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https://github.com/bigchaindb/bigchaindb.git
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77 lines
2.6 KiB
Python
77 lines
2.6 KiB
Python
"""Utility classes and functions to work with the pipelines."""
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import time
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import rethinkdb as r
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import logging
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from multipipes import Node
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from bigchaindb import Bigchain
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logger = logging.getLogger(__name__)
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class ChangeFeed(Node):
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"""This class wraps a RethinkDB changefeed adding a `prefeed`.
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It extends the ``multipipes::Node`` class to make it pluggable in
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other Pipelines instances, and it makes usage of ``self.outqueue``
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to output the data.
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A changefeed is a real time feed on inserts, updates, and deletes, and
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it's volatile. This class is a helper to create changefeeds. Moreover
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it provides a way to specify a `prefeed`, that is a set of data (iterable)
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to output before the actual changefeed.
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"""
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INSERT = 1
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DELETE = 2
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UPDATE = 4
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def __init__(self, table, operation, prefeed=None, bigchain=None):
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"""Create a new RethinkDB ChangeFeed.
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Args:
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table (str): name of the table to listen to for changes.
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operation (int): can be ChangeFeed.INSERT, ChangeFeed.DELETE, or
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ChangeFeed.UPDATE. Combining multiple operation is possible using
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the bitwise ``|`` operator
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(e.g. ``ChangeFeed.INSERT | ChangeFeed.UPDATE``)
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prefeed (iterable): whatever set of data you want to be published
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first.
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bigchain (``Bigchain``): the bigchain instance to use (can be None).
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"""
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super().__init__(name='changefeed')
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self.prefeed = prefeed if prefeed else []
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self.table = table
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self.operation = operation
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self.bigchain = bigchain or Bigchain()
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def run_forever(self):
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for element in self.prefeed:
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self.outqueue.put(element)
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while True:
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try:
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self.run_changefeed()
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break
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except (r.ReqlDriverError, r.ReqlOpFailedError) as exc:
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logger.exception(exc)
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time.sleep(1)
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def run_changefeed(self):
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for change in self.bigchain.connection.run(r.table(self.table).changes()):
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is_insert = change['old_val'] is None
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is_delete = change['new_val'] is None
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is_update = not is_insert and not is_delete
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if is_insert and (self.operation & ChangeFeed.INSERT):
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self.outqueue.put(change['new_val'])
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elif is_delete and (self.operation & ChangeFeed.DELETE):
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self.outqueue.put(change['old_val'])
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elif is_update and (self.operation & ChangeFeed.UPDATE):
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self.outqueue.put(change['new_val'])
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