Google Apps Engine Tips

Rollback

If an update for GAE (Google App Engine) doesn’t complete it will cause an error (similar to : Another transaction by user xxxx┬á is already in progress for this app and major version. That user can undo the transaction with appcfg.py’s “rollback” command.) and not allow you to upload new updates. The rollback can de done with a batch file. A faster solution to fix this problem is incrementing the version number in the app.yaml file and activating the new version in the online console. The same error arise if you want to delete an a app with failed update. The only solution in this case is to do the rollback.

Google App Engine (GAE)

Google App Engine

GAE (Google App Engine) is a platform for developing and hosting web applications in Google-managed data centers. It was first released as a beta version in April 2008. GAE is cloud computing technology. It virtualizes applications across multiple servers and data centers. GAE is Platform as a Service while AWS (Amazon Web Services) is Infrastructure as a Service.

GAE is free up to a certain level of used resources. Fees are charged for additional storage, bandwidth, or CPU cycles required by the application.

The applications of the logged Google developer are available at https://appengine.google.com/

List of GAE applications

The dashboard allows to manage the different applications (quotas, instances, logs, cron jobs, task queues, blacklists, datastore, blob viewer, settings, permissions, billing, resources, …). A very efficient feature is the version control based on the app.yaml file :

GAE version control

Another useful feature is the error logging :

GAE error logging reports