Async call semaphore

multicall/call.py

@@ -7,7 +7,7 @@
 from web3 import Web3
 
 from multicall import Signature
-from multicall.constants import Network, w3
+from multicall.constants import Network, w3, ASYNC_SEMAPHORE
 from multicall.exceptions import StateOverrideNotSupported
 from multicall.loggers import setup_logger
 from multicall.utils import (chain_id, get_async_w3, run_in_subprocess,
@@ -100,6 +100,9 @@ def __call__(self, args: Optional[Any] = None, _w3: Optional[Web3] = None) -> An
             self.signature,
             self.returns,
         )
+
+    async def __await__(self) -> Any:
+        return await self.coroutine()
 
     @eth_retry.auto_retry
     async def coroutine(self, args: Optional[Any] = None, _w3: Optional[Web3] = None) -> Any:
@@ -108,17 +111,18 @@ async def coroutine(self, args: Optional[Any] = None, _w3: Optional[Web3] = None
         if self.state_override_code and not state_override_supported(_w3):
             raise StateOverrideNotSupported(f'State override is not supported on {Network(chain_id(_w3)).__repr__()[1:-1]}.')
 
-        args = await run_in_subprocess(
-            prep_args,
-            self.target,
-            self.signature,
-            args or self.args,
-            self.block_id,
-            self.gas_limit,
-            self.state_override_code,
-        )
-
-        output = await get_async_w3(_w3).eth.call(*args)
+        async with ASYNC_SEMAPHORE:
+            output = await get_async_w3(_w3).eth.call(
+                *await run_in_subprocess(
+                    prep_args,
+                    self.target,
+                    self.signature,
+                    args or self.args,
+                    self.block_id,
+                    self.gas_limit,
+                    self.state_override_code,
+                )
+            )
 
         return await run_in_subprocess(Call.decode_output, output, self.signature, self.returns)
 

multicall/constants.py

@@ -1,3 +1,4 @@
+import asyncio
 import os
 from enum import IntEnum
 from typing import Dict
@@ -176,3 +177,7 @@ class Network(IntEnum):
 NUM_PROCESSES = min(user_choice, parallelism_capacity)
 
 NO_STATE_OVERRIDE = [ Network.Gnosis, Network.Harmony, Network.Moonbeam, Network.Moonriver, Network.Kovan, Network.Fuse ]
+
+# NOTE: If we run too many async calls at once, we'll have memory issues.
+#       Feel free to increase this with the "MULTICALL_CALL_SEMAPHORE" env var if you know what you're doing.
+ASYNC_SEMAPHORE = asyncio.Semaphore(int(os.environ.get("MULTICALL_CALL_SEMAPHORE", 1000)))

multicall/multicall.py

@@ -7,8 +7,9 @@
 from web3 import Web3
 
 from multicall import Call
-from multicall.constants import (GAS_LIMIT, MULTICALL2_ADDRESSES, MULTICALL2_BYTECODE,
-                                 MULTICALL3_BYTECODE, MULTICALL3_ADDRESSES, w3)
+from multicall.constants import (ASYNC_SEMAPHORE, GAS_LIMIT,
+                                 MULTICALL2_ADDRESSES, MULTICALL3_ADDRESSES,
+                                 MULTICALL3_BYTECODE, w3)
 from multicall.loggers import setup_logger
 from multicall.utils import (await_awaitable, chain_id, gather,
                              run_in_subprocess, state_override_supported)
@@ -54,9 +55,12 @@ def __init__(
 
     def __call__(self) -> Dict[str,Any]:
         start = time()
-        response = await_awaitable(self.coroutine())
+        response = await_awaitable(self)
         logger.debug(f"Multicall took {time() - start}s")
         return response
+
+    async def __await__(self) -> Dict[str,Any]:
+        return await self.coroutine()
 
     async def coroutine(self) -> Dict[str,Any]:
         batches = await gather([
@@ -77,21 +81,22 @@ async def fetch_outputs(self, calls: List[Call], ConnErr_retries: int = 0, id: s
         if calls is None:
             calls = self.calls
 
