Application Insights for Node.js

The SDK uses W3C trace context to automatically correlate telemetry across distributed systems. To enable correlation between a frontend application (using @microsoft/applicationinsights-web) and this Node.js backend SDK, you must ensure the frontend is configured with enableCorsCorrelation: true.

Supported headers:

• traceparent: (Required) W3C trace context header in format 00-traceId-spanId-flags.
• tracestate: (Optional) W3C trace state header for vendor-specific data.

When a request arrives at the backend, the SDK automatically extracts these headers, creates a correlation context, and associates all subsequent telemetry with that context. No manual backend code is required for this process.

// Example of frontend setup with Application Insights
const appInsights = new ApplicationInsights({
  config: {
    connectionString: "your-connection-string",
    enableCorsCorrelation: true  // Important for cross-domain correlation
  }
});
appInsights.loadAppInsights();

All SDK configuration must be completed before calling start(). In version 3.X, changes made after start() will not take effect. You can configure the SDK using method-based chaining on the appInsights.setup() object or by modifying the config property of a TelemetryClient.

To include console.log calls in your telemetry, use setAutoCollectConsole(true, true). By default, it only collects from supported third-party loggers like winston or bunyan.

To use a different connection string for web instrumentation than the one used for the SDK, use enableWebInstrumentation(true, "your-connection-string").

let appInsights = require("applicationinsights");
appInsights.setup("<YOUR_CONNECTION_STRING>")
    .setAutoCollectRequests(true)
    .setAutoCollectPerformance(true, true)
    .setAutoCollectExceptions(true)
    .setAutoCollectDependencies(true)
    .setAutoCollectConsole(true, false)
    .setAutoCollectPreAggregatedMetrics(true)
    .setSendLiveMetrics(false)
    .setInternalLogging(false, true)
    .enableWebInstrumentation(false)
    .start();

To begin monitoring your Node.js application, follow these steps:

1. Create a resource: Create an Application Insights resource in Azure and retrieve your Connection String.
2. Install the SDK: Run npm install --save applicationinsights.
3. Load the SDK early: Import the package as early as possible in your application code (before other packages) to ensure proper instrumentation of dependencies.
4. Configure: Call appInsights.setup() with your connection string or via the APPLICATIONINSIGHTS_CONNECTION_STRING environment variable.
5. Start: Call appInsights.start() to begin collecting and sending telemetry.

Note on ESM: If you are importing the 3.X SDK as an ESM module, you must follow the OpenTelemetry instrumentation hook requirements.

// 1. Load as early as possible
let appInsights = require('applicationinsights');

// 2. Configure with connection string
appInsights.setup('YOUR_CONNECTION_STRING');

// 3. Start telemetry collection
appInsights.start();

Application Insights SDK logs warnings to the console by default. To diagnose issues with the SDK itself, you can enable debug logging and generate telemetry for internal logs using .setInternalLogging(true, true) and .setAutoCollectConsole(true, true) during setup.

Alternatively, you can use environment variables:

• APPLICATIONINSIGHTS_ENABLE_DEBUG_LOGS: Enables debug logs.
• APPLICATIONINSIGHTS_DISABLE_WARNING_LOGS: Disables warning logs.
• APPLICATIONINSIGHTS_LOG_DESTINATION: Set to file or file+console to write logs to a file.
• APPLICATIONINSIGHTS_LOGDIR: Specifies the directory for log files (defaults to /tmp on *nix or USERDIR/AppData/Local/Temp on Windows).

let appInsights = require("applicationinsights");
appInsights.setup("<YOUR_CONNECTION_STRING>")
    .setInternalLogging(true, true) // Enable both debug and warning logging
    .setAutoCollectConsole(true, true) // Generate Trace telemetry for winston/bunyan and console logs
    .start();

You can control the SDK's internal logging behavior using environment variables. This is useful for debugging the SDK itself.

Log Level

Set APPLICATIONINSIGHTS_INSTRUMENTATION_LOGGING_LEVEL to one of the following values:

• NONE
• ERROR
• WARN
• INFO
• DEBUG
• VERBOSE
• ALL

Log Destination and Directory

• APPLICATIONINSIGHTS_LOG_DESTINATION: Set to file or file+console to write logs to a file.
• APPLICATIONINSIGHTS_LOGDIR: Set the directory where logs should be stored.

By default, if using file, a file named applicationinsights.log is generated in the system's temporary folder (/tmp on *nix or USERDIR/AppData/Local/Temp on Windows).

process.env.APPLICATIONINSIGHTS_INSTRUMENTATION_LOGGING_LEVEL = "VERBOSE";
process.env.APPLICATIONINSIGHTS_LOG_DESTINATION = "file";
process.env.APPLICATIONINSIGHTS_LOGDIR = "C:/applicationinsights/logs";

// Application Insights SDK setup....