tracing

What is Trace Events?

Think of Trace Events as a special detective that tracks everything happening inside your Node.js program like a secret agent. It records every action, every step taken by your code.

How to Use Trace Events?

There are two ways to turn on the Trace Events detective:

Using a Command:

node --trace-event-categories v8,node,node.async_hooks server.js

Using Code:

const trace_events = require("node:trace_events");
const tracing = trace_events.createTracing({ categories: ["node.perf"] });
tracing.enable(); // Start recording
// Do your code here
tracing.disable(); // Stop recording

What Categories Can Trace Events Track?

Here's what Trace Events can track:

Node.js Core: This category tracks major events in Node.js, like when it starts up or when it's doing networking.
V8 (JavaScript Engine): This category tracks events related to JavaScript, like when functions are called or when garbage collection happens.
Node.js Async Hooks: This category tracks asynchronous operations, which are actions that don't happen instantly, like reading a file or making a network request.
Performance API: This category tracks measurements related to how fast your code runs, like how long it takes to load a module or run a function.
Promises: This category tracks how Promises are handled, including how many are rejected (unresolved) or handled after being rejected.

How to View Trace Event Recordings?

Once Trace Events has collected all the information, it saves it in a special file. To see what's recorded, you can open this file in a tool called chrome://tracing in Google Chrome.

Real-World Examples

Here's how Trace Events can help you in real life:

Debugging Performance Issues: You can use Trace Events to pinpoint why your code is running slow. For example, you can check if there are any bottlenecks in network requests or if a particular function is taking too long to execute.
Understanding Async Code: Trace Events can help you visualize how asynchronous operations are executed in your code. This can be especially useful for understanding complex async codebases.
Monitoring Promise Handling: Trace Events lets you track how Promises are being handled, which can be helpful for debugging and optimizing promise-based code.

Overall, Trace Events is a powerful tool that can help you understand and improve your Node.js applications.

Introduction to `node:trace_events` Module

The node:trace_events module provides an interface to trace events generated by Node.js. It allows you to record and analyze performance data about your Node.js applications.

Tracing Basics

What are trace events?

Trace events are time-stamped records of specific events that occur during the execution of a program. They can include information such as:

Function calls and their duration
Memory allocations
I/O operations
User interactions

Why trace events?

Tracing events can help you:

Identify performance bottlenecks
Understand the behavior of your application
Diagnose and fix bugs

Using the `node:trace_events` Module

Enabling tracing

To enable tracing, you can use the trace-events command-line flag when starting your Node.js application. For example:

node --trace-events my_app.js

This will generate a trace event file in the output.etw file.

Loading the module

Once tracing is enabled, you can load the node:trace_events module in your application:

const traceEvents = require('trace_events');

Accessing trace events

The traceEvents module provides several methods for accessing trace events. The most common method is getCategories(), which returns an array of category names. Each category represents a specific type of event, such as "function" or "heap".

const categories = traceEvents.getCategories();

Creating a trace listener

To listen for trace events, you can create a trace listener using the createTrace() method:

const trace = traceEvents.createTrace();

The trace listener has several event handlers that you can use to listen for specific types of events. For example, the on() method allows you to listen for events by category:

trace.on('function', (event) => {
  console.log(event);
});

Real World Example

Here's an example of using the node:trace_events module to identify a performance problem in a Node.js application:

const traceEvents = require('trace_events');

const categories = traceEvents.getCategories();

const trace = traceEvents.createTrace();

trace.on('function', (event) => {
  console.log(event.name, event.duration);
});

// Run your application code here...

// Stop tracing
trace.end();

// Analyze the trace file to identify performance bottlenecks

By analyzing the trace file, you can identify which functions are taking the most time and where potential optimizations can be made.

Potential Applications

The node:trace_events module can be used in a variety of real-world applications, including:

Performance profiling
Bug fixing
Application debugging

Tracing in Node.js

What is Tracing?

Tracing is a technique used to record events that occur in a program. This information can then be used to troubleshoot problems, optimize performance, or track user behavior.

The Tracing Object

The Tracing object in Node.js allows you to control which types of events are traced.

Creating a Tracing Object

To create a Tracing object, use the createTracing() method:

const { traceEvents } = require('trace_events');

const tracing = traceEvents.createTracing();

Enabling and Disabling Tracing

Initially, tracing is disabled. To enable tracing, call the enable() method:

tracing.enable();

To disable tracing, call the disable() method:

tracing.disable();

Real-World Example

Suppose you have a function that is taking too long to run. You can use tracing to identify the part of the function that is causing the slowdown:

const tracing = traceEvents.createTracing();

// Enable tracing for the "my-function" category
tracing.enableCategories(['my-function']);

// Call the function you want to trace
myFunction();

// Disable tracing
tracing.disable();

// Save the trace data to a file
const traceData = tracing.getTraceEvents();
traceData.saveToFile('trace.json');

You can then use a tool like Chrome DevTools to visualize the trace data and identify the bottleneck.

