Errors and logging

When something throws

If a middleware throws or its promise rejects, the chain stops, the error is logged at error, and the client gets 500 Internal Server Error as text. If the response had already started, it's cut off instead, since its status can't be changed.

The same happens for a route handler written without defineMiddleware, and for any handler that finishes without responding, so no error goes unhandled and no request is left waiting.

To send your own error response, catch the error in the middleware and send it there:

async ({ incomingMessage, serverResponse }) => {
  try {
    await saveOrder(await incomingMessage.useJSONBody())
    serverResponse.sendCreatedJSONResponse()
  }
  catch (error) {
    if (error instanceof ValidationError) {
      return serverResponse.sendBadRequestJSONResponse({ message: error.message })
    }
    throw error // anything else becomes a 500
  }
}

The logger

The server logs to the logger it's given, and puts the same logger on every request's context, so middleware logs to the same place:

async ({ logger, incomingMessage }) => {
  logger.info(`Signed in from ${incomingMessage.socket.remoteAddress}`)
}

A logger is anything with debug, info, warn and error methods, so console fits. Without one, the server uses defaultLogger, the console without debug lines. silentLogger drops everything, which suits tests.

What webframe logs

Level
debug	The routes, as the server is defined. Every request, if you use useLogRequest.
info	Requests that matched no route.
error	Errors thrown by middleware, and chains that sent no response.

For JSON log files and readable console lines, use @webframe/logger:

import { createLogger } from '@webframe/logger'

defineServer({
  port: 3000,
  routes,
  logger: createLogger({ level: 'debug', directory: '/var/log/users' }),
})