About the operation of failure occurrence in the AP server under the WEB server

Question

Please tell me again about the behavior when the following failure occurs

When the dynamic content is accessed by the user in (1) and is routed to the web server on the AZ1 side (2)

When normal, it is recognition that the response to the request is returned from ③ to ②.

When an error occurs

What kind of operation will be performed if an OS failure occurs in the AP server in ③?

It becomes impossible to return the response to the request from ②
Error code 5xx: Is it wrong to recognize that a server error is notified to ②?

When the above failure occurs
Please tell me how ALB works?

return an error notification to the user?

Will it be routed to the web server in (3) on the AZ2 side?![Enter image description here](/media/postImages/original/IM7lzAXuWqSlOg2_J7om61IA)

Answer

Hi.  
ALB simply routes requests.

It forwards the request to AZ1, and if an error occurs along the way, ALB just forwards the error to the client.

After that, the ALB health check should fail, so further requests will only be routed to AZ2.

ALB is only doing sanity checks and where to forward requests. It does not retry across multiple AZs while processing a request.

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