Different uncaughtException handling (#4511)

* Different uncaughtException handling

We've seen some uncaught exceptions where the process exits before logs are apparently flushed. This hopefully addresses that. Also start up sentry earlier, and catch top level exits differently.

With ref to winstonjs/winston#1504 (comment) and https://nodejs.org/api/process.html#event-uncaughtexception

app.js

@@ -453,6 +453,11 @@ const awsProps = props.propsFor('aws');
 // eslint-disable-next-line max-statements
 async function main() {
     await aws.initConfig(awsProps);
+    // Initialise express and then sentry. Sentry as early as possible to catch errors during startup.
+    const webServer = express(),
+        router = express.Router();
+    setupSentry(aws.getConfig('sentryDsn'));
+
     startWineInit();
 
     const clientOptionsHandler = new ClientOptionsHandler(sources, compilerProps, defArgs);
@@ -505,9 +510,6 @@ async function main() {
         process.exit(0);
     }
 
-    const webServer = express(),
-        router = express.Router();
-    setupSentry(aws.getConfig('sentryDsn'));
     const healthCheckFilePath = ceProps('healthCheckFilePath', false);
 
     const handlerConfig = {
@@ -818,24 +820,29 @@ if (opts.version) {
     process.exit(0);
 }
 
-process.on('uncaughtException', terminationHandler('uncaughtException', 1));
-process.on('SIGINT', terminationHandler('SIGINT', 0));
-process.on('SIGTERM', terminationHandler('SIGTERM', 0));
-process.on('SIGQUIT', terminationHandler('SIGQUIT', 0));
+process.on('uncaughtException', uncaughtHandler);
+process.on('SIGINT', signalHandler('SIGINT'));
+process.on('SIGTERM', signalHandler('SIGTERM'));
+process.on('SIGQUIT', signalHandler('SIGQUIT'));
 
-function terminationHandler(name, code) {
-    return error => {
+function signalHandler(name) {
+    return () => {
         logger.info(`stopping process: ${name}`);
-        if (error && error instanceof Error) {
-            logger.error(error);
-        }
-        process.exit(code);
+        process.exit(0);
     };
 }
 
+function uncaughtHandler(err, origin) {
+    logger.info(`stopping process: Uncaught exception: ${err}\nException origin: ${origin}`);
+    // The app will exit naturally from here, but if we call `process.exit()` we may lose log lines.
+    // see https://github.com/winstonjs/winston/issues/1504#issuecomment-1033087411
+    process.exitCode = 1;
+}
+
 // Once we move to modules, we can remove this and use a top level await.
 // eslint-disable-next-line unicorn/prefer-top-level-await
 main().catch(err => {
     logger.error('Top-level error (shutting down):', err);
-    process.exit(1);
+    // Shut down after a second to hopefully let logs flush.
+    setTimeout(() => process.exit(1), 1000);
 });