feat: add foreign key constraints and metrics for blockchain node

apps/blockchain-node/src/aitbc_chain/metrics.py

@@ -15,6 +15,7 @@ class MetricsRegistry:
     def __init__(self) -> None:
         self._counters: Dict[str, float] = {}
         self._gauges: Dict[str, float] = {}
+        self._summaries: Dict[str, tuple[float, float]] = {}
         self._lock = Lock()
 
     def increment(self, name: str, amount: float = 1.0) -> None:
@@ -25,6 +26,17 @@ class MetricsRegistry:
         with self._lock:
             self._gauges[name] = value
 
+    def observe(self, name: str, value: float) -> None:
+        with self._lock:
+            count, total = self._summaries.get(name, (0.0, 0.0))
+            self._summaries[name] = (count + 1.0, total + value)
+
+    def reset(self) -> None:
+        with self._lock:
+            self._counters.clear()
+            self._gauges.clear()
+            self._summaries.clear()
+
     def render_prometheus(self) -> str:
         with self._lock:
             lines: list[str] = []
@@ -34,6 +46,10 @@ class MetricsRegistry:
             for name, value in sorted(self._gauges.items()):
                 lines.append(f"# TYPE {name} gauge")
                 lines.append(f"{name} {value}")
+            for name, (count, total) in sorted(self._summaries.items()):
+                lines.append(f"# TYPE {name} summary")
+                lines.append(f"{name}_count {count}")
+                lines.append(f"{name}_sum {total}")
             return "\n".join(lines) + "\n"