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I am using aws lambda function to convert uploaded wav file in a bucket to mp3 format and later move file to another bucket. It is working correctly. But there's a problem with triggering. When i upload small wav files,lambda function is called once. But when i upload a large sized wav file, this function is triggered multiple times.

I have googled this issue and found that it is stateless, so it will be called multiple times(not sure this trigger is for multiple upload or a same upload).

https://aws.amazon.com/lambda/faqs/

Is there any method to call this function once for a single upload?

Steffen Opel
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Ijas Ahamed N
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  • *"not sure this trigger is for multiple upload or a same upload"* ... doesn't it seem like that should be the first thing you should work toward figuring out? Statelessness has nothing to do with it. Examine the actual event content, create a log of what you are receiving in the S3 event and store it for review, and the explanation should become obvious. Most likely, behavior in whatever you are using to originally upload the object is doing more S3 operations than you realize. – Michael - sqlbot Aug 18 '15 at 10:38
  • You need to expand this question with more specific information. Ideally a code sample. – adamkonrad Aug 19 '15 at 13:11
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    Sounds like the upload is being broken into parts. You'll want to create an event specify that the event is only executed on `s3:ObjectCreated:CompleteMultiPartUpload`, [this tutorial](http://docs.aws.amazon.com/lambda/latest/dg/with-s3-example-configure-event-source.html) shows how to do that just replace `s3:ObjectCreated:*` with `s3:ObjectCreated:CompleteMultiPartUpload`. – philippjfr Jan 24 '16 at 16:16

6 Answers6

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Short version: Try increasing timeout setting in your lambda function configuration.

Long version:

I guess you are running into the lambda function being timed out here.

S3 events are asynchronous in nature and lambda function listening to S3 events is retried atleast 3 times before that event is rejected. You mentioned your lambda function is executed only once (with no error) during smaller sized upload upon which you do conversion and re-upload. There is a possibility that the time required for conversion and re-upload from your code is greater than the timeout setting of your lambda function.

Therefore, you might want to try increasing the timeout setting in your lambda function configuration.

By the way, one way to confirm that your lambda function is invoked multiple times is to look into cloudwatch logs for the event id (67fe6073-e19c-11e5-1111-6bqw43hkbea3) occurrence -

START RequestId: 67jh48x4-abcd-11e5-1111-6bqw43hkbea3 Version: $LATEST

This event id represents a specific event for which lambda was invoked and should be same for all lambda executions that are responsible for the same S3 event.

Also, you can look for execution time (Duration) in the following log line that marks end of one lambda execution -

REPORT RequestId: 67jh48x4-abcd-11e5-1111-6bqw43hkbea3  Duration: 244.10 ms Billed Duration: 300 ms Memory Size: 128 MB Max Memory Used: 20 MB

If not a solution, it will at least give you some room to debug in right direction. Let me know how it goes.

rk2
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    +1 Not Specific to S3, For me, this is happening for CloudWatch Lambda Triggers as well. Is there an option prevent this other than increasing the timeout. – titogeo Nov 28 '17 at 12:57
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    Mine is fired exactly 3 times, every time. It reads from dynamoDB and stores in another table. Every time 3 different request IDs – Baked Inhalf May 03 '18 at 07:12
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    i think the answer here shows that its not always just a timeout: https://stackoverflow.com/questions/57286268/aws-lambda-function-triggering-multiple-times-for-a-same-event-with-same-time-st & aws-labs themselves recently added some open source tools to standardize dealing with this issue of multiple executions: https://awslabs.github.io/aws-lambda-powertools-python/api/utilities/idempotency/index.html – jcp Mar 29 '21 at 23:03
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Any event Executing Lambda several times is due to retry behavior of Lambda as specified in AWS document.

Your code might raise an exception, time out, or run out of memory. The runtime executing your code might encounter an error and stop. You might run out concurrency and be throttled.

There could be some error in Lambda which makes the client or service invoking the Lambda function to retry.

Use CloudWatch logs to find the error and resolving it could resolve the problem.

I too faced the same problem, in my case it's because of application error, resolving it helped me.

Recently AWS Lambda has new property to change the default Retry nature. Set the Retry attempts to 0 (default 2) under Asynchronous invocation settings.

Tarun Mootala
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  • In my case there is absolutely no error and my timeout is 10 minutes which is way above what I need. Do you think the use of `finally` might cause this behavior? – Matteo Feb 24 '20 at 10:32
  • Resolving application errors is generally considered good practice. – Nico Müller Apr 19 '20 at 06:42
  • My problem was a special instance of this scenario: I was returning results from the handler (so the very last thing I do in my function) that was not serializable causing an exception, hence the event's need to retry. CloudWatch logs is your friend here. – peter n Jun 11 '20 at 14:52
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For some in-depth understanding on this issue, you should look into message delivery guarantees. Then you can implement a solution using the idempotent consumers pattern.

The context object contains information on which request ID you are currently handling. This ID won't change even if the same event fires multiple times. You could save this ID for every time an event triggers and then check that the ID hasn't already been processed before processing a message.

maxpaj
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  • thanks @maxpaj, Could you please let us know if there is any similar option for python handler. I am doing a requests .post from lamda function ,to my application endpoint .and if it takes more than 3 seconds to respond with the status code. it is retyring it , adding extract function triggers. – lazarus Jun 26 '18 at 06:35
  • I had some issue with this implementation. I have a cloud watch event invoking a lambda function one time and noticed it would run the function multiple times randomly but each one had a different requestId associated to it. – skrusetvt Dec 04 '20 at 05:28
  • can u check if your function was timing out or not? @skrusetvt – neo73 Dec 05 '20 at 07:29
  • @neo73 I checked out my CloudWatch logs and there was no error thrown. I did however increase the timeout from 15 seconds to 3 minutes and I have not seen this behavior anymore. – skrusetvt Dec 08 '20 at 17:53
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In the Lambda Configuration look for "Asynchronous invocation" there is an option "Retry attempts" that is the maximum number of times to retry when the function returns an error.

Here you can also configure Dead-letter queue service

enriqueojedalara
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1

Multiple retry can also happen due read time out. I fixed with '--cli-read-timeout 0'.

e.g. If you are invoking lambda with aws cli or jenkins execute shell:

aws lambda invoke --cli-read-timeout 0 --invocation-type RequestResponse \
   --function-name ${functionName} --region ${region} --log-type Tail \
   --payload {""} out --log-type Tail \
   --query 'LogResult' --output text | base64 -d
Nick K9
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Anand Kumar
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0

I was also facing this issue earlier, try to keep retry count to 0 under 'Asynchronous Invocations'.

nats
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