mirror of
https://github.com/bigchaindb/bigchaindb.git
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541 lines
20 KiB
Python
541 lines
20 KiB
Python
import random
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import math
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import operator
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import rethinkdb as r
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import rapidjson
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import bigchaindb
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from bigchaindb import util
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from bigchaindb import config_utils
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from bigchaindb import exceptions
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from bigchaindb import crypto
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class GenesisBlockAlreadyExistsError(Exception):
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pass
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class Bigchain(object):
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"""Bigchain API
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Create, read, sign, write transactions to the database
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"""
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def __init__(self, host=None, port=None, dbname=None,
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public_key=None, private_key=None, keyring=[],
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consensus_plugin=None):
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"""Initialize the Bigchain instance
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There are three ways in which the Bigchain instance can get its parameters.
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The order by which the parameters are chosen are:
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1. Setting them by passing them to the `__init__` method itself.
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2. Setting them as environment variables
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3. Reading them from the `config.json` file.
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Args:
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host (str): hostname where the rethinkdb is running.
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port (int): port in which rethinkb is running (usually 28015).
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dbname (str): the name of the database to connect to (usually bigchain).
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public_key (str): the base58 encoded public key for the ED25519 curve.
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private_key (str): the base58 encoded private key for the ED25519 curve.
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keyring (list[str]): list of base58 encoded public keys of the federation nodes.
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"""
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config_utils.autoconfigure()
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self.host = host or bigchaindb.config['database']['host']
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self.port = port or bigchaindb.config['database']['port']
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self.dbname = dbname or bigchaindb.config['database']['name']
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self.me = public_key or bigchaindb.config['keypair']['public']
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self.me_private = private_key or bigchaindb.config['keypair']['private']
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self.federation_nodes = keyring or bigchaindb.config['keyring']
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self.consensus = config_utils.load_consensus_plugin(consensus_plugin)
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if not self.me or not self.me_private:
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raise exceptions.KeypairNotFoundException()
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self._conn = None
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@property
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def conn(self):
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if not self._conn:
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self._conn = self.reconnect()
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return self._conn
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def reconnect(self):
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return r.connect(host=self.host, port=self.port, db=self.dbname)
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def create_transaction(self, *args, **kwargs):
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"""Create a new transaction
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Refer to the documentation of your consensus plugin.
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Returns:
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dict: newly constructed transaction.
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"""
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return self.consensus.create_transaction(*args, **kwargs)
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def sign_transaction(self, transaction, *args, **kwargs):
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"""Sign a transaction
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Refer to the documentation of your consensus plugin.
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Returns:
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dict: transaction with any signatures applied.
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"""
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return self.consensus.sign_transaction(transaction, *args, **kwargs)
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def verify_signature(self, signed_transaction, *args, **kwargs):
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"""Verify the signature(s) of a transaction.
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Refer to the documentation of your consensus plugin.
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Returns:
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bool: True if the transaction's required signature data is present
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and correct, False otherwise.
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"""
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return self.consensus.verify_signature(
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signed_transaction, *args, **kwargs)
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def write_transaction(self, signed_transaction, durability='soft'):
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"""Write the transaction to bigchain.
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When first writing a transaction to the bigchain the transaction will be kept in a backlog until
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it has been validated by the nodes of the federation.
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Args:
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signed_transaction (dict): transaction with the `signature` included.
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Returns:
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dict: database response
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"""
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# we will assign this transaction to `one` node. This way we make sure that there are no duplicate
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# transactions on the bigchain
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if self.federation_nodes:
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assignee = random.choice(self.federation_nodes)
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else:
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# I am the only node
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assignee = self.me
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# update the transaction
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signed_transaction.update({'assignee': assignee})
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# write to the backlog
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response = r.table('backlog').insert(signed_transaction, durability=durability).run(self.conn)
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return response
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def get_transaction(self, txid):
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"""Retrieve a transaction with `txid` from bigchain.
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Queries the bigchain for a transaction that was already included in a block.
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Args:
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txid (str): transaction id of the transaction to query
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Returns:
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A dict with the transaction details if the transaction was found.
