Application Insights for Node.js

Azure Application Insights monitors your backend services and components after you deploy them to help you discover and rapidly diagnose performance and other issues. Add this SDK to your Node.js services to include deep info about Node.js processes and their external dependencies such as database and cache services. You can use this SDK for your Node.js services hosted anywhere: your datacenter, Azure VMs and Web Apps, and even other public clouds.

This library tracks the following out-of-the-box:

Incoming and outgoing HTTP requests
Important system metrics such as CPU usage
Unhandled exceptions
Events from many popular third-party libraries (see Automatic third-party instrumentation)

You can manually track more aspects of your app and system using the API described in the Track custom telemetry section.

Getting Started

Create an Application Insights resource in Azure by following these instructions.
Grab the Instrumentation Key (aka "ikey") from the resource you created in step 1. Later, you'll either add it to your app's environment variables or use it directly in your scripts.
Add the Application Insights Node.js SDK to your app's dependencies and package.json:
```
npm install --save applicationinsights
```
Note: If you're using TypeScript, do not install a separate "typings" package. This NPM package contains built-in typings.
As early as possible in your app's code, load the Application Insights package:
```
let appInsights = require('applicationinsights');
```
Configure the local SDK by calling appInsights.setup('_your_ikey_');, using the ikey you grabbed in step 2. Or put this ikey in the APPINSIGHTS_INSTRUMENTATIONKEY environment variable and call appInsights.setup() without parameters.

For more configuration options see below.
Finally, start automatically collecting and sending data by calling appInsights.start();.

Basic Usage

For out-of-the-box collection of HTTP requests, popular third-party library events, unhandled exceptions, and system metrics:

let appInsights = require("applicationinsights");
appInsights.setup("_your_ikey_").start();

If the instrumentation key is set in the environment variable APPINSIGHTS_INSTRUMENTATIONKEY, .setup() can be called with no arguments. This makes it easy to use different ikeys for different environments.

Load the Application Insights library (i.e. require("applicationinsights")) as early as possible in your scripts, before loading other packages. This is needed so that the Application Insights library can prepare later packages for tracking. If you encounter conflicts with other libraries doing similar preparation, try loading the Application Insights library after those.

Because of the way JavaScript handles callbacks, additional work is necessary to track a request across external dependencies and later callbacks. By default this additional tracking is enabled; disable it by calling setAutoDependencyCorrelation(false) as described in the Configuration section below.

Migrating from versions prior to 0.22

There are breaking changes between releases prior to version 0.22 and after. These changes are designed to bring consistency with other Application Insights SDKs and allow future extensibility. Please review this README for new method and property names.

In general, you can migrate with the following:

Replace references to appInsights.client with appInsights.defaultClient
Replace references to appInsights.getClient() with new appInsights.TelemetryClient()
Replace all arguments to client.track* methods with a single object containing named properties as arguments. See your IDE's built-in type hinting, or TelemetryTypes, for the expected object for each type of telemetry.

If you access SDK configuration functions without chaining them to appInsights.setup(), you can now find these functions at appInsights.Configuration (eg. appInsights.Configuration.setAutoCollectDependencies(true)). Take care to review the changes to the default configuration in the next section.

Configuration

The appInsights object provides a number of configuration methods. They are listed in the following snippet with their default values.

let appInsights = require("applicationinsights");
appInsights.setup("<instrumentation_key>")
    .setAutoDependencyCorrelation(true)
    .setAutoCollectRequests(true)
    .setAutoCollectPerformance(true, true)
    .setAutoCollectExceptions(true)
    .setAutoCollectDependencies(true)
    .setAutoCollectConsole(true)
    .setUseDiskRetryCaching(true)
    .setSendLiveMetrics(false)
    .setDistributedTracingMode(appInsights.DistributedTracingModes.AI)
    .start();

Please review their descriptions in your IDE's built-in type hinting, or applicationinsights.ts for detailed information on what these control, and optional secondary arguments.

