AWS Lambda: async C# handler

Question

The AWS document states that

Using Async in C# Functions with AWS Lambda

If you know your Lambda function will require a long-running process, such as uploading large files to Amazon S3 or reading a large stream of records from DynamoDB, you can take advantage of the async/await pattern. By creating a handler with this signature, Lambda will execute the function synchronously and wait a maximum of 5 minutes for execution to complete before returning or timing out.

I feel very confused Lambda will

execute the function synchronously and wait a maximum of 5 minutes

When Lambda support up to 15 minutes of processing time. Does that mean if I put async on the handler, I can only process one event in 5 minutes?

@TheGeneral Thanks. I removed the broad part and would ask the AWS support instead. I do have some basic understanding about async in .NET and used both async/non async in Lambda integration. I will create an answer if I can get a definitive one from AWS support — qkhanhpro
– qkhanhpro, Commented Dec 28, 2018 at 3:44
This to me was an interesting question I have a feeling the documentation has not been updated and should read: "By creating a handler with this signature, Lambda will execute the function synchronously and wait a maximum of 15 minutes for execution to complete before returning or timing out." — David Webster
– David Webster, Commented Dec 28, 2018 at 13:02

qkhanhpro · Accepted Answer · 2019-01-04 03:33:22Z

7

The final answer of AWS support at the time:

The document was not up to date. It should run at maximum 15 minute timeout ( depend on the Lambda function configuration )
The async modifier does not change how AWS behave, they will just await it.
The behaviour diference is only on the .NET side

answered Jan 4, 2019 at 3:33

qkhanhpro

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2 Comments

Jim Aho Over a year ago

"The behaviour diference is only on the .NET side" What does this mean?

qkhanhpro Over a year ago

The support meant that the difference is that of an await-ed async .NET function vs synchronous invocation. AWS do not do anything notable with it

iikkoo · Accepted Answer · 2018-12-28 12:15:50Z

0

AWS recently changed the timeout for Lamdba. The execution timeout is changed from 5 minutes to 15 minutes.

https://aws.amazon.com/about-aws/whats-new/2018/10/aws-lambda-supports-functions-that-can-run-up-to-15-minutes/

answered Dec 28, 2018 at 12:15

iikkoo

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