Daemon's send takes a processor

Simplest way to process the result and still be able to raise exceptions
in the daemon request loop.  In particular, we can pass missing txs through
as None in getrawtransactions.

Fixes #9

server/daemon.py

@@ -45,83 +45,84 @@ class Daemon(util.LoggedClass):
                              .format(height))
             self._height = height
 
-    async def _post(self, data):
-        '''Send data to the daemon and handle the response.'''
-        async with self.workqueue_semaphore:
-            async with aiohttp.post(self.url, data=data) as resp:
-                result = await resp.json()
-
-        if isinstance(result, list):
-            errs = [item['error'] for item in result]
-            if not any(errs):
-                return [item['result'] for item in result]
-            if any(err.get('code') == self.WARMING_UP for err in errs if err):
-                raise DaemonWarmingUpError
-            raise DaemonError(errs)
-        else:
-            err = result['error']
-            if not err:
-                return result['result']
-            if err.get('code') == self.WARMING_UP:
-                raise DaemonWarmingUpError
-            raise DaemonError(err)
-
-    async def _send(self, payload):
+    async def _send(self, payload, processor):
         '''Send a payload to be converted to JSON.
 
         Handles temporary connection issues.  Daemon reponse errors
         are raise through DaemonError.
         '''
-        secs = 1
         prior_msg = None
-        skip_count = 10
+        skip_count = None
 
-        async def sleep(msg, *, skip_once=False):
-            skip_count -= 1
-            if skip_once and msg != prior_msg:
+        def log_error(msg, skip_once=False):
+            if skip_once and skip_count is None:
                 skip_count = 1
-            elif msg != prior_msg or skip_count == 0:
+            if msg != prior_msg or skip_count == 0:
+                skip_count = 10
+                prior_msg = msg
                 self.logger.error('{}.  Retrying between sleeps...'
                                   .format(msg))
-                skip_count = 10
-            prior_msg = msg
-            await asyncio.sleep(secs)
-            secs = min(16, secs * 2)
+            skip_count -= 1
 
         data = json.dumps(payload)
+        secs = 1
         while True:
             try:
-                result = await self._post(data)
-                if prior_msg:
-                    self.logger.info('connection successfully restored')
-                return result
+                async with self.workqueue_semaphore:
+                    async with aiohttp.post(self.url, data=data) as resp:
+                        result = processor(await resp.json())
+                        if prior_msg:
+                            self.logger.info('connection restored')
+                        return result
             except (asyncio.CancelledError, DaemonError):
                 raise
             except asyncio.TimeoutError:
-                sleep('timeout error', skip_once=True)
+                log_error('timeout error', skip_once=True)
             except aiohttp.ClientHttpProcessingError:
-                sleep('HTTP error', skip_once=True)
+                log_error('HTTP error', skip_once=True)
             except aiohttp.ServerDisconnectedError:
-                sleep('disconnected', skip_once=True)
+                log_error('disconnected', skip_once=True)
             except aiohttp.ClientConnectionError:
-                sleep('connection problem - is your daemon running?')
+                log_error('connection problem - is your daemon running?')
             except DaemonWarmingUpError:
-                sleep('still starting up checking blocks...')
+                log_error('still starting up checking blocks...')
             except Exception as e:
-                sleep('request gave unexpected error: {}'.format(e))
+                log_error('request gave unexpected error: {}'.format(e))
+            await asyncio.sleep(secs)
+            secs = min(16, secs * 2)
 
     async def _send_single(self, method, params=None):
         '''Send a single request to the daemon.'''
+        def processor(result):
+            err = result['error']
+            if not err:
+                return result['result']
+            if err.get('code') == self.WARMING_UP:
+                raise DaemonWarmingUpError
+            raise DaemonError(err)
+
         payload = {'method': method}
         if params:
             payload['params'] = params
-        return await self._send(payload)
+        return await self._send(payload, processor)
+
+    async def _send_vector(self, method, params_iterable, replace_errs=False):
+        '''Send several requests of the same method.
+
+        The result will be an array of the same length as params_iterable.
+        If replace_errs is true, any item with an error is returned as None,
+        othewise an exception is raised.'''
+        def processor(result):
+            errs = [item['error'] for item in result if item['error']]
+            if not errs or replace_errs:
+                return [item['result'] for item in result]
+            if any(err.get('code') == self.WARMING_UP for err in errs):
+                raise DaemonWarmingUpError
+            raise DaemonError(errs)
 
-    async def _send_vector(self, method, params_iterable):
-        '''Send several requests of the same method.'''
         payload = [{'method': method, 'params': p} for p in params_iterable]
         if payload:
-            return await self._send(payload)
+            return await self._send(payload, processor)
         return []
 
     async def block_hex_hashes(self, first, count):
@@ -156,14 +157,15 @@ class Daemon(util.LoggedClass):
         '''Return the serialized raw transaction with the given hash.'''
         return await self._send_single('getrawtransaction', (hex_hash, 0))
 
-    async def getrawtransactions(self, hex_hashes):
+    async def getrawtransactions(self, hex_hashes, replace_errs=True):
         '''Return the serialized raw transactions with the given hashes.
 
-        Breaks large requests up.  Yields after each sub request.'''
+        Replaces errors with None by default.'''
         params_iterable = ((hex_hash, 0) for hex_hash in hex_hashes)
-        txs = await self._send_vector('getrawtransaction', params_iterable)
+        txs = await self._send_vector('getrawtransaction', params_iterable,
+                                      replace_errs=replace_errs)
         # Convert hex strings to bytes
-        return [bytes.fromhex(tx) for tx in txs]
+        return [bytes.fromhex(tx) if tx else None for tx in txs]
 
     async def sendrawtransaction(self, params):
         '''Broadcast a transaction to the network.'''