Note that by default setAutoCollectConsole is configured to exclude calls to console.log (and other console methods). By default, only calls to supported third-party loggers (e.g. winston, bunyan) will be collected. You can change this behavior to include calls to console methods by using setAutoCollectConsole(true, true).

Sampling

By default, the SDK will send all collected data to the Application Insights service. If you collect a lot of data, you might want to enable sampling to reduce the amount of data sent. Set the samplingPercentage field on the Config object of a Client to accomplish this. Setting samplingPercentage to 100 (the default) means all data will be sent, and 0 means nothing will be sent.

If you are using automatic correlation, all data associated with a single request will be included or excluded as a unit.

Add code such as the following to enable sampling:

const appInsights = require("applicationinsights");
appInsights.setup("<instrumentation_key>");
appInsights.defaultClient.config.samplingPercentage = 33; // 33% of all telemetry will be sent to Application Insights
appInsights.start();

Multiple roles for multi-component applications

If your application consists of multiple components that you wish to instrument all with the same Instrumentation Key and still see these components as separate units in the Portal as if they were using separate Instrumentation Keys (for example, as separate nodes on the Application Map) you may need to manually configure the RoleName field to distinguish one component's telemetry from other components sending data to your Application Insights resource. (See Monitor multi-component applications with Application Insights (preview))

Use the following to set the RoleName field:

const appInsights = require("applicationinsights");
appInsights.setup("<instrumentation_key>");
appInsights.defaultClient.context.tags[appInsights.defaultClient.context.keys.cloudRole] = "MyRoleName";
appInsights.start();

Automatic third-party instrumentation

In order to track context across asynchronous calls, some changes are required in third party libraries such as mongodb and redis. By default ApplicationInsights will use diagnostic-channel-publishers to monkey-patch some of these libraries. This can be disabled by setting the APPLICATION_INSIGHTS_NO_DIAGNOSTIC_CHANNEL environment variable. Note that by setting that environment variable, events may no longer be correctly associated with the right operation. Individual monkey-patches can be disabled by setting the APPLICATION_INSIGHTS_NO_PATCH_MODULES environment variable to a comma separated list of packages to disable, e.g. APPLICATION_INSIGHTS_NO_PATCH_MODULES=console,redis to avoid patching the console and redis packages.

Currently there are 9 packages which are instrumented: bunyan, console, mongodb, mongodb-core, mysql, redis, winston, pg, and pg-pool. Visit the diagnostic-channel-publishers' README for information about exactly which versions of these packages are patched.

The bunyan, winston, and console patches will generate Application Insights Trace events based on whether setAutoCollectConsole is enabled. The rest will generate Application Insights Dependency events based on whether setAutoCollectDependencies is enabled.

Live Metrics

To enable sending live metrics of your app to Azure, use setSendLiveMetrics(true). Filtering of live metrics in the Portal is currently not supported.

Extended Metrics

Note: The ability to send extended native metrics was added in version 1.4.0

To enable sending extended native metrics of your app to Azure, simply install the separate native metrics package. The SDK will automatically load it when it is installed and start collecting Node.js native metrics.

npm install applicationinsights-native-metrics

Currently, the native metrics package performs autocollection of Garbage Collection CPU time, Event Loop ticks, and heap usage:

Garbage Collection: The amount of CPU time spent on each type of garbage collection, and how many occurrences of each type.
Event Loop: How many ticks occurred and how much CPU time was spent in total.
Heap vs Non-Heap: How much of your app's memory usage is in the heap or non-heap.

