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API Gateway HTTP API

Trigger AWS Lambda with API Gateway HTTP API​

API Gateway to AWS Lambda diagram

In this pattern, we will walk through how to trigger AWS Lambda from an API call to an API Gateway HTTP API endpoint.

Packages Required​

install

dotnet add package Amazon.Lambda.APIGatewayEvents

Function Code​

The API Gateway to Lambda integration is what is known as a synchronous invoke. API Gateway will wait for Lambda to return a response that is then passed back to the caller. For that reason, we have a APIGatewayHttpApiV2ProxyRequest as our event payload and APIGatewayHttpApiV2ProxyResponse as our method response.

Function.cs

public class Function
{
public async Task<APIGatewayHttpApiV2ProxyResponse> FunctionHandler(APIGatewayHttpApiV2ProxyRequest apigProxyEvent, ILambdaContext context)
{
try
{
if (!apigProxyEvent.RequestContext.Http.Method.Equals(HttpMethod.Get.Method))
{
return new APIGatewayHttpApiV2ProxyResponse
{
Body = "Only GET allowed",
StatusCode = (int)HttpStatusCode.MethodNotAllowed,
};
}
// Perform business logic
// apigProxyEvent.Body to access the body of the request sent to API Gateway.
return new APIGatewayHttpApiV2ProxyResponse
{
Body = JsonSerializer.Serialize(new {
"hello": "world"
}),
StatusCode = 200,
Headers = new Dictionary<string, string> {{"Content-Type", "application/json"}}
};
}
catch (Exception)
{
// Log exception, incremement failure metrics etc.
return new APIGatewayHttpApiV2ProxyResponse
{
StatusCode = (int)HttpStatusCode.InternalServerError,
};
}
}
}

Best Practices​

  • Catch exceptions and return a useful response to API Gateway