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validatord: honor X-Lakehouse-Trace-Id even when Langfuse is off

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Surfaced by the 2026-05-02 cross-runtime test: when a caller
forwarded X-Lakehouse-Trace-Id but the langfuse middleware was a
passthrough (no Langfuse env), the header was never read — Go minted
a fallback id, breaking cross-daemon parent-trace linkage.

The middleware only honored the header when its lf client was
non-nil. With LANGFUSE_URL unset on the persistent stack, every
inbound iterate request lost the parent linkage.

Fix: validatord's iterate handler reads the header DIRECTLY (matches
Rust's iterate.rs pattern) before falling through to the ctx value
+ fallback id. Now Go behavior matches Rust regardless of Langfuse
configuration.

Resolution order is:
  1. req.TraceID (caller put it in the JSON body)
  2. X-Lakehouse-Trace-Id header (read directly here)
  3. context value from langfuse middleware (when configured)
  4. fallback to a locally-minted time-ordered hex id

Verified end-to-end:
  curl -H 'X-Lakehouse-Trace-Id: go-cmp-fixed' POST /v1/iterate
  → response.trace_id = "go-cmp-fixed" ✓
  → sessions.jsonl row session_id = "go-cmp-fixed" ✓

Pre-fix (this commit's parent ran from /tmp/val-fresh3 binary):
  same call → trace_id minted as 18abbb5a008061b7-008061e9
  (header silently ignored)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
This commit is contained in:
root 2026-05-02 06:16:25 -05:00
parent 1263720497
commit 6847bbc180
1 changed files with 17 additions and 9 deletions
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26
cmd/validatord/main.go
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@ -244,15 +244,23 @@ func (h *handlers) handleIterate(w http.ResponseWriter, r *http.Request) {
return
}
// Pull the per-request trace id from the langfuse middleware. If
// the caller forwarded an upstream trace via X-Lakehouse-Trace-Id
// the middleware reuses that one; otherwise it minted a fresh trace
// at HTTP entry. When Langfuse isn't configured at all the
// middleware skips the mint, so we generate a fallback id locally —
// session_id MUST always be populated so the JSONL log + Langfuse
// (when later configured) can correlate by id across logs.
// Surfaced 2026-05-02 deploy: empty session_id breaks DuckDB
// joins on coordinator_sessions.jsonl ↔ replay_runs.jsonl.
// Resolve the parent trace id, in priority order:
// 1. req.TraceID (caller put it in the JSON body)
// 2. X-Lakehouse-Trace-Id header (read DIRECTLY here so the path
// works even when Langfuse is off and the middleware is a
// passthrough — matches Rust's iterate handler shape)
// 3. context value set by the langfuse middleware (when Langfuse
// is configured)
// 4. fallback to a locally-minted time-ordered hex id
//
// Surfaced 2026-05-02 cross-runtime test: Go was minting fallback
// even when caller forwarded the header, because middleware
// passthrough mode never read it. Reading the header here closes
// the gap and makes Go behavior match Rust regardless of
// Langfuse configuration.
if req.TraceID == "" {
req.TraceID = r.Header.Get(shared.TraceIDHeader)
}
if req.TraceID == "" {
req.TraceID = shared.TraceIDFromCtx(r.Context())
}