AWS Lambda: Task timed out

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?

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.

It seems you configured the timeout for 15 seconds.You may increase the timeout as described in this screenshot and as per lambda settings maximum time it allow you to execute is 15 minutes.

In my case when the task worked fine locally but timed out on Lambda, it was because I needed to increase the Memory allocated to the Lambda instance.

For those running into this timeout problem when using async, note that the pattern is different for the handler for async functions.

Instead of

exports.handler = function (event, context, callback) {
    callback(null, {
        statusCode: 200,
        body: JSON.stringify({/* return stuff here */})
    });
};

it's

exports.handler = async function (event, context) {
    return {
        statusCode: 200,
        body: JSON.stringify({/* return stuff here */})
    };
};

You can increase the timeout for lambda function upto 15 min or you can increase the memory allocation to lambda function to make it fast. You can increase memory upto 3008MB. Its minimum value is 128MB. It goes like this if you have: Allocated large memory allocation to your lambda function than it takes less time to execute that lambda function and vice versa. Large memory allocation would cost you more per execution of lambda function. You need to figure out your balance with timeout time and memory allocated to lambda function. Don't just assign large chunk of memory so that you can see the result soon analyse the cost and your need also. A figure is attached where change timeout and memory allocation. Goto Your Lambda function -> Configuration -> Basic Setting to find settings.

I solved the problem by placing the AWS-SDK outside the function body:

var AWS = require("aws-sdk");
exports.handler = function(event, context, callback)
{
//var AWS = require("aws-sdk"); //Error: Task timed out after 3.00 seconds
var docClient = new AWS.DynamoDB.DocumentClient();
console.log("Lambda starts");
...

Recently, I was working on a POC to work with AWS Lambda function. I was also facing same issue (Task timed out after 15.01 seconds). I just increased memory allocation and it resolved the problem. Beauty is that I could get response with in couple of seconds. So, I think error is little misleading. It should provide exact root cause of failure.

I faced the same issue but it was occurring intermittently. I wasted way more time in debugging with Insights n XRay, but didnt get anything from that.

Finally i tried one thing, i have 2 subnet in my VPC, private n public. So i kept only Private subnet and removed the other one.

And Voila!!

Its not failing anymore.. But reason for this i still dont know, will keep it posted. Try running lambda with single subnet if it works or not.

Firstly, why write into /tmp/? You write to the same location where the Lambda function is getting executed?

However, a better thing to do is, if you want to write a string as an S3 file then you can create an S3Object and write it directly to AWS S3. Here's a post that shows an example: https://stackoverflow.com/a/29844224/358013