This large (sorry) commit

1. switches from a composable plugin model to a single-plugin model
2. switches class methods to static methods in the BaseConsensusRules class
3. adds create_transaction, sign_transaction, and verify_transaction to
the plugin API

TODO: If we adopt this model, all references in e.g. client.py to util
methods like `sign_tx` need to be routed through the plugin methods, and
possibly need to be added to the plugin interface.

bigchaindb/config_utils.py

@@ -20,6 +20,7 @@ import collections
 from pkg_resources import iter_entry_points, ResolutionError
 
 import bigchaindb
+from bigchaindb.consensus import AbstractConsensusRules
 
 logger = logging.getLogger(__name__)
 CONFIG_DEFAULT_PATH = os.environ.setdefault(

bigchaindb/consensus.py

@@ -19,7 +19,7 @@ class AbstractConsensusRules(metaclass=ABCMeta):
         """Validate a transaction.
 
         Args:
-            bigchain (Bigchain): an instantiated bigchaindb.Bigchain object.
+            bigchain (Bigchain): an instantiated ``bigchaindb.Bigchain`` object.
             transaction (dict): transaction to validate.
 
         Returns:
@@ -37,7 +37,7 @@ class AbstractConsensusRules(metaclass=ABCMeta):
         """Validate a block.
 
         Args:
-            bigchain (Bigchain): an instantiated bigchaindb.Bigchain object.
+            bigchain (Bigchain): an instantiated ``bigchaindb.Bigchain`` object.
             block (dict): block to validate.
 
         Returns:
@@ -48,19 +48,55 @@ class AbstractConsensusRules(metaclass=ABCMeta):
             Descriptive exceptions indicating the reason the block failed.
             See the `exceptions` module for bigchain-native error classes.
         """
-        return block
+        raise NotImplementedError
 
- class ConsensusRules(AbstractConsensusRules):
+    @abstractmethod
+    def create_transaction(*args, **kwargs):
+        """Create a new transaction.
+
+        Args:
+            The signature of this method is left to plugin authors to decide.
+
+        Returns:
+            dict: newly constructed transaction.
+        """
+        raise NotImplementedError
+
+    @abstractmethod
+    def sign_transaction(transaction, *args, **kwargs):
+        """Sign a transaction.
+
+        Args:
+            transaction (dict): transaction to sign.
+            any other arguments are left to plugin authors to decide.
+
+        Returns:
+            dict: transaction with any signatures applied.
+        """
+        raise NotImplementedError
+
+    @abstractmethod
+    def verify_signature(signed_transaction):
+        """Verify the signature of a transaction.
+
+        Args:
+            signed_transaction (dict): signed transaction to verify
+
+        Returns:
+            bool: True if the transaction's required signature data is present
+                and correct, False otherwise.
+        """
+        raise NotImplementedError
+
+
+class BaseConsensusRules(AbstractConsensusRules):
     """Base consensus rules for Bigchain.
 
-    This class can be copied to write your own consensus rules!
-
-    Note: Consensus plugins will be executed in the order that they're listed in
-    the bigchain config file.
+    This class can be copied or overridden to write your own consensus rules!
     """
 
-    @classmethod
-    def validate_transaction(cls, bigchain, transaction):
+    @staticmethod
+    def validate_transaction(bigchain, transaction):
         """Validate a transaction.
 
         Args:
@@ -126,14 +162,14 @@ class AbstractConsensusRules(metaclass=ABCMeta):
             raise exceptions.InvalidHash()
 
         # Check signature
-        if not bigchain.verify_signature(transaction):
+        if not util.verify_signature(transaction):
             raise exceptions.InvalidSignature()
 
         return transaction
 
-    # TODO: check that the votings structure is correctly constructed
-    @classmethod
-    def validate_block(cls, bigchain, block):
+    # TODO: Unsure if a bigchain parameter is really necessary here?
+    @staticmethod
+    def validate_block(bigchain, block):
         """Validate a block.
 
         Args:
@@ -154,3 +190,32 @@ class AbstractConsensusRules(metaclass=ABCMeta):
             raise exceptions.InvalidHash()
 
         return block
+
+    @staticmethod
+    def create_transaction(current_owner, new_owner, tx_input, operation,
+                           payload=None):
+        """Create a new transaction
+
+        Refer to the documentation of ``bigchaindb.util.create_tx``
+        """
+
+        return util.create_tx(current_owner, new_owner, tx_input, operation,
+                              payload)
+
+    @staticmethod
+    def sign_transaction(transaction, private_key):
+        """Sign a transaction
+
+        Refer to the documentation of ``bigchaindb.util.sign_tx``
+        """
+
+        return util.sign_tx(transaction, private_key)
+
+    @staticmethod
+    def verify_signature(signed_transaction):
+        """Verify the signature of a transaction.
+
+        Refer to the documentation of ``bigchaindb.util.verify_signature``
+        """
+
+        return util.verify_signature(signed_transaction)

bigchaindb/core.py

@@ -27,7 +27,7 @@ class Bigchain(object):
 
     def __init__(self, host=None, port=None, dbname=None,
                  public_key=None, private_key=None, keyring=[],
-                 consensus_plugins=['base']):
+                 consensus_plugin=None):
         """Initialize the Bigchain instance
 
