plugins/bcli: fake minimum fee if we're in regtest mode.

Saves a great deal of confusion for regtest users.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Changelog-Changed: JSON-RPC: If bitcoind won't give a fee estimate in regtest, use minimum.

plugins/bcli.c

@@ -69,6 +69,14 @@ struct bitcoind {
 
 	/* Percent of CONSERVATIVE/2 feerate we'll use for commitment txs. */
 	u64 commit_fee_percent;
+
+	/* Whether we fake fees (regtest) */
+	bool fake_fees;
+
+#if DEVELOPER
+	/* Override in case we're developer mode for testing*/
+	bool no_fake_fees;
+#endif
 };
 
 static struct bitcoind *bitcoind;
@@ -431,6 +439,11 @@ estimatefees_parse_feerate(struct bitcoin_cli *bcli, u64 *feerate)
 		/* Paranoia: if it had a feerate, but was malformed: */
 		if (json_get_member(bcli->output, tokens, "feerate"))
 			return command_err_bcli_badjson(bcli, "cannot scan");
+		/* Regtest fee estimation is generally awful: Fake it at min. */
+		if (bitcoind->fake_fees) {
+			*feerate = 1000;
+			return NULL;
+		}
 		/* We return null if estimation failed, and bitcoin-cli will
 		 * exit with 0 but no feerate field on failure. */
 		return estimatefees_null_response(bcli);
@@ -874,6 +887,11 @@ static const char *init(struct plugin *p, const char *buffer UNUSED,
 			const jsmntok_t *config UNUSED)
 {
 	wait_and_check_bitcoind(p);
+
+	/* Usually we fake up fees in regtest */
+	if (streq(chainparams->network_name, "regtest"))
+		bitcoind->fake_fees = IFDEV(!bitcoind->no_fake_fees, true);
+
 	plugin_log(p, LOG_INFORM,
 		   "bitcoin-cli initialized and connected to bitcoind.");
 
@@ -938,6 +956,9 @@ static struct bitcoind *new_bitcoind(const tal_t *ctx)
 	bitcoind->rpcport = NULL;
 	bitcoind->max_fee_multiplier = 10;
 	bitcoind->commit_fee_percent = 100;
+#if DEVELOPER
+	bitcoind->no_fake_fees = false;
+#endif
 
 	return bitcoind;
 }
@@ -994,6 +1015,10 @@ int main(int argc, char *argv[])
 				  " closed more often due to fee fluctuations,"
 				  " large values may result in large fees.",
 				  u32_option, &bitcoind->max_fee_multiplier),
+		    plugin_option("dev-no-fake-fees",
+				  "bool",
+				  "Suppress fee faking for regtest",
+				  bool_option, &bitcoind->no_fake_fees),
 #endif /* DEVELOPER */
 		    NULL);
 }

tests/test_connection.py

@@ -2282,7 +2282,7 @@ def test_fundee_forget_funding_tx_unconfirmed(node_factory, bitcoind):
 
 @unittest.skipIf(not DEVELOPER, "needs dev_fail")
 def test_no_fee_estimate(node_factory, bitcoind, executor):
-    l1 = node_factory.get_node(start=False)
+    l1 = node_factory.get_node(start=False, options={'dev-no-fake-fees': True})
 
     # Fail any fee estimation requests until we allow them further down
     l1.daemon.rpcproxy.mock_rpc('estimatesmartfee', {

tests/test_misc.py

@@ -1438,7 +1438,8 @@ def test_ipv4_and_ipv6(node_factory):
     "FEERATE_FLOOR on testnets, and we test the new API."
 )
 def test_feerates(node_factory):
-    l1 = node_factory.get_node(options={'log-level': 'io'}, start=False)
+    l1 = node_factory.get_node(options={'log-level': 'io',
+                                        'dev-no-fake-fees': True}, start=False)
     l1.daemon.rpcproxy.mock_rpc('estimatesmartfee', {
         'error': {"errors": ["Insufficient data or no feerate found"], "blocks": 0}
     })