Make the blockchain class not a thread

Remove interface communication out of blockchain.py
into network.py.  network.py handles protocol requests
for headers and chunks.  blockchain.py continues to
handle their analysis and verification.

If an interface provides a header chain that doesn't
connect, it is dismissed, as per a previous TODO comment.

This removes a thread and another source of timeouts.
I see no performance issues with this when truncating the
blockchain.

Rename 'result' to 'header' for clarity.

lib/network.py

@@ -13,6 +13,7 @@ import util
 from bitcoin import *
 import interface
 from blockchain import Blockchain
+from collections import deque
 
 DEFAULT_PORTS = {'t':'50001', 's':'50002', 'h':'8081', 'g':'8082'}
 
@@ -141,6 +142,8 @@ class Network(util.DaemonThread):
         self.queue = Queue.Queue()
         self.requests_queue = pipe.send_queue
         self.response_queue = pipe.get_queue
+        # A deque of interface header requests, processed left-to-right
+        self.bc_requests = deque()
         # Server for addresses and transactions
         self.default_server = self.config.get('server')
         # Sanitize default server
@@ -295,11 +298,6 @@ class Network(util.DaemonThread):
         for i in range(self.num_server - 1):
             self.start_random_interface()
 
-    def start(self):
-        self.running = True
-        self.blockchain.start()
-        util.DaemonThread.start(self)
-
     def set_proxy(self, proxy):
         self.proxy = proxy
         if proxy:
@@ -405,7 +403,6 @@ class Network(util.DaemonThread):
         # Our set of interfaces changed
         self.notify('interfaces')
 
-
     def process_response(self, i, response):
         # the id comes from the daemon or the network proxy
         _id = response.get('id')
@@ -428,6 +425,10 @@ class Network(util.DaemonThread):
             addr = response.get('params')[0]
             self.addr_responses[addr] = result
             self.response_queue.put(response)
+        elif method == 'blockchain.block.get_chunk':
+            self.on_get_chunk(i, response)
+        elif method == 'blockchain.block.get_header':
+            self.on_get_header(i, response)
         else:
             self.response_queue.put(response)
 
@@ -490,10 +491,91 @@ class Network(util.DaemonThread):
                 else:
                     self.switch_to_interface(self.default_server)
 
+    def request_chunk(self, interface, data, idx):
+        interface.print_error("requesting chunk %d" % idx)
+        interface.send_request({'method':'blockchain.block.get_chunk', 'params':[idx]})
+        data['chunk_idx'] = idx
+        data['req_time'] = time.time()
+
+    def on_get_chunk(self, interface, response):
+        '''Handle receiving a chunk of block headers'''
+        if self.bc_requests:
+            req_if, data = self.bc_requests[0]
+            req_idx = data.get('chunk_idx')
+            # Ignore unsolicited chunks
+            if req_if == interface and req_idx == response['params'][0]:
+                idx = self.blockchain.connect_chunk(req_idx, response['result'])
+                # If not finished, get the next chunk
+                if idx < 0 or self.get_local_height() >= data['if_height']:
+                    self.bc_requests.popleft()
+                else:
+                    self.request_chunk(interface, data, idx)
+
+    def request_header(self, interface, data, height):
+        interface.print_error("requesting header %d" % height)
+        interface.send_request({'method':'blockchain.block.get_header', 'params':[height]})
+        data['header_height'] = height
+        data['req_time'] = time.time()
+        if not 'chain' in data:
+            data['chain'] = []
+
+    def on_get_header(self, interface, response):
+        '''Handle receiving a single block header'''
+        if self.bc_requests:
+            req_if, data = self.bc_requests[0]
+            req_height = data.get('header_height', -1)
+            # Ignore unsolicited headers
+            if req_if == interface and req_height == response['params'][0]:
+                next_height = self.blockchain.connect_header(data['chain'], response['result'])
+                # If not finished, get the next header
+                if next_height in [True, False]:
+                    self.bc_requests.popleft()
+                    if not next_height:
+                        interface.print_error("header didn't connect, dismissing interface")
+                        interface.stop()
+                else:
+                    self.request_header(interface, data, next_height)
+
+    def bc_request_headers(self, interface, data):
+        '''Send a request for the next header, or a chunk of them, if necessary'''
+        local_height, if_height = self.get_local_height(), data['if_height']
+        if if_height <= local_height:
+            return False
+        elif if_height > local_height + 50:
+            self.request_chunk(interface, data, (local_height + 1) / 2016)
+        else:
+            self.request_header(interface, data, if_height)
+        return True
+
+    def handle_bc_requests(self):
+        '''Work through each interface that has notified us of a new header.
+        Send it requests if it is ahead of our blockchain object'''
+        while self.bc_requests:
+            interface, data = self.bc_requests.popleft()
+            # If the connection was lost move on
+            if not interface.is_connected():
+                continue
+
+            req_time = data.get('req_time')
+            if not req_time:
+                # No requests sent yet.  This interface has a new height.
+                # Request headers if it is ahead of our blockchain
+                if not self.bc_request_headers(interface, data):
+                    continue
+            elif time.time() - req_time > 10:
+                interface.print_error("blockchain request timed out")
+                interface.stop()
+                continue
+            # Put updated request state back at head of deque
+            self.bc_requests.appendleft((interface, data))
+            break
+
     def run(self):
+        self.blockchain.init()
         while self.is_running():
             self.check_interfaces()
             self.handle_requests()
+            self.handle_bc_requests()
             try:
                 i, response = self.queue.get(timeout=0.1)
             except Queue.Empty:
@@ -508,19 +590,19 @@ class Network(util.DaemonThread):
         self.stop_network()
         self.print_error("stopped")
 
-
     def on_header(self, i, r):
-        result = r.get('result')
-        if not result:
+        header = r.get('result')
+        if not header:
             return
-        height = result.get('block_height')
+        height = header.get('block_height')
         if not height:
             return
         self.heights[i.server] = height
-        self.merkle_roots[i.server] = result.get('merkle_root')
-        self.utxo_roots[i.server] = result.get('utxo_root')
-        # notify blockchain about the new height
-        self.blockchain.queue.put((i,result))
+        self.merkle_roots[i.server] = header.get('merkle_root')
+        self.utxo_roots[i.server] = header.get('utxo_root')
+
+        # Queue this interface's height for asynchronous catch-up
+        self.bc_requests.append((i, {'if_height': height}))
 
         if i == self.interface:
             self.switch_lagging_interface()