Metrics with Micrometer in Spring Boot - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a counter metric using Micrometer.

Spring Boot

Counter counter = Counter.builder("[1]")
    .description("Counts user logins")
    .register(meterRegistry);

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

Auser_logins_total

BloginCounter

CuserLoginCount

DcounterUserLogins

Attempts:

3 left

💡 Hint

Common Mistakes

Using camelCase instead of snake_case for metric names.

Using variable names instead of metric names.

The metric name should be a clear, dot-separated string like user_logins_total to follow Micrometer naming conventions.

2fill in blank

medium

Complete the code to increment the counter when a user logs in.

Spring Boot

public void onUserLogin() {
    [1].increment();
}

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

AmeterRegistry.counter("user_logins_total")

BCounter.builder("user_logins_total")

Ccounter

DmeterRegistry.get("user_logins_total")

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to create a new counter inside the method.

Using meterRegistry.counter() inside the method instead of the existing counter.

You increment the existing counter object, not create or get a new one each time.

3fill in blank

hard

Fix the error in the code to record a timer metric for method execution time.

Spring Boot

Timer timer = Timer.builder("[1]")
    .description("Execution time of processData")
    .register(meterRegistry);

public void processData() {
    timer.[2](() -> {
        // processing logic
    });
}

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

Aprocess_data_time

Brecord

CrecordCallable

Dtime

Attempts:

3 left

💡 Hint

Common Mistakes

Using camelCase for metric names.

Using time instead of record for timing code blocks.

The timer metric name should be descriptive and use underscores. The method to record execution time with a Runnable is record.

4fill in blank

hard

Fill both blanks to create a gauge metric that tracks the current size of a queue.

Spring Boot

Gauge.builder("[1]", queue, [2])
    .description("Current size of the task queue")
    .register(meterRegistry);

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

Atask_queue_size

Bqueue::size

Cqueue.size()

DgetSize

Attempts:

3 left

💡 Hint

Common Mistakes

Calling queue.size() directly instead of passing a method reference.

Using camelCase for metric names.

The gauge name should be descriptive and use underscores. The method reference queue::size correctly provides the current size.

5fill in blank

hard

Fill all three blanks to create a custom meter with tags and record a value.

Spring Boot

DistributionSummary summary = DistributionSummary.builder("[1]")
    .description("Response sizes")
    .tags("endpoint", "[2]")
    .register(meterRegistry);

summary.[3](responseSize);

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

Aresponse_size_bytes

B/api/data

Crecord

Dcount

Attempts:

3 left

💡 Hint

Common Mistakes

Using count instead of record to add values.

Using generic or unclear metric names.

The metric name should be descriptive. Tags add context like the endpoint. Use record to add a new value to the summary.

Practice

1. What is the primary purpose of Micrometer in a Spring Boot application?

easy

A. To manage database connections efficiently

B. To collect and expose application metrics like counters and timers

C. To handle user authentication and authorization

D. To serve static web content like images and CSS

Solution

1. Step 1: Understand Micrometer's role

   Micrometer is designed to collect metrics such as counters, timers, and gauges to monitor app performance.

2. Step 2: Compare with other options

   Options B, C, and D relate to database, security, and web content, which are not Micrometer's focus.

3. Final Answer:

   To collect and expose application metrics like counters and timers -> Option B

4. Quick Check:

   Micrometer = Metrics collection [OK]

Hint: Micrometer is for metrics, not security or database [OK]

Common Mistakes:

• Confusing Micrometer with security or database tools
• Thinking Micrometer serves static files
• Assuming Micrometer manages app logic

2. Which of the following is the correct way to create a counter metric using Micrometer in Spring Boot?

easy

A. Counter counter = Counter.builder("my.counter").register(meterRegistry);

B. Counter counter = new Counter("my.counter");

C. Counter counter = meterRegistry.createCounter("my.counter");

D. Counter counter = Counter.create("my.counter");

Solution

1. Step 1: Recall Micrometer counter creation syntax

   Micrometer uses builder pattern: Counter.builder(name).register(meterRegistry) to create counters.

2. Step 2: Check other options for correctness

   Options B, C, and D use incorrect constructors or methods not available in Micrometer.

3. Final Answer:

   Counter counter = Counter.builder("my.counter").register(meterRegistry); -> Option A

4. Quick Check:

   Use builder().register() to create counters [OK]

Hint: Use builder() and register() to create metrics [OK]

Common Mistakes:

• Trying to instantiate Counter with new keyword
• Using non-existent createCounter method
• Missing register() call after builder()

3. Given the following code snippet in a Spring Boot app using Micrometer:

Counter counter = Counter.builder("requests.count").register(meterRegistry);
counter.increment();
counter.increment(2);

What will be the value of the counter after these calls?

medium

A. 3

B. 2

C. 0

D. 1

Solution

1. Step 1: Analyze the increment calls

   The first call increments the counter by 1, the second increments by 2.

2. Step 2: Calculate total increments

   Total increments = 1 + 2 = 3.

3. Final Answer:

   3 -> Option A

4. Quick Check:

   1 + 2 = 3 increments [OK]

Hint: Add all increment values to get total count [OK]

Common Mistakes:

• Ignoring the second increment call
• Assuming increment() resets counter
• Confusing increment() with set()

4. Consider this Spring Boot code snippet using Micrometer:

Counter counter = Counter.builder("api.calls").register(meterRegistry);
counter.increment(-1);

What is the issue with this code?

medium

A. meterRegistry is not initialized properly

B. Counter names cannot contain dots

C. Counters cannot be incremented by negative values; this will throw an exception

D. increment() method does not exist on Counter

Solution

1. Step 1: Understand Counter increment rules

   Counters only allow positive increments; negative values cause errors.

2. Step 2: Validate other options

   Counter names with dots are allowed, meterRegistry is assumed valid, and increment() exists.

3. Final Answer:

   Counters cannot be incremented by negative values; this will throw an exception -> Option C

4. Quick Check:

   Counter increments must be positive [OK]

Hint: Counters only accept positive increments [OK]

Common Mistakes:

• Trying to decrement counters with negative increments
• Thinking dots in metric names are invalid
• Assuming increment() method is missing

5. You want to measure the duration of a method execution in a Spring Boot app using Micrometer. Which approach correctly uses a Timer to record the time taken by a method processData()?

hard

A. Timer timer = new Timer("process.time");
timer.start();
processData();
timer.stop();

B. Timer timer = Timer.create("process.time");
timer.record(processData());

C. meterRegistry.timer("process.time").start();
processData();
meterRegistry.timer("process.time").stop();

D. Timer timer = Timer.builder("process.time").register(meterRegistry);
timer.record(() -> processData());

Solution

1. Step 1: Identify correct Timer usage in Micrometer

   Micrometer uses Timer.builder(name).register() and timer.record(Runnable) to measure durations.

2. Step 2: Check other options for errors

   Options A, C, and D use invalid constructors or methods not supported by Micrometer.

3. Final Answer:

   Timer timer = Timer.builder("process.time").register(meterRegistry); timer.record(() -> processData()); -> Option D

4. Quick Check:

   Use Timer.builder().register() and record() for timing [OK]

Hint: Use timer.record(() -> method()) to measure duration [OK]

Common Mistakes:

• Trying to instantiate Timer with new or create()
• Calling start() and stop() manually on Timer
• Passing method call directly instead of lambda to record()