From cb0160901f5f2223fe5452b67c41903cd5bfe167 Mon Sep 17 00:00:00 2001
From: Neil Booth <kyuupichan@gmail.com>
Date: Tue, 24 Jan 2017 21:14:41 +0900
Subject: [PATCH 1/5] Unify executor and futures logic

---
 server/block_processor.py |  18 +++----
 server/controller.py      | 105 ++++++++++++++++++++++----------------
 server/mempool.py         |   9 ++--
 server/peers.py           |  37 ++------------
 server/session.py         |   1 -
 5 files changed, 78 insertions(+), 92 deletions(-)

diff --git a/server/block_processor.py b/server/block_processor.py
index ea8fb8c..74ae878 100644
--- a/server/block_processor.py
+++ b/server/block_processor.py
@@ -138,9 +138,10 @@ class BlockProcessor(server.db.DB):
     Coordinate backing up in case of chain reorganisations.
     '''
 
-    def __init__(self, env, daemon):
+    def __init__(self, env, controller, daemon):
         super().__init__(env)
         self.daemon = daemon
+        self.controller = controller
 
         # These are our state as we move ahead of DB state
         self.fs_height = self.db_height
@@ -190,6 +191,7 @@ class BlockProcessor(server.db.DB):
 
     async def main_loop(self):
         '''Main loop for block processing.'''
+        self.controller.ensure_future(self.prefetcher.main_loop())
         await self.prefetcher.reset_height()
 
         while True:
@@ -205,16 +207,11 @@ class BlockProcessor(server.db.DB):
             self.logger.info('flushing state to DB for a clean shutdown...')
             self.flush(True)
 
-    async def executor(self, func, *args, **kwargs):
-        '''Run func taking args in the executor.'''
-        loop = asyncio.get_event_loop()
-        await loop.run_in_executor(None, partial(func, *args, **kwargs))
-
     async def first_caught_up(self):
         '''Called when first caught up to daemon after starting.'''
         # Flush everything with updated first_sync->False state.
         self.first_sync = False
-        await self.executor(self.flush, True)
+        await self.controller.run_in_executor(self.flush, True)
         if self.utxo_db.for_sync:
             self.logger.info('{} synced to height {:,d}'
                              .format(VERSION, self.height))
@@ -240,7 +237,8 @@ class BlockProcessor(server.db.DB):
 
         if hprevs == chain:
             start = time.time()
-            await self.executor(self.advance_blocks, blocks, headers)
+            await self.controller.run_in_executor(self.advance_blocks,
+                                                  blocks, headers)
             if not self.first_sync:
                 s = '' if len(blocks) == 1 else 's'
                 self.logger.info('processed {:,d} block{} in {:.1f}s'
@@ -277,14 +275,14 @@ class BlockProcessor(server.db.DB):
             self.logger.info('chain reorg detected')
         else:
             self.logger.info('faking a reorg of {:,d} blocks'.format(count))
-        await self.executor(self.flush, True)
+        await self.controller.run_in_executor(self.flush, True)
 
         hashes = await self.reorg_hashes(count)
         # Reverse and convert to hex strings.
         hashes = [hash_to_str(hash) for hash in reversed(hashes)]
         for hex_hashes in chunks(hashes, 50):
             blocks = await self.daemon.raw_blocks(hex_hashes)
-            await self.executor(self.backup_blocks, blocks)
+            await self.controller.run_in_executor(self.backup_blocks, blocks)
         await self.prefetcher.reset_height()
 