Distributed Tracing Modes

By default, this SDK will send headers understood by other applications/services instrumented with an Application Insights SDK. You can optionally enable sending/receiving of W3C Trace Context headers in addition to the existing AI headers, so you will not break correlation with any of your existing legacy services. Enabling W3C headers will allow your app to correlate with other services not instrumented with Application Insights, but do adopt this W3C standard.

const appInsights = require("applicationinsights");
appInsights
  .setup("<your ikey>")
  .setDistributedTracingMode(appInsights.DistributedTracingModes.AI_AND_W3C)
  .start()

Track custom telemetry

You can track any request, event, metric or exception using the Application Insights client. Examples follow:

let appInsights = require("applicationinsights");
appInsights.setup().start(); // assuming ikey in env var. start() can be omitted to disable any non-custom data
let client = appInsights.defaultClient;
client.trackEvent({name: "my custom event", properties: {customProperty: "custom property value"}});
client.trackException({exception: new Error("handled exceptions can be logged with this method")});
client.trackMetric({name: "custom metric", value: 3});
client.trackTrace({message: "trace message"});
client.trackDependency({target:"http://dbname", name:"select customers proc", data:"SELECT * FROM Customers", duration:231, resultCode:0, success: true, dependencyTypeName: "ZSQL"});
client.trackRequest({name:"GET /customers", url:"http://myserver/customers", duration:309, resultCode:200, success:true});

let http = require("http");
http.createServer( (req, res) => {
  client.trackNodeHttpRequest({request: req, response: res}); // Place at the beginning of your request handler
});

An example utility using trackMetric to measure how long event loop scheduling takes:

function startMeasuringEventLoop() {
  var startTime = process.hrtime();
  var sampleSum = 0;
  var sampleCount = 0;

  // Measure event loop scheduling delay
  setInterval(() => {
    var elapsed = process.hrtime(startTime);
    startTime = process.hrtime();
    sampleSum += elapsed[0] * 1e9 + elapsed[1];
    sampleCount++;
  }, 0);

  // Report custom metric every second
  setInterval(() => {
    var samples = sampleSum;
    var count = sampleCount;
    sampleSum = 0;
    sampleCount = 0;

    if (count > 0) {
      var avgNs = samples / count;
      var avgMs = Math.round(avgNs / 1e6);
      client.trackMetric({name: "Event Loop Delay", value: avgMs});
    }
  }, 1000);
}

Preprocess data with Telemetry Processors

public addTelemetryProcessor(telemetryProcessor: (envelope: Contracts.Envelope, context: { http.RequestOptions, http.ClientRequest, http.ClientResponse, correlationContext }) => boolean)

You can process and filter collected data before it is sent for retention using Telemetry Processors. Telemetry processors are called one by one in the order they were added before the telemetry item is sent to the cloud.

If a telemetry processor returns false that telemetry item will not be sent.

All telemetry processors receive the telemetry data and its envelope to inspect and modify. They also receive a context object. The contents of this object is defined by the contextObjects parameter when calling a track method for manually tracked telemetry. For automatically collected telemetry, this object is filled with available request information and the persistent request context as provided by appInsights.getCorrelationContext() (if automatic dependency correlation is enabled).

The TypeScript type for a telemetry processor is:

telemetryProcessor: (envelope: ContractsModule.Contracts.Envelope, context: { http.RequestOptions, http.ClientRequest, http.ClientResponse, correlationContext }) => boolean;

For example, a processor that removes stack trace data from exceptions might be written and added as follows:

function removeStackTraces ( envelope, context ) {
  if (envelope.data.baseType === "Microsoft.ApplicationInsights.ExceptionData") {
    var data = envelope.data.baseData;
    if (data.exceptions && data.exceptions.length > 0) {
      for (var i = 0; i < data.exceptions.length; i++) {
        var exception = data.exceptions[i];
        exception.parsedStack = null;
        exception.hasFullStack = false;
      }
    }
  }
  return true;
}

appInsights.defaultClient.addTelemetryProcessor(removeStackTraces);

More info on the telemetry API is available in the docs.

