CODEWITHSUNDEEP
javagoogle-app-enginejakarta-eetask-queue
user1154644
user1154644

Reputation: 4609

Using GAE Task Queues for handling persistence operations

Looking to get opinions on whether or not it would be a good idea to hand persistence operations off to a task queue. For example, a user submits a new 'order', I use bean validation to verify that everything is ok, and then hand over the processing/persisting of the order to a task queue, and respond back to the user faster.

My hesitance is that the persistence 'could' fail, but once I've validated the bean, the chances are low. Are task queues usually used to handle tasks that are relatively trivial? My main concern is what happens if a task that the task queue has fails, since it's done asynchronously, how can I notify the user?

Upvotes: 1

Views: 86

Answers (2)

Mason
Mason

Reputation: 403

We have implemented a huge app of logistic flows and some of our processes take 2-3 minutes to read lot of data from BigQuery, do the work and send an e-mail with attachments.

To notify the user you can use the Channel API and/or send an e-mail. You'll have to provide the user id, mail address or something like that into the task parameters because it is run by the system. You can't ask to App Engine the current logged user, it will null everytime.

Like said Andrei :

you need to worry only about cases where a failure was caused by your code (code bug) or data (validation bug).

Don't let an exception go out of the task otherwise the entire task will be run again.

Upvotes: 0

Andrei Volgin
Andrei Volgin

Reputation: 41089

Tasks will retry automatically. If the failure is caused by the infrastructure, the task will be completed on a subsequent try. So you need to worry only about cases where a failure was caused by your code (code bug) or data (validation bug). If you iron out the bugs, you can use tasks with no hesitations and don't worry about the notifications.

In either case, if processing an order takes a couple of seconds, I probably wouldn't bother with task queues. From a user experience perspective, users want to feel that the app did some work with their order, so a 1-2 seconds delay with response is acceptable and even expected.

Upvotes: 1

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