     async def reorg_hashes(self, count):
diff --git a/server/controller.py b/server/controller.py
index 803d557..2ef9b44 100644
--- a/server/controller.py
+++ b/server/controller.py
@@ -11,6 +11,7 @@ import json
 import os
 import ssl
 import time
+import traceback
 from bisect import bisect_left
 from collections import defaultdict
 from concurrent.futures import ThreadPoolExecutor
@@ -49,9 +50,9 @@ class Controller(util.LoggedClass):
         self.start_time = time.time()
         self.coin = env.coin
         self.daemon = Daemon(env.coin.daemon_urls(env.daemon_url))
-        self.bp = BlockProcessor(env, self.daemon)
-        self.mempool = MemPool(self.bp)
-        self.peers = PeerManager(env)
+        self.bp = BlockProcessor(env, self, self.daemon)
+        self.mempool = MemPool(self.bp, self)
+        self.peers = PeerManager(env, self)
         self.env = env
         self.servers = {}
         # Map of session to the key of its list in self.groups
@@ -63,6 +64,7 @@ class Controller(util.LoggedClass):
         self.max_sessions = env.max_sessions
         self.low_watermark = self.max_sessions * 19 // 20
         self.max_subs = env.max_subs
+        self.futures = set()
         # Cache some idea of room to avoid recounting on each subscription
         self.subs_room = 0
         self.next_stale_check = 0
@@ -199,43 +201,59 @@ class Controller(util.LoggedClass):
                 if session.items:
                     self.enqueue_session(session)
 
+    async def run_in_executor(self, func, *args):
+        '''Wait whilst running func in the executor.'''
+        return await self.loop.run_in_executor(None, func, *args)
+
+    def schedule_executor(self, func, *args):
+        '''Schedule running func in the executor, return a task.'''
+        return self.ensure_future(self.run_in_executor(func, *args))
+
+    def ensure_future(self, coro):
+        '''Schedule the coro to be run.'''
+        future = asyncio.ensure_future(coro)
+        future.add_done_callback(self.on_future_done)
+        self.futures.add(future)
+        return future
+
+    def on_future_done(self, future):
+        '''Collect the result of a future after removing it from our set.'''
+        self.futures.remove(future)
+        try:
+            future.result()
+        except asyncio.CancelledError:
+            pass
+        except Exception:
+            self.log_error(traceback.format_exc())
+
+    async def wait_for_bp_catchup(self):
+        '''Called when the block processor catches up.'''
+        await self.bp.caught_up_event.wait()
+        self.logger.info('block processor has caught up')
+        self.ensure_future(self.peers.main_loop())
+        self.ensure_future(self.start_servers())
+        self.ensure_future(self.mempool.main_loop())
+        self.ensure_future(self.enqueue_delayed_sessions())
+        self.ensure_future(self.notify())
+        for n in range(4):
+            self.ensure_future(self.serve_requests())
+
+    async def main_loop(self):
+        '''Controller main loop.'''
+        self.ensure_future(self.bp.main_loop())
+        self.ensure_future(self.wait_for_bp_catchup())
+
+        # Shut down cleanly after waiting for shutdown to be signalled
+        await self.shutdown_event.wait()
+        self.logger.info('shutting down')
+        await self.shutdown()
+        self.logger.info('shutdown complete')
+
     def initiate_shutdown(self):
         '''Call this function to start the shutdown process.'''
         self.shutdown_event.set()
 
-    async def main_loop(self):
-        '''Controller main loop.'''
-        def add_future(coro):
-            futures.append(asyncio.ensure_future(coro))
-
-        async def await_bp_catchup():
-            '''Wait for the block processor to catch up.
-
-            Then start the servers and the peer manager.
-            '''
-            await self.bp.caught_up_event.wait()
-            self.logger.info('block processor has caught up')
-            add_future(self.peers.main_loop())
-            add_future(self.start_servers())
-            add_future(self.mempool.main_loop())
-            add_future(self.enqueue_delayed_sessions())
-            add_future(self.notify())
-            for n in range(4):
-                add_future(self.serve_requests())
-
-        futures = []
-        add_future(self.bp.main_loop())
-        add_future(self.bp.prefetcher.main_loop())
-        add_future(await_bp_catchup())
-
-        # Perform a clean shutdown when this event is signalled.
-        await self.shutdown_event.wait()
-
-        self.logger.info('shutting down')
-        await self.shutdown(futures)
-        self.logger.info('shutdown complete')
-
-    async def shutdown(self, futures):
+    async def shutdown(self):
         '''Perform the shutdown sequence.'''
         self.state = self.SHUTTING_DOWN
 
