RFC: Custom logger on the start server

[zrosenbauer]

Problem

Currently all of the server-side logging is done via good ole' console but I'd like to be able to use a dedicated logger across the board. This would allow developers to hook into logging tools because the logs need to follow a certain format. If we are unable to do this I would be unable to create metrics etc.

Solution

Provide a way for developers to inject a logger of their choice, such as pino or bunyan.

Note

There is already some-level of support via the middleware https://tanstack.com/start/latest/docs/framework/react/middleware

API

I'm proposing to mirror the API from Fastify (https://fastify.dev/docs/latest/Reference/Server/#loggerinstance) as it's well defined.

import createLogger from 'my-logger';

interface StartLoggerLogFn {
  <T extends object>(obj: T, msg?: string, ...args: any[]): void;
  (obj: unknown, msg?: string, ...args: any[]): void;
  (msg: string, ...args: any[]): void;
}

interface StartLogger {
  fatal: StartLoggerLogFn;
  error: StartLoggerLogFn;
  warn: StartLoggerLogFn;
  info: StartLoggerLogFn;
  debug: StartLoggerLogFn;
  trace: StartLoggerLogFn;
  silent: StartLoggerLogFn;
}

export default createStartHandler({
  createRouter,
  getRouterManifest,
  logger,
})(defaultStreamHandler);

Polyfill / Example

I created a quick polyfill to test it out.

import createLogger from 'pino';
const logger = createLogger();
console.log = logger.info.bind(logger);
console.error = logger.error.bind(logger);
console.info = logger.info.bind(logger);
console.debug = logger.debug.bind(logger);
console.warn = logger.warn.bind(logger);

Output:

LOE

I'm not a 100% sure on the level of effort, but a quick search in VS Code under the packages/start-* dirs, I found 78 results across 29 files that include the text console..

I don't believe ALL of these would need or should be migrated as some could be client-side, others could be migrated later just probably need to include the primary paths.

Questions

• Should this just be router middleware aka provide a way to hook into request/response lifecycle?
• Should we default to a standard logger i.e. pino?
• Should we allow injecting a logger on the frontend, i.e. to allow silencing the output
• Could we just create an internal logger, following a semi-standard output aka something other than raw console.log