import random
from time import time
from bigchaindb import exceptions as core_exceptions
from bigchaindb.common import crypto, exceptions
from bigchaindb.common.utils import gen_timestamp, serialize
from bigchaindb.common.transaction import TransactionLink
import bigchaindb
from bigchaindb import backend, config_utils, utils
from bigchaindb.consensus import BaseConsensusRules
from bigchaindb.models import Block, Transaction
[docs]class Bigchain(object):
"""Bigchain API
Create, read, sign, write transactions to the database
"""
# return if a block has been voted invalid
BLOCK_INVALID = 'invalid'
# return if a block is valid, or tx is in valid block
BLOCK_VALID = TX_VALID = 'valid'
# return if block is undecided, or tx is in undecided block
BLOCK_UNDECIDED = TX_UNDECIDED = 'undecided'
# return if transaction is in backlog
TX_IN_BACKLOG = 'backlog'
[docs] def __init__(self, public_key=None, private_key=None, keyring=[], connection=None, backlog_reassign_delay=None):
"""Initialize the Bigchain instance
A Bigchain instance has several configuration parameters (e.g. host).
If a parameter value is passed as an argument to the Bigchain
__init__ method, then that is the value it will have.
Otherwise, the parameter value will come from an environment variable.
If that environment variable isn't set, then the value
will come from the local configuration file. And if that variable
isn't in the local configuration file, then the parameter will have
its default value (defined in bigchaindb.__init__).
Args:
public_key (str): the base58 encoded public key for the ED25519 curve.
private_key (str): the base58 encoded private key for the ED25519 curve.
keyring (list[str]): list of base58 encoded public keys of the federation nodes.
connection (:class:`~bigchaindb.backend.connection.Connection`):
A connection to the database.
"""
config_utils.autoconfigure()
self.me = public_key or bigchaindb.config['keypair']['public']
self.me_private = private_key or bigchaindb.config['keypair']['private']
self.nodes_except_me = keyring or bigchaindb.config['keyring']
if backlog_reassign_delay is None:
backlog_reassign_delay = bigchaindb.config['backlog_reassign_delay']
self.backlog_reassign_delay = backlog_reassign_delay
consensusPlugin = bigchaindb.config.get('consensus_plugin')
if consensusPlugin:
self.consensus = config_utils.load_consensus_plugin(consensusPlugin)
else:
self.consensus = BaseConsensusRules
self.connection = connection if connection else backend.connect(**bigchaindb.config['database'])
if not self.me or not self.me_private:
raise exceptions.KeypairNotFoundException()
federation = property(lambda self: set(self.nodes_except_me + [self.me]))
""" Set of federation member public keys """
[docs] def write_transaction(self, signed_transaction):
"""Write the transaction to bigchain.
When first writing a transaction to the bigchain the transaction will be kept in a backlog until
it has been validated by the nodes of the federation.
Args:
signed_transaction (Transaction): transaction with the `signature` included.
Returns:
dict: database response
"""
signed_transaction = signed_transaction.to_dict()
# we will assign this transaction to `one` node. This way we make sure that there are no duplicate
# transactions on the bigchain
if self.nodes_except_me:
assignee = random.choice(self.nodes_except_me)
else:
# I am the only node
assignee = self.me
signed_transaction.update({'assignee': assignee})
signed_transaction.update({'assignment_timestamp': time()})
# write to the backlog
return backend.query.write_transaction(self.connection, signed_transaction)
[docs] def reassign_transaction(self, transaction):
"""Assign a transaction to a new node
Args:
transaction (dict): assigned transaction
Returns:
dict: database response or None if no reassignment is possible
"""
other_nodes = tuple(
self.federation.difference([transaction['assignee']])
)
new_assignee = random.choice(other_nodes) if other_nodes else self.me
return backend.query.update_transaction(
self.connection, transaction['id'],
{'assignee': new_assignee, 'assignment_timestamp': time()})
[docs] def delete_transaction(self, *transaction_id):
"""Delete a transaction from the backlog.
Args:
*transaction_id (str): the transaction(s) to delete
Returns:
The database response.
"""
return backend.query.delete_transaction(self.connection, *transaction_id)
[docs] def get_stale_transactions(self):
"""Get a cursor of stale transactions.
