feat(gateway): add per-request logging to gateway with --request-logging

[rvagg]

Logs POST bodies too, so probably not ideal for environments where performance is critical, or where you think there might be data leakage (although the gateway is intended for non-sensitive traffic).

This was just a private branch feature but I found it super useful for debugging and decided there's a good chance I'm going to want this again. I also tried logging to stdout, but having it interleaved with error logs ended up being more useful. Unfortunately the JSON bodies get escaped to be reproduced as JSON output, but it's not terrible.

Another alternative I considered was providing a filename, so it ends up a bit like a classic HTTP server log, --request-logging=access.log, but it goes a bit further than HTTP server logging with the request body capture so it may be best to not give the impression that this is the right thing to do.

{"level":"info","ts":"2025-05-28T22:58:32.768+1000","logger":"gateway","caller":"gateway/handler.go:380","msg":"request","remote_ip":"192.168.1.12","method":"POST","url":"/rpc/v1","body":"{\"id\":\"0f6d72ba-f240-4ef9-83c8-9ecc42f5a635\",\"jsonrpc\":\"2.0\",\"method\":\"eth_getBalance\",\"params\":[\"0x0542c82a785fab8b53c7c59aaad7093d87265f3a\",\"0x29414a\"]}"}
{"level":"info","ts":"2025-05-28T22:58:32.769+1000","logger":"gateway","caller":"gateway/handler.go:380","msg":"request","remote_ip":"192.168.1.12","method":"POST","url":"/rpc/v1","body":"{\"id\":\"e764c4b6-234c-44c0-b59c-5b75407488fe\",\"jsonrpc\":\"2.0\",\"method\":\"eth_call\",\"params\":[{\"to\":\"0x0e690d3e60b0576d01352ab03b258115eb84a047\",\"data\":\"0x01ffc9a780
ac58cd00000000000000000000000000000000000000000000000000000000\"},\"0x29414a\"]}"}                                                                                                          {"level":"warn","ts":"2025-05-28T22:58:32.773+1000","logger":"rpc","caller":"go-jsonrpc@v0.7.0/handler.go:421","msg":"error in RPC call to 'eth_call': message execution failed (exit=[33],
revert reason=[message failed with backtrace:\n00: f0162143 (method 3844450837) -- contract reverted at 86 (33)\n01: f0162143 (method 6) -- contract reverted at 349 (33)\n (RetCode=33)], vm error=[none])"}

[Copilot]

Pull Request Overview

This PR introduces an optional request-logging middleware that captures incoming HTTP requests (including POST bodies) for debugging.

• Adds a --request-logging CLI flag and wires it into the gateway handler options.
• Implements LoggingHandler middleware that reads, optionally truncates, and logs request details.
• Provides a helper to extract the remote IP address.

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

File	Description
gateway/handler.go	Add LoggingHandler, WithRequestLogging option, and body logging logic
cmd/lotus-gateway/main.go	Add request-logging CLI flag and pass it to WithRequestLogging

Comments suppressed due to low confidence (1)

gateway/handler.go:354

• LoggingHandler lacks unit tests. Add tests to verify behavior for different HTTP methods, body sizes, and error scenarios.

// LoggingHandler logs incoming HTTP requests with details

[rvagg]

some good copilot suggestions in there, I'll tweak when I have time

[BigLep]

@rvagg : are you able to land this week?

[rvagg]

Maybe

[rvagg]

Rebased and some of the minor suggestions addressed 🤞