NestJS + PG Aurora Serverless cold start about serverless-express

[brettstack]

Hi @lays147 in this case you should catch the error and respond with the response format expected by ALB, which I believe is this format:

{
    statusCode,
    body,
    headers,
    multiValueHeaders,
    isBase64Encoded
  }

[lays147]

@brettstack yeah, but where can I catch the error? If I return the json instead of the app on the nestApp.ts, handling the error inside the if condition, won't that be a problem for the serverless-express?

[brettstack]

Maybe something like this:

try {
  const app = await nestApp();

  await app.init();

  const expressApp = app.getHttpAdapter().getInstance();
  return serverlessExpress({ app: expressApp });
} catch(error) {
  return {
    statusCode,
    body,
    headers,
    multiValueHeaders,
    isBase64Encoded
  }
}

[lays147]

Amazon Q gave me a hand and suggested doing in the handler func:

export const handler: Handler = async (
  event: any,
  context: Context,
  callback: Callback,
) => {
  try {
    cachedServer = cachedServer ?? (await bootstrap());
    return cachedServer(event, context, callback);
  } catch (error) {
    callback(null, {
      statusCode: 502,
      body: JSON.stringify({
        error: 'Initialization process failed.',
        message: error.message,
      }),
      headers: {
        'Content-Type': 'application/json',
      },
    });
  }
};

I'll try this and get back to this issue.