Mira-logger-js NPM

mira-logger-js

An opinionated logging client for Node and the browser.

Usage

Initializing the client

const { MiraLogger } = require('mira-logger-js');

const logger = new MiraLogger({
  token: env.LOGGLY_CUSTOMER_TOKEN,
  environment: env.ENVIRONMENT,
  revision: env.REVISION,
  service: 'my-service',
});

See MiraLoggerOptions for the full set of options.

Log levels

logger.debug('debug message');
logger.info('info message');
logger.warn('warning message');
logger.error('error message');
logger.error(new Error('error message'));

// Send logs.
await logger.flush();

Setting context (optional)

Set the context to send with each subsequent log.

logger.setContext({ requestId: 'some-uuid' });

...

// Context passed in with an individual log is merged in with
// the default context set with `setContext`.
logger.info('info message', { statusCode: 200 });

// Logs [{ message: 'info message', requestId: 'some-uuid', statusCode: 200 }]
await logger.flush();

See Context for the full set of options.

Wrapping functions

Wrap a function with logger.wrap to automatically log errors and flush on return. Works with async functions too.

logger.wrap(async event => {
  // Thrown errors are automatically logged.
  throw Error('Oops!');

  // logger.flush() is called when this function returns;
  const data = await doStuff();
  return data;
});

Examples

Http Errors

class HttpError extends Error {
  constructor(code, message) {
    super(message);
    this.name = 'HttpError';
    // statusCode will automatically be logged.
    this.statusCode = code;
  }
}

const res = await fetch('https://example.com');

if (!res.ok) {
  logger.error(new HttpError(res.status, res.statusText));
}

Lambda Scheduled Event

const logger = new MiraLogger({
  token: env.LOGGLY_CUSTOMER_TOKEN,
  environment: env.ENVIRONMENT,
  service: 'my-service',
  // We manually flush at the end of the lambda so there's not
  // much point in keeping auto flushing enabled.
  enableAutoFlush: false
});

module.exports.handler = logger.wrap(async event => {
  logger.setContext({
    requestId: event.id,
    source: event.resources.join(','),
  });

  logger.info('Doing stuff...');

  const res = await fetch('https://example.com');
  if (!res.ok) {
    throw new Error(`Failed to fetch: ${res.status} | ${res.statusText}`);
  }

  logger.info('Done doing stuff.');

  ...

  // logger will flush after returning.
  return data
})