From 3e55b61872cce81cf12e57c2baa668af57836438 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=B6ren=20Johanson?= <soeren@soeren.codes>
Date: Thu, 19 Dec 2024 13:02:59 +0100
Subject: [PATCH] Add final exception handler to prevent container crashes
 (#629)

---
 .../src/filters/global-exception.filter.ts    | 62 +++++++++++++++++++
 teammapper-backend/src/main.ts                | 17 +++++
 2 files changed, 79 insertions(+)
 create mode 100644 teammapper-backend/src/filters/global-exception.filter.ts

diff --git a/teammapper-backend/src/filters/global-exception.filter.ts b/teammapper-backend/src/filters/global-exception.filter.ts
new file mode 100644
index 00000000..2ac3e5f4
--- /dev/null
+++ b/teammapper-backend/src/filters/global-exception.filter.ts
@@ -0,0 +1,62 @@
+import { ExceptionFilter, Catch, ArgumentsHost, Logger, HttpException } from '@nestjs/common';
+
+// This is for any unhandled gateway and "internal" NestJS related errors - like if the gateway can't reach clients or things like that.
+// It will try to always keep clients and their websockets alive and gracefully send errors over the wire, without revealing internal error reasons.
+@Catch()
+export class GlobalExceptionFilter implements ExceptionFilter {
+  private readonly logger = new Logger(GlobalExceptionFilter.name);
+
+  catch(exception: Error | HttpException | unknown, host: ArgumentsHost) {
+    const ctx = host.getType();
+
+    this.logger.error({
+      error: exception,
+      type: exception?.constructor?.name || typeof exception,
+      message: exception?.message || 'Unknown error',
+      stack: exception?.stack,
+      context: ctx,
+    });
+
+    try {
+      switch (ctx) {
+        case 'http': {
+          const response = host.switchToHttp().getResponse();
+          return response.status(500).json({
+            statusCode: 500,
+            message: 'Internal server error',
+            timestamp: new Date().toISOString(),
+          });
+        }
+
+        case 'ws': {
+          const client = host.switchToWs().getClient();
+          const error = {
+            event: 'error',
+            data: {
+              message: 'Internal server error',
+              timestamp: new Date().toISOString(),
+            },
+          };
+
+          if (typeof client.emit === 'function') {
+            client.emit('error', error);
+          } else if (typeof client.send === 'function') {
+            client.send(JSON.stringify(error));
+          }
+          break;
+        }
+
+        default: {
+          // Handle any runtime errors outside HTTP/WS contexts
+          this.logger.error(`Unhandled exception type: ${ctx}`);
+          // Emit to process handler as last resort
+          process.emit('uncaughtException', exception);
+        }
+      }
+    } catch (handlerError) {
+      // If the error handler itself fails, log it and emit to process
+      this.logger.error('Global exception handler failed: ', handlerError);
+      process.emit('uncaughtException', exception);
+    }
+  }
+}
\ No newline at end of file
diff --git a/teammapper-backend/src/main.ts b/teammapper-backend/src/main.ts
index 861a1e65..f2097df7 100644
--- a/teammapper-backend/src/main.ts
+++ b/teammapper-backend/src/main.ts
@@ -2,12 +2,29 @@ import { NestFactory } from '@nestjs/core'
 import AppModule from './app.module'
 import configService from './config.service'
 import { createProxyMiddleware } from 'http-proxy-middleware'
+import { GlobalExceptionFilter } from './filters/global-exception.filter';
+import { Logger } from '@nestjs/common'
 
 async function bootstrap() {
+  const logger = new Logger('Main Process');
+
+  // Process-level handlers for uncaught errors - anything that happens outside of NestJS, such as type errors.
+  // This is only logged server-side so we log the whole stack for better review.
+  process.on('uncaughtException', (error) => {
+    logger.error('Uncaught Exception: ', error.stack);
+  });
+
+  process.on('unhandledRejection', (reason: unknown) => {
+    const stack = reason instanceof Error ? reason.stack : 'No stack trace available';
+    logger.error('Unhandled Rejection. Stack trace: ', stack);
+  });
+
   const app = await NestFactory.create(AppModule, {
     logger: ['log', 'error', 'warn', 'debug'],
   })
 
+  app.useGlobalFilters(new GlobalExceptionFilter());
+
   app.use(
     '/arasaac/api',
     createProxyMiddleware({