Can we make Traffic Callout Extensions in a GCP load balancer async?

[varkey98]

I configured a traffic callout extension on my external load balancer following this guide: https://cloud.google.com/service-extensions/docs/configure-callout. It's working as expected, but I was wondering if it's possible to make the call to the callout backend async? I noticed that there's an async field in envoy api as well, but not sure how or what configuration will set it.

[dchiesa1]

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@varkey98 wrote:

if it's possible to make the call to the callout backend async

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I don't know for certain but reading this documentation page, it says

Load balancers run traffic extensions last in the request processing path and first in the response processing path.

These extensions let you modify the headers and payloads of both requests and responses without impacting the choice of the backend service. You can also use traffic callouts for custom logging by specifying the information that you want to log, the format, and the external provider.

That sounds synchronous to me.

How would it work if these calls were "asynchronous"?  What behavior would you expect if it were "async" ?

[varkey98]

I missed this documentation, thanks. My use case is just logging and dont want to mutate the headers/payload in which case asynchronous call would be fine. For the mutations to happen, as you said, the call has to be synchronous.