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HomeSoftware DevelopmentFind out how to use App Engine Blobstore (Module 15)

Find out how to use App Engine Blobstore (Module 15)

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

Introduction and background

In our ongoing Serverless Migration Station mini-series geared toward serving to builders modernize their serverless purposes, one of many key targets for Google App Engine builders is to improve to the newest language runtimes, equivalent to from Python 2 to three or Java 8 to 17. One other purpose is to exhibit how you can transfer away from App Engine legacy APIs (now known as “bundled providers”) to Cloud standalone alternative providers. As soon as this has been completed, apps are rather more transportable, making them versatile sufficient to:

Builders constructing net apps that present for person uploads or serve massive information like movies or audio clips can profit from handy “blob” storage backing such performance, and App Engine’s Blobstore serves this particular objective. As talked about above, shifting away from proprietary App Engine providers like Blobstore makes person apps extra transportable. The unique underlying Blobstore infrastructure finally merged with the Cloud Storage service anyway, so it is logical to maneuver fully to Cloud Storage when handy, and this content material is inform on this course of.

Displaying App Engine customers how you can use its Blobstore service

In at present’s Module 15 video, we start this journey by exhibiting customers how you can add Blobstore utilization to a pattern app, setting us up for our subsequent transfer to Cloud Storage in Module 16. Comparable movies on this sequence including use of an App Engine bundled service begin with a Python 2 pattern app that has already migrated net 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 have 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 difficulty as a result of we modernize this app fully 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, however it suffices to say that after these migrations are full, the ensuing app turns into transportable sufficient for all the chances talked about on the prime.

Including use of Blobstore

The unique pattern app registers particular person net web page “visits,” storing customer info such because the IP deal with and person agent, then displaying the latest visits to the end-user. In at present’s video, we add one extra function: 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: an extra hyperlink to view a go to artifact if one’s out there.

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

Beneath 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 modifications required of the primary handler. Upon the preliminary GET request, the artifact kind is offered. When the person submits an artifact or skips, the add handler POSTs again to dwelling (“/”) by way of an HTTP 307 to protect the verb, after which the latest visits web page is rendered as anticipated. There, if the end-user needs to view a go to artifact, they will 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 strains characterize the brand new or altered code.

Including App Engine Blobstore utilization to pattern app


On this “migration,” we added Blobstore utilization to help 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 comply with 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 group prolonged help of most of the bundled providers to 2nd technology runtimes (which have a 1st technology runtime), which means you’re now 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 providers from next-generation runtimes

When you do need 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]) will be accessed at its open supply repo. Whereas our content material initially focuses on Python customers, the Cloud group is engaged on masking different language runtimes, so keep tuned. For extra video content material, take a look at our broader Serverless Expeditions sequence.



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