Get Call Event

Survey how to get event with ETH RPC in Golang when usgin estimate method, e.g. eth_call, debug_XXX...

It means the transaction won't be mined, it even can be reverted!

Environment

• Go: 1.21.0
• The testing contract has only deployed on Sepolia, make sure giving RPC_URL in correct network in .env.

debug_traceCall Problems

• The Infura doesn't supoort debug_traceCall, and Alchemy only supports debug_traceCall for Growth, Scale, or Enterprise, not available on the Free tier. (ref.)

curl https://eth-sepolia.g.alchemy.com/v2/<your_api_key> \
-X POST \
-H "Content-Type: application/json" \
--data '{"method":"debug_traceCall","params":[{"from":null,"to":"0x1A37E0A92f6F2E06088607B5D87DfeeB95A4BEC2","data":"0xc5fde5e5"}, "latest", {"tracer": "callTracer"}],"id":1,"jsonrpc":"2.0"}'

• However, A bundler should be considered as an extension, or a side-car, to a full node. It requires full access to the node's debug API for custom JS tracing. Most RPC providers do not support this. For maximum performance, it is also recommended to run the bundler in the same machine as the node. (ref.)
• In order to implement the full spec storage access rules and opcode banning, it must run against a GETH node, which supports debug_traceCall with javascript "tracer" Specifically, hardhat node and ganache do NOT support this API. You can still run the bundler with such nodes, but with --unsafe so it would skip these security checks(ref.)

Hence, after open the Geth on http://localhost:8545, you can:

curl http://localhost:8545 \
-X POST \
-H "Content-Type: application/json" \
--data '{"method":"debug_traceCall","params":[{"from":null,"to":"0x1A37E0A92f6F2E06088607B5D87DfeeB95A4BEC2","data":"0xc5fde5e5"}, "latest", {"tracer": "callTracer"}],"id":1,"jsonrpc":"2.0"}'
>
{"jsonrpc":"2.0","id":1,"result":{"type":"CALL","from":"0x0000000000000000000000000000000000000000","to":"0x1a37e0a92f6f2e06088607b5d87dfeeb95a4bec2","value":"0x0","gas":"0x2fa9e38","gasUsed":"0x0","input":"0xc5fde5e5","output":"0x"}}

Or custom tracer:

curl http://localhost:8545 \
-X POST \
-H "Content-Type: application/json" \
--data '{"jsonrpc":"2.0","method":"debug_traceCall","params":[{"from":null,"to":"0x1A37E0A92f6F2E06088607B5D87DfeeB95A4BEC2","data":"0xc5fde5e5"}, "latest", {"tracer": "{\"data\":[],\"fault\":function(log){},\"step\":function(log){var topicCount=(log.op.toString().match(/LOG(\\d)/)||[])[1];if(topicCount){var res={address:log.contract.getAddress(),data:log.memory.slice(parseInt(log.stack.peek(0)),parseInt(log.stack.peek(0))+parseInt(log.stack.peek(1))),};for(var i=0;i<topicCount;i++)res[`topic`+i.toString()]=log.stack.peek(i+2);this.data.push(res);}},\"result\":function(){return this.data;}}" }],"id":1}'
>
{"jsonrpc":"2.0","id":1,"result":[]}

Run

Open the Geth with docker in sepolia:

docker run --rm -ti --name geth -p 8545:8545 ethereum/client-go:v1.10.26 \
  --miner.gaslimit 12000000 \
  --http --http.api personal,eth,net,web3,debug \
  --http.vhosts '*,localhost,host.docker.internal' --http.addr "0.0.0.0" \
  --ignore-legacy-receipts --allow-insecure-unlock --rpc.allow-unprotected-txs \
  --dev \
  --verbosity 2 \
  --nodiscover --maxpeers 0 --mine --miner.threads 1 \
  --networkid 11155111

Fetch the event:

$ go mod download
$ go run *.go

Result

Reference

• debug Namespace
• Ethereum JSON-RPC Specification
• Alchemy: debug_traceCall
• Skaled returns error on valid debug_traceCall request #1748
• debug_traceCall
• Extracting emitted events (logs) from geth transaction trace (debug_traceCall)