JSON-RPC endpoint does not accept []-enclosed requests

[jsoares]

Issue type

Bug

Have you reproduced the bug with the latest dev version?

Yes

Version

dev

Custom code

No

OS platform and distribution

No response

Describe the issue

While trying to deploy blockscout, I met the following error:

request:
backend                         | 
backend                         |     url: http://host.docker.internal:8545/
backend                         | 
backend                         |     body: [{"id":0,"jsonrpc":"2.0","method":"eth_getBlockByNumber","params":["latest",false]}]
backend                         | 
backend                         |   response:
backend                         | 
backend                         |     status code: 422
backend                         | 
backend                         |     body: Failed to deserialize the JSON body into the target type: [0]: invalid type: map, expected a borrowed string at line 1 column 1

This seems to be caused by those array brackets [ ] surrounding the body. Turns out that blockscout formats every request as batched, and we don't support it.

Without [ ]

ubuntu@ip-172-26-4-182:~/ipc$ curl http://localhost:8545/   -X POST   -H "Content-Type: application/json"   --data '{"method":"eth_getBlockByNumber","params":["latest",false],"id":1,"jsonrpc":"2.0"}' 
{"jsonrpc":"2.0","result":{"hash":"0x54a59570be03a907ffe81fc5cddb7a89baf9c4e8580d34df35ff3076eab54cb5","parentHash":"0xf69882a9edd08c04ee93864241599c8dcbe9dbad189a9c369891a18972112949","sha3Uncles":"0x1dcc4de8dec75d7aab85b567b6ccd41ad312451b948a7413f0a142fd40d49347","miner":"0x4a8066af00db95d7e2b0d8f20bc37de52d284882","stateRoot":"0xa175763416f64f25127e963ba6ad626a65718e4b11f6e33197e97c6b7ab7a0a5","transactionsRoot":"0x56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421","receiptsRoot":"0x56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421","number":"0x12c","gasUsed":"0x0","gasLimit":"0x0","extraData":"0x","logsBloom":"0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000","timestamp":"0x6545427d","difficulty":"0x0","totalDifficulty":null,"sealFields":[],"uncles":[],"transactions":[],"size":"0x0","mixHash":null,"nonce":null,"baseFeePerGas":"0x3e8"},"id":1}

With [ ]

ubuntu@ip-172-26-4-182:~/ipc$ curl http://localhost:8545/   -X POST   -H "Content-Type: application/json"   --data '[{"method":"eth_getBlockByNumber","params":["latest",false],"id":1,"jsonrpc":"2.0"}]'
Failed to deserialize the JSON body into the target type: [0]: invalid type: map, expected a borrowed string at line 1 column 1

On the contrary, both work fine with public ethereum endpoints, e.g.

ubuntu@ip-172-26-4-182:~/ipc$ curl https://eth.public-rpc.com   -X POST   -H "Content-Type: application/json"   --data '{"method":"eth_getBlockByNumber","params":["latest",false],"id":1,"jsonrpc":"2.0"}' 
{"jsonrpc":"2.0","id":1,"result":{"baseFeePerGas":"0x4f46ceaab","difficulty":"0x0","extraData":"0x496c6c756d696e61746520446d6f63726174697a6520447374726962757465","gasLimit":"0x1c9c380","gasUsed":"0x10b5fd0","hash":"0xf6307927df417bcdd7ba260d8d24a10421d8d86a7c5456c3fc1e8db3a3d863ff","logsBloom":"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","miner":"0xdafea492d9c6733ae3d56b7ed1adb60692c98bc5","mixHash":"0xc632397c9c35fa65832c99aa1addefc060902827b2672c7430b1c7a07375bc57","nonce":"0x0000000000000000","number":"0x11a3164","parentHash":"0x420fa95c62d4aff62c9f6303df8b5bc0d049bce1a6db0e52bcb9212f0741e75c","receiptsRoot":"0x45929f10063f3d61910073c0e89fe92e1daae09542d273666c0952af57126563","sha3Uncles":"0x1dcc4de8dec75d7aab85b567b6ccd41ad312451b948a7413f0a142fd40d49347","size":"0x16343","stateRoot":"0x71105e13a224a9925eeaf948702627057af0b15dc876c966cbaed4a1fbee9d7b","timestamp":"0x65455247","totalDifficulty":"0xc70d815d562d3cfa955","transactions": ...
...

ubuntu@ip-172-26-4-182:~/ipc$ curl https://eth.public-rpc.com   -X POST   -H "Content-Type: application/json"   --data '[{"method":"eth_getBlockByNumber","params":["latest",false],"id":1,"jsonrpc":"2.0"}]' 
[{"jsonrpc":"2.0","id":1,"result":{"baseFeePerGas":"0x5145110a4","difficulty":"0x0","extraData":"0x496c6c756d696e61746520446d6f63726174697a6520447374726962757465","gasLimit":"0x1c9c380","gasUsed":"0xe41009","hash":"0x8ece208e6a923d1795e47b075e3f5dbca9ac08f1b16275c9326995b836541069","logsBloom":"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","miner":"0xdafea492d9c6733ae3d56b7ed1adb60692c98bc5","mixHash":"0x9aec5613084c02be7f9210e0ad3aa17f1b17e1437584c90cf2ed27539012de1a","nonce":"0x0000000000000000","number":"0x11a3169","parentHash":"0x6888961f7eb5077d5d45923dc33cd36cab036ab418622460a46d3500e2be25e8","receiptsRoot":"0x0e5bf192204a4b08e2e99f347b70710a92834f52c07ecab335275b0eee0d6321","sha3Uncles":"0x1dcc4de8dec75d7aab85b567b6ccd41ad312451b948a7413f0a142fd40d49347","size":"0x575ca","stateRoot":"0x4a8bdfee493dc45bed7527bb48874625d85b16158dbd84cefb8c80a822fc7810","timestamp":"0x65455283","totalDifficulty":"0xc70d815d562d3cfa955","transactions": ...

This may break compatibility with other ethereum tooling.

Repro steps

Run curl above against a fendermint eth rpc.

Relevant log output

No response

[raulk]

Lotus does not support batched requests either -- but they have less need to because the Filecoin network has other explorers, and this isn't a popular feature in general (esp. when both the client and server support WebSockets as a transport). However, it should be easy to implement here. Ideally we'd want to handle individual requests in parallel, with some limit to prevent attacks.

[jsoares]

@raulk We already have a fix in consensus-shipyard/fendermint#395.

Fwiw, this is not even a batched request; it's just formatted as such. It might be enough to accept said formatting, but we'll see what other surprises blockscout has in store (inc. actual batched requests, maybe).

[raulk]

@jsoares I'd expect to find multiple requests when loading listing and detail pages, or when indexing blocks and transactions. I suspect the explorer became blocked here and we didn't get to see further, more elaborate requests.

[jsoares]

Indeed, that's what I expect too. That and tracing...

[jsoares]

The fix works and allows for batch requests. New issues in #168.