@@ -244,13 +262,13 @@ class Controller(util.LoggedClass):
         for session in self.sessions:
             self.close_session(session)
 
-        # Cancel the futures
-        for future in futures:
+        # Cancel pending futures
+        for future in self.futures:
             future.cancel()
 
         # Wait for all futures to finish
-        while any(not future.done() for future in futures):
-            await asyncio.sleep(1)
+        while not all (future.done() for future in self.futures):
+            await asyncio.sleep(0.1)
 
         # Finally shut down the block processor and executor
         self.bp.shutdown(self.executor)
@@ -694,8 +712,7 @@ class Controller(util.LoggedClass):
             limit = self.env.max_send // 97
             return list(self.bp.get_history(hashX, limit=limit))
 
-        loop = asyncio.get_event_loop()
-        history = await loop.run_in_executor(None, job)
+        history = await self.run_in_executor(job)
         self.history_cache[hashX] = history
         return history
 
@@ -725,8 +742,8 @@ class Controller(util.LoggedClass):
         '''Get UTXOs asynchronously to reduce latency.'''
         def job():
             return list(self.bp.get_utxos(hashX, limit=None))
-        loop = asyncio.get_event_loop()
-        return await loop.run_in_executor(None, job)
+
+        return await self.run_in_executor(job)
 
     def get_chunk(self, index):
         '''Return header chunk as hex.  Index is a non-negative integer.'''
diff --git a/server/mempool.py b/server/mempool.py
index 0a0a952..387b12c 100644
--- a/server/mempool.py
+++ b/server/mempool.py
@@ -31,9 +31,10 @@ class MemPool(util.LoggedClass):
     A pair is a (hashX, value) tuple.  tx hashes are hex strings.
     '''
 
-    def __init__(self, bp):
+    def __init__(self, bp, controller):
         super().__init__()
         self.daemon = bp.daemon
+        self.controller = controller
         self.coin = bp.coin
         self.db = bp
         self.touched = bp.touched
@@ -139,7 +140,6 @@ class MemPool(util.LoggedClass):
                 break
 
     def async_process_some(self, unfetched, limit):
-        loop = asyncio.get_event_loop()
         pending = []
         txs = self.txs
 
@@ -162,9 +162,8 @@ class MemPool(util.LoggedClass):
                 deferred = pending
                 pending = []
 
-            def job():
-                return self.process_raw_txs(raw_txs, deferred)
-            result, deferred = await loop.run_in_executor(None, job)
+            result, deferred = await self.controller.run_in_executor \
+                (self.process_raw_txs, raw_txs, deferred)
 
             pending.extend(deferred)
             hashXs = self.hashXs
diff --git a/server/peers.py b/server/peers.py
index 31519a3..2f1e832 100644
--- a/server/peers.py
+++ b/server/peers.py
@@ -7,11 +7,8 @@
 
 '''Peer management.'''
 
-import asyncio
 import socket
-import traceback
 from collections import namedtuple
-from functools import partial
 
 import lib.util as util
 from server.irc import IRC
@@ -30,12 +27,11 @@ class PeerManager(util.LoggedClass):
     VERSION = '1.0'
     DEFAULT_PORTS = {'t': 50001, 's': 50002}
 
-    def __init__(self, env):
+    def __init__(self, env, controller):
         super().__init__()
         self.env = env
-        self.loop = asyncio.get_event_loop()
+        self.controller = controller
         self.irc = IRC(env, self)
-        self.futures = set()
         self.identities = []
         # Keyed by nick
         self.irc_peers = {}
@@ -51,10 +47,6 @@ class PeerManager(util.LoggedClass):
                                                env.report_ssl_port_tor,
                                                '_tor'))
 
-    async def executor(self, func, *args, **kwargs):
-        '''Run func taking args in the executor.'''
-        await self.loop.run_in_executor(None, partial(func, *args, **kwargs))
-
     @classmethod
     def real_name(cls, identity):
         '''Real name as used on IRC.'''
@@ -70,38 +62,19 @@ class PeerManager(util.LoggedClass):
         ssl = port_text('s', identity.ssl_port)
         return '{} v{}{}{}'.format(identity.host, cls.VERSION, tcp, ssl)
 
