run specific queue on new service in GAE java8 standard environment

Question

We have a project which is setup on GAE with java8 standard environment and the app runs on default service. Now I would like to add a new service to the app so that I can run some tasks in a dedicated service as I need more memory.

All the documents point me to add the app.yaml for new service but google cloud document https://cloud.google.com/appengine/docs/standard/java-gen2/config/appref say that app.yaml configuration file is not available in java8 environment.

Still I tried adding app.yaml and deploy it to the cloud but I am getting the error.

my app.yaml file content

service: <service-name>
runtime: java8
threadsafe: true
skip_files:
- ^(.*/)?.*\.log$
handlers:
- url: <url>
  script: unused
  login: optional
  secure: always

ERROR: (gcloud.app.deploy) INVALID_ARGUMENT: WEB-INF/appengine-web.xml is required for this runtime.

problem statement: I have a task running in a push queue which requires more memory so I would like to create a service with enough memory to run this task. The queue.yaml document https://cloud.google.com/appengine/docs/standard/java/config/queueref-yaml says that we can specify the service in the element target to run the push queue in that service.

I would like to know how to setup a service for java8 in GAE and run the task in the new service. Any other solution would also be helpful.