Django Changefeed¶

Install¶

cd my_project
git clone https://github.com/synw/django-changefeed.git && mv django-changefeed/changefeed . && rm -rf django-changefeed
pip install rethinkdb celery

Then add 'changefeed', to INSTALLED_APPS.

Now create your database and table in the Rethinkdb client.

Settings¶

Required settings¶

SITE_SLUG = "mysite"

This is required for internal prefixing

Optional settings¶

You can set a default database and default table to be used:

# default database is set to SITE_SLUG+'_changefeed'
CHANGEFEED_DB = "mydb"
# default table is set to "changefeed"
CHANGEFEED_TABLE = "mytable"

The worker is verbose by default. To silence it use this:

CHANGEFEED_VERBOSE = False

The feed listener is launched by default. If you wish not to listen to the changefeed:

CHANGEFEED_LISTEN = False

Run¶

Run Rethinkdb and Launch a Celery worker:

celery -A project_name worker  -l info --broker='redis://localhost:6379/0'
# or any option you want

Push a document to Rethinkdb¶

from changefeed.tasks import push_to_flow, push_to_db

data = {"field_name":"field_value"}
# this is to push to the default db and table
push_to_feed.delay(data)

# this is to push to a db and table of your choice
push_to_db.delay("database_name", "table_name", data)

Handle the changes events¶

To handle the data changes create a r_handlers.py file in your project directory (where settings.py is).

Set the ReQL query¶

The listener will use by default the following ReQL query, listening to all changes in the table:

r.db(database).table(table).changes()

You can set a custom ReQL query for the listener in r_handlers.py with a r_query function:

def r_query():
     return r.db("mydb").table("mytable").pluck('message').changes()

Write the handlers¶

# in settings.py
CHANGEFEED_LISTEN = True

In your root directory (SITE_SLUG) create a r_handlers.py file and a feed_handlers function to do whatever you want, like to broadcast the data to a websocket:

# this function will be triggered on every change in the Rethinkdb data
def feed_handlers(database, table, change):
    print database
    print table
    print str(change['old_val'])
    print str(change['new_val'])
    return

You can also manage handlers directly from your apps by creating a file with a feed_handlers function, and launch a listener from the __init__.py file of your app:

from changefeed.tasks import feed_listener
feed_listener.delay("database", "table", "mymodule.r_handlers")

Example¶

Example hello world:

Make a “testdb” and a “testtable” in the Rethinkdb client.

# in settings.py
CHANGEFEED_DB = "testdb"
CHANGEFEED_TABLE = "testtable"

CHANGEFEED_HANDLERS = ['mymodule.r_handlers']
# or just use a r_handlers.py file in your main app directory

# in mymodule/r_handlers.py
def feed_handlers(database, table, change):
     message = change['new_val']['message']
     print message
  return

 # optionaly define a ReQL query in mymodule/r_handlers.py
 def r_query():
     r.db("testdb").table("testtable").pluck('message').changes()

# anywhere in your code
from changefeed.tasks import push_to_feed

push_to_feed({"message":"Hello world"})