Transactions are considered stale if they have been assigned a node, but are still in the
backlog after some amount of time specified in the configuration
"""
return backend.query.get_stale_transactions(self.connection, self.backlog_reassign_delay)
[docs] def validate_transaction(self, transaction):
"""Validate a transaction.
Args:
transaction (Transaction): transaction to validate.
Returns:
The transaction if the transaction is valid else it raises an
exception describing the reason why the transaction is invalid.
"""
return self.consensus.validate_transaction(self, transaction)
[docs] def is_new_transaction(self, txid, exclude_block_id=None):
"""
Return True if the transaction does not exist in any
VALID or UNDECIDED block. Return False otherwise.
Args:
txid (str): Transaction ID
exclude_block_id (str): Exclude block from search
"""
block_statuses = self.get_blocks_status_containing_tx(txid)
block_statuses.pop(exclude_block_id, None)
for status in block_statuses.values():
if status != self.BLOCK_INVALID:
return False
return True
[docs] def get_block(self, block_id, include_status=False):
"""Get the block with the specified `block_id` (and optionally its status)
Returns the block corresponding to `block_id` or None if no match is
found.
Args:
block_id (str): transaction id of the transaction to get
include_status (bool): also return the status of the block
the return value is then a tuple: (block, status)
"""
block = backend.query.get_block(self.connection, block_id)
status = None
if include_status:
if block:
status = self.block_election_status(block)
return block, status
else:
return block
[docs] def get_transaction(self, txid, include_status=False):
"""Get the transaction with the specified `txid` (and optionally its status)
This query begins by looking in the bigchain table for all blocks containing
a transaction with the specified `txid`. If one of those blocks is valid, it
returns the matching transaction from that block. Else if some of those
blocks are undecided, it returns a matching transaction from one of them. If
the transaction was found in invalid blocks only, or in no blocks, then this
query looks for a matching transaction in the backlog table, and if it finds
one there, it returns that.
Args:
txid (str): transaction id of the transaction to get
include_status (bool): also return the status of the transaction
the return value is then a tuple: (tx, status)
Returns:
A :class:`~.models.Transaction` instance if the transaction
was found in a valid block, an undecided block, or the backlog table,
otherwise ``None``.
If :attr:`include_status` is ``True``, also returns the
transaction's status if the transaction was found.
"""
response, tx_status = None, None
validity = self.get_blocks_status_containing_tx(txid)
check_backlog = True
if validity:
# Disregard invalid blocks, and return if there are no valid or undecided blocks
validity = {_id: status for _id, status in validity.items()
if status != Bigchain.BLOCK_INVALID}
if validity:
# The transaction _was_ found in an undecided or valid block,
# so there's no need to look in the backlog table
check_backlog = False
tx_status = self.TX_UNDECIDED
# If the transaction is in a valid or any undecided block, return it. Does not check
# if transactions in undecided blocks are consistent, but selects the valid block
# before undecided ones
for target_block_id in validity:
if validity[target_block_id] == Bigchain.BLOCK_VALID:
tx_status = self.TX_VALID
break
# Query the transaction in the target block and return
response = backend.query.get_transaction_from_block(self.connection, txid, target_block_id)
if check_backlog:
response = backend.query.get_transaction_from_backlog(self.connection, txid)
if response:
tx_status = self.TX_IN_BACKLOG
if response:
response = Transaction.from_dict(response)
if include_status:
return response, tx_status
else:
return response
[docs] def get_status(self, txid):
"""Retrieve the status of a transaction with `txid` from bigchain.
Args:
txid (str): transaction id of the transaction to query
Returns:
(string): transaction status ('valid', 'undecided',
or 'backlog'). If no transaction with that `txid` was found it
returns `None`
"""
_, status = self.get_transaction(txid, include_status=True)
return status
[docs] def get_blocks_status_containing_tx(self, txid):
"""Retrieve block ids and statuses related to a transaction
Transactions may occur in multiple blocks, but no more than one valid block.
Args:
txid (str): transaction id of the transaction to query
Returns:
A dict of blocks containing the transaction,
e.g. {block_id_1: 'valid', block_id_2: 'invalid' ...}, or None
"""
# First, get information on all blocks which contain this transaction
blocks = backend.query.get_blocks_status_from_transaction(self.connection, txid)
if blocks:
# Determine the election status of each block
validity = {block['id']: self.block_election_status(block)
for block in blocks}
# NOTE: If there are multiple valid blocks with this transaction,
# something has gone wrong
if list(validity.values()).count(Bigchain.BLOCK_VALID) > 1:
block_ids = str([block for block in validity
if validity[block] == Bigchain.BLOCK_VALID])
raise core_exceptions.CriticalDoubleInclusion(
'Transaction {tx} is present in '
'multiple valid blocks: {block_ids}'
.format(tx=txid, block_ids=block_ids))
return validity
else:
return None
[docs] def get_asset_by_id(self, asset_id):
"""Returns the asset associated with an asset_id.
