@krakenjs/beaver-logger

beaver-logger

Front-end logger, which will:

• Buffer your front-end logs and periodically send them to the server side
• Allow you to log page transitions and gather performance stats
• Automatically log window performance stats, where available, and watch for event loop delays
• Automatically flush logs for any errors or warnings

This is a great tool to use if you want to do logging on the client side in the same way you do on the server, without worrying about sending off a million beacons. You can quickly get an idea of what's going on on your client, including error cases, page transitions, or anything else you care to log!

Overview

Basic logging

$logger.info(<event>, <payload>);

Queues a log. Options are debug, info, warn, error.

For example:

$logger.error('something_went_wrong', { error: err.toString() })

$logger.track(<payload>);

Call this to attach general tracking information to the current page. This is useful if the data is not associated with a specific event, and will be sent to the server the next time the logs are flushed.

Transitions

$logger.startTransition();

Call this when you start an ajax call or some other loading period, with the intention of moving to another page.

$logger.endTransition(<nextStateName>);

Call this when you transition to the next page. beaver-logger will automatically log the transition, and how long it took. The logs will be auto-flushed after this call.

$logger.transition(<nextStateName>);

This is a short-hand for logger.startTransition(); $logger.endTransition(<nextStateName>); when there is no loading time, and the transition from one state to another is instant. The logs will be auto-flushed after this call.

Initialization and configuration

$logger.init(<config>);

Set the logger up with your configuration options. This is optional. Configuration options are listed below.

Advanced

$logger.addMetaBuilder(<function>);

Attach a method which is called and will attach general information to the logging payload whenever the logs are flushed

$logger.addMetaBuilder(function() {
    return {
        current_page: getMyCurrentPage()
    };
});

$logger.addPayloadBuilder(<function>);

Attach a method which is called and will attach values to each individual log's payload whenever the logs are flushed

$logger.addPayloadBuilder(function() {
    return {
        performance_ts: window.performance.now()
    };
});

$logger.addTrackingBuilder(<function>);

Attach a method which is called and will attach values to each individual log's tracking whenever the logs are flushed

$logger.addTrackingBuilder(function() {
    return {
        pageLoadTime: getPageLoadTime()
    };
});

$logger.addHeaderBuilder(<function>);

Attach a method which is called and will attach values to each individual log requests' headers whenever the logs are flushed

$logger.addHeaderBuilder(function() {
    return {
        'x-csrf-token': getCSRFToken()
    };
});

$logger.flush();

Flushes the logs to the server side. Recommended you don't call this manually, as it will happen automatically on page transitions, or after a configured interval.

Installing

• Install via npm or bower

npm install --save beaver-logger or bower install --save beaver-logger

• Include in your project

<script src="/js/beaver-logger.min.js"></script>

or

let $logger = require('beaver-logger');

Front-End Configuration

$logger.init({

    // URI to post logs to
    uri: '/api/log',

    // State name to post logs under
    initial_state_name: 'init',

    // Interval at which to automatically flush logs to the server
    flushInterval:    10 * 60 * 1000,

    // Interval at which to debounce $logger.flush calls
    debounceInterval: 10,

    // Limit on number of logs before auto-flush happens
    sizeLimit: 300,

    // Supress `console.log`s when `true`
    // Recommended for production usage
    silent: false,

    // Enable or disable heartbeats, which run on an interval
    heartbeat: true,

    // Heartbeat log interval
    heartbeatInterval: 5000,

    // Maximum number of sequential heartbeat logs
    heartbeatMaxThreshold: 50,

    // Monitors for event loop delays and triggers a toobusy event
    heartbeatTooBusy: false,

    // Event loop delay which triggers a toobusy event
    heartbeatTooBusyThreshold: 10000,

    // Log levels which trigger an auto-flush to the server
    autoLog: ['warn', 'error'],

    // Log window.onunload and window.beforeUnload events?
    logUnload: true,

    // Log unload synchronously, to guarantee the log gets through?
    logUnloadSync: false,

    // Log performance stats from the browser automatically?
    logPerformance:  true
});

Server Side

beaver-logger includes a small node endpoint which will automatically accept the logs sent from the client side. You can mount this really easily:

let beaverLogger = require('beaver-logger/server');

myapp.use(beaverLogger.expressEndpoint({

    // URI to recieve logs at
    uri: '/api/log',

    // Custom logger (optional, by default logs to console)
    logger: myLogger,

    // Enable cross-origin requests to your logging endpoint
    enableCors: false
}))

Or if you're using kraken, you can add this in your config.json as a middleware:

      "beaver-logger": {
          "priority": 106,
          "module": {
              "name": "beaver-logger/server",
              "method": "expressEndpoint",
              "arguments": [
                  {
                      "uri": "/api/log",
                      "logger": "require:my-custom-logger-module"
                  }
              ]
          }
      }

Custom backend logger

Setting up a custom logger is really easy, if you need to transmit these logs to some backend logging service rather than just logging them to your server console:

module.exports = {

    log: function(req, level, event, payload) {

        logSocket.send(JSON.stringify({
            level: level,
            event: event,
            payload: payload
        }));
    }
}

Data Flow