feat(controlplane): always sample batch subgraph publish traces

controlplane/src/core/sentry.config.ts

@@ -17,6 +17,44 @@ const {
   SENTRY_ENABLE_LOGS,
 } = sentryEnvVariables.parse(process.env);
 
+// RPC paths we always trace at 100%, regardless of SENTRY_TRACES_SAMPLE_RATE.
+const ALWAYS_SAMPLE_PATHS = ['/wg.cosmo.platform.v1.PlatformService/PublishFederatedSubgraphs'];
+
+const matchesAlwaysSample = (value: unknown): boolean => {
+  if (typeof value !== 'string') {
+    return false;
+  }
+  for (const path of ALWAYS_SAMPLE_PATHS) {
+    if (value.includes(path)) {
+      return true;
+    }
+  }
+  return false;
+};
+
+const publishAwareTracesSampler: NonNullable<Sentry.NodeOptions['tracesSampler']> = (ctx) => {
+  const attrs = ctx.attributes;
+
+  // Some paths are always traced
+  if (
+    matchesAlwaysSample(ctx.name) ||
+    (attrs &&
+      [attrs['http.route'], attrs['http.target'], attrs['url.path'], attrs['url.full']].some((value) =>
+        matchesAlwaysSample(value),
+      ))
+  ) {
+    return 1;
+  }
+
+  // Otherwise honor an upstream sampling decision exactly so distributed traces stay intact:
+  // a parent that opted out (parentSampled === false) must not leave orphaned child spans.
+  if (typeof ctx.parentSampled === 'boolean') {
+    return ctx.parentSampled ? 1 : 0;
+  }
+
+  return SENTRY_TRACES_SAMPLE_RATE;
+};
+
 if (SENTRY_ENABLED && SENTRY_DSN) {
   Sentry.init({
     dsn: SENTRY_DSN,
@@ -28,7 +66,9 @@ if (SENTRY_ENABLED && SENTRY_DSN) {
     ],
     profileSessionSampleRate: SENTRY_PROFILE_SESSION_SAMPLE_RATE,
     sendDefaultPii: SENTRY_SEND_DEFAULT_PII,
-    tracesSampleRate: SENTRY_TRACES_SAMPLE_RATE,
+    // tracesSampler takes precedence over tracesSampleRate; the sampler falls back to
+    // SENTRY_TRACES_SAMPLE_RATE for everything that isn't in ALWAYS_SAMPLE_PATHS.
+    tracesSampler: publishAwareTracesSampler,
     profileLifecycle: SENTRY_PROFILE_LIFECYCLE,
     enableLogs: SENTRY_ENABLE_LOGS,
     spotlight: process.env.NODE_ENV !== 'production',