The AppEngine Python SDK has a great module when it comes to easily run some code "later": the deferred library (if you are unfamiliar with this library, please have a look at its documentation first).

However the library has a few drawbacks that we solve here:

• No asynchronous method (issue 9530)
• The internal request handler inherits from webapp instead of webapp2 which can be an issue when using some webapp2 features (like webapp2.get_request)
• It uses pickle instead of leveraging cPickle available with the Python 2.7 runtime.
• The Route it uses is internal and will skip your middlewares unless you define them in a special appengine_config.py module.
• Task could fail to properly execute when hitting a fresh instance which did not had all code loaded
• Logging is a bit verbose: it uses the INFO level to show task headers that are redundant with what we can see by default in the AppEngine logs

We also added a couple of features to it:

• Explicit URLs for tasks: instead of just seeing /_ah/queue/deferred in your logs you will see something like /_cb/deferred/app.module.name/funcName
• Possibility to spread tasks over several queues in case of high throughput
• Improved logging in case of error
• Possibility to tie it to a background module to optimize serving requests

And some helpers:

• isFromTaskQueue(): Check if we are currently running from a task queue
• getRetryCount(): Returns the current number of times the current task is being retried
• logAsRetried(): Depending on # of times the task is being retried, we will increase the logging level.

Our module still makes use of the deferred exceptions types SingularTaskFailure and PermanentTaskFailure to be compatible with existing code.

1. Copy the tasks module inside your project.
2. Add a route to your webapp2 application mapping to where you included the tasks module: webapp2.Route('/_cb/deferred/<module>/<name>', 'tasks.DeferredHandler')
3. Optionally, better integrate with your application by updating the tasks module parameters:

• tasks.WARMUP_MODULE
• tasks.DEFAULT_QUEUES
• tasks.BACKGROUND_MODULE

(See the tasks module documentation for more details)

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GAME DEVELOPMENT in NYC at FreshPlanet/SongPop

Join us at our new offices across from the Empire State Building on 34th and 5th Avenue. FreshPlanet is a NYC based mobile game development firm and we are looking for senior Python engineers to join our back-end team.

Work on back-end services that support mobile games entertaining millions of players around the world.

Please contact Tom Cassidy (tcassidy@freshplanet.com) or apply at http://freshplanet.com/jobs/