Potential Applications

Tracing can be used in a variety of applications, including:

Performance Optimization: Identifying bottlenecks and optimizing performance.
Troubleshooting: Debugging errors and tracking down issues.
User Behavior Analysis: Tracking user interactions and understanding user behavior.

`tracing.categories`

Definition

tracing.categories is a comma-separated list of the trace event categories covered by a specific Tracing object.

Explanation

Imagine you have a program that generates a lot of events. These events can be categorized based on their type, such as network requests, database queries, or user interactions. The tracing.categories property allows you to specify which categories of events you want to track.

Example

Consider the following code snippet:

const { Tracing } = require("@google-cloud/trace-agent");

const tracing = new Tracing({
  // Only trace events related to network requests
  categories: "network",
});

In this example, we're creating a Tracing object that will only trace events related to network requests. Any other categories of events will be ignored.

Potential Applications

Tracking specific categories of events can be useful for performance analysis or debugging. For example, you could trace only network requests to identify any slow or unresponsive endpoints.

Real-World Example

Suppose you have a web application that experiences occasional performance issues. You suspect that the issues may be caused by slow database queries. Using the tracing.categories property, you can configure your tracing system to track only database queries. This will allow you to drill down into the details of the database queries and identify any potential bottlenecks.

Tracing is a powerful debugging tool that allows you to record and visualize events that occur within your code.

The tracing.disable() method disables tracing for a specific Tracing object. This means that the Tracing object will no longer record any events, and it will not be considered when determining which trace event categories to enable.

Only trace event categories that are not covered by other enabled Tracing objects and are not specified by the --trace-event-categories flag will be disabled.

Here is an example of how to use the tracing.disable() method:

const trace_events = require("trace_events");
const t1 = trace_events.createTracing({ categories: ["node", "v8"] });
const t2 = trace_events.createTracing({ categories: ["node.perf", "node"] });

t1.enable();
t2.enable();

// Prints 'node,node.perf,v8'
console.log(trace_events.getEnabledCategories());

t2.disable(); // Will only disable emission of the 'node.perf' category

// Prints 'node,v8'
console.log(trace_events.getEnabledCategories());

In this example, we first create two Tracing objects: t1 and t2. We then enable both Tracing objects, and print the list of enabled trace event categories.

Next, we disable the t2 Tracing object. This will disable the emission of the node.perf trace event category, but the other categories that are enabled by t1 will still be enabled.

We then print the list of enabled trace event categories again, and we can see that the node.perf category has been removed from the list.

Potential Applications in Real World

Tracing can be used to debug a wide variety of performance issues, including:

Slowdowns
Memory leaks
Deadlocks

By recording and visualizing the events that occur within your code, you can identify the root cause of a performance issue and take steps to resolve it.

Here are some specific examples of how tracing has been used to solve real-world problems:

Identifying a memory leak in a web application
Tracking down a performance issue in a database query
Debugging a deadlock in a multithreaded application

Conclusion

Tracing is a powerful tool that can be used to debug a wide variety of performance issues. The tracing.disable() method can be used to disable tracing for a specific Tracing object, which can be useful for fine-tuning the tracing process.

I hope this explanation is helpful. Please let me know if you have any other questions.

`tracing.enable()`

Simplified Explanation:

trace.enable() allows you to turn on tracing for specific events or categories of events in your Node.js application. By enabling tracing, you can collect and analyze data about what's happening in your app during runtime.

Topics in Detail:

1. Tracing

Tracing is a way to track and analyze the flow of events in your application. It can help you identify performance bottlenecks, debug issues, and understand the overall behavior of your app.

2. Tracing Categories

Tracing categories are groups of events that are related to a specific aspect of your application. For example, you could have a category for HTTP requests, database queries, or user actions.

3. Enabling Tracing

trace.enable() takes a list of tracing categories as input. When you call this function, tracing is enabled for all events that belong to those categories.

Code Example:

// Enable tracing for HTTP requests
const { trace } = require("@google-cloud/trace-agent");
trace.enable("http");

Real-World Applications:

1. Performance Optimization:

Tracing can help you identify slow or inefficient parts of your app by tracking how long different events take to complete.

2. Debug:

Tracing can be used to debug issues by providing a detailed record of what happened in your app before an error occurred.

3. Capacity Planning:

Tracing data can be used to predict future resource usage and plan for capacity needs.

