django-ethereum-events 0.1.4

Django Ethereum Events

######################
django-ethereum-events
######################

Ethereum Contract Event Log monitoring in Django

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:target: https://pypi.python.org/pypi/django-ethereum-events


********
Overview
********

This package provides an easy way to monitor an ethereum blockchain for transactions that invoke `Contract Events`_ that are of particular interest.

The main concept was inspired by the following project:

- https://github.com/gnosis/django-eth-events

.. _`Contract Events`: http://solidity.readthedocs.io/en/develop/contracts.html#events

************
Installation
************

1. Either checkout ``django-ethereum-events`` from GitHub, or install using pip:

::

pip install django-ethereum-events


2. Make sure to include ``'django_ethereum_events'`` in your ``INSTALLED_APPS``

::

INSTALLED_APPS += ('django_ethereum_events')


3. Make necessary migrations

::

python manage.py migrate django_ethereum_events


*****
Usage
*****

1. In your ``settings`` file, specify the following settings

::

ETHEREUM_NODE_HOST = 'localhost'
ETHEREUM_NODE_PORT = 8545
ETHEREUM_NODE_SSL = False
ETHEREUM_EVENTS = []


2. ``ETHEREUM_EVENTS`` parameter is a list of that holds information about the specific events to monitor for. Its syntax is the following

::

ETHEREUM_EVENTS = [
{
'CONTRACT_ADDRESS': 'contract address',
'EVENT_ABI': 'abi of the event(not the whole contract abi)',
'EVENT_RECEIVER': 'custom event handler'
}
]


3. Create an appropriate ``EVENT_RECEIVER``

::

from django_ethereum_events.chainevents import AbstractEventReceiver

class CustomEventReceiver(AbsractEventReceiver):
def save(self, decoded_event):
# custom logic goes here

The ``decoded_event`` parameter is the decoded log as provided from `web3.utils.events.get_event_data`_ method.

.. _`web3.utils.events.get_event_data`: https://github.com/pipermerriam/web3.py/blob/master/web3/utils/events.py#L140

4. To start monitoring the blockchain, either run the celery task ``django_ethereum_events.tasks.event_listener`` or better, use ``celerybeat`` to run it as a periodical task

::

from celery.beat import crontab

CELERYBEAT_SCHEDULE = {
'ethereum_events': {
'task': 'django_ethereum_events.tasks.event_listener',
'schedule': crontab(minute='*/5') # run every 5 minutes
}
}

You can also set the optional ``ETHEREUM_LOGS_BATCH_SIZE`` setting which limits the maximum amount of the blocks that can be read at a time from the celery task.


*****
Resetting the internal state
*****
Blocks are processed only once. The last block processed is stored in the ``.models.Daemon`` entry.

To reset the number of blocks processed, run the ``reset_block_daemon`` command optionally specifying the block number (-b, --block) to reset to (defaults to zero). If you reset it to zero, the next time the ``event_listener`` is fired, it will start processing blocks from the genesis block.

The ``Daemon`` entry can also be changed from the django admin backend.