App engine Flex: "an upstream response is buffered to a temporary file"

[Nickolas Daskalou]

Hi all,

We're using App Engine Flexible environment, python 3 runtime.

We are seeing a lot of these entries in the nginx.error log:

an upstream response is buffered to a temporary file

Is this normal behaviour or is there something wrong with Flex?

Our instances do restart quite a lot, without turning up much in the logs, although they do not restart as often as the above message appears in the nginx.error log.

Thanks,

Nick

[Alex (Cloud Platform Support)]

Hi Nickolas,

A good overview of the NGINX buffering mechanism can found on this third-party website. As described, “When buffering of responses from the proxied server is enabled, and the whole response does not fit into the buffers set by the proxy_buffer_size and proxy_buffers directives, a part of the response can be saved to a temporary file.”. Therefore, it will be important to look at the response generating these warning and check for any inconsistencies to determine if something is wrong with the App Engine Flexible environment. Also, determining if this warning is linked to any particular handler or endpoint may give additional insight to the root cause. Would you be able to provide some sort of stack trace of the response?

Now as to how to mitigate these warnings themselves, you may be able to disable the response buffer by setting the X-Accel-Buffering response header to “no” as demonstrated in this Request Handling concept page.

[Nickolas Daskalou]

Thanks for your reply Alex.

I will have a read of those links and let you know if I have any other questions.

Nick

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