appengine/standard/ndb/transactions/main.py

# Copyright 2015 Google Inc. # # Licensed under the Apache License, Version 2.0 (the "License"); # you may not use this file except in compliance with the License. # You may obtain a copy of the License at # # http://www.apache.org/licenses/LICENSE-2.0 # # Unless required by applicable law or agreed to in writing, software # distributed under the License is distributed on an "AS IS" BASIS, # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. # See the License for the specific language governing permissions and # limitations under the License. import cgi import random import urllib import flask # [START gae_ndb_transactions_import] from google.appengine.api import taskqueue from google.appengine.ext import ndb # [END gae_ndb_transactions_import] class Note(ndb.Model): """Models an individual Note entry with content.""" content = ndb.StringProperty() def parent_key(page_name): return ndb.Key("Parent", page_name) app = flask.Flask(__name__) @app.route("/") def main_page(): page_name = flask.request.args.get("page_name", "default") response = """ <html><body> <h2>Permanent note page: %s</h2>""" % cgi.escape( page_name ) parent = parent_key(page_name) notes = Note.query(ancestor=parent).fetch(20) for note in notes: response += "<h3>%s</h3>" % cgi.escape(note.key.id()) response += "<blockquote>%s</blockquote>" % cgi.escape(note.content) response += """<hr> <form action="/add?%s" method="post"> Submit Note: <input value="Title" name="note_title"><br> <textarea value="Note" name="note_text" rows="4" cols="60"> </textarea> <input type="submit" value="Etch in stone"></form>""" % urllib.urlencode( {"page_name": page_name} ) response += """ <hr> <form>Switch page: <input value="%s" name="page_name"> <input type="submit" value="Switch"></form> </body> </html>""" % cgi.escape( page_name, quote=True ) return response # [START gae_ndb_transactions_insert_standard] @ndb.transactional def insert_if_absent(note_key, note): fetch = note_key.get() if fetch is None: note.put() return True return False # [END gae_ndb_transactions_insert_standard] # [START gae_ndb_transactions_insert_two_tries] @ndb.transactional(retries=1) def insert_if_absent_2_retries(note_key, note): # do insert # [END gae_ndb_transactions_insert_two_tries] fetch = note_key.get() if fetch is None: note.put() return True return False # [START gae_ndb_transactions_insert_cross_group] @ndb.transactional(xg=True) def insert_if_absent_xg(note_key, note): # do insert # [END gae_ndb_transactions_insert_cross_group] fetch = note_key.get() if fetch is None: note.put() return True return False # [START gae_ndb_transactions_insert_sometimes] def insert_if_absent_sometimes(note_key, note): # do insert # [END gae_ndb_transactions_insert_sometimes] fetch = note_key.get() if fetch is None: note.put() return True return False # [START gae_ndb_transactions_insert_independent] @ndb.transactional(propagation=ndb.TransactionOptions.INDEPENDENT) def insert_if_absent_indep(note_key, note): # do insert # [END gae_ndb_transactions_insert_independent] fetch = note_key.get() if fetch is None: note.put() return True return False # [START gae_ndb_transactions_insert_task_queue] @ndb.transactional def insert_if_absent_taskq(note_key, note): taskqueue.add(url=flask.url_for("taskq_worker"), transactional=True) # do insert # [END gae_ndb_transactions_insert_task_queue] fetch = note_key.get() if fetch is None: note.put() return True return False @app.route("/worker") def taskq_worker(): pass def pick_random_insert(note_key, note): choice = random.randint(0, 5) if choice == 0: # [START gae_ndb_transactions_insert_standard_calling_2] inserted = insert_if_absent(note_key, note) # [END gae_ndb_transactions_insert_standard_calling_2] elif choice == 1: inserted = insert_if_absent_2_retries(note_key, note) elif choice == 2: inserted = insert_if_absent_xg(note_key, note) elif choice == 3: # [START gae_ndb_transactions_insert_sometimes_callback] inserted = ndb.transaction(lambda: insert_if_absent_sometimes(note_key, note)) # [END gae_ndb_transactions_insert_sometimes_callback] elif choice == 4: inserted = insert_if_absent_indep(note_key, note) elif choice == 5: inserted = insert_if_absent_taskq(note_key, note) return inserted @app.route("/add", methods=["POST"]) def add_note(): page_name = flask.request.args.get("page_name", "default") note_title = flask.request.form["note_title"] note_text = flask.request.form["note_text"] parent = parent_key(page_name) choice = random.randint(0, 1) if choice == 0: # Use transactional function # [START gae_ndb_transactions_insert_standard_calling_1] note_key = ndb.Key(Note, note_title, parent=parent) note = Note(key=note_key, content=note_text) # [END gae_ndb_transactions_insert_standard_calling_1] if pick_random_insert(note_key, note) is False: return 'Already there<br><a href="%s">Return</a>' % flask.url_for( "main_page", page_name=page_name ) return flask.redirect(flask.url_for("main_page", page_name=page_name)) elif choice == 1: # Use get_or_insert, which is transactional note = Note.get_or_insert(note_title, parent=parent, content=note_text) if note.content != note_text: return 'Already there<br><a href="%s">Return</a>' % flask.url_for( "main_page", page_name=page_name ) return flask.redirect(flask.url_for("main_page", page_name=page_name))

appengine/standard/ndb/transactions/main.py (114 lines of code) (raw):