debug: add poll latency instrumentation

src/nostr_handler.c

@@ -2041,9 +2041,38 @@ int nostr_handler_poll(int timeout_ms) {
         return -1;
     }
 
+    double start_ms = -1.0;
+    struct timespec ts_start;
+    if (clock_gettime(CLOCK_MONOTONIC, &ts_start) == 0) {
+        start_ms = ts_start.tv_sec * 1000.0 + ts_start.tv_nsec / 1000000.0;
+    }
+
     int rc = nostr_relay_pool_poll(g_pool, timeout_ms);
     g_poll_counter++;
 
+    if (start_ms >= 0.0) {
+        struct timespec ts_end;
+        if (clock_gettime(CLOCK_MONOTONIC, &ts_end) == 0) {
+            const double end_ms = ts_end.tv_sec * 1000.0 + ts_end.tv_nsec / 1000000.0;
+            const double elapsed_ms = end_ms - start_ms;
+            const double expected_ms = timeout_ms > 0 ? (double)timeout_ms : 0.0;
+
+            if (elapsed_ms > expected_ms + 250.0) {
+                DEBUG_WARN("[didactyl] poll latency spike: nostr_relay_pool_poll(timeout=%d) took %.1fms rc=%d count=%llu",
+                           timeout_ms,
+                           elapsed_ms,
+                           rc,
+                           (unsigned long long)g_poll_counter);
+            } else if ((g_poll_counter % 200ULL) == 0ULL) {
+                DEBUG_TRACE("[didactyl] poll heartbeat: timeout=%d elapsed=%.1fms rc=%d count=%llu",
+                            timeout_ms,
+                            elapsed_ms,
+                            rc,
+                            (unsigned long long)g_poll_counter);
+            }
+        }
+    }
+
     log_relay_state_changes();
 
     return rc;