README

stackdriver-logging-winston-koa

This module provides an Koa middleware for working with Stackdriver Logging, compatible with Winston.

The implementation is adapted from the existing express middleware implementation in nodejs-logging-winston module.

For general documentation on winston logging to Stackdriver please refer to the nodejs-logging-winston module.

Quickstart

Installing the client library

npm install stackdriver-logging-winston-koa

Using the koa middleware

We provide a middleware that can be used in an koa application. Apart from being easy to use, this enables some more powerful features of Stackdriver Logging: request bundling. Any application logs emitted on behalf of a specific request will be shown nested inside the request log.

The middleware adds a winston-style log function to the ctx object. You can use this wherever you have access to the ctx object. All log entries that are made on behalf of a specific request are shown bundled together in the Stackdriver Logging UI.

const lw = require('stackdriver-logging-winston-koa');
const winston = require('winston');

// Import koa module and create an http server.
const koa = require('koa');
const logger = winston.createLogger();

async function startServer() {
  // Create a middleware that will use the provided logger.
  // A Stackdriver Logging transport will be created automatically
  // and added onto the provided logger.
  const mw = await lw.koa.makeMiddleware(logger);
  // Alternatively, you can construct a LoggingWinston transport
  // yourself and pass it int.
  // const transport = new LoggingWinston({...});
  // const mw = await lw.koa.makeMiddleware(logger, transport);
  const app = koa();

  // Install the logging middleware. This ensures that a Winston-style `log`
  // function is available on the `context` object. Attach this as one of the
  // earliest middleware to make sure that log function is available in all the
  // subsequent middleware and routes.
  app.use(mw);

  // Setup an http route and a route handler.
  app.use(async (ctx) => {
    // `ctx.log` can be used as a winston style log method. All logs generated
    // using `ctx.log` use the current request context. That is, all logs
    // corresponding to a specific request will be bundled in the Stackdriver
    // UI.
    ctx.log.info('this is an info log message');
    ctx.body = 'hello world';
  });

  // `logger` can be used as a global logger, one not correlated to any specific
  // request.
  logger.info('bonjour');

  // Start listening on the http server.
  app.listen(8080, () => {
    console.log('http server listening on port 8080');
  });
}

startServer();

Contributing

Contributions welcome!

License

Apache Version 2.0

Usage no npm install needed!