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If no transaction with that `txid` was found it returns `None`
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"""
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# First, get information on all blocks which contain this transaction
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response = r.table('bigchain').get_all(txid, index='transaction_id')\
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.pluck('votes', 'id', {'block': ['voters']}).run(self.conn)
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blocks = list(response)
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if blocks:
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# Determine the election status of each block
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validity = {block['id']: self.block_election_status(block) for block in blocks}
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# Disregard invalid blocks, and return if there are no valid or undecided blocks
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validity = {_id: status for _id, status in validity.items() if status != 'invalid'}
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if not validity:
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return None
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# If there are multiple valid blocks with this transaction, something has gone wrong
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if list(validity.values()).count('valid') > 1:
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raise Exception('Transaction {tx} is present in multiple valid blocks: {block_ids}'
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.format(tx=txid,
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block_ids=str([block for block in validity if validity[block] == 'valid'])))
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# If the transaction is in a valid or any undecided block, return it. Does not check
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# if transactions in undecided blocks are consistent, but selects the valid block before
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# undecided ones
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for _id in validity:
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target_block_id = _id
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if validity[_id] == 'valid':
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break
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# Query the transaction in the target block and return
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response = r.table('bigchain').filter(lambda block: block['id'] == target_block_id).nth(0)\
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.get_field('block').get_field('transactions').filter(lambda tx: tx['id'] == txid).run(self.conn)
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return response[0]
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else:
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return None
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def get_tx_by_payload_hash(self, payload_hash):
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"""Retrieves transactions related to a digital asset.
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When creating a transaction one of the optional arguments is the `payload`. The payload is a generic
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dict that contains information about the digital asset.
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To make it easy to query the bigchain for that digital asset we create a sha3-256 hash of the
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serialized payload and store it with the transaction. This makes it easy for developers to keep track
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of their digital assets in bigchain.
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Args:
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payload_hash (str): sha3-256 hash of the serialized payload.
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Returns:
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A list of transactions containing that payload. If no transaction exists with that payload it
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returns an empty list `[]`
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"""
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cursor = r.table('bigchain') \
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.get_all(payload_hash, index='payload_hash') \
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.run(self.conn)
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transactions = list(cursor)
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return transactions
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def get_spent(self, tx_input):
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"""Check if a `txid` was already used as an input.
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A transaction can be used as an input for another transaction. Bigchain needs to make sure that a
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given `txid` is only used once.
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Args:
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tx_input (dict): Input of a transaction in the form `{'txid': 'transaction id', 'cid': 'condition id'}`
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Returns:
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The transaction that used the `txid` as an input if it exists else it returns `None`
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"""
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# checks if an input was already spent
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# checks if the bigchain has any transaction with input {'txid': ..., 'cid': ...}
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response = r.table('bigchain').concat_map(lambda doc: doc['block']['transactions'])\
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.filter(lambda transaction: transaction['transaction']['fulfillments']
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.contains(lambda fulfillment: fulfillment['input'] == tx_input))\
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.run(self.conn)
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# a transaction_id should have been spent at most one time
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transactions = list(response)
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if transactions:
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if len(transactions) != 1:
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raise exceptions.DoubleSpend('`{}` was spent more then once. There is a problem with the chain'.format(
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tx_input['txid']))
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else:
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return transactions[0]
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else:
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return None
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def get_owned_ids(self, owner):
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"""Retrieve a list of `txids` that can we used has inputs.
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Args:
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owner (str): base58 encoded public key.
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Returns:
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list: list of `txids` currently owned by `owner`
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"""
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# get all transactions in which owner is in the `new_owners` list
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response = r.table('bigchain') \
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.concat_map(lambda doc: doc['block']['transactions']) \
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.filter(lambda tx: tx['transaction']['conditions']
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.contains(lambda c: c['new_owners']
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.contains(owner))) \
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.run(self.conn)
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owned = []
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for tx in response:
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# a transaction can contain multiple outputs (conditions) so we need to iterate over all of them
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# to get a list of outputs available to spend
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for condition in tx['transaction']['conditions']:
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# for simple signature conditions there are no subfulfillments
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# check if the owner is in the condition `new_owners`
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if len(condition['new_owners']) == 1:
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if condition['condition']['details']['public_key'] == owner:
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tx_input = {'txid': tx['id'], 'cid': condition['cid']}
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else:
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# for transactions with multiple `new_owners` there will be several subfulfillments nested
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# in the condition. We need to iterate the subfulfillments to make sure there is a
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# subfulfillment for `owner`
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for subfulfillment in condition['condition']['details']['subfulfillments']:
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if subfulfillment['public_key'] == owner:
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tx_input = {'txid': tx['id'], 'cid': condition['cid']}
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# check if input was already spent
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if not self.get_spent(tx_input):
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owned.append(tx_input)
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return owned
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def validate_transaction(self, transaction):
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"""Validate a transaction.
