Metrics with Micrometer in Spring Boot - Step-by-Step Execution

Concept Flow - Metrics with Micrometer

Start Application

↓

Micrometer Initialized

↓

Create MeterRegistry

↓

Define Metrics (Counters, Gauges, Timers)

↓

Application Runs

↓

Metrics Updated on Events

↓

Metrics Exported to Monitoring System

↓

End

Micrometer sets up a registry, defines metrics, updates them during app events, and exports data to monitoring tools.

Execution Sample

Spring Boot

Counter counter = registry.counter("requests_total");
counter.increment();
Timer.Sample sample = Timer.start(registry);
// code to time
sample.stop(registry.timer("request_latency"));

This code creates a counter and timer metric, increments the counter, and measures elapsed time for a code block.

Execution Table

Step	Action	Metric Type	Metric Name	Value Before	Value After	Description
1	Create counter	Counter	requests_total	0	0	Counter initialized at zero
2	Increment counter	Counter	requests_total	0	1	Counter increments by 1 on event
3	Start timer sample	Timer	request_latency	-	-	Timer sample started to measure duration
4	Stop timer sample	Timer	request_latency	0 ms	120 ms	Timer records 120 milliseconds duration
5	Export metrics	All	-	-	-	Metrics sent to monitoring system
6	End	-	-	-	-	Application continues running or stops

💡 Metrics are updated during app events and exported continuously or on demand.

Variable Tracker

Variable	Start	After Step 2	After Step 4	Final
requests_total (Counter)	0	1	1	1
request_latency (Timer)	-	-	120 ms	120 ms

Key Moments - 3 Insights

Why does the counter start at zero and not increment automatically?

Counters start at zero because they represent counts of events. They only increase when you explicitly call increment(), as shown in step 2 of the execution_table.

How does the timer measure the duration of code execution?

The timer starts when Timer.start() is called (step 3) and stops when sample.stop() is called (step 4), measuring the elapsed time between these calls.

When are metrics sent to the monitoring system?

Metrics are exported after updates or at configured intervals, as shown in step 5, ensuring monitoring tools receive current data.

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of the counter 'requests_total' after step 2?

A 0

B 1

C 2

D Undefined

💡 Hint

Check the 'Value After' column for step 2 in the execution_table.

At which step does the timer record the duration of the code execution?

A Step 2

B Step 3

C Step 4

D Step 5

💡 Hint

Look for when sample.stop() is called in the execution_table.

If the counter increment call is removed, what would be the value of 'requests_total' after step 2?

A 0

B 1

C Undefined

D Incremented by 2

💡 Hint

Refer to the variable_tracker and execution_table step 2 where increment happens.

Concept Snapshot

Micrometer Metrics Setup:
- Initialize MeterRegistry
- Define metrics: Counter, Gauge, Timer
- Increment counters on events
- Start/stop timers around code
- Export metrics to monitoring
- Metrics reflect app performance live

Full Transcript

Micrometer helps track app performance by creating metrics like counters and timers. You start by initializing a MeterRegistry, then define metrics such as counters for counting events and timers for measuring durations. When your app runs, you update these metrics by incrementing counters or timing code blocks. Finally, Micrometer exports these metrics to monitoring systems so you can see how your app behaves over time.

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()