AwsLambda.Host.Envelopes.CloudWatchLogs 1.3.1

AwsLambda.Host.Envelopes.CloudWatchLogs

Strongly-typed CloudWatch Logs event handling for the AwsLambda.Host framework.

Overview

This package provides envelope classes that extend the base CloudWatchLogsEvent with automatic base64 decoding, decompression, and deserialization of CloudWatch Logs data. Instead of manually decoding and decompressing data from Awslogs.Data, you access the deserialized payload directly via envelope.AwslogsContent.

Quick Start

Define your log data type and handler:

using System.Text.Json;
using AwsLambda.Host.Builder;
using AwsLambda.Host.Envelopes.CloudWatchLogs;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;

var builder = LambdaApplication.CreateBuilder();

builder.Services.ConfigureEnvelopeOptions(options =>
{
    options.JsonOptions.PropertyNamingPolicy = JsonNamingPolicy.SnakeCaseLower;
});

var lambda = builder.Build();

// CloudWatchLogsEnvelope<T> provides access to the CloudWatch Logs event with each log message
// deserialized into type T
lambda.MapHandler(
    ([Event] CloudWatchLogsEnvelope<Log> logs, ILogger<Program> logger) =>
    {
        foreach (var logEvent in logs.AwslogsContent!.LogEvents)
        {
            logger.LogInformation("Log level: {Level}", logEvent.MessageContent?.Level);
            logger.LogInformation("Log message: {Message}", logEvent.MessageContent?.Message);
            logger.LogInformation("Request ID: {RequestId}", logEvent.MessageContent?.RequestId);
        }
    }
);

await lambda.RunAsync();

public record Log(string Level, string Message, string RequestId);

Custom Envelopes

To implement custom deserialization logic, extend CloudWatchLogsEnvelopeBase<T>, override the ExtractPayload method, and call base.ExtractPayload(options) to deserialize the CloudWatch Logs envelope structure, then deserialize each log message:

// Example: Custom XML deserialization
public sealed class CloudWatchLogsXmlEnvelope<T> : CloudWatchLogsEnvelopeBase<T>
{
    private static readonly XmlSerializer Serializer = new(typeof(T));

    public override void ExtractPayload(EnvelopeOptions options)
    {
        base.ExtractPayload(options);

        foreach (var logEvent in AwslogsContent!.LogEvents)
        {
            using var stringReader = new StringReader(logEvent.Message);
            using var xmlReader = XmlReader.Create(stringReader, options.XmlReaderSettings);
            logEvent.MessageContent = (T)Serializer.Deserialize(xmlReader)!;
        }
    }
}

This pattern allows you to support multiple serialization formats while maintaining the same envelope interface.

AOT Support

When using .NET Native AOT, register both the envelope and payload types in your JsonSerializerContext:

[JsonSerializable(typeof(CloudWatchLogsEnvelope<LogData>))]
[JsonSerializable(typeof(LogData))]
internal partial class SerializerContext : JsonSerializerContext;

Register the serializer and configure envelope options to use the context:

builder.Services.AddLambdaSerializerWithContext<SerializerContext>();

builder.Services.ConfigureEnvelopeOptions(options =>
{
    options.JsonOptions.TypeInfoResolver = SerializerContext.Default;
});

Other Packages

Additional packages in the aws-lambda-host framework for abstractions, observability, and event source handling.

Package	NuGet	Downloads
AwsLambda.Host
AwsLambda.Host.Abstractions
AwsLambda.Host.OpenTelemetry
AwsLambda.Host.Envelopes.Sqs
AwsLambda.Host.Envelopes.ApiGateway
AwsLambda.Host.Envelopes.Sns
AwsLambda.Host.Envelopes.Kinesis
AwsLambda.Host.Envelopes.KinesisFirehose
AwsLambda.Host.Envelopes.Kafka
AwsLambda.Host.Envelopes.CloudWatchLogs
AwsLambda.Host.Envelopes.Alb

License

This project is licensed under the MIT License. See LICENSE for details.