Migrating from App Engine Blobstore to Cloud Storage (Module 16)

Posted by Wesley Chun (@wescpy), Developer Advocate, Google Cloud

The latest Serverless Migration Station video demonstrated methods to add use of the App Engine’s Blobstore service to a pattern Python 2 App Engine app, kicking off the primary of a 2-part collection on migrating away from Blobstore. In immediately’s Module 16 video, we full this journey, arriving at Cloud Storage. Shifting away from proprietary App Engine providers like Blobstore makes apps extra moveable, giving them sufficient flexibility to:

Exhibiting App Engine customers methods to migrate to Cloud Storage

Migrate from webapp2 (and webapp) to Flask

Migrate from App Engine NDB to Cloud NDB

Migrate from App Engine Blobstore to Cloud Storage

Migrate from Python 2 to Python (2 and) 3

Performing the migrations

Previous to modifying the applying code, quite a lot of configuration updates must be made. Updates making use of solely to Python 2 function a “Py2” designation whereas these migrating to Python 3 will see “Py3” annotations.

Take away the built-in Jinja2 library from app.yaml—Jinja2 already comes with Flask, so take away use of the older built-in model which can presumably battle with the modern Flask model you are utilizing. (Py2)

Use of Cloud shopper libraries (equivalent to these for Cloud NDB and Cloud Storage) require a pair of built-in libraries, grpcio and setuptools, so add these to app.yaml (Py2)

Take away all the things in app.yaml apart from a legitimate runtime (Py3)

Add Cloud NDB and Cloud Storage shopper libraries to necessities.txt (Py2 & Py3)

Create an appengine_config.py supporting each built-in (these in app.yaml) and non built-in (these in necessities.txt) libraries used (Py2)

The Module 15 app already migrated away from webapp2‘s (Django) templating system to Jinja2. That is helpful when migrating to Flask as a result of Jinja2 is Flask’s default template system. Switching from App Engine NDB to Cloud NDB is pretty easy because the latter was designed to be largely appropriate with the unique. The one change seen on this pattern app is to maneuver Datastore calls into Python with blocks.

Essentially the most vital modifications happen when transferring the add and obtain handlers from webapp to Cloud Storage. The video and corresponding codelab go extra in-depth into the mandatory modifications, however in abstract, these are the updates required in the principle utility:

1. webapp2 is changed by Flask. As a substitute of utilizing the older built-in model of Jinja2, use the model that comes with Flask.
2. App Engine Blobstore and NDB are changed by Cloud NDB and Cloud Storage, respectively.
3. The webapp Blobstore handler performance is changed by a mix of the io normal library module plus elements from Flask and Werkzeug. Moreover, the handler lessons and strategies are changed by Flask features.
4. The primary handler class and corresponding GET and POST strategies are all changed by a single Flask perform.

The outcomes

With all of the modifications carried out, the unique Module 15 app nonetheless operates identically in Module 16, beginning with a type requesting a go to artifact adopted by probably the most recents visits web page:

The pattern app’s artifact immediate web page

The pattern app’s most up-to-date visits web page.

The one distinction is that 4 migrations have been accomplished the place all the “infrastructure” is now taken care of by non-App Engine legacy providers. Moreover, the Module 16 app may very well be both a Python 2 or 3 app. So far as the end-user is anxious, “nothing occurred.”

Migrating pattern app from App Engine Blobstore to Cloud Storage

Wrap-up

Module 16 featured 4 completely different migrations, modernizing the Module 15 app from utilizing App Engine legacy providers like NDB and Blobstore to Cloud NDB and Cloud Storage, respectively. Whereas we advocate customers transfer to the newest choices from Google Cloud, migrating from Blobstore to Cloud Storage is not required, and must you decide to take action, can do it by yourself timeline. Along with immediately’s video, remember to take a look at the Module 16 codelab which leads you step-by-step by the migrations mentioned.

In Fall 2021, the App Engine crew prolonged help of lots of the bundled providers to 2nd era runtimes (which have a 1st era runtime), that means you’re not required emigrate to Cloud Storage when porting your app to Python 3. You may proceed utilizing Blobstore in your Python 3 app as long as you retrofit the code to entry bundled providers from next-generation runtimes.

If you happen to’re utilizing different App Engine legacy providers remember to take a look at the opposite Migration Modules on this collection. All Serverless Migration Station content material (codelabs, movies, supply code [when available]) will be accessed at its open supply repo. Whereas our content material initially focuses on Python customers, the Cloud crew is engaged on masking different language runtimes, so keep tuned. For added video content material, take a look at our broader Serverless Expeditions collection.