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Args:
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transaction (dict): transaction to validate.
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Returns:
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The transaction if the transaction is valid else it raises an
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exception describing the reason why the transaction is invalid.
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"""
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return self.consensus.validate_transaction(self, transaction)
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def is_valid_transaction(self, transaction):
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"""Check whether a transacion is valid or invalid.
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Similar to `validate_transaction` but does not raise an exception if the transaction is valid.
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Args:
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transaction (dict): transaction to check.
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Returns:
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bool: `True` if the transaction is valid, `False` otherwise
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"""
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try:
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self.validate_transaction(transaction)
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return transaction
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except (ValueError, exceptions.OperationError, exceptions.TransactionDoesNotExist,
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exceptions.TransactionOwnerError, exceptions.DoubleSpend,
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exceptions.InvalidHash, exceptions.InvalidSignature):
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return False
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def create_block(self, validated_transactions):
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"""Creates a block given a list of `validated_transactions`.
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Note that this method does not validate the transactions. Transactions should be validated before
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calling create_block.
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Args:
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validated_transactions (list): list of validated transactions.
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Returns:
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dict: created block.
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"""
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# Create the new block
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block = {
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'timestamp': util.timestamp(),
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'transactions': validated_transactions,
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'node_pubkey': self.me,
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'voters': self.federation_nodes + [self.me]
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}
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# Calculate the hash of the new block
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block_data = util.serialize(block)
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block_hash = crypto.hash_data(block_data)
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block_signature = crypto.SigningKey(self.me_private).sign(block_data)
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block = {
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'id': block_hash,
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'block': block,
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'signature': block_signature,
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'votes': []
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}
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return block
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# TODO: check that the votings structure is correctly constructed
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def validate_block(self, block):
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"""Validate a block.
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Args:
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block (dict): block to validate.
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Returns:
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The block if the block is valid else it raises and exception
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describing the reason why the block is invalid.
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"""
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# First: Run the plugin block validation logic
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self.consensus.validate_block(self, block)
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# Finally: Tentative assumption that every blockchain will want to
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# validate all transactions in each block
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for transaction in block['block']['transactions']:
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if not self.is_valid_transaction(transaction):
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# this will raise the exception
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self.validate_transaction(transaction)
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return block
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def is_valid_block(self, block):
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"""Check whether a block is valid or invalid.
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Similar to `validate_block` but does not raise an exception if the block is invalid.
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Args:
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block (dict): block to check.
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Returns:
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bool: `True` if the block is valid, `False` otherwise.
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"""
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try:
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self.validate_block(block)
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return True
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except Exception:
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return False
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def write_block(self, block, durability='soft'):
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"""Write a block to bigchain.
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Args:
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block (dict): block to write to bigchain.
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"""
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block_serialized = rapidjson.dumps(block)
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r.table('bigchain').insert(r.json(block_serialized), durability=durability).run(self.conn)
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# TODO: Decide if we need this method
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def transaction_exists(self, transaction_id):
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response = r.table('bigchain').get_all(transaction_id, index='transaction_id').run(self.conn)
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return True if len(response.items) > 0 else False
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# TODO: Unless we prescribe the signature of create_transaction, this will
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# also need to be moved into the plugin API.
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def create_genesis_block(self):
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"""Create the genesis block
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Block created when bigchain is first initialized. This method is not atomic, there might be concurrency
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problems if multiple instances try to write the genesis block when the BigchainDB Federation is started,
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but it's a highly unlikely scenario.
