Missing Init Duration field in Lambda report in CloudWatch

Question

Thanks for looking at this question!

So I am trying to figure out how long is the cold start phase for a lambda function. But when I searched Init Duration in the lambda CloudWatch log group, I can only find logs in 2020 that contained this field. The lambda function has been changed several times this year, so there must be some executions contains cold start.

I wonder why this field is missing and how can I get it back?

Thank you!

Answer 1

The Init Duration field should be there on the Report entry for every cold start execution. This also means that in a Lambda log group, each log stream should have an Init Duration exactly once and it should be on the Report entry of the oldest/first execution.

As far as I know, they have not changed the way they log this information, and I can still find it in lambda logs on my account. You could check manually for a log stream if the first entry contains it, otherwise, the only hint I can give is to check whether or not your filter is syntactically correct and your time window is big enough.