queues are empty after code change

[anoteboom]

When I'm debugging code, as soon as i change something, flask does a reload., and all queues are empty again.

I think I'm going back to the separate process for a task emulator. Or do you have an idea of how to keep the queues?

[JoshuaFox]

Thank you for the report. Now investigating.

[JoshuaFox]

What do you think of an implementation that stores emulator state in pickle files? The memory-based implementation would still be availble.

Advantages

• State stored across code-reload and across process restart
• Makes the implementation more complex than the 70-line single file.

Disadvantages

• You might not want state stored across process restarts in a debugging scenario (but you can delete the files)
• Pickles are not a robust datastore (but our goal here is simplicity)

[anoteboom]

The best situation would be to replicate behaviour of the old python2 dev_appserver. So when you explicitly would restart your flask_server, it is not a problem that it forgets all tasks.
And when the flask server detects a code changes and reloads, it should retain them.

I'm curious how the dev_appserver did that.
I would try to stay away from writing it in tempfiles, Keeping the code simple is important.

[JoshuaFox]

Flask uses Werkzeug which does not reload code. It completely restarts the process when it detects a code change. (Source code).

I could save queue state at exit, and reload on initialization. This would mean a temp file, but only used for "hibernating" , not as the regular place to hold state. This solution would mean that state is also preserved across intentional restarts. Does that make sense?

[JoshuaFox]

@anoteboom I implemented the "hibernate" approach. It can be turned off with hibernation=False in the constructor. Please let me know what you think.