-    def ensure_future(self, coro):
-        '''Convert a coro into a future and add it to our pending list
-        to be waited for.'''
-        self.futures.add(asyncio.ensure_future(coro))
-
     def start_irc(self):
         '''Start up the IRC connections if enabled.'''
         if self.env.irc:
             name_pairs = [(self.real_name(identity), identity.nick_suffix)
                           for identity in self.identities]
-            self.ensure_future(self.irc.start(name_pairs))
+            self.controller.ensure_future(self.irc.start(name_pairs))
         else:
             self.logger.info('IRC is disabled')
 
     async def main_loop(self):
-        '''Start and then enter the main loop.'''
+        '''Main loop.  No loop for now.'''
         self.start_irc()
 
-        try:
-            while True:
-                await asyncio.sleep(10)
-                done = [future for future in self.futures if future.done()]
-                self.futures.difference_update(done)
-                for future in done:
-                    try:
-                        future.result()
-                    except:
-                        self.log_error(traceback.format_exc())
-        finally:
-            for future in self.futures:
-                future.cancel()
-
     def dns_lookup_peer(self, nick, hostname, details):
         try:
             ip_addr = None
@@ -119,7 +92,7 @@ class PeerManager(util.LoggedClass):
 
     def add_irc_peer(self, *args):
         '''Schedule DNS lookup of peer.'''
-        self.ensure_future(self.executor(self.dns_lookup_peer, *args))
+        self.controller.schedule_executor(self.dns_lookup_peer, *args)
 
     def remove_irc_peer(self, nick):
         '''Remove a peer from our IRC peers map.'''
diff --git a/server/session.py b/server/session.py
index 8916f49..0b341e8 100644
--- a/server/session.py
+++ b/server/session.py
@@ -8,7 +8,6 @@
 '''Classes for local RPC server and remote client TCP/SSL servers.'''
 
 
-import asyncio
 import time
 import traceback
 from functools import partial

From 76b6899cf2645d663802d320d10aba9640195e8f Mon Sep 17 00:00:00 2001
From: Neil Booth <kyuupichan@gmail.com>
Date: Wed, 25 Jan 2017 08:01:48 +0900
Subject: [PATCH 2/5] Try to avoid asyncio log spew on shutdown

Closes #106.
This is a hacky workaround to an issue that needs to be
fixed in Python's asyncio library (where I filed issue 487
on github)
---
 server/controller.py | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/server/controller.py b/server/controller.py
index 2ef9b44..8692e27 100644
--- a/server/controller.py
+++ b/server/controller.py
@@ -12,6 +12,7 @@ import os
 import ssl
 import time
 import traceback
+import warnings
 from bisect import bisect_left
 from collections import defaultdict
 from concurrent.futures import ThreadPoolExecutor
@@ -247,6 +248,11 @@ class Controller(util.LoggedClass):
         await self.shutdown_event.wait()
         self.logger.info('shutting down')
         await self.shutdown()
+        # Avoid log spew on shutdown for partially opened SSL sockets
+        try:
+            del asyncio.sslproto._SSLProtocolTransport.__del__
+        except Exception:
+            pass
         self.logger.info('shutdown complete')
 
     def initiate_shutdown(self):
@@ -543,7 +549,7 @@ class Controller(util.LoggedClass):
     def lookup_session(self, session_id):
         try:
             session_id = int(session_id)
-        except:
+        except Exception:
             pass
         else:
             for session in self.sessions:
@@ -617,7 +623,7 @@ class Controller(util.LoggedClass):
         if isinstance(address, str):
             try:
                 return self.coin.address_to_hashX(address)
-            except:
+            except Exception:
                 pass
         raise RPCError('{} is not a valid address'.format(address))
 

From 551c04a3bc3201be9b7a9d5a8931ce1f2581177c Mon Sep 17 00:00:00 2001
From: Neil Booth <kyuupichan@gmail.com>
Date: Wed, 25 Jan 2017 08:02:09 +0900
Subject: [PATCH 3/5] Remove all uses of "except:"

