"""This module takes care of all the logic related to block status.
Specifically, what happens when a block becomes invalid. The logic is
encapsulated in the ``Election`` class, while the sequence of actions
is specified in ``create_pipeline``.
"""
import logging
from multipipes import Pipeline, Node
from bigchaindb.pipelines.utils import ChangeFeed
from bigchaindb.models import Block
from bigchaindb import Bigchain
logger = logging.getLogger(__name__)
[docs]class Election:
"""Election class."""
def __init__(self):
self.bigchain = Bigchain()
[docs] def check_for_quorum(self, next_vote):
"""
Checks if block has enough invalid votes to make a decision
Args:
next_vote: The next vote.
"""
next_block = self.bigchain.get_block(
next_vote['vote']['voting_for_block'])
block_status = self.bigchain.block_election_status(next_block['id'],
next_block['block']['voters'])
if block_status == self.bigchain.BLOCK_INVALID:
return Block.from_dict(next_block)
[docs] def requeue_transactions(self, invalid_block):
"""
Liquidates transactions from invalid blocks so they can be processed again
"""
logger.info('Rewriting %s transactions from invalid block %s',
len(invalid_block.transactions),
invalid_block.id)
for tx in invalid_block.transactions:
self.bigchain.write_transaction(tx)
return invalid_block
def get_changefeed():
return ChangeFeed(table='votes', operation=ChangeFeed.INSERT)
def create_pipeline():
election = Election()
election_pipeline = Pipeline([
Node(election.check_for_quorum),
Node(election.requeue_transactions)
])
return election_pipeline
def start():
pipeline = create_pipeline()
pipeline.setup(indata=get_changefeed())
pipeline.start()
return pipeline