Add synced_to_chain to the onchain matcher

Add synced_to_chain as a criterion to the onchain matcher.
synced_to_chain becomes false if LND is not synced to the
chain for more than 5 minutes. In the past, this was an
indicator of a severe issue that required a hotfix for lnd.

README.md

@@ -198,6 +198,7 @@ Currently available properties:
 | **onchain.conf_target** | defines the confirmation target that is used for the determination of the onchain fee rate (default: 6)|# blocks|
 | **onchain.min_fee_rate** | match on the onchain fee rate|# sat per vbyte|
 | **onchain.max_fee_rate** |  match on the onchain fee rate|# sat per vbyte|
+| **onchain.synced_to_chain** |  match on the synced to chain. False if lnd is not synced to chain for 5 minutes.|true\|false|
 
 
 File references should contain 1 item per line

charge_lnd/lnd.py

@@ -35,6 +35,7 @@ def __init__(self, lnd_dir, server, tls_cert_path=None, macaroon_path=None):
         self.graph = None
         self.info = None
         self.version = None
+        self.synced_to_chain = None
         self.channels = None
         self.node_info = {}
         self.chan_info = {}
@@ -68,6 +69,19 @@ def get_info(self):
 
     def supports_inbound_fees(self):
         return self.min_version(0, 18)
+
+    def get_synced_to_chain(self):
+        # It can happen that lnd is not synced to the chain for a few seconds, typically 
+        # after a new block has been found or after a restart of lnd. If lnd is still
+        # not synced to the chain after 5 minutes, we set the parameter to false.        
+        if self.synced_to_chain is None:
+            self.synced_to_chain = False
+            for _ in range(300):
+                if self.lnstub.GetInfo(ln.GetInfoRequest()).synced_to_chain:
+                    self.synced_to_chain = True
+                    break
+                time.sleep(1)
+        return self.synced_to_chain
 
     def get_feereport(self):
         feereport = self.lnstub.FeeReport(ln.FeeReportRequest())

charge_lnd/policy.py

@@ -382,12 +382,16 @@ def match_by_chan(self, channel, config):
         return True
 
     def match_by_onchain(self, channel, config):
-        accepted = ['min_fee_rate', 'max_fee_rate', 'conf_target']
+        accepted = ['min_fee_rate', 'max_fee_rate', 
+                    'conf_target', 'synced_to_chain']
 
         for key in config.keys():
             if key.split(".")[0] == 'onchain' and key.split(".")[1] not in accepted:
                 raise Exception("Unknown property '%s'" % key)
 
+        if 'onchain.synced_to_chain' in config and not config.getboolean('onchain.synced_to_chain') == self.lnd.get_synced_to_chain():
+            return False
+
         fee_rate = self.lnd.get_fee_estimate(config.getint('onchain.conf_target', DEFAULT_CONF_TARGET))
 
         if 'onchain.max_fee_rate' in config and not config.getfloat('onchain.max_fee_rate') >= fee_rate:

examples/complex-ruleset.config

@@ -21,6 +21,13 @@ base_fee_msat = 0
 onchan.min_fee_rate = 500
 base_fee_msat = 5_000
 
+[lost-onchain-sync]
+# The fact that lnd was not synchronized with the chain for more than 5 minutes
+# was an indicator of a severe problem in the past.
+onchain.synced_to_chain = false
+base_fee_msat = 210_000
+fee_ppm = 210_000
+
 [ignored_channels]
 # don't let charge-lnd set fees (strategy=ignore) for channels to/from the specified nodes
 node.id = 02da8d5a759ee9e4438da617cfdb61c87f723fb76c4b6371b877d0347abe953a4f,