Args:
asset_id (str): The asset id.
Returns:
dict if the asset exists else None.
"""
cursor = backend.query.get_asset_by_id(self.connection, asset_id)
cursor = list(cursor)
if cursor:
return cursor[0]['asset']
[docs] def get_spent(self, txid, output):
"""Check if a `txid` was already used as an input.
A transaction can be used as an input for another transaction. Bigchain needs to make sure that a
given `txid` is only used once.
Args:
txid (str): The id of the transaction
output (num): the index of the output in the respective transaction
Returns:
The transaction (Transaction) that used the `txid` as an input else
`None`
"""
# checks if an input was already spent
# checks if the bigchain has any transaction with input {'txid': ...,
# 'output': ...}
transactions = list(backend.query.get_spent(self.connection, txid, output))
# a transaction_id should have been spent at most one time
if transactions:
# determine if these valid transactions appear in more than one valid block
num_valid_transactions = 0
for transaction in transactions:
# ignore invalid blocks
# FIXME: Isn't there a faster solution than doing I/O again?
if self.get_transaction(transaction['id']):
num_valid_transactions += 1
if num_valid_transactions > 1:
raise core_exceptions.CriticalDoubleSpend(
'`{}` was spent more than once. There is a problem'
' with the chain'.format(txid))
if num_valid_transactions:
return Transaction.from_dict(transactions[0])
else:
# all queried transactions were invalid
return None
else:
return None
[docs] def get_outputs(self, owner):
"""Retrieve a list of links to transaction outputs for a given public
key.
Args:
owner (str): base58 encoded public key.
Returns:
:obj:`list` of TransactionLink: list of ``txid`` s and ``output`` s
pointing to another transaction's condition
"""
# get all transactions in which owner is in the `owners_after` list
response = backend.query.get_owned_ids(self.connection, owner)
links = []
for tx in response:
# disregard transactions from invalid blocks
validity = self.get_blocks_status_containing_tx(tx['id'])
if Bigchain.BLOCK_VALID not in validity.values():
if Bigchain.BLOCK_UNDECIDED not in validity.values():
continue
# NOTE: It's OK to not serialize the transaction here, as we do not
# use it after the execution of this function.
# a transaction can contain multiple outputs so we need to iterate over all of them
# to get a list of outputs available to spend
for index, output in enumerate(tx['outputs']):
# for simple signature conditions there are no subfulfillments
# check if the owner is in the condition `owners_after`
if len(output['public_keys']) == 1:
if output['condition']['details']['public_key'] == owner:
links.append(TransactionLink(tx['id'], index))
else:
# for transactions with multiple `public_keys` there will be several subfulfillments nested
# in the condition. We need to iterate the subfulfillments to make sure there is a
# subfulfillment for `owner`
if utils.condition_details_has_owner(output['condition']['details'], owner):
links.append(TransactionLink(tx['id'], index))
return links
[docs] def get_owned_ids(self, owner):
"""Retrieve a list of ``txid`` s that can be used as inputs.
Args:
owner (str): base58 encoded public key.
Returns:
:obj:`list` of TransactionLink: list of ``txid`` s and ``output`` s
pointing to another transaction's condition
"""
return self.get_outputs_filtered(owner, include_spent=False)
[docs] def get_outputs_filtered(self, owner, include_spent=True):
"""
Get a list of output links filtered on some criteria
"""
outputs = self.get_outputs(owner)
if not include_spent:
outputs = [o for o in outputs
if not self.get_spent(o.txid, o.output)]
return outputs
[docs] def get_transactions_filtered(self, asset_id, operation=None):
"""
Get a list of transactions filtered on some criteria
"""
txids = backend.query.get_txids_filtered(self.connection, asset_id,
operation)
for txid in txids:
tx, status = self.get_transaction(txid, True)
if status == self.TX_VALID:
yield tx
[docs] def create_block(self, validated_transactions):
"""Creates a block given a list of `validated_transactions`.
