[model-gateway] Add Redis support as a history backend (#16300)

sgl-model-gateway/bindings/python/src/sglang_router/router_args.py

@@ -117,6 +117,9 @@ class RouterArgs:
     oracle_pool_timeout_secs: int = 30
     postgres_db_url: Optional[str] = None
     postgres_pool_max: int = 16
+    redis_url: Optional[str] = None
+    redis_pool_max: int = 16
+    redis_retention_days: int = 30
     # mTLS configuration for worker communication
     client_cert_path: Optional[str] = None
     client_key_path: Optional[str] = None
@@ -200,6 +203,9 @@ class RouterArgs:
         postgres_group = parser.add_argument_group(
             "PostgreSQL Database", "PostgreSQL database backend configuration"
         )
+        redis_group = parser.add_argument_group(
+            "Redis Database", "Redis database backend configuration"
+        )
         tls_group = parser.add_argument_group(
             "TLS/mTLS Security", "TLS certificates for server and worker communication"
         )
@@ -663,7 +669,7 @@ class RouterArgs:
             f"--{prefix}history-backend",
             type=str,
             default=RouterArgs.history_backend,
-            choices=["memory", "none", "oracle", "postgres"],
+            choices=["memory", "none", "oracle", "postgres", "redis"],
             help="History storage backend for conversations and responses (default: memory)",
         )
 
@@ -733,6 +739,28 @@ class RouterArgs:
             help="Maximum PostgreSQL connection pool size (default: 16, env: POSTGRES_POOL_MAX)",
         )
 
+        # Redis configuration
+        redis_group.add_argument(
+            f"--{prefix}redis-url",
+            type=str,
+            default=os.getenv("REDIS_URL"),
+            help="Redis connection URL (env: REDIS_URL)",
+        )
+        redis_group.add_argument(
+            f"--{prefix}redis-pool-max",
+            type=int,
+            default=int(os.getenv("REDIS_POOL_MAX", RouterArgs.redis_pool_max)),
+            help="Maximum Redis connection pool size (default: 16, env: REDIS_POOL_MAX)",
+        )
+        redis_group.add_argument(
+            f"--{prefix}redis-retention-days",
+            type=int,
+            default=int(
+                os.getenv("REDIS_RETENTION_DAYS", RouterArgs.redis_retention_days)
+            ),
+            help="Redis data retention in days (-1 for persistent, default: 30, env: REDIS_RETENTION_DAYS)",
+        )
+
         # TLS/mTLS configuration
         tls_group.add_argument(
             f"--{prefix}client-cert-path",