OutputTypeset to Exe - Add the
bootstrapfile to the project as a content file to be copy to the output directory. - Add
PackageReferenceforAmazon.Lambda.RuntimeSupport
<Project Sdk="Microsoft.NET.Sdk.Web">
<PropertyGroup>
<TargetFramework>netcoreapp3.0</TargetFramework>
<GenerateRuntimeConfigurationFiles>true</GenerateRuntimeConfigurationFiles>
<AWSProjectType>Lambda</AWSProjectType>
</PropertyGroup>
<ItemGroup>
<Content Include="bootstrap">
<CopyToOutputDirectory>Always</CopyToOutputDirectory>
</Content>
</ItemGroup>
<ItemGroup>
<PackageReference Include="Amazon.Lambda.AspNetCoreServer" Version="3.1.9999-preview1" />
<PackageReference Include="Amazon.Lambda.RuntimeSupport" Version="1.0.0" />
</ItemGroup>
</Project>A Lambda function that uses Amazon.Lambda.RuntimeSupport is required to have a Main method to bootstrap the Lambda runtime. An ASP.NET Core project likely already has a Main method to run locally.
To work in both modes have the Main method check to see a Lambda specific environment variable is set. If it is not set then use regular ASP.NET Core startup code. If the environment variable is set then use the Lambda bootstrap code.
using System;`
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore;
using Microsoft.AspNetCore.Hosting;
using Amazon.Lambda.Core;
using Amazon.Lambda.APIGatewayEvents;
using Amazon.Lambda.RuntimeSupport;
using Amazon.Lambda.Serialization.Json;
namespace CustomRuntimeAspNetCore30
{
/// <summary>
/// The Main function can be used to run the ASP.NET Core application locally using the Kestrel webserver.
/// </summary>
public class Program
{
public static void Main(string[] args)
{
if (string.IsNullOrEmpty(Environment.GetEnvironmentVariable("AWS_LAMBDA_FUNCTION_NAME")))
{
CreateHostBuilder(args).Build().Run();
}
else
{
var lambdaEntry = new LambdaEntryPoint();
var functionHandler = (Func<APIGatewayProxyRequest, ILambdaContext, Task<APIGatewayProxyResponse>>)(lambdaEntry.FunctionHandlerAsync);
using (var handlerWrapper = HandlerWrapper.GetHandlerWrapper(functionHandler, new JsonSerializer()))
using (var bootstrap = new LambdaBootstrap(handlerWrapper))
{
bootstrap.RunAsync().Wait();
}
}
}
public static IHostBuilder CreateHostBuilder(string[] args) =>
Host.CreateDefaultBuilder(args)
.ConfigureWebHostDefaults(webBuilder =>
{
webBuilder.UseStartup<Startup>();
});
}
}In the serverless.template file set the Runtime property to provided to inform the Lambda service that the function should use custom runtimes.
"AspNetCoreFunction" : {
"Type" : "AWS::Serverless::Function",
"Properties": {
"Handler": "not-required",
"Runtime": "provided",
"CodeUri": "",
"MemorySize": 256,
"Timeout": 30,
"Policies": [ "AWSLambdaFullAccess" ],
"Events": {
"ProxyResource": {
"Type": "Api",
"Properties": {
"Path": "/{proxy+}",
"Method": "ANY"
}
},
"RootResource": {
"Type": "Api",
"Properties": {
"Path": "/",
"Method": "ANY"
}
}
}
}
}To deploy a .NET Core 3.0 Lambda function using Amazon.Lambda.RuntimeSupport the function must be deployed as self contained package.
This can be configured in the aws-lambda-tools-defaults.json by setting the msbuild-parameters property to --self-contained true.
{
"profile":"",
"region" : "us-west-2",
"configuration" : "Release",
"s3-prefix" : "CustomRuntimeAspNetCore30/",
"template" : "serverless.template",
"template-parameters" : "",
"msbuild-parameters": "--self-contained true"
}