fix(test): eliminate Winston uncaughtException listener leak (#3544)

* fix(test): eliminate Winston uncaughtException listener leak in jest test runs

Each jest.resetModules() call in beforeEach re-imports lib/services/logger.js,
creating a new Winston logger with handleExceptions:true. Winston registers a new
process.uncaughtException listener on every import but never removes orphaned
listeners from prior module registry generations. Across 1226 tests with
resetModules in beforeEach, this leaked ~570 listeners and ~285-1100MB of heap.

The billing PRs (#3535-#3539) amplified an existing pre-billing leak (162
instances) by +409 new instances (+252%) — pushing trawl_node past its 6144MB
cap.

Fix: guard handleExceptions with `process.env.NODE_ENV !== 'test'` on both the
Console transport (logger creation) and the File transport (setupFileLogger /
getLogOptions). Exception handling is preserved in production and development.

Also add `forceExit: true` to jest.config.js to prevent Jest from hanging on
open MongoDB handles from integration test afterAll disconnect races.

Verified: MaxListenersExceededWarning fully eliminated. 99 suites / 1226 tests
all pass.

* docs(logger): replace volatile metrics with stable explanation in handleExceptions guard

Author: PierreBrisorgueil

jest.config.js

@@ -162,6 +162,10 @@ export default {
   // The test environment that will be used for testing
   testEnvironment: 'node',
 
+  // Force Jest to exit after all tests complete — prevents hanging on open MongoDB
+  // handles from integration tests whose afterAll disconnect races with Jest's exit
+  forceExit: true,
+
   // Global timeout for tests and hooks (integration tests bootstrap MongoDB + Express)
   testTimeout: 15000,
 

lib/services/logger.js

@@ -28,7 +28,11 @@ const logger = new winston.createLogger({
     new winston.transports.Console({
       level: logLevel,
       format: consoleFormat,
-      handleExceptions: true,
+      // Disable exception handling in test env — each jest.resetModules() re-imports
+      // this module, and handleExceptions:true registers a new process.uncaughtException
+      // listener on every import without ever removing the old one, causing listener
+      // accumulation and heap growth across module reloads in beforeEach hooks.
+      handleExceptions: process.env.NODE_ENV !== 'test',
     }),
   ],
   exitOnError: false,
@@ -71,7 +75,8 @@ const getLogOptions = () => {
     eol: '\n',
     tailable: true,
     showLevel: true,
-    handleExceptions: true,
+    // Same guard as the Console transport — see comment at top of createLogger call
+    handleExceptions: process.env.NODE_ENV !== 'test',
     humanReadableUnhandledException: true,
   };
 };