Updating an AWS Lambda app to .NET 6.0

March 12, 2022 - 4 minutes read - 714 words

The long awaited support for .NET 6.0 on AWS Lambda has finally been released. My Twitter bot runs on .NET Core 3.1 in a Lambda function and I have been meaning to update it to .NET 6 for a while. So let’s do just that!

I’ll be following the steps on the announcement blog post to migrate to 6.0.

Project file

The following items need to be updated in the project file:

TargetFramework to net6.0
If using Top Level Statements (see below), set the OutputType to Exe

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>net6.0</TargetFramework>
    <OutputType>Exe</OutputType>    
    ...
  </PropertyGroup>
</Project>

CloudFormation template

The following items need to be updated in the CloudFormation template:

Runtime to dotnet6
If using Top Level Statements (see below), set the Handler to the name of your assembly

...
Resources:
  Retweet:
    ...
    Properties:
      Handler: DotNetTwitterBot
      Runtime: dotnet6

CodeBuild script

I’m using AWS CodeBuild for CI, but the CodeBuild images do not currently support .NET 6, so I need to install it directly:

version: 0.2
phases:
  install:
    commands:
      - /usr/local/bin/dotnet-install.sh --channel LTS
        ...

Note: I also updated my CodeBuild image to aws/codebuild/standard:5.0 as this is the latest version.

NuGet packages

The Lambda NuGet packages also need to be updated the latest versions. In my case I was already on the latest version for Amazon.Lambda.Core, 2.1.0.

New features

Top Level Statements

.NET 6 introduces Top Level Statements which can now be used in Lambda functions to reduce boilerplate code. This can be enabled by being on .NET 6 and adding the following package:

dotnet add package Amazon.Lambda.RuntimeSupport

Previously, my function looked like:

using System;
using System.Linq;
using System.Threading.Tasks;
using Amazon.Lambda.Core;
using Microsoft.ML.OnnxRuntime;
using Tweetinvi;
using Tweetinvi.Models;
using Tweetinvi.Parameters;

namespace DotNetTwitterBot
{
    public class Functions
    {
        static readonly string[] SearchTerms = new[]
        {
            "\".NET AND Framework\"",
            "\".NET AND Core\"",
            "\".NET AND 5\"",
            "\".NET AND 6\"",
            "\".NET AND 7\"",
            "#dotnet",
            "#dotnetcore",
            "#dotnet5",
            "#dotnet6",
            "#dotnet7"
        };

        public async Task Retweet(ILambdaContext context)
        {
            var creds = await SecretHelper.GetSecretAsync();
            Auth.SetUserCredentials(creds.ConsumerKey, creds.ConsumerSecret, creds.AccessToken, creds.AccessSecret);

            var searchSince = DateTime.UtcNow.Subtract(TimeSpan.FromMinutes(31));
            var me = User.GetAuthenticatedUser();

            await SearchAndRetweetTweets(SearchTerms, searchSince, me);

            static async Task SearchAndRetweetTweets(string[] terms, DateTime searchSince, IAuthenticatedUser me)
            {
                var query = string.Join(" OR ", terms);
                var param = new SearchTweetsParameters(query)
                {
                    Since = searchSince,
                    TweetSearchType = TweetSearchType.OriginalTweetsOnly,
                    Filters = TweetSearchFilters.Safe,
                    MaximumNumberOfResults = 1000
                };

                var tweets = await SearchAsync.SearchTweets(param);

                var spamFilter = new SpamFilter("spam_filter.onnx");

                var isSpam = spamFilter.Run(tweets.Select(t => $"RT @{t.CreatedBy.ScreenName} : {t.Text}")).ToArray();

                var tasks = tweets.Select(async (t, i) => {
                    if (!isSpam[i])
                        await t.PublishRetweetAsync();
                });

                await Task.WhenAll(tasks);
            }
        }
    }
}

After incorporating Top Level Statements, my function looks like:

using System;
using System.Linq;
using System.Threading.Tasks;
using Amazon.Lambda.Core;
using Amazon.Lambda.RuntimeSupport;
using DotNetTwitterBot;
using Tweetinvi;
using Tweetinvi.Models;
using Tweetinvi.Parameters;

var handler = async (ILambdaContext context) =>
{
    string[] searchTerms = new[]
    {
        "\".NET AND Framework\"",
        "\".NET AND Core\"",
        "\".NET AND 5\"",
        "\".NET AND 6\"",
        "\".NET AND 7\"",
        "#dotnet",
        "#dotnetcore",
        "#dotnet5",
        "#dotnet6",
        "#dotnet7"
    };

    var creds = await SecretHelper.GetSecretAsync();
    Auth.SetUserCredentials(creds.ConsumerKey, creds.ConsumerSecret, creds.AccessToken, creds.AccessSecret);

    var searchSince = DateTime.UtcNow.Subtract(TimeSpan.FromMinutes(31));
    var me = User.GetAuthenticatedUser();

    await SearchAndRetweetTweets(searchTerms, searchSince, me);

    async Task SearchAndRetweetTweets(string[] terms, DateTime searchSince, IAuthenticatedUser me)
    {
        var query = string.Join(" OR ", terms);
        var param = new SearchTweetsParameters(query)
        {
            Since = searchSince,
            TweetSearchType = TweetSearchType.OriginalTweetsOnly,
            Filters = TweetSearchFilters.Safe,
            MaximumNumberOfResults = 1000
        };

        var tweets = await SearchAsync.SearchTweets(param);

        var spamFilter = new SpamFilter("spam_filter.onnx");

        var isSpam = spamFilter.Run(tweets.Select(t => $"RT @{t.CreatedBy.ScreenName} : {t.Text}")).ToArray();

        var tasks = tweets.Select(async (t, i) => {
            if (!isSpam[i])
                await t.PublishRetweetAsync();
        });

        await Task.WhenAll(tasks);
    }
};

await LambdaBootstrapBuilder.Create(handler).Build().RunAsync();

Much cleaner!

Other new features

There are lots of new features that come with .NET 6.0 that can be utilised in AWS Lambda, such as:

Improved logging
Using source generator for JSON serialization
ASP.NET Core minimal APIs

Cool! That’s it for my app then. Let’s merge this into main and see how it goes!

Summary

In this post, I updated my Twitter bot app from .NET Core 3.1 to .NET 6.0. This was pretty straight forward, just updating the .NET version in a few files, adding/updating some NuGet packages and refactoring the function to support Top Level Statements. It was a very painless exercise and I recommend everyone do it for their apps; there’s lots of performance improvements in .NET 6.0 so if all of our code runs faster, that’s hopefully a lot of CO2 we could be saving!