refactor: utility for estimating maxPriorityFeePerGas via eth_feeHistory

Refactor idea from PR ethereum#2259 into sync and async fee utility methods. Change params passed into eth_feeHistory to values that allowed for better results when we tested locally. Add a min and max to the estimated fee history so that we don't allow unsuspecting users to contribute to fee bloating. Max and min values keep the priority fee within a range that healthy blocks should accept, so these transactions would be accepted when fee prices settle from high-fee periods.

newsfragments/2259.feature.rst

@@ -0,0 +1 @@
+Calculate a default ``maxPriorityFeePerGas`` using ``eth_feeHistory`` when ``eth_maxPriorityFeePerGas`` is not available, since the latter is not a part of the Ethereum JSON-RPC specs and only supported by certain clients.

tests/integration/test_ethereum_tester.py

@@ -7,9 +7,6 @@
 from eth_tester.exceptions import (
     TransactionFailed,
 )
-from eth_typing import (
-    BlockNumber,
-)
 from eth_utils import (
     is_checksum_address,
     is_dict,
@@ -295,12 +292,15 @@ def test_eth_getBlockByHash_pending(
         block = web3.eth.get_block('pending')
         assert block['hash'] is not None
 
+    @pytest.mark.xfail(reason='eth_feeHistory is not implemented on eth-tester')
     def test_eth_fee_history(self, web3: "Web3"):
         super().test_eth_fee_history(web3)
 
+    @pytest.mark.xfail(reason='eth_feeHistory is not implemented on eth-tester')
     def test_eth_fee_history_with_integer(self, web3: "Web3"):
-        super().test_eth_fee_history_with_integer(web3, BlockData(number=BlockNumber(1)))
+        super().test_eth_fee_history_with_integer(web3)
 
+    @pytest.mark.xfail(reason='eth_feeHistory is not implemented on eth-tester')
     def test_eth_fee_history_no_reward_percentiles(self, web3: "Web3"):
         super().test_eth_fee_history_no_reward_percentiles(web3)
 

web3/_utils/fee_utils.py

@@ -0,0 +1,53 @@
+from typing import (
+    TYPE_CHECKING,
+)
+
+from web3.types import (
+    FeeHistory,
+    Wei,
+)
+
+if TYPE_CHECKING:
+    from web3.eth import (
+        AsyncEth,  # noqa: F401
+        Eth,  # noqa: F401
+    )
+
+PRIORITY_FEE_MAX = Wei(1500000000)  # 1.5 gwei
+PRIORITY_FEE_MIN = Wei(1000000000)  # 1 gwei
+
+# 5th percentile fee history from the last 10 blocks
+PRIORITY_FEE_HISTORY_PARAMS = (10, 'pending', [5.0])
+
+
+def _fee_history_priority_fee_estimate(fee_history: FeeHistory) -> Wei:
+    # grab only non-zero fees and average against only that list
+    non_empty_block_fees = [fee[0] for fee in fee_history['reward'] if fee[0] != 0]
+
+    # prevent division by zero in the extremely unlikely case that all fees within the polled fee
+    # history range for the specified percentile are 0
+    divisor = len(non_empty_block_fees) if len(non_empty_block_fees) != 0 else 1
+
+    priority_fee_average_for_percentile = Wei(
+        round(sum(non_empty_block_fees) / divisor)
+    )
+
+    return (  # keep estimated priority fee within a max / min range
+        PRIORITY_FEE_MAX if priority_fee_average_for_percentile > PRIORITY_FEE_MAX else
+        PRIORITY_FEE_MIN if priority_fee_average_for_percentile < PRIORITY_FEE_MIN else
+        priority_fee_average_for_percentile
+    )
+
+
+def fee_history_priority_fee(eth: "Eth") -> Wei:
+    # This is a tested internal call so no need for type hinting. We can keep better consistency
+    # between the sync and async calls by unpacking PRIORITY_FEE_HISTORY_PARAMS as constants here.
+    fee_history = eth.fee_history(*PRIORITY_FEE_HISTORY_PARAMS)  # type: ignore
+    return _fee_history_priority_fee_estimate(fee_history)
+
+
+async def async_fee_history_priority_fee(async_eth: "AsyncEth") -> Wei:
+    # This is a tested internal call so no need for type hinting. We can keep better consistency
+    # between the sync and async calls by unpacking PRIORITY_FEE_HISTORY_PARAMS as constants here.
+    fee_history = await async_eth.fee_history(*PRIORITY_FEE_HISTORY_PARAMS)  # type: ignore
+    return _fee_history_priority_fee_estimate(fee_history)

