////
This guide is maintained in the main Quarkus repository
and pull requests should be submitted there:
https://github.com/quarkusio/quarkus/tree/main/docs/src/main/asciidoc
////

= SmallRye Metrics

include::./attributes.adoc[]

The following guide demonstrates how a Quarkus application can use link:https://github.com/smallrye/smallrye-metrics/[SmallRye Metrics],
an implementation of the link:https://github.com/eclipse/microprofile-metrics/[MicroProfile Metrics] specification.

SmallRye Metrics allows applications to gather metrics and statistics that provide insights into what is happening inside an application. The metrics can be read remotely using the JSON or OpenMetrics format to be processed by additional tools such as Prometheus and stored for analysis and visualization.

Apart from application-specific metrics described in this guide, you may also use built-in metrics exposed by various Quarkus extensions. These are described in the guide for each particular extension that supports built-in metrics.

IMPORTANT: xref:micrometer.adoc[Micrometer] is the recommended approach to metrics for Quarkus. Use the SmallRye Metrics extension when it is required to retain MicroProfile specification compatibility.

== Prerequisites

include::includes/devtools/prerequisites.adoc[]

== Architecture

In this example, we build a very simple microservice that offers one REST endpoint. This endpoint serves for determining whether a number is prime. The implementation class is annotated with certain metric annotations so that while responding to users' requests, certain metrics are gathered. The meaning of each metric is explained later.

== Solution

We recommend that you follow the instructions in the next sections and create the application step by step. However, you can skip to the completed example.

. Clone the Git repository:
+
[source,bash,subs=attributes+]
----
git clone {quickstarts-clone-url}
----

* Alternatively, download a {quickstarts-archive-url}[Quickstarts archive]. The solution is located in the `microprofile-metrics-quickstart` {quickstarts-tree-url}/microprofile-metrics-quickstart[directory] and follow with the xref:running-and-using-the-application_{context}[] section.

[id="creating-a-maven-project_{context}"]
== Creating a Maven project

To create a new project:

:create-app-artifact-id: microprofile-metrics-quickstart
:create-app-extensions: resteasy,smallrye-metrics
include::includes/devtools/create-app.adoc[]

This command generates a Quarkus project that uses the `smallrye-metrics` extension.

If you already have your Quarkus project configured, you can add the `smallrye-metrics` extension to your project by running the following command in your project base directory:

:add-extension-extensions: smallrye-metrics
include::includes/devtools/extension-add.adoc[]

This adds the following to your build file:

[source,xml,role="primary asciidoc-tabs-target-sync-cli asciidoc-tabs-target-sync-maven"]
.pom.xml
----
<dependency>
    <groupId>io.quarkus</groupId>
    <artifactId>quarkus-smallrye-metrics</artifactId>
</dependency>
----

[source,gradle,role="secondary asciidoc-tabs-target-sync-gradle"]
.build.gradle
----
implementation("io.quarkus:quarkus-smallrye-metrics")
----

[id="writing-an-application_{context}"]
== Writing an application

The following procedures create a Quarkus application that consists of a single class that implements an algorithm for checking whether a number is prime. This algorithm is exposed over a REST interface. Additionally, specific annotations are required to ensure that the desired metrics are calculated over time and can be exported for manual analysis or processing by additional tooling.

The application will gather the following metrics:

* `performedChecks`: A counter that increases by one each time the user asks about a number.
* `highestPrimeNumberSoFar`: A gauge that stores the highest number asked about by the user if the number was determined to be prime.
* `checksTimer`: A compound metric that benchmarks how much time the primality tests take. Additional details are provided later.

The full source code looks as follows:
[source,java]
----
package org.acme.microprofile.metrics;

import org.eclipse.microprofile.metrics.MetricUnits;
import org.eclipse.microprofile.metrics.annotation.Counted;
import org.eclipse.microprofile.metrics.annotation.Gauge;
import org.eclipse.microprofile.metrics.annotation.Timed;
import org.jboss.resteasy.annotations.jaxrs.PathParam;

import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;

@Path("/")
public class PrimeNumberChecker {

    private long highestPrimeNumberSoFar = 2;

