From 8a9030e5c0269d989221446d1e3ec8f105a2df9c Mon Sep 17 00:00:00 2001
From: Matt Smith <matt.the.smith@gmail.com>
Date: Mon, 29 Feb 2016 18:38:33 -0800
Subject: [PATCH] Added a simple plugin system for consensus rules using
 setuputils entry_points

---
 bigchaindb/__init__.py           |  5 ++++-
 bigchaindb/config_utils.py       | 20 ++++++++++++++++++++
 bigchaindb/consensus/__init__.py |  0
 bigchaindb/core.py               |  4 +++-
 setup.py                         | 10 +++++++++-
 5 files changed, 36 insertions(+), 3 deletions(-)
 create mode 100644 bigchaindb/consensus/__init__.py

diff --git a/bigchaindb/__init__.py b/bigchaindb/__init__.py
index 4bb76c44..b728e103 100644
--- a/bigchaindb/__init__.py
+++ b/bigchaindb/__init__.py
@@ -39,7 +39,10 @@ config = {
         'host': e('BIGCHAIN_STATSD_HOST', default='localhost'),
         'port': e('BIGCHAIN_STATSD_PORT', default=8125),
         'rate': e('BIGCHAIN_STATSD_SAMPLERATE', default=0.01)
-    }
+    },
+    'consensus_plugins': [
+        'base'
+    ],
 }
 
 # We need to maintain a backup copy of the original config dict in case
diff --git a/bigchaindb/config_utils.py b/bigchaindb/config_utils.py
index bf3ed529..c273245d 100644
--- a/bigchaindb/config_utils.py
+++ b/bigchaindb/config_utils.py
@@ -17,6 +17,8 @@ import json
 import logging
 import collections
 
+from pkg_resources import iter_entry_points
+
 import bigchaindb
 
 logger = logging.getLogger(__name__)
@@ -100,3 +102,21 @@ def autoconfigure():
     except FileNotFoundError:
         logger.warning('Cannot find your config file. Run `bigchaindb configure` to create one')
 
+
+def get_plugins(plugin_names):
+    if not plugin_names:
+        plugin_names = bigchaindb.config.get('consensus_plugins', [])
+
+    plugins = []
+
+    # It's important to maintain plugin ordering as stated in the config file.
+    # e.g. Expensive validation tasks should happen after cheap ones.
+    #
+    # TODO: We might want to add some sort of priority system, but for now we
+    #       simply assume everything in a given plugin is designed to run at the
+    #       same time.
+    for name in plugin_names:
+        for entry_point in iter_entry_points('bigchaindb.plugins', name):
+            plugins.append(entry_point.load())
+
+    return plugins
diff --git a/bigchaindb/consensus/__init__.py b/bigchaindb/consensus/__init__.py
new file mode 100644
index 00000000..e69de29b
diff --git a/bigchaindb/core.py b/bigchaindb/core.py
index f2ba61dd..89cccd7e 100644
--- a/bigchaindb/core.py
+++ b/bigchaindb/core.py
@@ -30,7 +30,8 @@ class Bigchain(object):
     """
 
     def __init__(self, host=None, port=None, dbname=None,
-                 public_key=None, private_key=None, keyring=[]):
+                 public_key=None, private_key=None, keyring=[],
+                 consensus_plugins=['base']):
         """Initialize the Bigchain instance
 
         There are three ways in which the Bigchain instance can get its parameters.
@@ -56,6 +57,7 @@ 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)
 
         if not self.me or not self.me_private:
             raise KeypairNotFoundException()
diff --git a/setup.py b/setup.py
index 3fd8dae4..26f111fa 100644
--- a/setup.py
+++ b/setup.py
@@ -54,13 +54,21 @@ setup(
         'Operating System :: POSIX :: Linux',
     ],
 
-    packages=['bigchaindb', 'bigchaindb.commands', 'bigchaindb.db'],
+    packages=[
+        'bigchaindb',
+        'bigchaindb.commands',
+        'bigchaindb.db',
+        'bigchaindb.consensus'
+    ],
 
     entry_points={
         'console_scripts': [
             'bigchaindb=bigchaindb.commands.bigchain:main',
             'bigchaindb-benchmark=bigchaindb.commands.bigchain_benchmark:main'
         ],
+        'bigchaindb.plugins': [
+            'base=bigchaindb.consensus.base:ConsensusRules'
+        ]
     },
     install_requires=[
         'rethinkdb==2.2.0.post4',