Performance monitoring in Firebase - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to initialize Firebase Performance Monitoring in your app.

Firebase

import { getPerformance } from 'firebase/performance';

const perf = [1](app);

Drag options to blanks, or click blank then click option'

AgetPerformance

BinitializePerformance

CstartPerformance

DenablePerformance

Attempts:

3 left

💡 Hint

Common Mistakes

Using a function that does not exist like 'initializePerformance'.

Confusing initialization with enabling or starting.

The getPerformance function initializes Performance Monitoring for the Firebase app instance.

2fill in blank

medium

Complete the code to trace a custom performance metric named 'load_time'.

Firebase

const trace = perf.[1]('load_time');
trace.start();
// ... some code ...
trace.stop();

Drag options to blanks, or click blank then click option'

AstartTrace

Ctrace

DtraceTrace

Attempts:

3 left

💡 Hint

Common Mistakes

Using non-existent methods like 'startTrace' or 'traceTrace'.

Confusing the method name with the variable name.

The trace method creates a custom trace to measure performance.

3fill in blank

hard

Fix the error in the code to correctly enable data collection for Performance Monitoring.

Firebase

import { getPerformance, [1] } from 'firebase/performance';

const perf = getPerformance(app);
[1](perf, true);

Drag options to blanks, or click blank then click option'

AactivatePerformanceCollection

BsetPerformanceCollectionEnabled

CstartPerformanceCollection

DenablePerformanceCollection

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect function names that do not exist.

Confusing enabling with starting or activating.

The correct function to enable or disable data collection is setPerformanceCollectionEnabled.

4fill in blank

hard

Fill both blanks to create a trace and add a custom metric named 'items_processed' with value 5.

Firebase

const trace = perf.[1]('process_trace');
trace.[2]('items_processed', 5);
trace.start();
trace.stop();

Drag options to blanks, or click blank then click option'

Atrace

BputMetric

CincrementMetric

DaddMetric

Attempts:

3 left

💡 Hint

Common Mistakes

Using methods that do not exist like 'addMetric' or 'incrementMetric' for adding a value metric.

Confusing the trace creation method with metric methods.

Use trace to create the trace and putMetric to add a custom metric with a specific value.

5fill in blank

hard

Fill all three blanks to create a trace, increment a metric named 'clicks', and start the trace.

Firebase

const trace = perf.[1]('click_trace');
trace.[2]('clicks');
trace.[3]();

Drag options to blanks, or click blank then click option'

Atrace

BincrementMetric

Cstart

DputMetric

Attempts:

3 left

💡 Hint

Common Mistakes

Using putMetric instead of incrementMetric when incrementing.

Forgetting to start the trace after creating it.

Create the trace with trace, increment the metric with incrementMetric, and start the trace with start.

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