Performance monitoring in Firebase - Mini Project: Build & Apply

Firebase Performance Monitoring Setup

📖 Scenario: You are building a mobile app and want to track how fast your app loads and how long certain actions take. Firebase Performance Monitoring helps you see this data easily.

🎯 Goal: Set up Firebase Performance Monitoring in your app, create a custom trace to measure a specific action, and display the trace duration.

📋 What You'll Learn

Initialize Firebase Performance Monitoring in your app

Create a custom performance trace named app_startup

Start and stop the app_startup trace around a simulated startup task

Print the duration of the app_startup trace in milliseconds

💡 Why This Matters

🌍 Real World

Firebase Performance Monitoring helps developers see how fast their app runs and find slow parts to improve user experience.

💼 Career

Knowing how to set up and use performance monitoring is important for DevOps and mobile developers to maintain app quality and reliability.

1

Initialize Firebase Performance Monitoring

Import Firebase Performance Monitoring and initialize it by creating a variable called performance using getPerformance().

Firebase

// Import getPerformance and initialize performance
// Your code here

Hint

Use import { getPerformance } from "firebase/performance"; and then const performance = getPerformance(); to initialize.

2

Create a custom performance trace

Create a custom trace named app_startup by calling performance.trace('app_startup') and store it in a variable called trace.

Firebase

import { getPerformance } from "firebase/performance";

const performance = getPerformance();

// Create a trace named 'app_startup'
// Your code here

Hint

Use const trace = performance.trace('app_startup'); to create the trace.

3

Start and stop the custom trace

Start the trace by calling trace.start(), simulate a startup task with a 100ms delay using setTimeout, then stop the trace by calling trace.stop() inside the timeout callback.

Firebase

import { getPerformance } from "firebase/performance";

const performance = getPerformance();

const trace = performance.trace('app_startup');

// Start the trace
// Simulate 100ms delay
// Stop the trace inside the delay callback
// Your code here

Hint

Call trace.start() before the delay, then use setTimeout with 100ms, and call trace.stop() inside the callback.

4

Print the trace duration

After stopping the trace, print the duration of the app_startup trace in milliseconds using console.log and accessing trace.duration.

Firebase

import { getPerformance } from "firebase/performance";

const performance = getPerformance();

const trace = performance.trace('app_startup');

trace.start();

setTimeout(() => {
    trace.stop();
    // Print the trace duration here
    // Your code here
}, 100);

Hint

Use console.log(`Trace duration: ${trace.duration} ms`); inside the timeout callback after stopping the trace.

Practice

1. What is the main purpose of Firebase Performance Monitoring?

easy

A. To send notifications to users

B. To track app speed and identify slow parts

C. To store user data securely

D. To manage user authentication

Solution

1. Step 1: Understand the role of performance monitoring

   Performance monitoring is used to check how fast an app runs and find parts that slow it down.

2. Step 2: Compare with other Firebase features

   Features like data storage, notifications, and authentication serve different purposes unrelated to speed tracking.

3. Final Answer:

   To track app speed and identify slow parts -> Option B

4. Quick Check:

   Performance monitoring = track speed [OK]

Hint: Performance monitoring = tracking app speed [OK]

Common Mistakes:

• Confusing performance monitoring with data storage
• Thinking it manages user authentication
• Assuming it sends notifications

2. Which of the following is the correct way to initialize Firebase Performance Monitoring in your app?

easy

A. const perf = startPerformanceMonitoring(app);

B. const perf = initializePerformance();

C. const perf = getPerformance(app);

D. const perf = firebase.performance();

Solution

1. Step 1: Recall the official Firebase Performance Monitoring initialization

   The correct method is to call getPerformance(app) to start monitoring.

2. Step 2: Check other options for correctness

   Other options use incorrect or outdated function names that do not exist in Firebase SDK.

3. Final Answer:

   const perf = getPerformance(app); -> Option C

4. Quick Check:

   Use getPerformance(app) to start monitoring [OK]

Hint: Use getPerformance(app) to start monitoring [OK]

Common Mistakes:

• Using non-existent functions like initializePerformance()
• Calling firebase.performance() which is outdated
• Confusing function names with other Firebase services

3. Consider this code snippet:

const perf = getPerformance(app);
const trace = perf.trace('myTrace');
trace.start();
// some code
trace.stop();
console.log(trace.name);

What will be printed in the console?

medium

A. Error: trace.name is not defined

B. 'trace'

C. undefined

D. 'myTrace'

Solution

1. Step 1: Understand the trace creation and naming

   The trace is created with the name 'myTrace', so its name property holds 'myTrace'.

