Circuit breaker

server/src/services/documentParser.ts

@@ -11,6 +11,40 @@ const PROCESSING_TIMEOUT_MS = 30000;
 const SANDBOX_URL = process.env.SANDBOX_URL || 'http://localhost:3002';
 const USE_SANDBOX = process.env.USE_SANDBOX !== 'false';
 
+const CIRCUIT_BREAKER_THRESHOLD = 5;
+const CIRCUIT_BREAKER_RESET_MS = 60000;
+
+class CircuitBreaker {
+  private failures = 0;
+  private lastFailure = 0;
+  private open = false;
+
+  recordSuccess(): void {
+    this.failures = 0;
+    this.open = false;
+  }
+
+  recordFailure(): void {
+    this.failures++;
+    this.lastFailure = Date.now();
+    if (this.failures >= CIRCUIT_BREAKER_THRESHOLD) {
+      this.open = true;
+    }
+  }
+
+  isOpen(): boolean {
+    if (!this.open) return false;
+    if (Date.now() - this.lastFailure > CIRCUIT_BREAKER_RESET_MS) {
+      this.open = false;
+      this.failures = 0;
+      return false;
+    }
+    return true;
+  }
+}
+
+const sandboxCircuit = new CircuitBreaker();
+
 export const GEMINI_NATIVE_TYPES = [
   'application/pdf',
   'text/plain',
@@ -210,6 +244,10 @@ const LEGACY_TO_MODERN: Record<string, string> = {
 };
 
 async function convertViaSandbox(buffer: Buffer, extension: string): Promise<Buffer> {
+  if (sandboxCircuit.isOpen()) {
+    throw new Error('CIRCUIT_OPEN');
+  }
+
   const controller = new AbortController();
   const timeout = setTimeout(() => controller.abort(), PROCESSING_TIMEOUT_MS);
 
@@ -223,14 +261,20 @@ async function convertViaSandbox(buffer: Buffer, extension: string): Promise<Buf
 
     if (!response.ok) {
       const error = await response.json().catch(() => ({ error: 'Conversion failed' }));
+      sandboxCircuit.recordFailure();
       throw new Error(error.error || 'Document conversion failed');
     }
 
+    sandboxCircuit.recordSuccess();
     return Buffer.from(await response.arrayBuffer());
   } catch (err) {
     if (err instanceof Error && err.name === 'AbortError') {
+      sandboxCircuit.recordFailure();
       throw new Error('Document conversion timed out. Try a smaller file.');
     }
+    if (err instanceof Error && err.message !== 'CIRCUIT_OPEN') {
+      sandboxCircuit.recordFailure();
+    }
     throw err;
   } finally {
     clearTimeout(timeout);
@@ -282,9 +326,20 @@ async function convertLocally(buffer: Buffer, extension: string): Promise<Buffer
 }
 
 async function extractWithLibreOffice(buffer: Buffer, extension: string, useOcr: boolean = false): Promise<string> {
-  const convertedBuffer = USE_SANDBOX
-    ? await convertViaSandbox(buffer, extension)
-    : await convertLocally(buffer, extension);
+  let convertedBuffer: Buffer;
+
+  if (USE_SANDBOX) {
+    try {
+      convertedBuffer = await convertViaSandbox(buffer, extension);
+    } catch (err) {
+      if (err instanceof Error && err.message === 'CIRCUIT_OPEN') {
+        throw new Error('Document conversion service temporarily unavailable. Please try again in a minute.');
+      }
+      throw err;
+    }
+  } else {
+    convertedBuffer = await convertLocally(buffer, extension);
+  }
 
   const config = useOcr ? { extractAttachments: true, ocr: true, ocrLanguage: 'eng' } : {};
   const ast = await officeParser.parseOffice(convertedBuffer, config);