Bug Report

Description

When running mev-boost with JSON logging (-json flag), the following error is printed to stderr on every registerValidator call:

Failed to obtain reader, failed to marshal fields to JSON, json: unsupported type: func() (io.ReadCloser, error)

Root Cause

In server/register_validator.go:50-52, the full *http.Request struct is passed as a logrus field:

log.WithFields(logrus.Fields{
    "request": req,
}).Debug("sending the registerValidator request")

*http.Request contains the field GetBody func() (io.ReadCloser, error), which Go's encoding/json cannot marshal. When logrus's JSONFormatter calls json.Marshal() on the log fields, it fails with:

json: unsupported type: func() (io.ReadCloser, error)

Logrus (v1.9.3, used by mev-boost) catches this in entry.write() and prints the error to stderr. The log entry is then silently dropped.

This works fine with the text formatter (which uses fmt.Sprintf("%v", req)), but breaks with -json.

Affected Versions

Confirmed in v1.11 and v1.12 (same code present in both).