---
 lib/script.py | 2 +-
 query.py      | 2 +-
 server/env.py | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/lib/script.py b/lib/script.py
index d29ce1a..fbb2337 100644
--- a/lib/script.py
+++ b/lib/script.py
@@ -209,7 +209,7 @@ class Script(object):
                     n += dlen
 
                 ops.append(op)
-        except:
+        except Exception:
             # Truncated script; e.g. tx_hash
             # ebc9fa1196a59e192352d76c0f6e73167046b9d37b8302b6bb6968dfd279b767
             raise ScriptError('truncated script')
diff --git a/query.py b/query.py
index 3824d71..283f33d 100755
--- a/query.py
+++ b/query.py
@@ -50,7 +50,7 @@ def main():
     try:
         limit = int(sys.argv[argc])
         argc += 1
-    except:
+    except Exception:
         limit = 10
     for addr in sys.argv[argc:]:
         print('Address: ', addr)
diff --git a/server/env.py b/server/env.py
index 2304284..167b2aa 100644
--- a/server/env.py
+++ b/server/env.py
@@ -83,7 +83,7 @@ class Env(LoggedClass):
             return default
         try:
             return int(value)
-        except:
+        except Exception:
             raise self.Error('cannot convert envvar {} value {} to an integer'
                              .format(envvar, value))
 

From e56f188816f062f1a429f773a92ae14896260913 Mon Sep 17 00:00:00 2001
From: Neil Booth <kyuupichan@gmail.com>
Date: Tue, 24 Jan 2017 19:07:54 +0900
Subject: [PATCH 4/5] Implement peer subscriptions

Incremental updates are passed.
Also implement a server.features RPC
---
 docs/ENVIRONMENT.rst |  2 +-
 server/controller.py | 17 +++++++------
 server/peers.py      | 60 ++++++++++++++++++++++++++++----------------
 server/session.py    | 35 +++++++++++++++++++++++++-
 4 files changed, 84 insertions(+), 30 deletions(-)

diff --git a/docs/ENVIRONMENT.rst b/docs/ENVIRONMENT.rst
index 41f4284..0835acd 100644
--- a/docs/ENVIRONMENT.rst
+++ b/docs/ENVIRONMENT.rst
@@ -89,7 +89,7 @@ These environment variables are optional:
 * **SSL_PORT**
 
   If set ElectrumX will serve SSL clients on **HOST**:**SSL_PORT**.
-  If set SSL_CERTFILE and SSL_KEYFILE must be defined and be
+  If set then SSL_CERTFILE and SSL_KEYFILE must be defined and be
   filesystem paths to those SSL files.
 
 * **RPC_PORT**
diff --git a/server/controller.py b/server/controller.py
index 8692e27..334608b 100644
--- a/server/controller.py
+++ b/server/controller.py
@@ -91,12 +91,10 @@ class Controller(util.LoggedClass):
             ('server',
              'banner donation_address'),
         ]
-        handlers = {'.'.join([prefix, suffix]):
-                    getattr(self, suffix.replace('.', '_'))
-                    for prefix, suffixes in rpcs
-                    for suffix in suffixes.split()}
-        handlers['server.peers.subscribe'] = self.peers.subscribe
-        self.electrumx_handlers = handlers
+        self.electrumx_handlers = {'.'.join([prefix, suffix]):
+                                   getattr(self, suffix.replace('.', '_'))
+                                   for prefix, suffixes in rpcs
+                                   for suffix in suffixes.split()}
 
     async def mempool_transactions(self, hashX):
         '''Generate (hex_hash, tx_fee, unconfirmed) tuples for mempool
@@ -358,6 +356,11 @@ class Controller(util.LoggedClass):
             for session in sessions:
                 await session.notify(self.bp.db_height, touched)
 
+    def notify_peers(self, updates):
+        '''Notify of peer updates.'''
+        for session in self.sessions:
+            session.notify_peers(updates)
+
     def electrum_header(self, height):
         '''Return the binary header at the given height.'''
         if not 0 <= height <= self.bp.db_height:
@@ -605,7 +608,7 @@ class Controller(util.LoggedClass):
 
     def rpc_peers(self):
         '''Return a list of server peers, currently taken from IRC.'''
-        return self.peers.peer_list()
+        return self.peers.peer_dict()
 
     def rpc_reorg(self, count=3):
         '''Force a reorg of the given number of blocks.
diff --git a/server/peers.py b/server/peers.py
index 2f1e832..7017f04 100644
--- a/server/peers.py
+++ b/server/peers.py
@@ -7,6 +7,8 @@
 
 '''Peer management.'''
 
