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How To Create And Deploy Google App Engine Service

August 1, 2017
Services (previously known as modules) can be configured to use different runtime with different performance settings, while still share elements like memcache and datastore.

Google App Engine project can consist of one or more services. When you created an App Engine, it comes with a default service named default. You can add additional services to the application where each service have the following characteristics:

  • Code Isolation: each service’s code is independent
  • Shared Data: Datastore and Memcache are shared between services, however namespaces can be used to isolate data selectively.
  • Separate logs for each service and version
  • Each service can have different runtime (Python, Go, Java, etc.)
  • Each service can have different performance (CPU & RAM) and scaling settings
  • Each service can have multiple versions

Reference:
Services: The building blocks of App Engine
Microservices Architecture on Google App Engine

Create a new Service

Assuming you already have an existing App Engine application named hello-app.

Create a separate directory (indepedent of existing project) named hello-service

The setup for a Service is exactly the same as the setup of the default application except additional element in app.yaml. If you are using appcfg tools, you need to specify module element in app.yaml. If you are using gloud tools, you need to service element in app.yaml

Create a project directory for hello-service.

mkdir hello-service
cd hello-service

Create app.yaml with the following configuration. The service shall be named micro.

runtime: python27
api_version: 1
threadsafe: true
# used by gloud tools
service: micro

# the following is required if appcfg tool is used
# application: travelopyz
# module: micro
# version: 1

handlers:
- url: /.*
  script: main.app

Create main.py

import webapp2


class MainPage(webapp2.RequestHandler):
    def get(self):
        self.response.headers['Content-Type'] = 'text/plain'
        self.response.write("I am a micro service")


app = webapp2.WSGIApplication([
    ('/.*', MainPage),
], debug=True)

Deploy the service.

gcloud app deploy -v 1
# output
Services to deploy:

descriptor:      [/projects/hello-service/app.yaml]
source:          [/projects/hello-service/]
target project:  [projectid]
target service:  [micro]
target version:  [1]
target url:      [https://micro-dot-projectid.appspot.com]

Open the target url in browser to check if the service deployed succeefully.

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