2. Step 2: Check the console.log output

   Logging trace.name prints the string 'myTrace' to the console.

3. Final Answer:

   'myTrace' -> Option D

4. Quick Check:

   trace.name = 'myTrace' [OK]

Hint: trace.name holds the trace identifier string [OK]

Common Mistakes:

• Assuming trace.name is undefined or missing
• Confusing trace object with string 'trace'
• Expecting an error from accessing trace.name

4. You wrote this code to create a custom trace:

const perf = getPerformance(app);
const trace = perf.trace('loadTime');
trace.start;
// some loading code
trace.stop();

Why does the trace not record the duration correctly?

medium

A. Because trace.start is missing parentheses and not called as a function

B. Because trace.stop() should be called before trace.start()

C. Because getPerformance(app) must be called after trace creation

D. Because the trace name 'loadTime' is invalid

Solution

1. Step 1: Check how trace.start is used

   The code uses trace.start; without parentheses, so the function is not executed.

2. Step 2: Understand function call syntax

   To start the trace, trace.start() must be called with parentheses to run the function.

3. Final Answer:

   Because trace.start is missing parentheses and not called as a function -> Option A

4. Quick Check:

   trace.start() needs parentheses to run [OK]

Hint: Always call start() with parentheses to begin trace [OK]

Common Mistakes:

• Forgetting parentheses on start() call
• Calling stop() before start()
• Thinking trace name affects recording
• Misplacing getPerformance call

5. You want to measure the time taken by two different functions in your app using Firebase Performance Monitoring. Which approach correctly creates and uses two custom traces?

hard

A. const perf = getPerformance(app);
const traceA = perf.trace('funcA');
const traceB = perf.trace('funcB');
traceA.start();
funcA();
traceA.stop();
traceB.start();
funcB();
traceB.stop();

B. const perf = getPerformance(app);
const trace = perf.trace('funcA_funcB');
trace.start();
funcA();
funcB();
trace.stop();

C. const perf = getPerformance(app);
perf.trace('funcA').start();
funcA();
perf.trace('funcA').stop();
perf.trace('funcB').start();
funcB();
perf.trace('funcB').stop();

D. const perf = getPerformance(app);
const traceA = perf.trace('funcA');
traceA.start();
funcA();
traceA.stop();
traceA.start();
funcB();
traceA.stop();

Solution

1. Step 1: Understand how to create separate traces

   Each function should have its own trace object created with a unique name.

2. Step 2: Check the usage of start and stop for each trace

   Start and stop must be called on each trace around the respective function call.

3. Step 3: Analyze each option

   const perf = getPerformance(app); const traceA = perf.trace('funcA'); const traceB = perf.trace('funcB'); traceA.start(); funcA(); traceA.stop(); traceB.start(); funcB(); traceB.stop(); correctly creates two traces and starts/stops them separately. const perf = getPerformance(app); const trace = perf.trace('funcA_funcB'); trace.start(); funcA(); funcB(); trace.stop(); uses one trace for both functions, losing separate timing. const perf = getPerformance(app); perf.trace('funcA').start(); funcA(); perf.trace('funcA').stop(); perf.trace('funcB').start(); funcB(); perf.trace('funcB').stop(); calls start and stop on new trace objects without saving them, which is incorrect. const perf = getPerformance(app); const traceA = perf.trace('funcA'); traceA.start(); funcA(); traceA.stop(); traceA.start(); funcB(); traceA.stop(); reuses the same trace for two functions, which mixes timings.

4. Final Answer:

   const perf = getPerformance(app); const traceA = perf.trace('funcA'); const traceB = perf.trace('funcB'); traceA.start(); funcA(); traceA.stop(); traceB.start(); funcB(); traceB.stop(); -> Option A

5. Quick Check:

   Separate trace per function = const perf = getPerformance(app); const traceA = perf.trace('funcA'); const traceB = perf.trace('funcB'); traceA.start(); funcA(); traceA.stop(); traceB.start(); funcB(); traceB.stop(); [OK]

Hint: Create and use separate trace objects for each function [OK]

Common Mistakes:

• Using one trace for multiple functions
• Not saving trace objects before start/stop
• Reusing the same trace for different functions