synchronizer/verifier: ensure fairness between wallets (follow-up)

follow-up to 4346d2fc76

It's not just about the Synchronizer, the Verifier should not starve other jobs either...
(previously I thought the Verifier is not too important as it only makes
requests if there are new txs; however with LNWatcher its progress is not persisted)

electrum/lnverifier.py

@@ -110,8 +110,9 @@ class LNChannelVerifier(NetworkJobOnDefaultServer):
         # we are verifying channel announcements as they are from untrusted ln peers.
         # we use electrum servers to do this. however we don't trust electrum servers either...
         try:
-            result = await self.network.get_txid_from_txpos(
-                block_height, short_channel_id.txpos, True)
+            async with self._network_request_semaphore:
+                result = await self.network.get_txid_from_txpos(
+                    block_height, short_channel_id.txpos, True)
         except aiorpcx.jsonrpc.RPCError:
             # the electrum server is complaining about the txpos for given block.
             # it is not clear what to do now, but let's believe the server.
@@ -128,7 +129,8 @@ class LNChannelVerifier(NetworkJobOnDefaultServer):
             # the electrum server sent an incorrect proof. blame is on server, not the ln peer
             raise GracefulDisconnect(e) from e
         try:
-            raw_tx = await self.network.get_transaction(tx_hash)
+            async with self._network_request_semaphore:
+                raw_tx = await self.network.get_transaction(tx_hash)
         except aiorpcx.jsonrpc.RPCError as e:
             # the electrum server can't find the tx; but it was the
             # one who told us about the txid!! blame is on server

electrum/synchronizer.py

@@ -61,9 +61,6 @@ class SynchronizerBase(NetworkJobOnDefaultServer):
     def __init__(self, network: 'Network'):
         self.asyncio_loop = network.asyncio_loop
         self._reset_request_counters()
-        # Ensure fairness between Synchronizers. e.g. if multiple wallets
-        # are open, a large wallet should not starve the small wallets:
-        self._network_request_semaphore = asyncio.Semaphore(100)
 
         NetworkJobOnDefaultServer.__init__(self, network)
 

electrum/util.py

@@ -1171,6 +1171,10 @@ class NetworkJobOnDefaultServer(Logger):
         self.network = network
         self.interface = None  # type: Interface
         self._restart_lock = asyncio.Lock()
+        # Ensure fairness between NetworkJobs. e.g. if multiple wallets
+        # are open, a large wallet's Synchronizer should not starve the small wallets:
+        self._network_request_semaphore = asyncio.Semaphore(100)
+
         self._reset()
         asyncio.run_coroutine_threadsafe(self._restart(), network.asyncio_loop)
         register_callback(self._restart, ['default_server_changed'])

electrum/verifier.py

@@ -96,7 +96,8 @@ class SPV(NetworkJobOnDefaultServer):
 
     async def _request_and_verify_single_proof(self, tx_hash, tx_height):
         try:
-            merkle = await self.network.get_merkle_for_transaction(tx_hash, tx_height)
+            async with self._network_request_semaphore:
+                merkle = await self.network.get_merkle_for_transaction(tx_hash, tx_height)
         except UntrustedServerReturnedError as e:
             if not isinstance(e.original_exception, aiorpcx.jsonrpc.RPCError):
                 raise