Missing s3 events in AWS SQS

Question

I have an AWS Lambda function that is supposed to be triggered by messages from Simple Queue Service SQS. This SQS is supposed to get a notification when new json file is written into my s3 bucket, or when existing json file in s3 bucket is overwritten. Event type for both cases is s3:ObjectCreated, and I see notification for both cases is my SQS. Now, the problem is that pretty frequently there is a new file in s3 (or updated existing file in s3), but there is no corresponding message in sqs. So many files are missing and Lambda is not aware that those should be processed, In Lambda I print the whole content of received SQS payload into the log file, and then try to find those missed files with something like aws --profile aaa logs filter-log-events --log-group-name /aws/lambda/name --start-time 1554357600000 --end-time 1554396561982 --filter-pattern "missing_file_name_pattern" but can't find anything, which means that s3:objectCreated event was not generated for this missing file. Are there some conditions that prevents s3:objectCreated events for new/updated s3 files? Is there a way to fix it? Or workaround of some kind, may be?

Answer 1

According to AWS Documentation:

If two writes are made to a single non-versioned object at the same time, it is possible that only a single event notification will be sent. If you want to ensure that an event notification is sent for every successful write, you can enable versioning on your bucket. With versioning, every successful write will create a new version of your object and will also send an event notification.

https://docs.aws.amazon.com/AmazonS3/latest/dev/NotificationHowTo.html

Also, why not directly trigger lambda from S3?

Answer 2

Two possibilities:

1. Some events may be delayed or not sent at all : "Amazon S3 event notifications typically deliver events in seconds but can sometimes take a minute or longer. On very rare occasions, events might be lost." , although it is very rare.

2. You have some mistake and the lambda is either not printing what you expect when processing this message / you don't search correctly for the log.

You should also make sure on SQS that all the records were ingested and processed successfully.

Answer 3

Make sure that you have all of the create object events checked off as a trigger.

I had an issue where files > 8MB were being uploaded as multi-part uploads which are listed as another trigger separately to the PUT trigger.