I'm looking for a way to be notified when an object in s3 changes storage class. I thought there would be a bucket event notification for this but I don't see it as an option. How can I know when an object moves from STANDARD to GLACIER? We have systems that depend on objects not being in GLACIER. If they change to GLACIER, we need to be made aware and handle them accordingly.
1 Answers
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You can use S3 access logs to capture changes in life cycle, but i think thats about it:
Amazon S3 server access logs can be enabled in an S3 bucket to capture S3 Lifecycle-related actions such as object transition to another storage class
Taken from AWS docs - life-cycle and other bucket config
You could certainly roll your own notifications for storage class transitions - might be a bit more involved than you are hoping for though.... You need a separate bucket to write your access logs. Setup an S3 notification for object creation in your new logs bucket to trigger a lambda function to process each new log file. In your lambda function use Athena to query the logs and fire off an SNS alert or perform some corrective action in code.
There are some limitations to be aware of though - see best effort logging means you might not get logs for a few hours
Updated 28/5/21
If the logs are on you should see the various lifecycle operations logged as they happen +/- a few hours. If not are you definitely meeting the minimum criteria for transitioning objects to glacier? (eg it takes 30 days to transition from standard to glacier).
As for:
The log record for a particular request might be delivered long after the request was actually processed, or it might not be delivered at all.
Consider S3's eventual consistency model and the SLA on data durability - there is possibility of data loss for any object in S3. I think the risk is relatively low of loosing log records, but it could happen.
You could also go for a more active approach - use s3 api from a lambda function triggered by cloudwatch events (cron like scheduling) to scan all the objects in the bucket and do something accordingly (send an email, take corrective action etc). Bare in mind this might get expensive depending on how often you run the lambda and how many object are in your bucket but low volumes might even be in the free tier depending on your usage.
