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 easy 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 sequence on migrating away from Blobstore. In at this time’s Module 16 video, we full this journey, arriving at Cloud Storage. Transferring away from proprietary App Engine companies like Blobstore makes apps extra transportable, giving them sufficient flexibility to:

Displaying App Engine customers easy 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 have to be made. Updates making use of solely to Python 2 characteristic 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 probably battle with the up to date Flask model you are utilizing. (Py2)

Use of Cloud consumer libraries (resembling 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 every part in app.yaml aside from a legitimate runtime (Py3)

Add Cloud NDB and Cloud Storage consumer 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 principally suitable with the unique. The one change seen on this pattern app is to maneuver Datastore calls into Python with blocks.

Probably 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 required modifications, however in abstract, these are the updates required in the primary 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 customary library module plus elements from Flask and Werkzeug. Moreover, the handler lessons and strategies are changed by Flask capabilities.
4. The principle handler class and corresponding GET and POST strategies are all changed by a single Flask operate.

The outcomes

With all of the modifications carried out, the unique Module 15 app nonetheless operates identically in Module 16, beginning with a kind 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 the entire “infrastructure” is now taken care of by non-App Engine legacy companies. Moreover, the Module 16 app could possibly be both a Python 2 or 3 app. So far as the end-user is worried, “nothing occurred.”

Migrating pattern app from App Engine Blobstore to Cloud Storage

Wrap-up

Module 16 featured 4 totally different migrations, modernizing the Module 15 app from utilizing App Engine legacy companies like NDB and Blobstore to Cloud NDB and Cloud Storage, respectively. Whereas we suggest 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 at this time’s video, make sure to try the Module 16 codelab which leads you step-by-step via the migrations mentioned.

In Fall 2021, the App Engine workforce prolonged assist of most of the bundled companies to 2nd technology runtimes (which have a 1st technology runtime), which means you’re not required emigrate to Cloud Storage when porting your app to Python 3. You possibly can proceed utilizing Blobstore in your Python 3 app as long as you retrofit the code to entry bundled companies from next-generation runtimes.

For those who’re utilizing different App Engine legacy companies make sure to try the opposite Migration Modules on this sequence. All Serverless Migration Station content material (codelabs, movies, supply code [when available]) might be accessed at its open supply repo. Whereas our content material initially focuses on Python customers, the Cloud workforce is engaged on protecting different language runtimes, so keep tuned. For added video content material, try our broader Serverless Expeditions sequence.