applicationinsights

What is applicationinsights?

The applicationinsights npm package is a powerful tool for monitoring and diagnosing performance issues in your applications. It provides a range of features for collecting telemetry data, tracking custom events, and monitoring dependencies, among other capabilities.

What are applicationinsights's main functionalities?

Telemetry Client

The Telemetry Client allows you to track custom events and metrics. This example demonstrates how to set up the client and track a custom event.

const appInsights = require('applicationinsights');
appInsights.setup('YOUR_INSTRUMENTATION_KEY').start();
const client = appInsights.defaultClient;
client.trackEvent({ name: 'my custom event', properties: { customProperty: 'custom value' } });

Request Tracking

Request Tracking automatically collects and sends telemetry data for incoming HTTP requests. This example shows how to set up a basic HTTP server with request tracking enabled.

const appInsights = require('applicationinsights');
appInsights.setup('YOUR_INSTRUMENTATION_KEY').start();
const http = require('http');
http.createServer((req, res) => {
  res.writeHead(200, { 'Content-Type': 'text/plain' });
  res.end('Hello World\n');
}).listen(8080);

Dependency Tracking

Dependency Tracking allows you to monitor the performance and success of external dependencies. This example demonstrates how to manually track a dependency.

const appInsights = require('applicationinsights');
appInsights.setup('YOUR_INSTRUMENTATION_KEY').start();
const client = appInsights.defaultClient;
client.trackDependency({ target: 'http://example.com', name: 'GET /', data: 'http://example.com', duration: 100, resultCode: 200, success: true });

Exception Tracking

Exception Tracking captures and sends telemetry data for exceptions. This example shows how to track an exception.

const appInsights = require('applicationinsights');
appInsights.setup('YOUR_INSTRUMENTATION_KEY').start();
const client = appInsights.defaultClient;
try {
  throw new Error('Test error');
} catch (e) {
  client.trackException({ exception: e });
}

Other packages similar to applicationinsights

winston

Winston is a versatile logging library for Node.js. While it focuses more on logging rather than telemetry, it can be used to log events, errors, and other information. It does not provide the same level of built-in telemetry and performance monitoring as applicationinsights.

log4js

Log4js is another logging library for Node.js, inspired by the Java log4j library. It provides a variety of appenders for logging to different destinations. Like winston, it focuses on logging rather than telemetry and performance monitoring.

newrelic

New Relic is a comprehensive application performance monitoring tool that provides similar functionalities to applicationinsights, including telemetry, error tracking, and performance monitoring. It is a commercial product with a broader set of features and integrations.

datadog

Datadog is a monitoring and analytics platform for developers, IT operations teams, and business users. It offers extensive features for monitoring applications, including telemetry, performance metrics, and log management. It is a commercial product with a wide range of integrations and capabilities.

README

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

1. Create an Application Insights resource in Azure by following these instructions.
2. 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.
3. 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.

4. As early as possible in your app's code, load the Application Insights package:

   let appInsights = require('applicationinsights');
   

5. 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.

6. Finally, start automatically collecting and sending data by calling appInsights.start();.

Basic Usage

Important: applicationinsights must be setup and started before you import anything else. There may be resulting telemetry loss if other libraries are imported first.

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.

Azure Functions

Due to how Azure Functions (and other FaaS services) handle incoming requests, they are not seen as http requests to the Node.js runtime. For this reason, Request -> Dependency correlelation will not work out of the box. To enable tracking here, you simply need to grab the context from your Function request handler, and wrap your Function with that context.

Setting up Auto-Correlation for Azure Functions

You do not need to make any changes to your existing Function logic. Instead, you can update the default export of your httpTrigger to be wrapped with some Application Insights logic:

...

// Default export wrapped with Application Insights FaaS context propagation
export default async function contextPropagatingHttpTrigger(context, req) {
    // Start an AI Correlation Context using the provided Function context
    const correlationContext = appInsights.startOperation(context, req);

    // Wrap the Function runtime with correlationContext
    return appInsights.wrapWithCorrelationContext(async () => {
        const startTime = Date.now(); // Start trackRequest timer

        // Run the Function
        await httpTrigger(context, req);

        // Track Request on completion
        appInsights.defaultClient.trackRequest({
            name: context.req.method + " " + context.req.url,
            resultCode: context.res.status,
            success: true,
            url: req.url,
            duration: Date.now() - startTime,
            id: correlationContext.operation.parentId,
        });
        appInsights.defaultClient.flush();
    }, correlationContext)();
};

Azure Functions Example

An example of making an axios call to https://httpbin.org and returning the reponse.

const appInsights = require("applicationinsights");
appInsights.setup("ikey")
    .setAutoCollectPerformance(false)
    .start();

const axios = require("axios");

/**
 * No changes required to your existing Function logic
 */
const httpTrigger = async function (context, req) {
    const response = await axios.get("https://httpbin.org/status/200");

    context.res = {
        status: response.status,
        body: response.statusText,
    };
};

// Default export wrapped with Application Insights FaaS context propagation
export default async function contextPropagatingHttpTrigger(context, req) {
    // Start an AI Correlation Context using the provided Function context
    const correlationContext = appInsights.startOperation(context, req);

    // Wrap the Function runtime with correlationContext
    return appInsights.wrapWithCorrelationContext(async () => {
        const startTime = Date.now(); // Start trackRequest timer

        // Run the Function
        await httpTrigger(context, req);

        // Track Request on completion
        appInsights.defaultClient.trackRequest({
            name: context.req.method + " " + context.req.url,
            resultCode: context.res.status,
            success: true,
            url: req.url,
            duration: Date.now() - startTime,
            id: correlationContext.operation.parentId,
        });
        appInsights.defaultClient.flush();
    }, correlationContext)();
};

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_AND_W3C)
    .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();

If running in Azure App service or Azure functions the SDK will automatically populate the cloud role when following code is added:

const appInsights = require("applicationinsights");
appInsights.setup("<instrumentation_key>");
appInsights.defaultClient.setAutoPopulateAzureProperties(true);
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. Make sure that applicationinsights is imported before any 3rd-party packages for them to be instrumented successfully.

Automatic instrumentation for several Azure SDKs is also available, you must manually install @opentelemetry/tracing to enable this automatic tracing. No additional configuration is required Currently Cognitive Search, Communication Common and Cosmos DB SDKs are not supported. Javascript Azure SDKs

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
});

Note that custom properties are converted to their string representation before being sent, see Using properties for more information.

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 === "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)

Migrating to applicationinsights@2.0.0 (Beta)

An experimental / beta version of the SDK is also available, but not recommended for production. It is built on top of the OpenTelemetry SDK + APIs, while keeping the API surface of this SDK the same.

npm install applicationinsights@beta

applicationinsights@2.0.0 Overview

• Autocollection parity with applicationinsights@1.x
• API parity with applicationinsights@1.x
• "Getting Started" parity with applicationinsights@1.x
• New autocollection scenarios out-of-the-box contribued by the OpenTelemetry community, e.g. gRPC, express, ioredis
• Built on top of an Open Standard for Telemetry APIs and SDKs

Migrating from 1.x to 2.x is meant to be seamless and straightforward, there should be no breaking API changes at all. Please file a bug if something doesn't look right to you!

Included in applicationinsights@2.0.0 is every Node.js Plugin available in the default OpenTelemetry Node.js SDK. Please check out the projects board for progress updates on 2.x.

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

1. Install all dependencies with npm install.
2. 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>
   

3. 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 [e-mail] with any additional questions or comments.