Fix OpenTelemetry multiple initialization issue

- Add _ot_initialized flag to prevent multiple setup calls
- Make setup_opentelemetry() idempotent
- Handle 'Address in use' error gracefully for Prometheus server
- Prevent OpenTelemetry setup failures due to multiple initialization

ivatar/opentelemetry_config.py

@@ -163,6 +163,14 @@ class OpenTelemetryConfig:
 
             logger.info(f"Prometheus metrics server started on {host}:{port}")
 
+        except OSError as e:
+            if e.errno == 98:  # Address already in use
+                logger.warning(
+                    f"Prometheus metrics server already running on {endpoint}"
+                )
+            else:
+                logger.error(f"Failed to start Prometheus metrics server: {e}")
+                self.enabled = False
         except Exception as e:
             logger.error(f"Failed to start Prometheus metrics server: {e}")
             self.enabled = False
@@ -202,6 +210,7 @@ class OpenTelemetryConfig:
 
 # Global OpenTelemetry configuration instance (lazy-loaded)
 _ot_config = None
+_ot_initialized = False
 
 
 def get_ot_config():
@@ -218,6 +227,12 @@ def setup_opentelemetry() -> None:
 
     This function should be called during Django application startup.
     """
+    global _ot_initialized
+
+    if _ot_initialized:
+        logger.debug("OpenTelemetry already initialized, skipping setup")
+        return
+
     logger.info("Setting up OpenTelemetry...")
 
     ot_config = get_ot_config()
@@ -230,6 +245,7 @@ def setup_opentelemetry() -> None:
             logger.info("OpenTelemetry setup completed successfully (export enabled)")
         else:
             logger.info("OpenTelemetry setup completed successfully (export disabled)")
+        _ot_initialized = True
     else:
         logger.info("OpenTelemetry setup failed")