+import asyncio
+import itertools
 import socket
 from collections import namedtuple
 
@@ -32,20 +34,27 @@ class PeerManager(util.LoggedClass):
         self.env = env
         self.controller = controller
         self.irc = IRC(env, self)
-        self.identities = []
+        self.pruning = None
+        self._identities = []
         # Keyed by nick
         self.irc_peers = {}
+        self.updated_nicks = set()
 
         # We can have a Tor identity inaddition to a normal one
-        self.identities.append(NetIdentity(env.report_host,
-                                           env.report_tcp_port,
-                                           env.report_ssl_port,
-                                           ''))
+        self._identities.append(self.identity(env.report_host,
+                                              env.report_tcp_port,
+                                              env.report_ssl_port,
+                                              ''))
         if env.report_host_tor.endswith('.onion'):
-            self.identities.append(NetIdentity(env.report_host_tor,
-                                               env.report_tcp_port_tor,
-                                               env.report_ssl_port_tor,
-                                               '_tor'))
+            self._identities.append(self.identity(env.report_host_tor,
+                                                  env.report_tcp_port_tor,
+                                                  env.report_ssl_port_tor,
+                                                  '_tor'))
+
+    @classmethod
+    def identity(self, host, tcp_port, ssl_port, suffix):
+        '''Returns a NetIdentity object.  Unpublished ports are None.'''
+        return NetIdentity(host, tcp_port or None, ssl_port or None, suffix)
 
     @classmethod
     def real_name(cls, identity):
@@ -62,19 +71,29 @@ class PeerManager(util.LoggedClass):
         ssl = port_text('s', identity.ssl_port)
         return '{} v{}{}{}'.format(identity.host, cls.VERSION, tcp, ssl)
 
-    def start_irc(self):
-        '''Start up the IRC connections if enabled.'''
+    def identities(self):
+        '''Return a list of network identities of this server.'''
+        return self._identities
+
+    async def refresh_peer_subs(self):
+        for n in itertools.count():
+            await asyncio.sleep(60)
+            updates = [self.irc_peers[nick] for nick in self.updated_nicks
+                       if nick in self.irc_peers]
+            if updates:
+                self.controller.notify_peers(updates)
+            self.updated_nicks.clear()
+
+    async def main_loop(self):
+        '''Not a loop for now...'''
+        self.controller.ensure_future(self.refresh_peer_subs())
         if self.env.irc:
             name_pairs = [(self.real_name(identity), identity.nick_suffix)
-                          for identity in self.identities]
+                          for identity in self._identities]
             self.controller.ensure_future(self.irc.start(name_pairs))
         else:
             self.logger.info('IRC is disabled')
 
-    async def main_loop(self):
-        '''Main loop.  No loop for now.'''
-        self.start_irc()
-
     def dns_lookup_peer(self, nick, hostname, details):
         try:
             ip_addr = None
@@ -83,6 +102,7 @@ class PeerManager(util.LoggedClass):
             except socket.error:
                 pass  # IPv6?
             ip_addr = ip_addr or hostname
+            self.updated_nicks.add(nick)
             self.irc_peers[nick] = IRCPeer(ip_addr, hostname, details)
             self.logger.info('new IRC peer {} at {} ({})'
                              .format(nick, hostname, details))
@@ -102,11 +122,9 @@ class PeerManager(util.LoggedClass):
     def count(self):
         return len(self.irc_peers)
 
-    def peer_list(self):
+    def peer_dict(self):
         return self.irc_peers
 
-    def subscribe(self):
-        '''Returns the server peers as a list of (ip, host, details) tuples.
-
-        Despite the name this is not currently treated as a subscription.'''
+    def peer_list(self):
+        '''Returns the server peers as a list of (ip, host, details) tuples.'''
         return list(self.irc_peers.values())
diff --git a/server/session.py b/server/session.py
index 0b341e8..a4e7fd0 100644
--- a/server/session.py
+++ b/server/session.py
@@ -7,7 +7,6 @@
 
 '''Classes for local RPC server and remote client TCP/SSL servers.'''
 
