Bugfix: QA: Ensure mempool_fee_histogram can adapt to feerate rounding correctly

Caution: This implementation is for a post-bitcoin#22949 codebase

Author: luke-jr

test/functional/mempool_fee_histogram.py

@@ -7,13 +7,28 @@
 from decimal import Decimal
 
 from test_framework.blocktools import COINBASE_MATURITY
+from test_framework.messages import (
+    COIN,
+)
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.util import (
     assert_equal,
     assert_greater_than,
     assert_greater_than_or_equal,
+    ceildiv,
 )
 
+def get_actual_fee_rate(fee_in_satoshis, vsize):
+    fee_rate = ceildiv(fee_in_satoshis, vsize)
+    return str(fee_rate)
+
+def get_tx_details(node, txid):
+    info = node.gettransaction(txid=txid)
+    info.update(node.getrawtransaction(txid=txid, verbose=True))
+    info['fee'] = int(-info['fee'] * COIN)  # convert to satoshis
+    info['feerate'] = get_actual_fee_rate(info['fee'], info['vsize'])
+    return info
+
 class MempoolFeeHistogramTest(BitcoinTestFramework):
     def add_options(self, parser):
         self.add_wallet_options(parser)
@@ -57,14 +72,15 @@ def run_test(self):
         node.lockunspent(False, [{"txid": utxos[1]["txid"], "vout": utxos[1]["vout"]}])
 
         self.log.info("Send tx1 transaction with 5 sat/vB fee rate")
-        node.sendtoaddress(address=node.getnewaddress(), amount=Decimal("50.0"), fee_rate=5, subtractfeefromamount=True)
+        tx1_txid = node.sendtoaddress(address=node.getnewaddress(), amount=Decimal("50.0"), fee_rate=5, subtractfeefromamount=True)
+        tx1_info = get_tx_details(node, tx1_txid)
 
-        self.log.info("Test fee rate histogram when mempool contains 1 transaction (tx1: 5 sat/vB)")
+        self.log.info(f"Test fee rate histogram when mempool contains 1 transaction (tx1: {tx1_info['feerate']} sat/vB)")
         info = node.getmempoolinfo([1, 3, 5, 10])
         (non_empty_groups, empty_groups, total_fees) = self.histogram_stats(info['fee_histogram'])
         assert_equal(1, non_empty_groups)
         assert_equal(3, empty_groups)
-        assert_equal(1, info['fee_histogram']['fee_rate_groups']['5']['count'])
+        assert_equal(1, info['fee_histogram']['fee_rate_groups'][tx1_info['feerate']]['count'])
         assert_equal(total_fees, info['fee_histogram']['total_fees'])
 
         assert_equal(0, info['fee_histogram']['fee_rate_groups']['1']['size'])
@@ -88,54 +104,57 @@ def run_test(self):
         assert_equal(10, info['fee_histogram']['fee_rate_groups']['10']['from'])
 
         self.log.info("Send tx2 transaction with 14 sat/vB fee rate (spends tx1 UTXO)")
-        node.sendtoaddress(address=node.getnewaddress(), amount=Decimal("25.0"), fee_rate=14, subtractfeefromamount=True)
+        tx2_txid = node.sendtoaddress(address=node.getnewaddress(), amount=Decimal("25.0"), fee_rate=14, subtractfeefromamount=True)
+        tx2_info = get_tx_details(node, tx2_txid)
 
-        self.log.info("Test fee rate histogram when mempool contains 2 transactions (tx1: 5 sat/vB, tx2: 14 sat/vB)")
+        self.log.info(f"Test fee rate histogram when mempool contains 2 transactions (tx1: {tx1_info['feerate']} sat/vB, tx2: {tx2_info['feerate']} sat/vB)")
         info = node.getmempoolinfo([1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15])
 
-        # Verify that both tx1 and tx2 are reported in 8 sat/vB fee rate group
+        # Verify that both tx1 and tx2 are reported in 9 sat/vB fee rate group
         (non_empty_groups, empty_groups, total_fees) = self.histogram_stats(info['fee_histogram'])
+        tx1p2_feerate = get_actual_fee_rate(tx1_info['fee'] + tx2_info['fee'], tx1_info['vsize'] + tx2_info['vsize'])
         assert_equal(1, non_empty_groups)
         assert_equal(14, empty_groups)
-        assert_equal(2, info['fee_histogram']['fee_rate_groups']['8']['count'])
+        assert_equal(2, info['fee_histogram']['fee_rate_groups'][tx1p2_feerate]['count'])
         assert_equal(total_fees, info['fee_histogram']['total_fees'])
 
