Any idea why wamer is causing API Gateway "cold starts"?

[briananstett]

I'm wondering if anyone can help me understand some interesting behavior I'm seeing when using the warmer.

If I invoke my function directly through the Lambda console, a cold start is about 6 seconds with subsequent invocations taking less than a second.

(First "cold" invocation)

(Second "warm" invocation)

However, I would expect now that the function is "warm", that invoking it through API Gateway would NOT result in a cold start but it does.

$ time curl -i https://apigateway.domain.com
real	0m5.787s
user	0m0.087s
sys	0m0.011s

A subsequent request through API Gateway does not have a cold start

$ time curl -i https://apigateway.domain.com
real	0m0.349s
user	0m0.082s
sys	0m0.020s

What's even stranger, if I quickly invoke the Lambda function again with a "warmer" event, it seems to break something in API Gateway causing it to have a cold start again when invoking through the API Gateway domain.

(Test event in Lambda console that mimics "warm" event)

{
  "concurrency": 5,
  "warmer": true
}

Now if I CURL the API Gateway URL after the "warm" event, I get the API Gateway "cold start" again.

$ time curl -i https://apigateway.domain.com
real	0m6.178s
user	0m0.046s
sys	0m0.007s

Does this behavior make sense to anyone else?

[naorpeled]

Hey @briananstett,
sorry for the huge delay, I missed your issue :(

I'm not entirely sure why it happens unfortunately,
if anyone has any insights on this I'd also like to know why this happens.