-
 import time
 import traceback
 from functools import partial
@@ -105,6 +104,7 @@ class ElectrumX(SessionBase):
         super().__init__(*args, **kwargs)
         self.subscribe_headers = False
         self.subscribe_height = False
+        self.subscribe_peers = False
         self.notified_height = None
         self.max_send = self.env.max_send
         self.max_subs = self.env.max_session_subs
@@ -114,6 +114,8 @@ class ElectrumX(SessionBase):
             'blockchain.headers.subscribe': self.headers_subscribe,
             'blockchain.numblocks.subscribe': self.numblocks_subscribe,
             'blockchain.transaction.broadcast': self.transaction_broadcast,
+            'server.features': self.server_features,
+            'server.peers.subscribe': self.peers_subscribe,
             'server.version': self.server_version,
         }
 
@@ -167,6 +169,23 @@ class ElectrumX(SessionBase):
         self.subscribe_height = True
         return self.height()
 
+    def peers_subscribe(self, incremental=False):
+        '''Returns the server peers as a list of (ip, host, details) tuples.
+
+        If incremental is False there is no subscription.  If True the
+        remote side will receive notifications of new or modified
+        peers (peers that disappeared are not notified).
+        '''
+        self.subscribe_peers = incremental
+        return self.controller.peers.peer_list()
+
+    def notify_peers(self, updates):
+        '''Notify of peer updates.  Updates are sent as a list in the same
+        format as the subscription reply, as the first parameter.
+        '''
+        if self.subscribe_peers:
+            self.send_notification('server.peers.subscribe', [updates])
+
     async def address_subscribe(self, address):
         '''Subscribe to an address.
 
@@ -180,6 +199,20 @@ class ElectrumX(SessionBase):
         self.hashX_subs[hashX] = address
         return status
 
+    def server_features(self):
+        '''Returns a dictionary of server features.'''
+        peers = self.controller.peers
+        hosts = {identity.host: {
+            'tcp_port': identity.tcp_port,
+            'ssl_port': identity.ssl_port,
+            'pruning': peers.pruning,
+            'version': peers.VERSION,
+        } for identity in self.controller.peers.identities()}
+
+        return {
+            'hosts': hosts,
+        }
+
     def server_version(self, client_name=None, protocol_version=None):
         '''Returns the server version as a string.
 

From 8bc9abf9c1dcbb758b27c709a6a4cd30049c99b1 Mon Sep 17 00:00:00 2001
From: Neil Booth <kyuupichan@gmail.com>
Date: Wed, 25 Jan 2017 20:30:02 +0900
Subject: [PATCH 5/5] Prepare 0.10.13

---
 README.rst        | 8 ++++++++
 server/version.py | 2 +-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/README.rst b/README.rst
index c39fdf0..0d49516 100644
--- a/README.rst
+++ b/README.rst
@@ -135,6 +135,14 @@ version prior to the release of 1.0.
 ChangeLog
 =========
 
+Version 0.10.13
+---------------
+
+* worked around asyncio issue to suppress the annoying log spew on shutdown
+  that makes it look like a bomb hit
+* implement peer subscriptions as real subscriptions with incremental updates
+* misc cleanups
+
 Version 0.10.12
 ---------------
 
diff --git a/server/version.py b/server/version.py
index ff7b40c..7c310f2 100644
--- a/server/version.py
+++ b/server/version.py
@@ -1 +1 @@
-VERSION = "ElectrumX 0.10.12"
+VERSION = "ElectrumX 0.10.13"