feat(stream-recognizer): nest log context under metadata for New Relic

Match server NR log shape (metadata.*), stringify nested metadata for NR,
dedupe stationID when metadata.stationID is present, and pass stationId
into Shazam discovery logs. Read prior fingerprint from Redis metadata
when skipping unchanged fingerprints.

Author: LandRover

stream-recognizer/src/index.js

@@ -35,9 +35,11 @@ const server = listenHost
 
 function onListen() {
     logger.info(
-        listenHost
-            ? { port, host: listenHost, component: 'bootstrap' }
-            : { port, component: 'bootstrap' },
+        {
+            metadata: listenHost
+                ? { port, host: listenHost, component: 'bootstrap' }
+                : { port, component: 'bootstrap' },
+        },
         'HTTP listening',
     );
     metrics.report('StreamRecognizerStarted', [
@@ -47,13 +49,13 @@ function onListen() {
     if (anyStationEnabled) {
         if (!probeBinary(ffmpegBin)) {
             logger.warn(
-                { bin: ffmpegBin, component: 'bootstrap' },
+                { metadata: { bin: ffmpegBin, component: 'bootstrap' } },
                 `ffmpeg not found. ${missingBinaryHint('ffmpeg', 'FFMPEG_BIN')}`,
             );
         }
         if (!probeBinary(fpcalcBin)) {
             logger.warn(
-                { bin: fpcalcBin, component: 'bootstrap' },
+                { metadata: { bin: fpcalcBin, component: 'bootstrap' } },
                 `fpcalc not found. ${missingBinaryHint('fpcalc', 'FPCALC_BIN')}`,
             );
         }
@@ -77,7 +79,10 @@ for (const station of stations) {
             recognitionBlacklist,
         }).catch((e) => {
             logger.error(
-                { err: e, stationID: station.id, component: 'bootstrap' },
+                {
+                    err: e,
+                    metadata: { stationID: station.id, component: 'bootstrap' },
+                },
                 'Initial station tick failed',
             );
         });
@@ -86,7 +91,10 @@ for (const station of stations) {
                 recognitionBlacklist,
             }).catch((e) => {
                 logger.error(
-                    { err: e, stationID: station.id, component: 'bootstrap' },
+                    {
+                        err: e,
+                        metadata: { stationID: station.id, component: 'bootstrap' },
+                    },
                     'Scheduled station tick failed',
                 );
             });
@@ -96,7 +104,7 @@ for (const station of stations) {
 }
 
 function shutdown() {
-    logger.info({ component: 'bootstrap' }, 'Shutting down');
+    logger.info({ metadata: { component: 'bootstrap' } }, 'Shutting down');
     for (const t of timers) {
         clearInterval(t);
     }

stream-recognizer/src/lib/redis_store.js

@@ -168,7 +168,7 @@ export async function pingRedis(logger) {
         return { ok: true };
     } catch (e) {
         logger.error(
-            { err: e, component: 'redis', operation: 'ping' },
+            { err: e, metadata: { component: 'redis', operation: 'ping' } },
             'Redis ping failed',
         );
         return { ok: false, reason: String(e?.message || e) };

stream-recognizer/src/logger.js

@@ -37,9 +37,36 @@ function isPlainObject(value) {
   return proto === Object.prototype || proto === null;
 }
 
+const METADATA_NR_JSON_MAX = 8000;
+
+/** Serialize nested metadata values for NR (primitives as-is; arrays/objects JSON-stringified). */
+function metadataValueForNr(mv) {
+  if (mv === undefined) {
+    return undefined;
+  }
+  if (
+    mv === null ||
+    typeof mv === 'string' ||
+    typeof mv === 'number' ||
+    typeof mv === 'boolean'
+  ) {
+    return mv;
+  }
+  if (Array.isArray(mv) || isPlainObject(mv)) {
+    try {
+      const s = JSON.stringify(mv);
+      return s.length > METADATA_NR_JSON_MAX ? `${s.slice(0, METADATA_NR_JSON_MAX)}…` : s;
+    } catch {
+      return String(mv);
+    }
+  }
+  return String(mv);
+}
+
 /**
- * Flat attributes for New Relic `recordLogEvent` (primitives only).
- * Nested `metadata` is flattened as `metadata.<key>` (same convention as server).
+ * Flat attributes for New Relic `recordLogEvent`.
+ * Nested `metadata` is flattened as `metadata.<key>` (same convention as server); non-primitive
+ * metadata values are JSON-stringified for NR.
  */
 function nrPrimitiveAttrs(o) {
   const out = {};
@@ -52,13 +79,9 @@ function nrPrimitiveAttrs(o) {
     }
     if (k === 'metadata' && isPlainObject(v)) {
       for (const [mk, mv] of Object.entries(v)) {
-        if (
-          mv === null ||
-          typeof mv === 'string' ||
-          typeof mv === 'number' ||
-          typeof mv === 'boolean'
-        ) {
-          out[`metadata.${mk}`] = mv;
+        const serialized = metadataValueForNr(mv);
+        if (serialized !== undefined) {
+          out[`metadata.${mk}`] = serialized;
         }
       }
       continue;
@@ -124,6 +147,11 @@ function forwardLogToNewRelic(args, levelVal, log) {
     payload.error = errObj;
   }
 
+  // Align with server NR convention: prefer metadata.stationID over duplicate top-level binding.
+  if (Object.prototype.hasOwnProperty.call(payload, 'metadata.stationID')) {
+    delete payload.stationID;
+  }
+
   try {
     newrelic.recordLogEvent(payload);
   } catch {