[model-gateway] extract circuit breaker state struct (#15098)

sgl-model-gateway/src/core/circuit_breaker.rs

@@ -53,6 +53,24 @@ impl std::fmt::Display for CircuitState {
     }
 }
 
+impl CircuitState {
+    pub fn as_str(&self) -> &'static str {
+        match self {
+            CircuitState::Closed => "closed",
+            CircuitState::Open => "open",
+            CircuitState::HalfOpen => "half_open",
+        }
+    }
+
+    pub fn to_int(&self) -> u8 {
+        match self {
+            CircuitState::Closed => 0u8,
+            CircuitState::Open => 1u8,
+            CircuitState::HalfOpen => 2u8,
+        }
+    }
+}
+
 /// Circuit breaker implementation
 #[derive(Debug)]
 pub struct CircuitBreaker {
@@ -196,16 +214,8 @@ impl CircuitBreaker {
                 }
             }
 
-            let from = match old_state {
-                CircuitState::Closed => "closed",
-                CircuitState::Open => "open",
-                CircuitState::HalfOpen => "half_open",
-            };
-            let to = match new_state {
-                CircuitState::Closed => "closed",
-                CircuitState::Open => "open",
-                CircuitState::HalfOpen => "half_open",
-            };
+            let from = old_state.as_str();
+            let to = new_state.as_str();
             info!("Circuit breaker state transition: {} -> {}", from, to);
         }
     }

sgl-model-gateway/src/core/worker.rs

@@ -16,7 +16,7 @@ use super::{
     CircuitBreaker, Endpoint, ModelCard, ModelType, ProviderType, WorkerError, WorkerResult,
 };
 use crate::{
-    core::{BasicWorkerBuilder, CircuitState, DPAwareWorkerBuilder},
+    core::{BasicWorkerBuilder, DPAwareWorkerBuilder},
     observability::metrics::RouterMetrics,
     protocols::worker_spec::WorkerInfo,
     routers::grpc::client::GrpcClient,
@@ -137,24 +137,12 @@ pub trait Worker: Send + Sync + fmt::Debug {
         let after = self.circuit_breaker().state();
 
         if before != after {
-            let from = match before {
-                CircuitState::Closed => "closed",
-                CircuitState::Open => "open",
-                CircuitState::HalfOpen => "half_open",
-            };
-            let to = match after {
-                CircuitState::Closed => "closed",
-                CircuitState::Open => "open",
-                CircuitState::HalfOpen => "half_open",
-            };
+            let from = before.as_str();
+            let to = after.as_str();
             RouterMetrics::record_cb_state_transition(self.url(), from, to);
         }
 
-        let state_code = match self.circuit_breaker().state() {
-            CircuitState::Closed => 0u8,
-            CircuitState::Open => 1u8,
-            CircuitState::HalfOpen => 2u8,
-        };
+        let state_code = self.circuit_breaker().state().to_int();
         RouterMetrics::set_cb_state(self.url(), state_code);
 
         // Update consecutive failures/successes gauges
@@ -1180,7 +1168,7 @@ mod tests {
     use std::{thread, time::Duration};
 
     use super::*;
-    use crate::core::CircuitBreakerConfig;
+    use crate::core::{CircuitBreakerConfig, CircuitState};
 
     #[test]
     fn test_worker_type_display() {