From 66fbf98d54bf4c6c17331de3f0e151689e16571e Mon Sep 17 00:00:00 2001
From: Julien Froidefond <julien.froidefond@cdbdx.biz>
Date: Tue, 21 Oct 2025 21:27:18 +0200
Subject: [PATCH] feat: integrate CircuitBreakerService and adjust request
 timeout and queue management for improved API stability

---
 src/lib/services/base-api.service.ts        | 12 ++--
 src/lib/services/circuit-breaker.service.ts | 78 +++++++++++++++++++++
 src/lib/services/request-queue.service.ts   | 11 ++-
 3 files changed, 95 insertions(+), 6 deletions(-)
 create mode 100644 src/lib/services/circuit-breaker.service.ts

diff --git a/src/lib/services/base-api.service.ts b/src/lib/services/base-api.service.ts
index ccc7187..2792ee6 100644
--- a/src/lib/services/base-api.service.ts
+++ b/src/lib/services/base-api.service.ts
@@ -8,6 +8,7 @@ import type { KomgaConfig } from "@/types/komga";
 import type { ServerCacheService } from "./server-cache.service";
 import { RequestMonitorService } from "./request-monitor.service";
 import { RequestQueueService } from "./request-queue.service";
+import { CircuitBreakerService } from "./circuit-breaker.service";
 
 export type { CacheType };
 
@@ -109,14 +110,16 @@ export abstract class BaseApiService {
       }
     }
 
-    // Timeout de 60 secondes au lieu de 10 par défaut
-    const timeoutMs = 60000;
+    // Timeout réduit à 15 secondes pour éviter les blocages longs
+    const timeoutMs = 15000;
     const controller = new AbortController();
     const timeoutId = setTimeout(() => controller.abort(), timeoutMs);
     
     try {
-      // Enqueue la requête pour limiter la concurrence
-      const response = await RequestQueueService.enqueue(async () => {
+      // Utiliser le circuit breaker pour éviter de surcharger Komga
+      const response = await CircuitBreakerService.execute(async () => {
+        // Enqueue la requête pour limiter la concurrence
+        return await RequestQueueService.enqueue(async () => {
         try {
           return await fetch(url, { 
             headers, 
@@ -166,6 +169,7 @@ export abstract class BaseApiService {
           
           throw fetchError;
         }
+        });
       });
       clearTimeout(timeoutId);
 
diff --git a/src/lib/services/circuit-breaker.service.ts b/src/lib/services/circuit-breaker.service.ts
new file mode 100644
index 0000000..ea035a4
--- /dev/null
+++ b/src/lib/services/circuit-breaker.service.ts
@@ -0,0 +1,78 @@
+/**
+ * Circuit Breaker pour éviter de surcharger Komga quand il est défaillant
+ * Évite l'effet avalanche en coupant les requêtes vers un service défaillant
+ */
+interface CircuitBreakerState {
+  state: 'CLOSED' | 'OPEN' | 'HALF_OPEN';
+  failureCount: number;
+  lastFailureTime: number;
+  nextAttemptTime: number;
+}
+
+class CircuitBreaker {
+  private state: CircuitBreakerState = {
+    state: 'CLOSED',
+    failureCount: 0,
+    lastFailureTime: 0,
+    nextAttemptTime: 0,
+  };
+
+  private readonly config = {
+    failureThreshold: 5, // Nombre d'échecs avant ouverture
+    recoveryTimeout: 30000, // 30s avant tentative de récupération
+    successThreshold: 3, // Nombre de succès pour fermer le circuit
+  };
+
+  async execute<T>(operation: () => Promise<T>): Promise<T> {
+    if (this.state.state === 'OPEN') {
+      if (Date.now() < this.state.nextAttemptTime) {
+        throw new Error('Circuit breaker is OPEN - Komga service unavailable');
+      }
+      this.state.state = 'HALF_OPEN';
+    }
+
+    try {
+      const result = await operation();
+      this.onSuccess();
+      return result;
+    } catch (error) {
+      this.onFailure();
+      throw error;
+    }
+  }
+
+  private onSuccess(): void {
+    if (this.state.state === 'HALF_OPEN') {
+      this.state.failureCount = 0;
+      this.state.state = 'CLOSED';
+      console.log('[CIRCUIT-BREAKER] ✅ Circuit closed - Komga recovered');
+    }
+  }
+
+  private onFailure(): void {
+    this.state.failureCount++;
+    this.state.lastFailureTime = Date.now();
+
+    if (this.state.failureCount >= this.config.failureThreshold) {
+      this.state.state = 'OPEN';
+      this.state.nextAttemptTime = Date.now() + this.config.recoveryTimeout;
+      console.warn(`[CIRCUIT-BREAKER] 🔴 Circuit OPEN - Komga failing (${this.state.failureCount} failures)`);
+    }
+  }
+
+  getState(): CircuitBreakerState {
+    return { ...this.state };
+  }
+
+  reset(): void {
+    this.state = {
+      state: 'CLOSED',
+      failureCount: 0,
+      lastFailureTime: 0,
+      nextAttemptTime: 0,
+    };
+    console.log('[CIRCUIT-BREAKER] 🔄 Circuit reset');
+  }
+}
+
+export const CircuitBreakerService = new CircuitBreaker();
diff --git a/src/lib/services/request-queue.service.ts b/src/lib/services/request-queue.service.ts
index e81583b..1a1b6f5 100644
--- a/src/lib/services/request-queue.service.ts
+++ b/src/lib/services/request-queue.service.ts
@@ -22,6 +22,12 @@ class RequestQueue {
 
   async enqueue<T>(execute: () => Promise<T>): Promise<T> {
     return new Promise<T>((resolve, reject) => {
+      // Limiter la taille de la queue pour éviter l'accumulation
+      if (this.queue.length >= 50) {
+        reject(new Error('Request queue is full - Komga may be overloaded'));
+        return;
+      }
+      
       this.queue.push({ execute, resolve, reject });
       this.processQueue();
     });
@@ -45,8 +51,9 @@ class RequestQueue {
     }
 
     try {
-      // Délai de 200ms entre chaque requête pour espacer la charge CPU sur Komga
-      await this.delay(200);
+      // Délai adaptatif : plus long si la queue est pleine
+      const delayMs = this.queue.length > 10 ? 500 : 200;
+      await this.delay(delayMs);
       const result = await request.execute();
       request.resolve(result);
     } catch (error) {