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Basically, all you have to do is create a subclass of bulkloader.Loader and implement (at a minimum) the generate_records method, which should yield lists of strings. This same strategy would work for loading data from XML files or ROT13-encrypted files or whatever. Note that the list of strings yielded by the generate_records method must match up (in length and order) with the "properties" list you provide when you initialize the loader (ie, the second argument to the AlbumLoader.__init__ method in this example). This approach actually provides a lot of flexibility: We're overriding the __init__ method on our JSONLoader implementation and automatically determining the kind of model we're loading and its list of properties to provide to the bulkloader.Loader parent class.

Now you can choose to put this in an existing version of your applications config.ru. Or you can choose to put it in a new version (ie. version just for bulk upload/download without your application code). Either way once a version with the RemoteApiServlet is uploaded run this command to download your data: bulkloader.py --dump --app_id="application id" --url="url_to_remote_api_servlet" --filename="file to download data to" Here is an example from one of my apps: bulkloader.py --dump --app_id=jsm277 --url=http://bulkmove.latest.jsm277.appspot.com/remote_api --filename=test_download_data This command will download every object in your applications Datastore. If you only want to download the objects of one kind then simple add the --kind= option. Another example: bulkloader.py --dump --app_id=jsm277 --url=http://bulkmove.latest.jsm277.appspot.com/remote_api --filename=test_download_data --kind=Posts In order to restore the data that you have just downloaded use this command: bulkloader.py --restore --url="url_to_remote_api_servlet" --filename="file name from dump command" --app_id="application id" Here is an example command: bulkloader.py --restore --url=http://bulkmove.latest.railsturbinetest.appspot.com/remote_api --filename=test_download_data --app_id=railsturbinetest There are several important thing to keep in mind when restoring the Datastore objectes. The restore command simple restores whatever is in the filename that you provide. So it does not matter if you dump your entire Datastore or just one kind you use the same command to restore them both. You can restore Datastore objects to a different application then the one that they were downloaded from. However, is important to keep in mind that the object's key is used to restore each object. So if there already esists an object in the Datastore with the same key as an object that is being restored the object in the Datastore will be overwritten The bulkloader.py is a good tool for moving data between applications on the Google App Engine and for locally backing up your data. However, it is not good for data conversion or manipulation in anyway since the data is stored in a binary form. So happy data moving.

As I understand it, the process of performing a single fetch (call to get())  from the dastastore using a key basically involves finding the host housing the entity, opening a socket, fetching the data, and then cleaning up the connection.  So to fetch something like 30 entities from the datastore, you're repeating the process 30 times over in serial, each time incurring whatever overhead is involved.  I also read that if you perform bulk fetches, (ie passing multiple keys at once) you can eliminate a great deal of that overhead.  In one of the videos I watched from Google I/0 2009, the presenter (whose name I forget - d'oh) said that performing a bulk fetch actually performs the fetches in parallel from the data store and you shoudl see requests noticeably faster.