Google cloud platform: http different http error for the same problem

I'm working with Cloud Run and I've checked that when the request is rejected because there are not enough instances available Cloud run is returning two different HTTP error codes.

The error is "The request was aborted because there was no available instance".

Randomly it is returning Http error 500 or HTTP 429 (this is what I expect).

is there any reason why GCP is returning different errors?

is it possible to analyze the reason?

is there any config to change it?

Regards

The 429 and 500 should be the same pending queue timeout issue when max clone is set to a low value, and rapid scaling cannot expand appserver pool when a spike of requests come in. In this case a small part of requests can loop over all available appservers, and then be appended for 10seconds at the last attempt, and aborted, and reply with 429/500.

Both 429 and 500 here are aborted requests after pending queue timeout.when a request is aborted, the system will check if current unassigned_max_clones is 0 or not. If it is 0, 429 is returned; otherwise, 500 is returned .

500s are essentially the same as original 429s, some are aborted by pending queue timeout, after that some are dropped by queue discipline. (whether the code is 429 or 500 currently depends on a number in app's serving state, which may be confusing)

You can also check this cloud run troubleshooting documentation

The request was aborted because there was no available instance is either HTTP 429 or HTTP 500

• You will receive HTTP 429: No available container instances

>When the resource is unable to scale due to the user-configured max_instances

• You will receive HTTP 500: Cloud Run couldn't manage the rate of traffic

>When the resource is unable to scale intrinsically due to the traffic