UseLambdaRun

Offloads synchronous run execution to an AWS Lambda function via direct SDK invocation instead of executing in-process. The call blocks until the Lambda completes and returns the train output. No public endpoint is created; access is governed by IAM policies.

Package

dotnet add package Trax.Scheduler.Lambda

Signature

public static SchedulerConfigurationBuilder UseLambdaRun(
    this SchedulerConfigurationBuilder builder,
    Action<LambdaRunOptions> configure
)

Defined in Trax.Scheduler.Lambda.Extensions.LambdaSchedulerExtensions.

Parameters

Returns

SchedulerConfigurationBuilder, for continued fluent chaining.

LambdaRunOptions

Examples

Basic Usage

using Trax.Scheduler.Lambda.Extensions;
 
services.AddTrax(trax => trax
    .AddEffects(effects => effects
        .UsePostgres(connectionString)
    )
    .AddMediator(assemblies)
    .AddScheduler(scheduler => scheduler
        .UseLambdaWorkers(
            lambda => lambda.FunctionName = "content-shield-runner",
            routing => routing.ForTrain<IMyTrain>()
        )
        .UseLambdaRun(lambda =>
            lambda.FunctionName = "content-shield-runner"
        )
    )
);

With Custom Region

.UseLambdaRun(lambda =>
{
    lambda.FunctionName = "content-shield-runner";
    lambda.ConfigureLambdaClient = config =>
        config.RegionEndpoint = Amazon.RegionEndpoint.EUWest1;
})

With LocalStack (Development)

.UseLambdaRun(lambda =>
{
    lambda.FunctionName = "content-shield-runner";
    lambda.ConfigureLambdaClient = config =>
        config.ServiceURL = "http://localhost:4566";
})

Registered Services

UseLambdaRun() registers:

Note: Without UseLambdaRun(), the default LocalRunExecutor executes trains in-process via ITrainBus.RunAsync(). UseLambdaRun() overrides this.

How It Works

When a GraphQL run* mutation is called, the IRunExecutor registered by UseLambdaRun():

1. Serializes a RemoteRunRequest containing the train name, input JSON, and input type
2. Wraps it in a LambdaEnvelope with Type = Run
3. Calls IAmazonLambda.InvokeAsync() with InvocationType.RequestResponse
4. Blocks until the Lambda completes
5. Reads response.FunctionError and throws RemoteRunException (a TrainException) with no public message if the Lambda failed at the infrastructure level
6. Deserializes the response payload as RemoteRunResponse
7. On success: returns the train output to GraphQL
8. On error (RemoteRunResponse.IsError): throws RemoteRunException with the remote error details and the runner's PublicMessage

Differences from UseRemoteRun

IAM Permissions

The scheduler process needs:

{
  "Effect": "Allow",
  "Action": "lambda:InvokeFunction",
  "Resource": "arn:aws:lambda:us-east-1:123456789012:function:content-shield-runner"
}

Limitations

• Payload size limit: Lambda response payloads are limited to 6 MB (synchronous). Train outputs exceeding this will fail.
• Execution timeout: Lambda functions have a maximum execution time of 15 minutes. Long-running trains may time out.
• Cancellation reaches the function through the database: a cancel sets the run's cancel flag, which the train sees at its next junction boundary when the function registers CancellationCheckProvider (via AddJunctionProgress()). A junction already running is not interrupted. See Remote Execution.

See Also

• Remote Execution: architecture overview and deployment models
• UseLambdaWorkers: dispatch queued trains to Lambda
• TraxLambdaFunction: the Lambda receiver base class
• UseRemoteRun: HTTP-based remote run execution (alternative transport)