How to set Cloud Tasks dispatch when load balancer and GAE are combined - google-app-engine

Question

I'm using Cloud Tasks from GAE now.
Also, by setting GAE as the backend of the load balancer, the following processing is tested.
batch-service is a service I created.
Request to /job/test_cron from local machine
go to Load balancer
go to GAE's service（batch-servise） from Load balancer
Create Cloud Task and request /job/test_task from GAE
go to GAE's service（batch-servise）
process and complete
I made each setting assuming the above flow, but the request when creating a task in GAE does not go to batch-servise, but goes to default service.
Therefore, the actual processing is as follows.
Request to /job/test_cron from local machine
go to Load balancer
go to GAE's servise（batch-servise） from Load balancer
Create Cloud Task and request /job/test_task from GAE
go to GAE's servise（default servise）
process and complete
GAE uses dispatch.yaml to direct all requests like /job/~ to batch-servise.
Therefore, Requesting /job/test_cron directly to GAE works as expected.
When using a load balancer, I think that dispatch.yaml cannot be used because the IP of GAE is not used. Is this correct?
Also, if anyone else knows how to configure GAE dispatch, it would be very helpful if you could tell me.

Answer 1

To override default service you can define AppEngineRouting which defines routing characteristics specific to App Engine - service, version, and instance.
You can refer this sample which routes to the default service's /log_payload endpoint. And update to this:
const task = {
appEngineHttpRequest: {
httpMethod: 'POST',
relativeUri: '/log_payload',
appEngineRouting: {
service: 'batch-servise'
}
},
};
When using a load balancer, I think that dispatch.yaml cannot be used because the IP of GAE is not used. Is this correct?
The load balancer does not interfere or interact with routing rules in your dispatch.yaml file. The dispatch.yaml rules are not evaluated until a serverless NEG directs traffic to App Engine.
Configuring dispatch.yaml:
The root element in the dispatch.yaml file is dispatch: and contains a list of routing definitions that are specified by the following subelements.
Dispatch rules are order dependent, and only the first rule that matches a URL will be applied.
You may have a look at these Examples
For more information, see How Requests are Routed.