Overview of migrating bundled App Engine services

The Python 3 runtime in the App Engine standard runtime doesn't include bundled services such as Memcache and Task Queues. Instead, Google Cloud provides standalone products that are equivalent to most of the bundled services in the Python 2 runtime. For the bundled services that are not available as separate products in Google Cloud, such as image processing, search, and messaging, this guide recommends third-party providers or other workarounds.

This page introduces the migration path for each bundled service. We will provide detailed migration guides for some of these services over the next few months.

Understanding Google Cloud permissions

Since your migrated app and the Google Cloud services that it uses are no longer running in the same "sandboxed" environment, your app needs authorization to access each service. For example, to interact with Datastore or Cloud Tasks, your app needs to supply the credentials of an account that is authorized to access those services.

By default apps in the App Engine standard runtime supply the credentials of the App Engine default service account, which is authorized to access databases in the same project as the app.

If any of the following conditions are true, you need to use an alternative authentication technique that explicitly provides credentials:

  • Your app and the Memorystore database are in different Google Cloud projects.

  • You have changed the roles assigned to the default App Engine service account.

For information about alternative authentication techniques, see Setting up Authentication for Server to Server Production Applications.

Authentication for local development

To develop or test your app locally, we recommend creating and using a service account. Do not use the App Engine default service account, since it has a high level of permissions for everything in your project. Instead, create and use a service account with the lowest level of permissions you need for your specific development and testing task.

For instructions on setting up a service account and connecting it to your app, see Obtaining and providing service account credentials manually.

Installing client libraries

The easiest way to use Google Cloud services from a Python app is to install the service's Python client library. (Google Cloud services also provide JSON REST and other interfaces.) The steps for installing the client libraries into the App Engine runtime are different for Python 2 apps and Python 3 apps.

Installing libraries for Python 2 apps

To install a library for your app to use when it's running in the Python 2 runtime:

  1. Create a directory to store your third-party libraries, such as lib/.

  2. Create a requirements.txt file in the same folder as your app.yaml file and add the name of a client library along with the googleapis_common_protos library.

    Python 2 apps require googleapis_common_protos to access Google Cloud services.

    For example, the following file can be used to install libraries for googleapis_common_protos, Pub/Sub and Cloud Tasks:

    googleapis_common_protos
google-cloud-pubsub
google-cloud-tasks

  3. Use pip install to install the libraries into the folder that you created. For example:

    pip install -t lib -r requirements.txt

  4. Specify the RPC library in the libraries section of your app.yaml file:

    libraries:
- name: grpcio
  version: 1.0.0

  5. Create an appengine_config.py file in the same folder as your app.yaml file if you do not already have one. Add the following to your appengine_config.py file:

    # appengine_config.py
import pkg_resources
from google.appengine.ext import vendor

# Set path to your libraries folder.
path = 'lib'
# Add libraries installed in the path folder.
vendor.add(path)
# Add libraries to pkg_resources working set to find the distribution.
pkg_resources.working_set.add_entry(path)

    Be sure to use thepkg_resources module, which ensures that your app uses the right distribution of the client libraries.

    The appengine_config.py file in the preceding example assumes that the the lib folder is located in the current working directory. If you can't guarantee that lib will always be in the current working directory, specify the full path to the lib folder. For example:

    import os
path = os.path.join(os.path.dirname(os.path.realpath(__file__)), 'lib')

  6. Deploy the app.

App Engine uploads all of the libraries in the directory you specified in the appengine_config.py file to the Python 2 runtime.

Installing libraries for Python 3 apps

To install a library for your app to use when it's running in the Python 3 runtime:

  1. Add the library name your app's requirements.txt file. For example:

    google-cloud-ndb

  2. Deploy the app.

App Engine automatically uploads all libraries listed in the requirements.txt file to the Python 3 runtime.

Migration paths for App Engine bundled services

Blobstore

To store and retrieve data, use Cloud Storage through the Cloud Client Libraries. To get started, see Migrating to the Cloud Client Library for Storage.

Datastore

If your Python 2 app uses NDB to interact with Datastore, migrate to the Cloud NDB Python 3 library. New Python 3 apps should use the Datastore mode client library.

For details, see:

Images

You can serve images from Cloud Storage, serve them directly, or use a third-party content delivery network (CDN).

To resize, convert, and manipulate images, use an image processing library such as Pillow or a Python interface for ImageMagick. To use one of these third-party libraries, add the library as a dependency and update your code to call the library's APIs.

The App Engine Images service also provided functionality to avoid dynamic requests to your application by handling image resizing using a serving URL. If you want similar functionality, you can generate the re-sized images ahead of time and upload them to Cloud Storage for serving. Alternatively, you could use a third-party content delivery network (CDN) service that offers image resizing.

Logging

Request logs still appear in Cloud Logging, but they are no longer automatically correlated. To implement your desired logging behavior, you can use the Cloud Logging client libraries.

Mail

To send email, use a third-party mail provider such as SendGrid, Mailgun, or Mailjet. All of these services offer APIs to send emails from applications.

Memcache

If your Python 2 app explicitly uses Memcache, you need to migrate to another caching solution before you can run your app in a Python 3 environment. We recommend using Memorystore for Redis as your caching service. For details, see Migrating Memcache to Memorystore.

Modules

To obtain information and modify your application's running services, use a combination of environment variables and the App Engine Admin API:

Service information How to access
Current application ID GAE_APPLICATION environment variable
Current project ID GOOGLE_CLOUD_PROJECT environment variable
Current service name GAE_SERVICE environment variable
Current service version GAE_VERSION environment variable
Current instance ID GAE_INSTANCE environment variable
Default hostname Admin API apps.get method
List of services Admin API apps.services.list method
List of versions for a service Admin API apps.services.versions.list method
Default version for a service, including any traffic splits Admin API apps.services.get method
List of running instances for a version Admin API apps.services.versions.instances.list method

For more information about the data available about your application's running services, see Python 2 Runtime Environment.

Namespaces

The Namespaces API enabled multitenant apps to partition data across tenants simply by specifying a unique namespace string for each tenant.

While Datastore supports multitenancy directly, other Google Cloud services do not. If your multitenant app uses other Google Cloud services, you will need to handle multitenancy manually. To have completely isolated instances of services, you can create new projects programmatically using the Cloud Resource Manager API and access resources across projects.

OAuth

Instead of using the App Engine OAuth service to verify OAuth 2.0 tokens, use the oauth2.tokeninfo method of the OAuth 2.0 API.

Host any full-text search database such as Elasticsearch on Compute Engine and access it from your service.

Task queue

Migrate pull queues to Pub/Sub and migrate push queues to Cloud Tasks. If your app uses both pull and push queues, migrate pull queues first to prevent unexpected behavior with Cloud Tasks.

For details on performing these migrations, see:

User authentication

For an alternative to the Users API, use any HTTP-based authentication mechanism such as: