Batch requests crash when an empty batch is requested against some Ethereum clients like Erigon

[soyccan]

What happened?

A batch request to an Ethereum RPC endpoint is responded with an array containing the responses to each request in the batch:

curl http://localhost:8545 -H "Content-Type: application/json" --data '[{"jsonrpc":"2.0", "id": 1, "method": "eth_blockNumber", "params": []}]'

[{"jsonrpc":"2.0","id":1,"result":"0x1410bb2"}]

So Web3.py assumes the response is an array while parsing it:

web3.py/web3/providers/rpc/rpc.py

Lines 187 to 188 in 3c412f8

	responses_list = cast(List[RPCResponse], self.decode_rpc_response(raw_response))
	return sort_batch_response_by_response_ids(responses_list)

However, when an empty batch is executed, some RPC endpoint (mine is Erigon) returns an object specifying the error instead of an array. This breaks the parsing and result in error: AttributeError: 'str' object has no attribute 'get'

curl http://localhost:8545 -H "Content-Type: application/json" --data '[]'

{"jsonrpc":"2.0","id":null,"error":{"code":-32600,"message":"empty batch"}}

The same happens when the batch size exceeds the limit:

{"jsonrpc":"2.0","id":null,"error":{"code":-32000,"message":"batch limit 100 exceeded (can increase by --rpc.batch.limit). Requested batch of size: 526"}}

Code that produced the error

from web3 import Web3, HTTPProvider
w3 = Web3(HTTPProvider("http://localhost:8545"))
with w3.batch_requests() as batch:
    batch.execute()

Full error output

AttributeError                            Traceback (most recent call last)
Cell In[222], line 5
      3 with w3.batch_requests() as batch:
----> 4     batch.execute()

File ~/.cache/pypoetry/virtualenvs/etherspect-dagster-jFkAMd9f-py3.12/lib/python3.12/site-packages/web3/_utils/batching.py:147, in RequestBatcher.execute(self)
    145 def execute(self) -> List["RPCResponse"]:
    146     self._validate_is_batching()
--> 147     responses = self.web3.manager._make_batch_request(self._requests_info)
    148     self._end_batching()
    149     return responses

File ~/.cache/pypoetry/virtualenvs/etherspect-dagster-jFkAMd9f-py3.12/lib/python3.12/site-packages/web3/manager.py:430, in RequestManager._make_batch_request(self, requests_info)
    426 provider = cast(JSONBaseProvider, self.provider)
    427 request_func = provider.batch_request_func(
    428     cast("Web3", self.w3), cast("MiddlewareOnion", self.middleware_onion)
    429 )
--> 430 responses = request_func(
    431     [
    432         (method, params)
    433         for (method, params), _response_formatters in requests_info
    434     ]
    435 )
    436 formatted_responses = [
    437     self._format_batched_response(info, resp)
    438     for info, resp in zip(requests_info, responses)
    439 ]
    440 return list(formatted_responses)

File ~/.cache/pypoetry/virtualenvs/etherspect-dagster-jFkAMd9f-py3.12/lib/python3.12/site-packages/web3/middleware/base.py:70, in Web3Middleware.wrap_make_batch_request.<locals>.middleware(requests_info)
     63 def middleware(
     64     requests_info: List[Tuple["RPCEndpoint", Any]]
     65 ) -> List["RPCResponse"]:
     66     req_processed = [
     67         self.request_processor(method, params)
     68         for (method, params) in requests_info
     69     ]
---> 70     responses = make_batch_request(req_processed)
     71     methods, _params = zip(*req_processed)
     72     formatted_responses = [
     73         self.response_processor(m, r) for m, r in zip(methods, responses)
     74     ]

File ~/.cache/pypoetry/virtualenvs/etherspect-dagster-jFkAMd9f-py3.12/lib/python3.12/site-packages/web3/middleware/base.py:70, in Web3Middleware.wrap_make_batch_request.<locals>.middleware(requests_info)
     63 def middleware(
     64     requests_info: List[Tuple["RPCEndpoint", Any]]
     65 ) -> List["RPCResponse"]:
     66     req_processed = [
     67         self.request_processor(method, params)
     68         for (method, params) in requests_info
     69     ]
---> 70     responses = make_batch_request(req_processed)
     71     methods, _params = zip(*req_processed)
     72     formatted_responses = [
     73         self.response_processor(m, r) for m, r in zip(methods, responses)
     74     ]

    [... skipping similar frames: Web3Middleware.wrap_make_batch_request.<locals>.middleware at line 70 (2 times)]

File ~/.cache/pypoetry/virtualenvs/etherspect-dagster-jFkAMd9f-py3.12/lib/python3.12/site-packages/web3/middleware/base.py:70, in Web3Middleware.wrap_make_batch_request.<locals>.middleware(requests_info)
     63 def middleware(
     64     requests_info: List[Tuple["RPCEndpoint", Any]]
     65 ) -> List["RPCResponse"]:
     66     req_processed = [
     67         self.request_processor(method, params)
     68         for (method, params) in requests_info
     69     ]
---> 70     responses = make_batch_request(req_processed)
     71     methods, _params = zip(*req_processed)
     72     formatted_responses = [
     73         self.response_processor(m, r) for m, r in zip(methods, responses)
     74     ]

File ~/.cache/pypoetry/virtualenvs/etherspect-dagster-jFkAMd9f-py3.12/lib/python3.12/site-packages/web3/providers/rpc/rpc.py:188, in HTTPProvider.make_batch_request(self, batch_requests)
    186 self.logger.debug("Received batch response HTTP.")
    187 responses_list = cast(List[RPCResponse], self.decode_rpc_response(raw_response))
--> 188 return sort_batch_response_by_response_ids(responses_list)

File ~/.cache/pypoetry/virtualenvs/etherspect-dagster-jFkAMd9f-py3.12/lib/python3.12/site-packages/web3/_utils/batching.py:203, in sort_batch_response_by_response_ids(responses)
    200 def sort_batch_response_by_response_ids(
    201     responses: List["RPCResponse"],
    202 ) -> List["RPCResponse"]:
--> 203     if all(response.get("id") is not None for response in responses):
    204         # If all responses have an `id`, sort them by `id, since the JSON-RPC 2.0 spec
    205         # doesn't guarantee order.
    206         return sorted(responses, key=lambda response: response["id"])
    207     else:
    208         # If any response is missing an `id`, which should only happen on particular
    209         # errors, return them in the order they were received and hope that the
    210         # provider is returning them in order. Issue a warning.

File ~/.cache/pypoetry/virtualenvs/etherspect-dagster-jFkAMd9f-py3.12/lib/python3.12/site-packages/web3/_utils/batching.py:203, in <genexpr>(.0)
    200 def sort_batch_response_by_response_ids(
    201     responses: List["RPCResponse"],
    202 ) -> List["RPCResponse"]:
--> 203     if all(response.get("id") is not None for response in responses):
    204         # If all responses have an `id`, sort them by `id, since the JSON-RPC 2.0 spec
    205         # doesn't guarantee order.
    206         return sorted(responses, key=lambda response: response["id"])
    207     else:
    208         # If any response is missing an `id`, which should only happen on particular
    209         # errors, return them in the order they were received and hope that the
    210         # provider is returning them in order. Issue a warning.

AttributeError: 'str' object has no attribute 'get'

Fill this section in if you know how this could or should be fixed

Revise the response parsing behavior in web3/providers/rpc/rpc.py:make_batch_request() and any other relevant files

web3 Version

7.4.0

Python Version

3.12.5

Operating System

linux

Output from pip freeze

aiohappyeyeballs==2.4.3
aiohttp==3.10.10
aiosignal==1.3.1
alembic==1.13.3
annotated-types==0.7.0
anyio==4.6.2.post1
asttokens==2.4.1
attrs==24.2.0
backoff==2.2.1
bitarray==3.0.0
certifi==2024.8.30
charset-normalizer==3.4.0
ckzg==2.0.1
click==8.1.7
coloredlogs==14.0
croniter==3.0.3
cytoolz==1.0.0
dagster==1.8.12
dagster-graphql==1.8.12
dagster-pipes==1.8.12
dagster-webserver==1.8.12
decorator==5.1.1
docstring_parser==0.16
eth-account==0.13.4
eth-hash==0.7.0
eth-keyfile==0.8.1
eth-keys==0.6.0
eth-rlp==2.1.0
eth-typing==5.0.1
eth-utils==5.1.0
eth_abi==5.1.0
executing==2.1.0
filelock==3.16.1
frozenlist==1.5.0
fsspec==2024.10.0
gql==3.5.0
graphene==3.4
graphql-core==3.2.5
graphql-relay==3.2.0
greenlet==3.1.1
grpcio==1.67.0
grpcio-health-checking==1.62.3
h11==0.14.0
hexbytes==1.2.1
httptools==0.6.4
humanfriendly==10.0
idna==3.10
iniconfig==2.0.0
ipdb==0.13.13
ipython==8.28.0
jedi==0.19.1
Jinja2==3.1.4
Mako==1.3.5
markdown-it-py==3.0.0
MarkupSafe==3.0.2
matplotlib-inline==0.1.7
mdurl==0.1.2
more-itertools==10.5.0
multidict==6.1.0
mypy==1.12.1
mypy-extensions==1.0.0
numpy==2.1.2
packaging==24.1
pandas==2.2.3
pandas-stubs==2.2.3.241009
parsimonious==0.10.0
parso==0.8.4
pexpect==4.9.0
pluggy==1.5.0
prompt_toolkit==3.0.48
propcache==0.2.0
protobuf==4.25.5
ptyprocess==0.7.0
pure_eval==0.2.3
pycryptodome==3.21.0
pydantic==2.9.2
pydantic_core==2.23.4
Pygments==2.18.0
pytest==8.3.3
python-dateutil==2.9.0.post0
python-dotenv==1.0.1
pytz==2024.2
pyunormalize==16.0.0
PyYAML==6.0.2
regex==2024.9.11
requests==2.32.3
requests-toolbelt==1.0.0
rich==13.9.2
rlp==4.0.1
setuptools==75.2.0
six==1.16.0
sniffio==1.3.1
SQLAlchemy==2.0.36
stack-data==0.6.3
starlette==0.41.0
structlog==24.4.0
tabulate==0.9.0
tomli==2.0.2
toolz==1.0.0
toposort==1.10
tqdm==4.66.5
traitlets==5.14.3
types-pytz==2024.2.0.20241003
types-requests==2.32.0.20241016
typing_extensions==4.12.2
tzdata==2024.2
universal_pathlib==0.2.5
urllib3==2.2.3
uvicorn==0.32.0
uvloop==0.21.0
watchdog==5.0.3
watchfiles==0.24.0
wcwidth==0.2.13
web3==7.4.0
websockets==13.1
yarl==1.15.5

[kclowes]

Thanks for the report. We'll put it in our queue.