how to retry client request when received 503 service unavailable error from target endpoint

[#1]

our backend service's load balancer is not stable, in order to increase our HA, we want to add a retry function on apigee edge layer.

the idea is like this:

client send a request to apigee api proxies, when target endpoint return a 503 service unavailable error, apigee api proxy wait for 500ms , then resend request to this target endpoint again, if it fail again on second attempt, then an error message will be returned back to client.

could this be done ?

[anilsr]

Dear @Yu.Huang ,

Welcome to Apigee Community 🙂

Yes, It's possible. You can use Service Callout Policy in response flow when ever target endpoint returns 503. Have a flag like variable so that you won't end up with infinite loop to break same.

Cheers,

Anil Sagar

[anilsr]

Dear @Yu.Huang , Also see similar question here.

[#4]

could you elaborate a bit more on this?

as i understand, using a servie callout policy means building a request from scratch and then invode an external api.

however, we already added several policies in request's preflow, if we do a service callout policy , how could we simply reuse those policies we have done to the request ?

a small example will be greatly appreciated.