Module trace 

Live match-trace channel — RFC 006 (in-process) + RFC 009 (transport).

Architecture

 HTTP handler ──► TraceEmitter::emit()
                        │
             tokio::sync::broadcast (bounded, 1024)
                        │
          ┌─────────────┴──────────────┐
     in-process                  TraceTransport::accept_loop
     subscriber                  (UDS on Unix, TCP fallback)
                                       │
                                 up to 4 GUI connections
                                 (newline-delimited JSON)

Transport variants

TraceTransportConfig	Platform	Notes
Uds { path }	Unix/macOS	Default when available
Tcp { addr }	All	Portable fallback; addr = "127.0.0.1:0" assigns ephemeral port
Disabled	All	No out-of-process forwarding (default)

Back-pressure

The broadcast channel is bounded by TRACE_CHANNEL_CAPACITY. When the channel is full, emit drops the event and increments an internal counter; the count is reported as dropped_count on the next event.

Slow out-of-process subscribers receive a RecvError::Lagged from the broadcast channel; the gap is reported in the next JSON line via dropped_count.

Subscriber cap

At most MAX_SUBSCRIBERS out-of-process connections are accepted. A fifth connection receives {"error":"max_subscribers_reached"} and is then closed.

Structs

MatchTraceEvent

A single request/response trace event.

RequestSummary

Key fields from the incoming HTTP request.

TraceEmitter

Shared handle to the trace broadcast channel.

TraceTransport

Enums

Outcome

What the server decided to do with the request.

TraceTransportConfig

Configuration for the out-of-process transport layer.

Constants

MAX_SUBSCRIBERS

Maximum concurrent out-of-process subscriber connections.

TRACE_CHANNEL_CAPACITY

Capacity of the broadcast channel (events).

Functions

now_ms

Current Unix time in milliseconds.