         # Unlock the second UTXO which we locked
         node.lockunspent(True, [{"txid": utxos[1]["txid"], "vout": utxos[1]["vout"]}])
 
         self.log.info("Send tx3 transaction with 6 sat/vB fee rate (spends all available UTXOs)")
-        node.sendtoaddress(address=node.getnewaddress(), amount=Decimal("99.9"), fee_rate=6, subtractfeefromamount=True)
+        tx3_txid = node.sendtoaddress(address=node.getnewaddress(), amount=Decimal("99.9"), fee_rate=6, subtractfeefromamount=True)
+        tx3_info = get_tx_details(node, tx3_txid)
 
-        self.log.info("Test fee rate histogram when mempool contains 3 transactions (tx1: 5 sat/vB, tx2: 14 sat/vB, tx3: 6 sat/vB)")
+        self.log.info(f"Test fee rate histogram when mempool contains 3 transactions (tx1: {tx1_info['feerate']} sat/vB, tx2: {tx2_info['feerate']} sat/vB, tx3: {tx3_info['feerate']} sat/vB)")
         info = node.getmempoolinfo([1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15])
 
-        # Verify that each of 6, 7 and 8 sat/vB fee rate groups contain one transaction
-        (non_empty_groups, empty_groups, total_fees) = self.histogram_stats(info['fee_histogram'])
-        assert_equal(3, non_empty_groups)
-        assert_equal(12, empty_groups)
-
-        for i in ['1', '2', '3', '4', '5', '9', '10', '11', '12', '13', '14', '15']:
-            assert_equal(0, info['fee_histogram']['fee_rate_groups'][i]['size'])
-            assert_equal(0, info['fee_histogram']['fee_rate_groups'][i]['count'])
-            assert_equal(0, info['fee_histogram']['fee_rate_groups'][i]['fees'])
-            assert_equal(int(i), info['fee_histogram']['fee_rate_groups'][i]['from'])
-
-        assert_equal(188, info['fee_histogram']['fee_rate_groups']['6']['size'])
-        assert_equal(1, info['fee_histogram']['fee_rate_groups']['6']['count'])
-        assert_equal(940, info['fee_histogram']['fee_rate_groups']['6']['fees'])
-        assert_equal(5, info['fee_histogram']['fee_rate_groups']['6']['from'])
-
-        assert_equal(356, info['fee_histogram']['fee_rate_groups']['7']['size'])
-        assert_equal(1, info['fee_histogram']['fee_rate_groups']['7']['count'])
-        assert_equal(2136, info['fee_histogram']['fee_rate_groups']['7']['fees'])
-        assert_equal(6, info['fee_histogram']['fee_rate_groups']['7']['from'])
-
-        assert_equal(141, info['fee_histogram']['fee_rate_groups']['8']['size'])
-        assert_equal(1, info['fee_histogram']['fee_rate_groups']['8']['count'])
-        assert_equal(1974, info['fee_histogram']['fee_rate_groups']['8']['fees'])
-        assert_equal(14, info['fee_histogram']['fee_rate_groups']['8']['from'])
-
-        assert_equal(total_fees, info['fee_histogram']['total_fees'])
+        # Verify that each of 6, 8 and 9 sat/vB fee rate groups contain one transaction
+        # tx1 should be grouped with tx2 + tx3 (descendants)
+        # tx2 should be grouped with tx1 (ancestors only)
+        # tx3 should be alone
+        expected_histogram = {
+            'fee_rate_groups': dict( (
+                (str(n), {
+                    'from': n,
+                    'count': 0,
+                    'fees': 0,
+                    'size': 0,
+                }) for n in range(1, 16)
+            ) ),
+            'total_fees': tx1_info['fee'] + tx2_info['fee'] + tx3_info['fee'],
+        }
+        expected_frg = expected_histogram['fee_rate_groups']
+        tx1p2p3_feerate = get_actual_fee_rate(expected_histogram['total_fees'], tx1_info['vsize'] + tx2_info['vsize'] + tx3_info['vsize'])
+        def inc_expected(feerate, txinfo):
+            this_frg = expected_frg[feerate]
+            this_frg['count'] += 1
+            this_frg['fees'] += txinfo['fee']
+            this_frg['size'] += txinfo['vsize']
+        inc_expected(tx1p2p3_feerate, tx1_info)
+        inc_expected(tx1p2_feerate, tx2_info)
+        inc_expected(tx3_info['feerate'], tx3_info)
+
+        assert_equal(expected_histogram, info['fee_histogram'])
 
     def histogram_stats(self, histogram):
         total_fees = 0