Implement a worker for batch exporting of usage logs

This will allow customers to request their usage logs for a repository or an entire namespace, and we can export the logs in a manner that doesn't absolutely destroy the database, with every step along the way timed.

workers/test/test_exportactionlogsworker.py

@@ -0,0 +1,66 @@
+import json
+
+from app import storage
+from datetime import datetime, timedelta
+
+from httmock import urlmatch, HTTMock
+
+from data import model, database
+from workers.exportactionlogsworker import ExportActionLogsWorker
+
+from test.fixtures import *
+
+
+@pytest.mark.parametrize('namespace,repo_name,expects_logs', [
+  ('buynlarge', 'orgrepo', True),
+  ('devtable', 'history', False),
+])
+def test_process_queue_item(namespace, repo_name, expects_logs, app):
+  end_time = datetime.utcnow() + timedelta(days=365)
+  start_time = datetime.utcnow() - timedelta(days=365)
+
+  repo = model.repository.get_repository(namespace, repo_name)
+
+  assert (model.log.get_maximum_id_for_logs(end_time, repository_id=repo.id) is not None) == expects_logs
+  assert (model.log.get_minimum_id_for_logs(start_time, repository_id=repo.id) is not None) == expects_logs
+
+  worker = ExportActionLogsWorker(None)
+  called = [{}]
+
+  @urlmatch(netloc=r'testcallback')
+  def handle_request(url, request):
+    called[0] = json.loads(request.body)
+    return {'status_code': 200, 'content': '{}'}
+
+  def format_date(datetime):
+    return datetime.strftime("%m/%d/%Y")
+
+  with HTTMock(handle_request):
+    worker.process_queue_item({
+      'export_id': 'someid',
+      'repository_id': repo.id,
+      'namespace_id': repo.namespace_user.id,
+      'namespace_name': namespace,
+      'repository_name': repo_name,
+      'start_time': format_date(start_time),
+      'end_time': format_date(end_time),
+      'callback_url': 'http://testcallback/',
+      'callback_email': None,
+    })
+
+  assert called[0]
+  assert called[0][u'export_id'] == 'someid'
+  assert called[0][u'status'] == 'success'
+
+  url = called[0][u'exported_data_url']
+  assert url.find('http://localhost:5000/exportedlogs/') == 0
+
+  storage_id = url[len('http://localhost:5000/exportedlogs/'):]
+  created = storage.get_content(storage.preferred_locations, 'exportedactionlogs/' + storage_id)
+  created_json = json.loads(created)
+
+  expected_count = database.LogEntry.select().where(database.LogEntry.repository == repo).count()
+  assert (expected_count > 1) == expects_logs
+
+  assert created_json['export_id'] == 'someid'
+  assert len(created_json['logs']) == (expected_count + 1)