Cloud Logging stream for Bunyan


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Cloud Logging for Bunyan: Node.js Client

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This module provides an easy to use, higher-level layer for working with Cloud Logging, compatible with Bunyan. Simply attach this as a transport to your existing Bunyan loggers.

A comprehensive list of changes in each version may be found in the CHANGELOG.

Read more about the client libraries for Cloud APIs, including the older Google APIs Client Libraries, in Client Libraries Explained.

Table of contents:


Before you begin

  1. Select or create a Cloud Platform project.
  2. Enable the Cloud Logging for Bunyan API.
  3. Set up authentication with a service account so you can access the API from your local workstation.

Installing the client library

npm install @google-cloud/logging-bunyan

Using the client library

const bunyan = require('bunyan');

// Imports the Google Cloud client library for Bunyan
const {LoggingBunyan} = require('@google-cloud/logging-bunyan');

// Creates a Bunyan Cloud Logging client
const loggingBunyan = new LoggingBunyan();

// Create a Bunyan logger that streams to Cloud Logging
// Logs will be written to: "projects/YOUR_PROJECT_ID/logs/bunyan_log"
const logger = bunyan.createLogger({
  // The JSON payload of the log as it appears in Cloud Logging
  // will contain "name": "my-service"
  name: 'my-service',
  streams: [
    // Log to the console at 'info' and above
    {stream: process.stdout, level: 'info'},
    // And log to Cloud Logging, logging at 'info' and above

// Writes some log entries
logger.error('warp nacelles offline');
logger.info('shields at 99%');

Using as an express middleware

NOTE: this feature is experimental. The API may change in a backwards incompatible way until this is deemed stable. Please provide us feedback so that we can better refine this express integration.

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

Request Bundling Example

The middleware adds a bunyan-style log function to the request object. You can use this wherever you have access to the request object (req in the sample below). All log entries that are made on behalf of a specific request are shown bundled together in the Cloud Logging UI.

const lb = require('@google-cloud/logging-bunyan');

// Import express module and create an http server.
const express = require('express');

async function startServer() {
  const {logger, mw} = await lb.express.middleware();
  const app = express();

  // Install the logging middleware. This ensures that a Bunyan-style `log`
  // function is available on the `request` object. Attach this as one of the
  // earliest middleware to make sure that log function is available in all the
  // subsequent middleware and routes.

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

  // `logger` can be used as a global logger, one not correlated to any specific
  // request.
  logger.info({port: 8080}, 'bonjour');

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


Error Reporting

Any Error objects you log at severity error or higher can automatically be picked up by [Cloud Error Reporting][error-reporting] if you have specified a serviceContext.service when instantiating a LoggingBunyan instance:

const loggingBunyan = new LoggingBunyan({
  serviceContext: {
    service: 'my-service', // required to report logged errors
                           // to the Google Cloud Error Reporting
                           // console
    version: 'my-version'

It is an error to specify a serviceContext but not specify serviceContext.service.

Make sure to add logs to your [uncaught exception][uncaught] and [unhandled rejection][unhandled] handlers if you want to see those errors too.

You may also want to see the [@google-cloud/error-reporting][@google-cloud/error-reporting] module which provides direct access to the Error Reporting API.

LogEntry Labels

If the bunyan log record contains a label property where all the values are strings, we automatically promote that property to be the LogEntry.labels value rather than being one of the properties in the payload fields. This makes it easier to filter the logs in the UI using the labels.

logger.info({labels: {someKey: 'some value'}}, 'test log message');

All the label values must be strings for this automatic promotion to work. Otherwise the labels are left in the payload.

Formatting Request Logs

To format your request logs you can provide a httpRequest property on the bunyan metadata you provide along with the log message. We will treat this as the [HttpRequest][http-request-message] message and Cloud logging will show this as a request log. Example:

Request Log Example

  httpRequest: {
    status: res.statusCode,
    requestUrl: req.url,
    requestMethod: req.method,
    remoteIp: req.connection.remoteAddress,
    // etc.
}, req.path);

The httpRequest property must be a properly formatted [HttpRequest][http-request-message] message. (Note: the linked protobuf documentation shows snake_case property names, but in JavaScript one needs to provide property names in camelCase.)

Correlating Logs with Traces

If you use [@google-cloud/trace-agent][trace-agent] module, then this module will set the Cloud Logging [LogEntry][LogEntry] trace property based on the current trace context when available. That correlation allows you to [view log entries][trace-viewing-log-entries] inline with trace spans in the Cloud Trace Viewer. Example:

Logs in Trace Example

If you wish to set the Cloud LogEntry trace property with a custom value, then write a Bunyan log entry property for 'logging.googleapis.com/trace', which is exported by this module as LOGGING_TRACE_KEY. For example:

const bunyan = require('bunyan');
// Node 6+
const {LoggingBunyan, LOGGING_TRACE_KEY} = require('@google-cloud/logging-bunyan');
const loggingBunyan = LoggingBunyan();


  [LOGGING_TRACE_KEY]: 'custom-trace-value'
}, 'Bunyan log entry with custom trace field');


Samples are in the samples/ directory. Each sample's README.md has instructions for running its sample.

Sample Source Code Try it
Express source code Open in Cloud Shell
Quickstart source code Open in Cloud Shell
Explict Auth Setup source code Open in Cloud Shell

The Cloud Logging for Bunyan Node.js Client API Reference documentation also contains samples.

Supported Node.js Versions

Our client libraries follow the Node.js release schedule. Libraries are compatible with all current active and maintenance versions of Node.js.

Client libraries targeting some end-of-life versions of Node.js are available, and can be installed via npm dist-tags. The dist-tags follow the naming convention legacy-(version).

Legacy Node.js versions are supported as a best effort:

  • Legacy versions will not be tested in continuous integration.
  • Some security patches may not be able to be backported.
  • Dependencies will not be kept up-to-date, and features will not be backported.

Legacy tags available

  • legacy-8: install client libraries from this dist-tag for versions compatible with Node.js 8.


This library follows Semantic Versioning.

This library is considered to be General Availability (GA). This means it is stable; the code surface will not change in backwards-incompatible ways unless absolutely necessary (e.g. because of critical security issues) or with an extensive deprecation period. Issues and requests against GA libraries are addressed with the highest priority.

More Information: Google Cloud Platform Launch Stages


Contributions welcome! See the Contributing Guide.

Please note that this README.md, the samples/README.md, and a variety of configuration files in this repository (including .nycrc and tsconfig.json) are generated from a central template. To edit one of these files, make an edit to its templates in directory.


Apache Version 2.0


If you find any bugs or have a feature request, please open an issue on github!

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