Google Cloud provides standalone products that offer similar functionality as some 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.
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 Firestore in Datastore mode (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:
Create a directory to store your third-party libraries, such as
lib/
.Create a
requirements.txt
file in the same folder as yourapp.yaml
file and add the name of a client library.For example, the following file can be used to install libraries for Pub/Sub and Cloud Tasks:
google-cloud-pubsub google-cloud-tasks
Use
pip install
to install the libraries into the folder that you created. For example:pip install -t lib -r requirements.txt
In your app's
app.yaml
file, specify the required Google RPC andsetuptools
libraries, and the optional SSL library in thelibraries
section:libraries: - name: grpcio version: 1.0.0 - name: setuptools version: 36.6.0 - name: ssl version: latest
Some client libraries don't need the SSL library. If you don't include the SSL library for a client library that needs it, you'll see an SSL error in the Logs Explorer when youf app receives a request.
Create an
appengine_config.py
file in the same folder as yourapp.yaml
file if you do not already have one. Add the following to yourappengine_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 the
pkg_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 thelib
folder is located in the current working directory. If you can't guarantee thatlib
will always be in the current working directory, specify the full path to thelib
folder. For example:import os path = os.path.join(os.path.dirname(os.path.realpath(__file__)), 'lib')
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:
Add the library name your app's
requirements.txt
file. For example:google-cloud-ndb
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 library. Cloud NDB is meant primarily as a transition tool for migrating Python 2 apps. We recommend that Python 3 apps 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
We recommend that you update your app to use Cloud Logging, which supports features such as viewing logs in the Logs Explorer, downloading logs, filtering messages by severity, and correlating app messages with specific requests. As an alternative, you can enable these features by writing log messages that contain specific data structured in a JSON object.
For more information, see Migrating to Cloud Logging.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, 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 |
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.
Search
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:
URL Fetch
By default, the Python 2.7 runtime uses the URL Fetch service to handle outbound HTTP(S) requests, even if you use standard Python libraries to issue those requests.
If your app uses URL Fetch APIs directly, for example to make asynchronous requests, we recommend migrating to a standard Python library such as the Requests library.
For more information, see Migrating Outbound Requests.
User authentication
For an alternative to the Users API, use any HTTP-based authentication mechanism such as:
- OAuth 2.0 and OpenID Connect which provide federated identity from the provider of your choice. Google is an OpenID Connect identity provider. There are also several other providers available.
- Firebase Authentication, which provides authentication using username/password and federated identity using Google, Facebook, Twitter, and more.
- Google Identity Platform, which provides many options for authentication and authorization of Google user accounts.
- Auth0, which provides authentication with various identity providers and single sign-on features.