Tracing Enabled

The tracing.enabled property in Node.js is a boolean that indicates whether tracing is enabled for the current process. Tracing is a way to track the execution of a program and record performance and other metrics.
If tracing.enabled is true, then tracing is enabled and events will be recorded. If tracing.enabled is false, then tracing is disabled and no events will be recorded.
By default, tracing is disabled. To enable tracing, you can use the tracing.start() method. To disable tracing, you can use the tracing.stop() method.
Here is an example of how to use the tracing.enabled property:

const tracing = require("@google-cloud/trace-agent");

// Check if tracing is enabled
if (tracing.enabled) {
  // Tracing is enabled
} else {
  // Tracing is disabled
}

Real-World Applications

Tracing can be used to diagnose performance issues and to understand the execution flow of a program. For example, you can use tracing to identify bottlenecks in your code or to track the flow of data through your application.

Potential Applications

Here are some potential applications of tracing:

Performance profiling: Tracing can be used to identify performance bottlenecks in your code. By recording the execution time of different parts of your program, you can identify which parts are taking the most time.
Error tracking: Tracing can be used to track errors and exceptions that occur in your program. By recording the stack trace and other information, you can identify the cause of the error and fix it.
Debugging: Tracing can be used to debug your code and understand the flow of execution. By recording the values of variables and the execution path, you can identify the source of a bug and fix it.

`trace_events.createTracing(options)`

Creating and tracing dependencies and paths can be very complex. The trace_events module helps simplify tracing by creating a Trace object that can be used to track events and dependencies.

options is an object that contains the following properties:
- categories is an array of strings that specify the categories of events to be traced. For example, ['node.perf', 'node.async_hooks'] would trace performance and asynchronous hook events.
The createTracing function returns a Tracing object that can be used to start and stop tracing, as well as to retrieve the traced data.

Here is a simple example of how to use the trace_events module:

const trace_events = require("node:trace_events");
const categories = ["node.perf", "node.async_hooks"];
const tracing = trace_events.createTracing({ categories });
tracing.enable();
// do stuff
tracing.disable();

In this example, we create a Tracing object for the node.perf and node.async_hooks categories. We then enable tracing by calling the enable method on the Tracing object. After we have finished tracing, we call the disable method to stop tracing.

The traced data can be retrieved by calling the getTraces method on the Tracing object. The traced data is returned as an array of Trace objects, which can be used to inspect the traced events and dependencies.

Potential Applications

The trace_events module can be used to trace a wide variety of events and dependencies in Node.js applications. Some potential applications include:

Profiling the performance of Node.js applications.
Debugging asynchronous code.
Identifying bottlenecks in Node.js applications.
Visualizing the flow of data through a Node.js application.

`trace_events.getEnabledCategories()`

Usage: trace_events.getEnabledCategories()
Returns: A comma-separated list of all currently-enabled trace event categories.

Explanation

The trace_events.getEnabledCategories() method returns a comma-separated list of all trace event categories that are currently enabled. These categories can be enabled either through Tracing objects or the --trace-event-categories command-line flag.

Example

The following code creates three Tracing objects, enables the first two, and then uses trace_events.getEnabledCategories() to get the list of enabled categories:

const trace_events = require("node:trace_events");
const t1 = trace_events.createTracing({ categories: ["node.async_hooks"] });
const t2 = trace_events.createTracing({ categories: ["node.perf"] });
const t3 = trace_events.createTracing({ categories: ["v8"] });

t1.enable();
t2.enable();

console.log(trace_events.getEnabledCategories()); // Output: 'node.async_hooks,node.perf'

Real-World Applications

Trace event categories can be used to filter which trace events are recorded. This can be useful for performance profiling, debugging, or other purposes. For example, you could use the following command to enable only the node.perf category:

node --trace-event-categories node.perf my_script.js

This would only record trace events related to performance, which could be useful for identifying performance bottlenecks.

Tracing

Tracing is a way to track the flow of a request through a system. It is useful for debugging, performance analysis, and troubleshooting.

Spans

A span is a unit of work that is tracked by a trace. Spans can be nested, and they can have labels that describe the work that is being done.

Trace

A trace is a collection of spans that represents a single request. Traces can be used to visualize the flow of a request through a system, and they can help to identify bottlenecks and other performance issues.

Tracing API

The tracing API provides a set of functions for creating and managing traces. These functions can be used to:

Create a new trace
Start a new span
Finish a span
Add labels to a span
Export a trace to a file or other destination

Real-world applications

Tracing can be used in a variety of real-world applications, including:

Debugging: Tracing can be used to debug errors in a system. By tracking the flow of a request, it is possible to identify the source of an error and fix it.
Performance analysis: Tracing can be used to analyze the performance of a system. By identifying bottlenecks and other performance issues, it is possible to improve the performance of the system.
Troubleshooting: Tracing can be used to troubleshoot problems in a system. By tracking the flow of a request, it is possible to identify the source of a problem and fix it.

