AWS Lambda: Task timed out

Question

We have been asked for my school project to write a Java code that runs in AWS Lambda. It is supposed to get the source code of the specific URLs and then upload it to an S3 bucket. The Java code should be running on AWS Lambda.

I get the source code to the String variable in Java. Then I have while loop that tries to write the String into a file in /tmp directory. Then the file is uploaded to S3.

Everything works but I get stuck with one specific URL. I have tracked the problem to this point:

try {
    BufferedWriter out = new BufferedWriter(new FileWriter("/tmp/url.txt"));
    out.write(source_code);  //Replace with the string 
    //you are trying to write  
    out.close();
}
catch (IOException e) {
    System.out.println("Exception ");
}

The weirdest thing is, when I test the code locally, everything works. File is created in /tmp directory on my computer and then it is uploaded to an S3 bucket. However, when I run the code in Lambda, I get the following error:

Task timed out after 15.00 seconds

Any idea why Lambda fails to write the file into its temp directory in this specific case and it works with others?

Answer 1

Amazon Lambda is designed to be used as an event-driven system that responds to events. The flow is:

• Something happens somewhere that triggers Lambda (eg an upload to Amazon S3, data coming into an Amazon Kinesis stream, an application invoking the Lambda function directly)
• The Lambda function is created, data from the trigger event is passed
• The Lambda function runs

Lambda functions are limited to a maximum execution time of 15 minutes (this was recently increased from the original 5 minutes timeout). The actual limit is configured when the Lambda function is created. The limit is in place because Lambda functions are meant to be small and quick rather than being large applications.

Your error message says Task timed out after 15.00 seconds. This means that AWS intentionally stopped the task once it hit a run-time of 15 seconds. It has nothing to do with what the function was doing at the time, nor the file that was being processed.

To fix: Increase the timeout setting on the configuration page of your Lambda function.