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Hapi process monitoring

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hapi process monitoring

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The 'Monitor' should be configured using a 'hapi' server instead of calling the 'Monitor' constructor directly.

good is a process monitor for three types of events:

  • System and process performance (ops) - CPU, memory, disk, and other metrics.
  • Requests logging (request) - framework and application generated logs generated during the lifecycle of each incoming request.
  • General events (log) - logging information not bound to a specific request such as system errors, background processing, configuration errors, etc. Described in General Events Logging.

Applications with multiple server instances, each with its own monitor should only include one log subscription per destination as general events are a process-wide facility and will result in duplicated log events. To override some or all of the defaults, set options to an object with the following optional settings:

  • broadcastInterval - the interval in milliseconds to send collected events to HTTP subscribers. 0 means send immediately. Defaults to 0.
  • opsInterval - the interval in milliseconds to sample system and process performance metrics. Minimum is 100ms. Defaults to 15 seconds.
  • leakDetection - determines if memory leaks should be detected. Any leaks will be logged with ops data. Defaults to false.
  • extendedRequests - determines if the full request log is sent or only the event summary. Defaults to false.
  • maxLogSize - the maximum byte size to allow log files to become before creating a new log file. Default is 0 which means log files will not be split. When split the log file extension will be incremented by 1. The initial log file has an extension of .001.
  • requestsEvent - the event type used to capture completed requests. Defaults to 'tail'. Options are:
    • 'response' - the response was sent but request tails may still be pending.
    • 'tail' - the response was sent and all request tails completed.
  • requestsTimeout - the number of milliseconds to set the request timeout to when broadcasting to HTTP subscribers
  • subscribers - an object where each key is a destination and each value is either an array or object with an array of subscriptions. The subscriptions that are available are ops, request, and log. The destination can be a URI, file or directory path, and console. Defaults to a console subscriber for ops, request, and log events. To disable the console output for the server instance pass an empty array into the subscribers "console" configuration.

For example:

var options = {
    subscribers: {
        console: ['ops', 'request', 'log'],
        'http://localhost/logs': ['log'],
        '/tmp/logs/': ['request', 'log']

hapi.plugin.require('good', options, function (err) {

    if (!err) {
        // Plugin loaded successfully

Disabling console output:

var options = {
    subscribers: {
        console: [],
        'http://localhost/logs': ['log']

Log messages are created with tags. Usually a log will include a tag to indicate if it is related to an error or info along with where the message originates. If, for example, the console should only output error's that were logged you can use the following configuration:

var options = {
    subscribers: {
        console: { tags: ['error'], events: ['log'] }

Log file subscribers can either be a file or a directory. When logging to a file (there isn't a trailing slash) then the files will be written with the file name in the provided path. Otherwise, when the subscriber is a directory the log files will be named with a timestamp and placed in the directory. All log files will have .001, .002, and .003 formatted extensions. Below is an example of file and directory subscribers:

var options = {
    subscribers: {
        '/logs/good_log': { tags: ['error'], events: ['log'] },     // Creates good_log.001 file in /logs/
        '/logs/': { events: ['request'] }                           // Creates {timestamp}.001 file in /logs/

Broadcast Request Structure

When good broadcasts data to a remote endpoint it sends json that has the following properties:

  • schema - the value of 'schemaName' in the settings. Default is 'good.v1'
  • host - the operating system hostname
  • appVer - the version of good
  • timestamp - the current time of the server
  • events - an array of the events that are subscribed to

Replaying request logs

Good includes a 'replay' script that is capabale of replaying any request events found in a log file. Below is the command to use to execute 'replay':

replay -l log.json -h host -n #_of_concurrent_requests

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