Logging heartbeats from AWS Lambdas

AWS Lambdas running on a schedule are great candidates for logging heartbeats to elmah.io. To send a healthy heartbeat when the Lambda runs successfully and an unhealthy heartbeat when an error happens, start by installing the Elmah.Io.Client NuGet package:

Install-Package Elmah.Io.Client

dotnet add package Elmah.Io.Client

<PackageReference Include="Elmah.Io.Client" Version="5.*" />

paket add Elmah.Io.Client

Include elmah.io API key, log ID, and heartbeat ID in your code. In this example, they are added as static fields:

private const string ApiKey = "API_KEY";
private const string HeartbeatId = "HEARTBEAT_ID";
private static Guid LogId = new Guid("LOG_ID");

Replace API_KEY with an API key with the Heartbeats | Write permission (Where is my API key?), HEARTBEAT_ID with the ID of the heartbeat available on the elmah.io UI, and LOG_ID with the ID of the log containing the heartbeat (Where is my log ID?).

Create the elmah.io client and store the IHeartbeat object somewhere. In the following example, it is initialized in the Main method and stored in a static field:

private static IHeartbeats heartbeats;

private static async Task Main(string[] args)
{
    heartbeats = ElmahioAPI.Create(ApiKey).Heartbeats;
    // ...
}

In the function handler, wrap your code in try/catch and call either the Healthy or Unhealthy method:

public static string FunctionHandler(string input, ILambdaContext context)
{
    try
    {
        // Lambda code goes here

        heartbeats.Healthy(LogId, HeartbeatId);
        return input?.ToUpper();
    }
    catch (Exception e)
    {
        heartbeats.Unhealthy(LogId, HeartbeatId, e.ToString());
        throw;
    }
}

When the lambda code runs (replace the Lambda code goes here comment with your code) without exceptions, a healthy heartbeat is logged to elmah.io. In case of an exception, an unhealthy heartbeat is logged to elmah.io. In case your Lambda doesn't run at all, elmah.io automatically logs a missing heartbeat.

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