         There are three ways in which the Bigchain instance can get its parameters.
@@ -53,7 +53,7 @@ class Bigchain(object):
         self.me = public_key or bigchaindb.config['keypair']['public']
         self.me_private = private_key or bigchaindb.config['keypair']['private']
         self.federation_nodes = keyring or bigchaindb.config['keyring']
-        self.consensus_plugins = config_utils.get_plugins(consensus_plugins)
+        self.consensus = config_utils.load_consensus_plugin(consensus_plugin)
 
         if not self.me or not self.me_private:
             raise exceptions.KeypairNotFoundException()
@@ -70,38 +70,40 @@ class Bigchain(object):
         return r.connect(host=self.host, port=self.port, db=self.dbname)
 
     @monitor.timer('create_transaction', rate=bigchaindb.config['statsd']['rate'])
-    def create_transaction(self, current_owner, new_owner, tx_input, operation, payload=None):
+    def create_transaction(self, *args, **kwargs):
         """Create a new transaction
 
-        Refer to the documentation of ``bigchaindb.util.create_tx``
+        Refer to the documentation of your consensus plugin.
+
+        Returns:
+            dict: newly constructed transaction.
         """
 
-        return util.create_tx(current_owner, new_owner, tx_input, operation, payload)
+        return self.consensus.create_transaction(*args, **kwargs)
 
-    def sign_transaction(self, transaction, private_key):
+    def sign_transaction(self, transaction, *args, **kwargs):
         """Sign a transaction
 
-        Refer to the documentation of ``bigchaindb.util.sign_tx``
+        Refer to the documentation of your consensus plugin.
+
+        Returns:
+            dict: transaction with any signatures applied.
         """
 
-        return util.sign_tx(transaction, private_key)
+        return self.consensus.sign_transaction(transaction, *args, **kwargs)
 
-    def verify_signature(self, signed_transaction):
-        """Verify the signature of a transaction.
+    def verify_signature(self, signed_transaction, *args, **kwargs):
+        """Verify the signature(s) of a transaction.
 
-        Refer to the documentation of ``bigchaindb.crypto.verify_signature``
+        Refer to the documentation of your consensus plugin.
+
+        Returns:
+            bool: True if the transaction's required signature data is present
+                and correct, False otherwise.
         """
 
-        data = signed_transaction.copy()
-
-        # if assignee field in the transaction, remove it
-        if 'assignee' in data:
-            data.pop('assignee')
-
-        signature = data.pop('signature')
-        public_key_base58 = signed_transaction['transaction']['current_owner']
-        public_key = crypto.PublicKey(public_key_base58)
-        return public_key.verify(util.serialize(data), signature)
+        return self.consensus.verify_signature(
+            signed_transaction, *args, **kwargs)
 
     @monitor.timer('write_transaction', rate=bigchaindb.config['statsd']['rate'])
     def write_transaction(self, signed_transaction, durability='soft'):
@@ -111,7 +113,7 @@ class Bigchain(object):
         it has been validated by the nodes of the federation.
 
         Args:
-            singed_transaction (dict): transaction with the `signature` included.
+            signed_transaction (dict): transaction with the `signature` included.
 
         Returns:
             dict: database response
@@ -250,11 +252,7 @@ class Bigchain(object):
             exception describing the reason why the transaction is invalid.
         """
 
-        for plugin in self.consensus_plugins:
-            transaction = plugin.validate_transaction(self, transaction)
-
-        return transaction
-
+        return self.consensus.validate_transaction(self, transaction)
 
     def is_valid_transaction(self, transaction):
         """Check whether a transacion is valid or invalid.
@@ -324,10 +322,8 @@ class Bigchain(object):
             describing the reason why the block is invalid.
         """
 
-        # First run all of the plugin block validation logic
-        for plugin in self.consensus_plugins:
-            transaction = plugin.validate_block(self, block)
-
+        # First: Run the plugin block validation logic
+        self.consensus.validate_block(self, block)
 
         # Finally: Tentative assumption that every blockchain will want to
         # validate all transactions in each block
@@ -372,6 +368,8 @@ class Bigchain(object):
         response = r.table('bigchain').get_all(transaction_id, index='transaction_id').run(self.conn)
         return True if len(response.items) > 0 else False
 
+    # TODO: Unless we prescribe the signature of create_transaction, this will
+    #       also need to be moved into the plugin API.
     def create_genesis_block(self):
         """Create the genesis block
 

setup.py

@@ -67,8 +67,8 @@ setup(
             'bigchaindb=bigchaindb.commands.bigchain:main',
             'bigchaindb-benchmark=bigchaindb.commands.bigchain_benchmark:main'
         ],
-        'bigchaindb.plugins': [
-            'base=bigchaindb.consensus.base:ConsensusRules'
+        'bigchaindb.consensus': [
+            'default=bigchaindb.consensus:BaseConsensusRules'
         ]
     },
     install_requires=[