Wednesday, February 15, 2023
HomeSoftware Developmentuse App Engine Blobstore (Module 15)

use App Engine Blobstore (Module 15)

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

ongoing Serverless Migration Station mini-series geared toward serving to builders modernize their serverless purposes, one of many key aims for Google App Engine builders is to improve to the most recent language runtimes, resembling from Python 2 to three or Java 8 to 17. One other aim is to exhibit methods to transfer away from App Engine legacy APIs (now known as “bundled companies”) to Cloud standalone substitute companies. As soon as this has been completed, apps are way more moveable, making them versatile sufficient to:

Builders constructing internet apps that present for consumer uploads or serve giant recordsdata like movies or audio clips can profit from handy “blob” storage backing such performance, and App Engine’s Blobstore serves this particular function. As talked about above, transferring away from proprietary App Engine companies like Blobstore makes consumer apps extra moveable. The unique underlying Blobstore infrastructure finally merged with the Cloud Storage service anyway, so it is logical to maneuver utterly to Cloud Storage when handy, and this content material is inform on this course of.

Exhibiting App Engine customers methods to use its Blobstore service

In immediately’s Module 15 video, we start this journey by exhibiting customers methods to add Blobstore utilization to a pattern app, setting us up for our subsequent transfer to Cloud Storage in Module 16. Related movies on this collection including use of an App Engine bundled service begin with a Python 2 pattern app that has already migrated internet frameworks from webapp2 to Flask, however not this time.

Blobstore for Python 2 has a dependency on webapp, the unique App Engine micro framework changed by webapp2 when the Python 2.5 runtime was deprecated in favor of two.7. As a result of the Blobstore handlers had been left “caught” in webapp, it is higher to begin with a extra generic webapp2 app prior to a Flask migration. This is not a problem as a result of we modernize this app utterly in Module 16 by:

  • Migrating from webapp2 (and webapp) to Flask
  • Migrating from App Engine NDB to Cloud NDB
  • Migrating from App Engine Blobstore to Cloud Storage
  • Migrating from Python 2 to Python (2 and) 3

We’ll go into extra element in Module 16, but it surely suffices to say that when these migrations are full, the ensuing app turns into moveable sufficient for all the probabilities talked about on the high.

Including use of Blobstore

The unique pattern app registers particular person internet web page “visits,” storing customer info such because the IP handle and consumer agent, then displaying the newest visits to the end-user. In immediately’s video, we add one extra characteristic: permitting guests to optionally increase their visits with a file artifact, like a picture. As a substitute of registering a go to instantly, the customer is first prompted to offer the artifact, as illustrated under.

The up to date pattern app’s new artifact immediate web page

The top-user can select to take action or click on a “Skip” button to opt-out. As soon as this course of is full, the identical most up-to-date visits web page is then rendered, with one distinction: a further hyperlink to view a go to artifact if one’s accessible.

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

Under is pseudocode representing the core a part of the app that was altered so as to add Blobstore utilization, particularly new add and obtain handlers in addition to the adjustments required of the primary handler. Upon the preliminary GET request, the artifact type is offered. When the consumer submits an artifact or skips, the add handler POSTs again to house (“/”) by way of an HTTP 307 to protect the verb, after which the newest visits web page is rendered as anticipated. There, if the end-user needs to view a go to artifact, they’ll click on a “view” hyperlink the place the obtain handler which fetches and returns the corresponding artifact from the Blobstore service, in any other case an HTTP 404 if the artifact wasn’t discovered. The bolded traces signify the brand new or altered code.

Including App Engine Blobstore utilization to pattern app


On this “migration,” we added Blobstore utilization to assist go to artifacts to the Module 0 baseline pattern app and arrived on the end line with the Module 15 pattern app. To get hands-on expertise doing it your self, do the codelab by hand and observe together with the video. Then you definitely’ll be able to improve to Cloud Storage do you have to select to take action. 

In Fall 2021, the App Engine staff prolonged assist of lots 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’ll be able to proceed utilizing Blobstore in your Python 3 app as long as you retrofit the code to entry bundled companies from next-generation runtimes

In the event you do wish to transfer to Cloud Storage, Module 16 is subsequent. You may as well attempt its codelab to get a head begin. All Serverless Migration Station content material (codelabs, movies, supply code [when available]) could be accessed at its open supply repo. Whereas our content material initially focuses on Python customers, the Cloud staff is engaged on protecting different language runtimes, so keep tuned. For added video content material, take a look at our broader Serverless Expeditions collection.


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