web3/eth.py

@@ -49,6 +49,10 @@
 from web3._utils.encoding import (
     to_hex,
 )
+from web3._utils.fee_utils import (
+    async_fee_history_priority_fee,
+    fee_history_priority_fee,
+)
 from web3._utils.filters import (
     select_filter_method,
 )
@@ -356,11 +360,18 @@ async def hashrate(self) -> int:
 
     @property
     async def max_priority_fee(self) -> Wei:
-        fee_history = await self.fee_history(20, 'pending', [float(1)])
-        priority_fees_per_gas = fee_history['reward']
-        fees_sum = sum([fee[0] for fee in priority_fees_per_gas])
-        max_priority_fee_estimate = round(fees_sum / len(priority_fees_per_gas))
-        return Wei(max_priority_fee_estimate)
+        """
+        Try to use eth_maxPriorityFeePerGas but, since this is not part of the spec and is only
+        supported by some clients, fall back to an eth_feeHistory calculation with min and max caps.
+        """
+        try:
+            return await self._max_priority_fee()  # type: ignore
+        except ValueError:
+            warnings.warn(
+                "There was an issue with the method eth_maxPriorityFeePerGas. Calculating using "
+                "eth_feeHistory."
+            )
+            return await async_fee_history_priority_fee(self)
 
     @property
     async def mining(self) -> bool:
@@ -608,11 +619,18 @@ def chainId(self) -> int:
 
     @property
     def max_priority_fee(self) -> Wei:
-        fee_history = self.fee_history(20, 'pending', [float(1)])
-        priority_fees_per_gas = fee_history['reward']
-        fees_sum = sum([fee[0] for fee in priority_fees_per_gas])
-        max_priority_fee_estimate = round(fees_sum / len(priority_fees_per_gas))
-        return Wei(max_priority_fee_estimate)
+        """
+        Try to use eth_maxPriorityFeePerGas but, since this is not part of the spec and is only
+        supported by some clients, fall back to an eth_feeHistory calculation with min and max caps.
+        """
+        try:
+            return self._max_priority_fee()
+        except ValueError:
+            warnings.warn(
+                "There was an issue with the method eth_maxPriorityFeePerGas. Calculating using "
+                "eth_feeHistory."
+            )
+            return fee_history_priority_fee(self)
 
     def get_storage_at_munger(
         self,

web3/providers/eth_tester/defaults.py

@@ -213,12 +213,7 @@ def personal_send_transaction(eth_tester: "EthereumTester", params: Any) -> HexS
         'mining': static_return(False),
         'hashrate': static_return(0),
         'chainId': static_return('0x3d'),
-        'feeHistory': static_return(
-            {'baseFeePerGas': [134919017071, 134775902021, 117928914269],
-             'gasUsedRatio': [0.4957570088140204, 0.0],
-             'oldestBlock': 13865084,
-             'reward': [[2500000000], [1500000000]]}
-        ),
+        'feeHistory': not_implemented,
         'maxPriorityFeePerGas': static_return(10 ** 9),
         'gasPrice': static_return(10 ** 9),  # must be >= base fee post-London
         'accounts': call_eth_tester('get_accounts'),