Does local GAE read and write to a local datastore file on the hard drive while it's running?

I have just noticed that when I have a running instance of my GAE application, there nothing happens with the datastore file when I add or remove entries using Python code or in admin console. I can even remove the file and still have all data safe and sound in admin area and accessible from code. But when I restart my application, all data obviously goes away and I have a blank datastore. So, the question - does GAE reads all data from the file only when it starts and then deals with it in the memory, saving the data after I stop the application? Does it make any requests to the datastore file when the application is running? If it doesn't save anything to the file while it's running, then, possibly, data may be lost if the application unexpectedly stops? Please make it clear for me if you know how 开发者_开发知识库it works in this aspect.

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How the datastore reads and writes its underlying files varies - the standard datastore is read on startup, and written progressively, journal-style, as the app modifies data. The SQLite backend uses a SQLite database.

You shouldn't have to care, though - neither backend is designed for robustness in the face of failure, as they're development backends. You shouldn't be modifying or deleting the underlying files, either.

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By default the dev_appserver will store it's data in a temporary location (which is why it disappears and you can't see anything changing)

If you don't want your data to disappear on restart set --datastore_path when running your dev server like:

dev_appserver.py --datastore_path /path/to/app/myapp.db /path/to/app

As nick said, the dev server is not built to be bulletproof, it's designed to help you quickly develop your app. The production setup is very different and will not do anything unexpected when you are dealing with exceptional circumstances.