Add circuit breaker

internal/server/server.go

@@ -2,6 +2,7 @@ package server
 
 import (
 	"encoding/json"
+	"errors"
 	"fmt"
 	"log/slog"
 	"net/http"
@@ -9,6 +10,7 @@ import (
 	"time"
 
 	"github.com/google/uuid"
+	"github.com/sony/gobreaker"
 
 	"github.com/ajac-zero/latticelm/internal/api"
 	"github.com/ajac-zero/latticelm/internal/conversation"
@@ -40,6 +42,11 @@ func New(registry ProviderRegistry, convs conversation.Store, logger *slog.Logge
 	}
 }
 
+// isCircuitBreakerError checks if the error is from a circuit breaker.
+func isCircuitBreakerError(err error) bool {
+	return errors.Is(err, gobreaker.ErrOpenState) || errors.Is(err, gobreaker.ErrTooManyRequests)
+}
+
 // RegisterRoutes wires the HTTP handlers onto the provided mux.
 func (s *GatewayServer) RegisterRoutes(mux *http.ServeMux) {
 	mux.HandleFunc("/v1/responses", s.handleResponses)
@@ -173,7 +180,13 @@ func (s *GatewayServer) handleSyncResponse(w http.ResponseWriter, r *http.Reques
 				slog.String("error", err.Error()),
 			)...,
 		)
-		http.Error(w, "provider error", http.StatusBadGateway)
+
+		// Check if error is from circuit breaker
+		if isCircuitBreakerError(err) {
+			http.Error(w, "service temporarily unavailable - circuit breaker open", http.StatusServiceUnavailable)
+		} else {
+			http.Error(w, "provider error", http.StatusBadGateway)
+		}
 		return
 	}
 
@@ -409,6 +422,15 @@ loop:
 				slog.String("error", streamErr.Error()),
 			)...,
 		)
+
+		// Determine error type based on circuit breaker state
+		errorType := "server_error"
+		errorMessage := streamErr.Error()
+		if isCircuitBreakerError(streamErr) {
+			errorType = "circuit_breaker_open"
+			errorMessage = "service temporarily unavailable - circuit breaker open"
+		}
+
 		failedResp := s.buildResponse(origReq, &api.ProviderResult{
 			Model: origReq.Model,
 		}, provider.Name(), responseID)
@@ -416,8 +438,8 @@ loop:
 		failedResp.CompletedAt = nil
 		failedResp.Output = []api.OutputItem{}
 		failedResp.Error = &api.ResponseError{
-			Type:    "server_error",
-			Message: streamErr.Error(),
+			Type:    errorType,
+			Message: errorMessage,
 		}
 		s.sendSSE(w, flusher, &seq, "response.failed", &api.StreamEvent{
 			Type:     "response.failed",