Add Spark Control hardware backend (diarize, queue, discovery)

server/spark-control-events.js

@@ -0,0 +1,58 @@
+// Passive error reporting to Spark Control's /api/health-event
+// endpoint. When a hardware-backed transcribe or analyze call fails
+// (Parakeet 503, vLLM model not found, network timeout to Gemma,
+// etc.), the relay fires a small POST so the operator's Spark
+// Control dashboard can surface the failure in real time — without
+// waiting for its own 5s health-check poll to catch the outage.
+//
+// Fire-and-forget: the request is kicked off but NOT awaited by the
+// caller's error path, so reporting failure to Spark Control never
+// adds latency to the user's transcribe-failed response.
+//
+// Reuses the operator's `relay_spark_control_url` config field
+// (already used for /api/endpoints discovery). The relay just swaps
+// the path for /api/health-event, keeping the operator config
+// surface to one URL.
+
+import { getConfigSnapshot } from "./config.js";
+
+const REPORT_TIMEOUT_MS = 3_000;
+
+// Fire-and-forget. service ∈ { "parakeet", "vllm", "gemma", ... }
+// matching whatever Spark Control's poller knows about. Errors are
+// swallowed silently — observability hiccups shouldn't bleed into
+// the relay's error path.
+export function reportHealthEvent({ service, ok = false, error, ms }) {
+  // Wrap the actual work in setImmediate so the caller's microtask
+  // queue isn't blocked at all.
+  setImmediate(async () => {
+    try {
+      const cfg = await getConfigSnapshot();
+      const base = (cfg.relay_spark_control_url || "").trim();
+      if (!base) return; // not configured — silent no-op
+      // Strip any path the operator may have configured (they
+      // typically set the /api/endpoints URL) and append health-event.
+      let origin;
+      try {
+        origin = new URL(base).origin;
+      } catch {
+        return;
+      }
+      const url = `${origin}/api/health-event`;
+      await fetch(url, {
+        method: "POST",
+        headers: { "Content-Type": "application/json" },
+        body: JSON.stringify({
+          service,
+          ok,
+          source: "recap-relay",
+          error: typeof error === "string" ? error.slice(0, 280) : null,
+          ms: typeof ms === "number" ? ms : null,
+        }),
+        signal: AbortSignal.timeout(REPORT_TIMEOUT_MS),
+      });
+    } catch {
+      // Best-effort — swallow.
+    }
+  });
+}