Use multiple instrumentation keys

You can create multiple Azure Application Insights resources and send different data to each by using their respective instrumentation keys ("ikey"). For example:

let appInsights = require("applicationinsights");

// configure auto-collection under one ikey
appInsights.setup("_ikey-A_").start();

// track some events manually under another ikey
let otherClient = new appInsights.TelemetryClient("_ikey-B_");
otherClient.trackEvent({name: "my custom event"});

Examples

Track dependencies

let appInsights = require("applicationinsights");
let client = new appInsights.TelemetryClient();

var success = false;
let startTime = Date.now();
// execute dependency call here....
let duration = Date.now() - startTime;
success = true;

client.trackDependency({target:"http://dbname", name:"select customers proc", data:"SELECT * FROM Customers", duration:duration, resultCode:0, success: true, dependencyTypeName: "ZSQL"});

Assign custom properties to be included with all events

appInsights.defaultClient.commonProperties = {
  environment: process.env.SOME_ENV_VARIABLE
};

Manually track all HTTP GET requests

Note that all requests are tracked by default. To disable automatic collection, call .setAutoCollectRequests(false) before calling start().

appInsights.defaultClient.trackRequest({name:"GET /customers", url:"http://myserver/customers", duration:309, resultCode:200, success:true});

Alternatively you can track requests using trackNodeHttpRequest method:

var server = http.createServer((req, res) => {
  if ( req.method === "GET" ) {
      appInsights.defaultClient.trackNodeHttpRequest({request:req, response:res});
  }
  // other work here....
  res.end();
});

Track server startup time

let start = Date.now();
server.on("listening", () => {
  let duration = Date.now() - start;
  appInsights.defaultClient.trackMetric({name: "server startup time", value: duration});
});

Advanced configuration options

The Client object contains a config property with many optional settings for advanced scenarios. These can be set as follows:

client.config.PROPERTYNAME = VALUE;

These properties are client specific, so you can configure appInsights.defaultClient separately from clients created with new appInsights.TelemetryClient().

Property	Description
instrumentationKey	An identifier for your Application Insights resource
endpointUrl	The ingestion endpoint to send telemetry payloads to
quickPulseHost	The Live Metrics Stream host to send live metrics telemetry to
proxyHttpUrl	A proxy server for SDK HTTP traffic (Optional, Default pulled from `http_proxy` environment variable)
proxyHttpsUrl	A proxy server for SDK HTTPS traffic (Optional, Default pulled from `https_proxy` environment variable)
httpAgent	An http.Agent to use for SDK HTTP traffic (Optional, Default undefined)
httpsAgent	An https.Agent to use for SDK HTTPS traffic (Optional, Default undefined)
maxBatchSize	The maximum number of telemetry items to include in a payload to the ingestion endpoint (Default `250`)
maxBatchIntervalMs	The maximum amount of time to wait to for a payload to reach maxBatchSize (Default `15000`)
disableAppInsights	A flag indicating if telemetry transmission is disabled (Default `false`)
samplingPercentage	The percentage of telemetry items tracked that should be transmitted (Default `100`)
correlationIdRetryIntervalMs	The time to wait before retrying to retrieve the id for cross-component correlation (Default `30000`)
correlationHeaderExcludedDomains	A list of domains to exclude from cross-component correlation header injection (Default See Config.ts)

Branches

Ongoing development takes place on the develop branch. Please submit pull requests to this branch.
Releases are merged to the master branch and published to npm.

Contributing

Install all dependencies with npm install.

Set an environment variable to your instrumentation key (optional).

// windows
set APPINSIGHTS_INSTRUMENTATIONKEY=<insert_your_instrumentation_key_here>
// linux/macos
export APPINSIGHTS_INSTRUMENTATIONKEY=<insert_your_instrumentation_key_here>

Run tests

npm run test
npm run backcompattest
npm run functionaltest

Note: Functional tests require Docker

This project has adopted the Microsoft Open Source Code of Conduct. For more information see the Code of Conduct FAQ or contact opencode@microsoft.com with any additional questions or comments.

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