Note that this method does not validate the transactions. Transactions
should be validated before calling create_block.
Args:
validated_transactions (list(Transaction)): list of validated
transactions.
Returns:
Block: created block.
"""
# Prevent the creation of empty blocks
if not validated_transactions:
raise exceptions.OperationError('Empty block creation is not '
'allowed')
voters = list(self.federation)
block = Block(validated_transactions, self.me, gen_timestamp(), voters)
block = block.sign(self.me_private)
return block
# TODO: check that the votings structure is correctly constructed
[docs] def validate_block(self, block):
"""Validate a block.
Args:
block (Block): block to validate.
Returns:
The block if the block is valid else it raises and exception
describing the reason why the block is invalid.
"""
return self.consensus.validate_block(self, block)
[docs] def has_previous_vote(self, block_id):
"""Check for previous votes from this node
Args:
block_id (str): the id of the block to check
Returns:
bool: :const:`True` if this block already has a
valid vote from this node, :const:`False` otherwise.
"""
votes = list(backend.query.get_votes_by_block_id_and_voter(self.connection, block_id, self.me))
el, _ = self.consensus.voting.partition_eligible_votes(votes, [self.me])
return bool(el)
[docs] def write_block(self, block):
"""Write a block to bigchain.
Args:
block (Block): block to write to bigchain.
"""
return backend.query.write_block(self.connection, block)
[docs] def prepare_genesis_block(self):
"""Prepare a genesis block."""
metadata = {'message': 'Hello World from the BigchainDB'}
transaction = Transaction.create([self.me], [([self.me], 1)],
metadata=metadata)
# NOTE: The transaction model doesn't expose an API to generate a
# GENESIS transaction, as this is literally the only usage.
transaction.operation = 'GENESIS'
transaction = transaction.sign([self.me_private])
# create the block
return self.create_block([transaction])
[docs] def create_genesis_block(self):
"""Create the genesis block
Block created when bigchain is first initialized. This method is not atomic, there might be concurrency
problems if multiple instances try to write the genesis block when the BigchainDB Federation is started,
but it's a highly unlikely scenario.
"""
# 1. create one transaction
# 2. create the block with one transaction
# 3. write the block to the bigchain
blocks_count = backend.query.count_blocks(self.connection)
if blocks_count:
raise exceptions.GenesisBlockAlreadyExistsError('Cannot create the Genesis block')
block = self.prepare_genesis_block()
self.write_block(block)
return block
[docs] def vote(self, block_id, previous_block_id, decision, invalid_reason=None):
"""Create a signed vote for a block given the
:attr:`previous_block_id` and the :attr:`decision` (valid/invalid).
Args:
block_id (str): The id of the block to vote on.
previous_block_id (str): The id of the previous block.
decision (bool): Whether the block is valid or invalid.
invalid_reason (Optional[str]): Reason the block is invalid
"""
if block_id == previous_block_id:
raise exceptions.CyclicBlockchainError()
vote = {
'voting_for_block': block_id,
'previous_block': previous_block_id,
'is_block_valid': decision,
'invalid_reason': invalid_reason,
'timestamp': gen_timestamp()
}
vote_data = serialize(vote)
signature = crypto.PrivateKey(self.me_private).sign(vote_data.encode())
vote_signed = {
'node_pubkey': self.me,
'signature': signature.decode(),
'vote': vote
}
return vote_signed
[docs] def write_vote(self, vote):
"""Write the vote to the database."""
return backend.query.write_vote(self.connection, vote)
[docs] def get_last_voted_block(self):
"""Returns the last block that this node voted on."""
return Block.from_dict(backend.query.get_last_voted_block(self.connection, self.me))
[docs] def get_unvoted_blocks(self):
"""Return all the blocks that have not been voted on by this node.
Returns:
:obj:`list` of :obj:`dict`: a list of unvoted blocks
"""
# XXX: should this return instaces of Block?
return backend.query.get_unvoted_blocks(self.connection, self.me)
def block_election(self, block):
if type(block) != dict:
block = block.to_dict()
votes = list(backend.query.get_votes_by_block_id(self.connection,
block['id']))
return self.consensus.voting.block_election(block, votes,
self.federation)
[docs] def block_election_status(self, block):
"""Tally the votes on a block, and return the status:
valid, invalid, or undecided."""
return self.block_election(block)['status']