-        try:
-            args = await run_in_subprocess(get_args, calls, self.require_success)
-            if self.require_success is True:
-                _, outputs = await self.aggregate.coroutine(args)
-                outputs = await run_in_subprocess(unpack_aggregate_outputs, outputs)
-            else:
-                _, _, outputs = await self.aggregate.coroutine(args)
-            outputs = await gather([
-                run_in_subprocess(Call.decode_output, output, call.signature, call.returns, success)
-                for call, (success, output) in zip(calls, outputs)
-            ])
-            logger.debug(f"coroutine {id} finished")
-            return outputs
-        except Exception as e:
-            _raise_or_proceed(e, len(calls), ConnErr_retries=ConnErr_retries)
+        async with ASYNC_SEMAPHORE:
+            try:
+                args = await run_in_subprocess(get_args, calls, self.require_success)
+                if self.require_success is True:
+                    _, outputs = await self.aggregate.coroutine(args)
+                    outputs = await run_in_subprocess(unpack_aggregate_outputs, outputs)
+                else:
+                    _, _, outputs = await self.aggregate.coroutine(args)
+                outputs = await gather([
+                    run_in_subprocess(Call.decode_output, output, call.signature, call.returns, success)
+                    for call, (success, output) in zip(calls, outputs)
+                ])
+                logger.debug(f"coroutine {id} finished")
+                return outputs
+            except Exception as e:
+                _raise_or_proceed(e, len(calls), ConnErr_retries=ConnErr_retries)
 
         # Failed, we need to rebatch the calls and try again.
         batch_results = await gather([

multicall/signature.py

@@ -1,3 +1,4 @@
+from functools import lru_cache
 from typing import Any, List, Optional, Tuple
 
 # For eth_abi versions < 2.2.0, `decode` and `encode` have not yet been added.
@@ -11,6 +12,8 @@
 from eth_utils import function_signature_to_4byte_selector
 
 
+get_4byte_selector = lru_cache(maxsize=None)(function_signature_to_4byte_selector)
+
 def parse_signature(signature: str) -> Tuple[str, List[TypeStr], List[TypeStr]]:
     """
     Breaks 'func(address)(uint256)' into ['func', ['address'], ['uint256']]
@@ -58,7 +61,10 @@ class Signature:
     def __init__(self, signature: str) -> None:
         self.signature = signature
         self.function, self.input_types, self.output_types = parse_signature(signature)
-        self.fourbyte = function_signature_to_4byte_selector(self.function)
+
+    @property
+    def fourbyte(self) -> bytes:
+        return get_4byte_selector(self.function)
 
     def encode_data(self, args: Optional[Any] = None) -> bytes:
         return self.fourbyte + encode(self.input_types, args) if args else self.fourbyte

tests/test_call.py

@@ -29,7 +29,7 @@ def test_call_with_predefined_args():
 
 def test_call_async():
     call = Call(CHAI, 'name()(string)', [['name', None]])
-    assert await_awaitable(call.coroutine()) == {'name': 'Chai'}
+    assert await_awaitable(call) == {'name': 'Chai'}
 
 
 def test_call_with_args_async():
@@ -39,7 +39,7 @@ def test_call_with_args_async():
 
 def test_call_with_predefined_args_async():
     call = Call(CHAI, ['balanceOf(address)(uint256)', CHAI], [['balance', from_wei]])
-    assert isinstance(await_awaitable(call.coroutine())['balance'], float)
+    assert isinstance(await_awaitable(call)['balance'], float)
 
 
 def test_call_threading():

tests/test_multicall.py

@@ -56,7 +56,7 @@ def test_multicall_async():
         Call(CHAI, 'totalSupply()(uint256)', [['supply', from_wei]]),
         Call(CHAI, ['balanceOf(address)(uint256)', CHAI], [['balance', from_ray]]),
     ])
-    result = await_awaitable(multi.coroutine())
+    result = await_awaitable(multi)
     print(result)
     assert isinstance(result['supply'], float)
     assert isinstance(result['balance'], float)
@@ -69,7 +69,7 @@ def test_multicall_no_success_async():
         ],
         require_success=False
     )
-    result = await_awaitable(multi.coroutine())
+    result = await_awaitable(multi)
     print(result)
     assert isinstance(result['success'], tuple)
     assert isinstance(result['balance'], tuple)