Code examples

The following code example shows how to use the tracing API to create a trace and add spans to it:

const { Tracer } = require("@google-cloud/trace-agent");
const tracer = new Tracer();
const trace = tracer.startTrace();

const span1 = trace.startSpan("span1");
span1.addLabel("key", "value");

const span2 = trace.startSpan("span2", {
  parent: span1,
});
span2.addLabel("key", "value");

span2.end();
span1.end();

trace.end();

This code example shows how to use the tracing API to export a trace to a file:

const { Tracer } = require("@google-cloud/trace-agent");
const tracer = new Tracer();
const trace = tracer.startTrace();

const span1 = trace.startSpan("span1");
span1.addLabel("key", "value");

const span2 = trace.startSpan("span2", {
  parent: span1,
});
span2.addLabel("key", "value");

span2.end();
span1.end();

trace.end();

trace.exportJSON((err, json) => {
  if (err) {
    console.error(err);
    return;
  }

  fs.writeFileSync("trace.json", json);
});

Trace Events Data with Inspector

Introduction

The Trace Events Data module allows you to collect and inspect performance data about your Node.js applications. It uses the Chrome DevTools protocol to communicate with the Chrome DevTools Inspector, which provides real-time profiling and debugging capabilities.

Setting Up

To use the Trace Events Data module, you need to:

Start a Chrome DevTools session: Open Chrome DevTools and navigate to the "Performance" tab. Click on the "Record" button to start a new recording.
Connect to the Inspector session: Use the inspector.Session class to establish a connection to the Inspector session.

Collecting Data

Once you have a connection to the Inspector session, you can start collecting trace events data by sending an appropriate message to the Inspector. For example, the following code starts collecting trace events for the "v8" category:

await post("NodeTracing.start", {
  traceConfig: { includedCategories: ["v8"] },
});

You can then perform some actions in your application while the trace events are being collected. For example, you could run a series of tests or execute a specific function.

Stopping Data Collection

Once you have finished collecting trace events data, you can stop the collection by sending a 'NodeTracing.stop' message to the Inspector.

Analyzing Data

The collected trace events data is returned as a series of chunks. You can process these chunks to extract the performance data you are interested in. For example, you could use the trace-viewer tool to visualize the trace events and identify performance bottlenecks.

Applications

The Trace Events Data module can be used to analyze the performance of your Node.js applications in a variety of ways. For example, you could use it to:

Identify performance bottlenecks
Optimize code execution
Troubleshoot memory leaks
Debug asynchronous code

Example

The following is a complete example of how to use the Trace Events Data module to collect and analyze trace events data:

const { Session } = require("inspector");
const session = new Session();

session.connect();

async function collect() {
  const data = [];
  session.on("NodeTracing.dataCollected", (chunk) => data.push(chunk));
  session.on("NodeTracing.tracingComplete", () => {
    // done
  });
  const traceConfig = { includedCategories: ["v8"] };
  await post("NodeTracing.start", { traceConfig });
  // do something
  setTimeout(() => {
    post("NodeTracing.stop").then(() => {
      session.disconnect();
      console.log(data);
    });
  }, 1000);
}

collect();

This example starts collecting trace events data for the "v8" category. After a second has passed, the data collection is stopped and the collected data is logged to the console.

Previoustimers Nexturl

What is Trace Events?

How to Use Trace Events?

What Categories Can Trace Events Track?

How to View Trace Event Recordings?

Real-World Examples

Introduction to node:trace_events Module

Tracing Basics

Using the node:trace_events Module

Potential Applications

tracing.categories

Definition

Explanation

Example

Potential Applications

Real-World Example

Potential Applications in Real World

Conclusion

tracing.enable()

Topics in Detail:

Code Example:

Real-World Applications:

Tracing Enabled

Real-World Applications

Potential Applications

trace_events.createTracing(options)

Potential Applications

trace_events.getEnabledCategories()

Explanation

Example

Real-World Applications

Tracing

Spans

Trace

Tracing API

Real-world applications

Code examples

Trace Events Data with Inspector

Introduction

Setting Up

Collecting Data

Stopping Data Collection

Analyzing Data

Applications

Example

Introduction to `node:trace_events` Module

Using the `node:trace_events` Module

`tracing.categories`

`tracing.enable()`

`trace_events.createTracing(options)`

`trace_events.getEnabledCategories()`