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"""
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# 1. create one transaction
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# 2. create the block with one transaction
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# 3. write the block to the bigchain
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blocks_count = r.table('bigchain').count().run(self.conn)
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if blocks_count:
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raise GenesisBlockAlreadyExistsError('Cannot create the Genesis block')
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payload = {'message': 'Hello World from the BigchainDB'}
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transaction = self.create_transaction([self.me], [self.me], None, 'GENESIS', payload=payload)
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transaction_signed = self.sign_transaction(transaction, self.me_private)
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# create the block
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block = self.create_block([transaction_signed])
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# add block number before writing
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block['block_number'] = 0
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self.write_block(block, durability='hard')
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return block
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def vote(self, block, previous_block_id, decision, invalid_reason=None):
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"""Cast your vote on the block given the previous_block_hash and the decision (valid/invalid)
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return the block to the updated in the database.
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Args:
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block (dict): Block to vote.
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previous_block_id (str): The id of the previous block.
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decision (bool): Whether the block is valid or invalid.
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invalid_reason (Optional[str]): Reason the block is invalid
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"""
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vote = {
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'voting_for_block': block['id'],
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'previous_block': previous_block_id,
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'is_block_valid': decision,
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'invalid_reason': invalid_reason,
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'timestamp': util.timestamp()
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}
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vote_data = util.serialize(vote)
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signature = crypto.SigningKey(self.me_private).sign(vote_data)
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vote_signed = {
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'node_pubkey': self.me,
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'signature': signature,
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'vote': vote
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}
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return vote_signed
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def write_vote(self, block, vote, block_number):
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"""Write the vote to the database."""
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update = {'votes': r.row['votes'].append(vote)}
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# We need to *not* override the existing block_number, if any
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# FIXME: MIGHT HAVE RACE CONDITIONS WITH THE OTHER NODES IN THE FEDERATION
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if 'block_number' not in block:
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update['block_number'] = block_number
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r.table('bigchain') \
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.get(vote['vote']['voting_for_block']) \
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.update(update) \
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.run(self.conn)
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def get_last_voted_block(self):
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"""Returns the last block that this node voted on."""
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# query bigchain for all blocks this node is a voter but didn't voted on
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last_voted = r.table('bigchain') \
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.filter(r.row['block']['voters'].contains(self.me)) \
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.filter(lambda doc: doc['votes'].contains(lambda vote: vote['node_pubkey'] == self.me)) \
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.order_by(r.desc('block_number')) \
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.limit(1) \
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.run(self.conn)
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# return last vote if last vote exists else return Genesis block
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last_voted = list(last_voted)
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if not last_voted:
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return list(r.table('bigchain')
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.filter(r.row['block_number'] == 0)
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.run(self.conn))[0]
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return last_voted[0]
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def get_unvoted_blocks(self):
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"""Return all the blocks that has not been voted by this node."""
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unvoted = r.table('bigchain') \
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.filter(lambda doc: doc['votes'].contains(lambda vote: vote['node_pubkey'] == self.me).not_()) \
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.order_by(r.asc((r.row['block']['timestamp']))) \
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.run(self.conn)
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if unvoted and unvoted[0].get('block_number') == 0:
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unvoted.pop(0)
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return unvoted
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def block_election_status(self, block):
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"""
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Tallies the votes on a block, and returns the status: valid, invalid, or undecided
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"""
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n_voters = len(block['block']['voters'])
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vote_cast = [vote['vote']['is_block_valid'] for vote in block['votes']]
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vote_validity = [self.consensus.verify_vote_signature(block, vote) for vote in block['votes']]
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# element-wise product of stated vote and validity of vote
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vote_list = list(map(operator.mul, vote_cast, vote_validity))
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# validate votes here
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n_valid_votes = sum(vote_list)
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n_invalid_votes = len(vote_list) - n_valid_votes
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# The use of ceiling and floor is to account for the case of an
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# even number of voters where half the voters have voted 'invalid'
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# and half 'valid'. In this case, the block should be marked invalid
|
|
# to avoid a tie. In the case of an odd number of voters this is not
|
|
# relevant, since one side must be a majority.
|
|
if n_invalid_votes >= math.ceil(n_voters / 2):
|
|
return 'invalid'
|
|
elif n_valid_votes > math.floor(n_voters / 2):
|
|
return 'valid'
|
|
else:
|
|
return 'undecided'
|