    @GET
    @Path("/{number}")
    @Produces(MediaType.TEXT_PLAIN)
    @Counted(name = "performedChecks", description = "How many primality checks have been performed.")
    @Timed(name = "checksTimer", description = "A measure of how long it takes to perform the primality test.", unit = MetricUnits.MILLISECONDS)
    public String checkIfPrime(@PathParam long number) {
        if (number < 1) {
            return "Only natural numbers can be prime numbers.";
        }
        if (number == 1) {
            return "1 is not prime.";
        }
        if (number == 2) {
            return "2 is prime.";
        }
        if (number % 2 == 0) {
            return number + " is not prime, it is divisible by 2.";
        }
        for (int i = 3; i < Math.floor(Math.sqrt(number)) + 1; i = i + 2) {
            if (number % i == 0) {
                return number + " is not prime, is divisible by " + i + ".";
            }
        }
        if (number > highestPrimeNumberSoFar) {
            highestPrimeNumberSoFar = number;
        }
        return number + " is prime.";
    }

    @Gauge(name = "highestPrimeNumberSoFar", unit = MetricUnits.NONE, description = "Highest prime number so far.")
    public Long highestPrimeNumberSoFar() {
        return highestPrimeNumberSoFar;
    }

}
----

[id="running-and-using-the-application_{context}"]
== Running and using the application

To execute the application created in xref:writing-an-application_{context}[], do the following:

:devtools-wrapped:
. Run the microservice in dev mode:
+
include::includes/devtools/dev.adoc[]
:!devtools-wrapped:

. Generate values for the metrics.

.. Query the endpoint to determine whether some numbers are prime numbers:
+
[source,bash]
----
curl localhost:8080/350
----
+
The application will respond that 350 is not a prime number because it can be divided by 2.

* For large prime numbers, the test takes more time.
+
[source,bash]
----
curl localhost:8080/629521085409773
----
+
The application will respond that 629521085409773 is a prime number. 

.. Perform additional calls with numbers of your choice.

. Review the generated metrics:
+
[source,bash]
----
curl -H"Accept: application/json" localhost:8080/q/metrics/application
----
+
You will receive a response such as:
+
[source,json]
----
{
  "org.acme.microprofile.metrics.PrimeNumberChecker.checksTimer" : {			                    <1>
    "p50": 217.231273,										                                        <2>
    "p75": 217.231273,
    "p95": 217.231273,
    "p98": 217.231273,
    "p99": 217.231273,
    "p999": 217.231273,
    "min": 0.58961,										                                            <3>
    "mean": 112.15909190834819,								                                        <4>
    "max": 217.231273,									                                            <5>
    "stddev": 108.2721053982776,							    	                                <6>
    "count": 2,											                                            <7>
    "meanRate": 0.04943519091742238,							                                    <8>
    "oneMinRate": 0.2232140583080189,
    "fiveMinRate": 0.3559527083952095,
    "fifteenMinRate": 0.38474303050928976
  },
  "org.acme.microprofile.metrics.PrimeNumberChecker.performedChecks" : 2,		                    <9>
  "org.acme.microprofile.metrics.PrimeNumberChecker.highestPrimeNumberSoFar" : 629521085409773		<10>
}
----

<1> `checksTimer`: A compound metric that benchmarks how much time the primality tests take. All durations are measured in milliseconds. It consists of these values below.
<2> `p50, p75, p95, p99, p999`: Percentiles of the durations. For example, the value in `p95` means that 95 % of the measurements were faster than this duration.
<3> `min`: The shortest duration it took to perform a primality test was probably performed for a small number.
<4> `mean`: The mean value of the measured durations.
<5> `max`: The longest duration, probably it was with a large prime number.
<6> `stddev`: The standard deviation.
<7> `count`: The number of observations, the value of which is the same as `performedChecks`.
<8> `meanRate, oneMinRate, fiveMinRate, fifteenMinRate`: Mean throughput and one-, five-, and fifteen-minute exponentially-weighted moving average throughput.
<9> `performedChecks`: A counter which is increased by one each time the user asks about a number.
<10> `highestPrimeNumberSoFar`: A gauge that stores the highest number that was asked about by the user and which was determined to be prime.

NOTE: If you prefer an OpenMetrics export rather than the JSON format, remove the `-H"Accept: application/json"` argument from your command line.

.Configuration Reference

include::{generated-dir}/config/quarkus-smallrye-metrics.adoc[opts=optional, leveloffset=+1]
