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

Parameter	Type	Required	Description
`configure`	`Action<LambdaRunOptions>`	Yes	Callback to set the Lambda function name and client options

Returns

SchedulerConfigurationBuilder, for continued fluent chaining.

LambdaRunOptions

Property	Type	Default	Description
`FunctionName`	`string`	(required)	The Lambda function name, ARN, or partial ARN to invoke
`ConfigureLambdaClient`	`Action<AmazonLambdaConfig>?`	`null`	Optional callback to configure the `AmazonLambdaConfig` (set region, endpoint override for LocalStack, etc.)

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:

Service	Lifetime	Description
`LambdaRunOptions`	Singleton	Configuration options
`IAmazonLambda`	Singleton	AWS Lambda client
`IRunExecutor` -> `LambdaRunExecutor`	Scoped	Dispatches run requests via Lambda SDK, blocks until response

> 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 LambdaRunExecutor:

Serializes a RemoteRunRequest containing the train name, input JSON, and input type
Wraps it in a LambdaEnvelope with Type = Run
Calls IAmazonLambda.InvokeAsync() with InvocationType.RequestResponse
Blocks until the Lambda completes
Reads response.FunctionError and throws TrainException if the Lambda failed at the infrastructure level
Deserializes the response payload as RemoteRunResponse
On success: returns the train output to GraphQL
On error (RemoteRunResponse.IsError): throws TrainException with the remote error details

Differences from UseRemoteRun

	UseLambdaRun	UseRemoteRun
Transport	AWS SDK direct invocation	HTTP POST
Public endpoint	None (IAM-governed)	Required (Function URL, API Gateway, or similar)
Package	`Trax.Scheduler.Lambda`	`Trax.Scheduler` (built-in)
Retry	Configurable `LambdaRetryOptions`	Configurable `HttpRetryOptions`
Timeout	Lambda execution timeout (AWS config)	`RemoteRunOptions.Timeout` (default 5 min)

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 is process-local: Same limitation as other remote execution models.