Load a backup of Google Datastore into your local dev_appserver.py

1. Create the backup
2. Download the backup
3. Re-hydrate the backup data into ndb.Model entities

1. Create a backup of datastore in a Google Cloud Storage bucket using one of the following methods. (~5 minutes + backup time)

   1. Instructions for creating backup
   2. Instructions for creating periodic backup (Alpha)

2. Download the backup from the Google Cloud Storage bucket created in the above step.

   1. Install and setup the Google Cloud Tools. The easiest way to do so is to download the bucket using gsutil (available here as the latest Google Cloud SDK).
   2. Switch to the project that contains the backups.

      # List out all the projects you have
      > gcloud projects list
      
      # switch active configuration to example-project-name
      > gcloud config set project example-project

   3. Download the actual bucket using the name of the bucket that you specified in step 1.

      # This will download the specified bucket to `.ds_backup`
      > ./dsbackup.py <bucket_name>

3. Use the same APPLICATION_ID on your dev_appserver or webtest that you use on your production server. This can be done by setting the APPLICATION_ID on your testbed test or setting the APPLICATION_ID as an environment variable in your dev_appserver. Note that your APPLICATION_ID in production seems to be "s~" + <project_id>. So this project's APPLICATION_ID would be s~example-project.

4. Hydrate the backup into Datastore entities in test or within dev_appserver using the following guiding example.

   from google.appengine.api.files import records
   from google.appengine.datastore import entity_pb
   from google.appengine.ext import ndb
   import dsbackup
   
   # Be sure to import all the ndb.Models that your project needs to hydrate!
   # This project only has `User` `ndb.Model`'s so the following is needed:
   from user import User # user.py not included (only example)
   
   def hydrate():
       for f in dsbackup.get_files():
           raw = open(f, 'r')
           reader = records.RecordsReader(raw)
           for record in reader:
               entity_proto = entity_pb.EntityProto(contents=record)
               entity = ndb.Model._from_pb(entity_proto)
               entity.put()