fix: refactor fee estimation

plugins/aea-ledger-ethereum/aea_ledger_ethereum/ethereum.py

@@ -84,6 +84,8 @@
 POLYGON_GAS_ENDPOINT = "https://gasstation-mainnet.matic.network/v2"
 MAX_GAS_FAST = 1500
 RPC_CALL_MAX_WORKERS = 1
+N_RETRIES = 3
+PERCENTILE_INCREASE = 5
 
 # How many blocks to consider for priority fee estimation
 FEE_HISTORY_BLOCKS = 10
@@ -174,16 +176,26 @@ def estimate_priority_fee(
     if default_priority_fee is not None:
         return default_priority_fee
 
-    fee_history = web3_object.eth.fee_history(
-        fee_history_blocks, block_number, [fee_history_percentile]  # type: ignore
-    )
+    for _ in range(N_RETRIES):
+        fee_history = web3_object.eth.fee_history(
+            fee_history_blocks, block_number, [fee_history_percentile]  # type: ignore
+        )
+
+        # This is going to break if more percentiles are introduced in the future,
+        # i.e., `fee_history_percentile` param becomes a `List[int]`.
+        rewards = sorted(
+            [reward[0] for reward in fee_history.get("reward", []) if reward[0] > 0]
+        )
 
-    # This is going to break if more percentiles are introduced in the future,
-    # i.e., `fee_history_percentile` param becomes a `List[int]`.
-    rewards = sorted(
-        [reward[0] for reward in fee_history.get("reward", []) if reward[0] > 0]
-    )
-    if len(rewards) == 0:
+        # we need atleast 2 rewards to proceed further
+        if len(rewards) >= 2:
+            break
+
+        # Increment percentile for next attempt
+        fee_history_percentile = min(100, fee_history_percentile + PERCENTILE_INCREASE)
+
+    # Return None if fewer than 2 rewards after retries
+    if len(rewards) < 2:
         return None
 
     # Calculate percentage increases from between ordered list of fees