fix(sglang): fix IPv6 support for ZMQ endpoint (#4403)

Signed-off-by: Dmitrii Gabor <[email protected]>

Author: dmitrygx

components/src/dynamo/sglang/publisher.py

@@ -10,7 +10,7 @@
 import zmq
 import zmq.asyncio
 from prometheus_client import CollectorRegistry, multiprocess
-from sglang.srt.utils import get_local_ip_auto, get_zmq_socket
+from sglang.srt.utils import get_local_ip_auto, get_zmq_socket, maybe_wrap_ipv6_address
 
 from dynamo.common.utils.prometheus import register_engine_metrics_callback
 from dynamo.llm import (
@@ -26,6 +26,30 @@
 from dynamo.sglang.args import Config
 
 
+def format_zmq_endpoint(endpoint_template: str, ip_address: str) -> str:
+    """Format ZMQ endpoint by replacing wildcard with IP address.
+
+    Properly handles IPv6 addresses by wrapping them in square brackets.
+    Uses SGLang's maybe_wrap_ipv6_address for consistent formatting.
+
+    Args:
+        endpoint_template: ZMQ endpoint template with wildcard (e.g., "tcp://*:5557")
+        ip_address: IP address to use (can be IPv4 or IPv6)
+
+    Returns:
+        Formatted ZMQ endpoint string
+
+    Example:
+        >>> format_zmq_endpoint("tcp://*:5557", "192.168.1.1")
+        'tcp://192.168.1.1:5557'
+        >>> format_zmq_endpoint("tcp://*:5557", "2a02:6b8:c46:2b4:0:74c1:75b0:0")
+        'tcp://[2a02:6b8:c46:2b4:0:74c1:75b0:0]:5557'
+    """
+    # Use SGLang's utility to wrap IPv6 addresses in brackets
+    formatted_ip = maybe_wrap_ipv6_address(ip_address)
+    return endpoint_template.replace("*", formatted_ip)
+
+
 class DynamoSglangPublisher:
     """
     Handles SGLang kv events and metrics reception and publishing.
@@ -121,7 +145,7 @@ def init_kv_event_publish(self) -> Optional[ZmqKvEventPublisher]:
         if self.server_args.kv_events_config:
             kv_events = json.loads(self.server_args.kv_events_config)
             ep = kv_events.get("endpoint")
-            zmq_ep = ep.replace("*", get_local_ip_auto()) if ep else None
+            zmq_ep = format_zmq_endpoint(ep, get_local_ip_auto()) if ep else None
 
             zmq_config = ZmqKvEventPublisherConfig(
                 worker_id=self.generate_endpoint.connection_id(),