[Disagg] Add retry with exponential backoff for prefill bootstrap reg… (#25125)

python/sglang/srt/disaggregation/common/conn.py

@@ -374,7 +374,7 @@ class CommonKVManager(BaseKVManager):
         return synced_port
 
     def register_to_bootstrap(self):
-        """Register prefill server info to bootstrap server via HTTP POST."""
+        """Register prefill server info to bootstrap server via HTTP PUT."""
         if self.dist_init_addr:
             # Multi-node case: bootstrap server's host is dist_init_addr
             host = NetworkAddress.parse(self.dist_init_addr).resolved().host
@@ -402,18 +402,33 @@ class CommonKVManager(BaseKVManager):
             "load_balance_method": self.server_args.load_balance_method,
         }
 
-        try:
-            response = requests.put(url, json=payload, timeout=5)
-            if response.status_code == 200:
-                logger.debug("Prefill successfully registered to bootstrap server.")
-            else:
-                logger.error(
-                    f"Prefill instance failed to connect to bootstrap server: {response.status_code}, {response.text}"
+        max_retries, initial_delay, max_delay = 5, 1.0, 30.0
+        for attempt in range(max_retries):
+            try:
+                response = requests.put(url, json=payload, timeout=5)
+                if response.status_code == 200:
+                    logger.debug("Prefill successfully registered to bootstrap server.")
+                    return
+                logger.warning(
+                    f"Prefill register attempt {attempt + 1}/{max_retries} failed: status {response.status_code}"
                 )
-        except Exception as e:
-            logger.error(
-                f"Prefill instance failed to register to bootstrap server: {e}"
+            except Exception as e:
+                # Walk to root cause to skip misleading urllib3 wrapper messages
+                cause = e
+                while cause.__cause__ is not None:
+                    cause = cause.__cause__
+                logger.warning(
+                    f"Prefill register attempt {attempt + 1}/{max_retries} failed: {cause}"
+                )
+            if attempt == max_retries - 1:
+                break
+            delay = min(initial_delay * (2**attempt), max_delay) * (
+                0.75 + 0.25 * (time.monotonic() % 1)
             )
+            time.sleep(delay)
+        logger.error(
+            f"Prefill instance failed to register to bootstrap server after {max_retries} retries"
+        )
 
     @cache
     def _connect(self, endpoint: str, is_ipv6: bool = False):