Is there any way to output logs using log4js on Cloud Functions?

Question

I'm using GCP's cloud function. What I want to achieve is to output logs by log4js.

I know and have tried that using console.xxx() works well.

Environment: - Google Cloud Functions - Functions-framework - nodejs10 as Runtime

logger.js

const log4js = require('log4js');

const logger = exports = module.exports = {};

log4js.configure({
  appenders: {
    out: { type: 'console' },
    trail: {
      type: 'dateFile',
      filename: './logs/trail',
      pattern: '-yyyy-MMdd-hh.log',
      alwaysIncludePattern: true
    }
  },
  categories: {
    default: { appenders: [ 'out' ], level: 'info' },
    trail: { appenders: [ 'trail' ], level: 'DEBUG' }
  }
})

logger.trail = log4js.getLogger('trail')

index.js

const { logger } = require('./logger');

exports.spTest = (pubSubEvent, context) => {
  console.log('console.log should appear'); // => properly logged
  logger.trail.error('logger should appear'); => doesn't show up
};

Thanks in advance!

Answer 1

According to the oficial documentation link:

Cloud Logging is part of the Google Cloud's operations suite of products in Google Cloud. It includes storage for logs, a user interface called the Logs Viewer, and an API to manage logs programmatically.

Also Custom StackDriver logs

Cloud Functions logs are backed by StackDriver Logging. You can use the StackDriver Logging library for Node.js to log events with structured data, enabling easier analysis and monitoring.

const { Logging } = require('@google-cloud/logging');

// ...

// Instantiate the StackDriver Logging SDK. The project ID will
// be automatically inferred from the Cloud Functions environment.
const logging = new Logging();
const log = logging.log('my-custom-log-name');

// This metadata is attached to each log entry. This specifies a fake
// Cloud Function called 'Custom Metrics' in order to make your custom
// log entries appear in the Cloud Functions logs viewer.
const METADATA = {
  resource: {
    type: 'cloud_function',
    labels: {
      function_name: 'CustomMetrics',
      region: 'us-central1'
    }
  }
};

// ...

// Data to write to the log. This can be a JSON object with any properties
// of the event you want to record.
const data = {
  event: 'my-event',
  value: 'foo-bar-baz',

  // Optional 'message' property will show up in the Firebase
  // console and other human-readable logging surfaces
  message: 'my-event: foo-bar-baz'
};

// Write to the log. The log.write() call returns a Promise if you want to
// make sure that the log was written successfully.
const entry = log.entry(METADATA, data);
log.write(entry);index.js

Therefore, I do not think you can use log4js on Cloud Functions.