public String simpleHello() {
    return "Hello!";
}

@Counted // ← 追加
public String simpleHello() {
    return "Hello!";
}

curl -H 'Accept:application/json' localhost:7001/metrics
{
  ...
  "io.extact.mp.sample.metrics.HelloRandomResource.simpleHello": 2,
  ...
}

@ApplicationScoped
@Path("/hello")
public class HelloRandomResource {
    private static final Random RANDOM = new Random();
    private static final List<String> HELLO_LIST = 
        List.of("こんにちは", "Hello", "ニイハオ", "ボンジュール", "アンニョンハセヨ");
    private AtomicInteger wordCount = new AtomicInteger(0);
  	@GET
    @Produces(MediaType.TEXT_PLAIN)
    public String randomHello() {
        var rand = RANDOM.nextInt(5);
        var hitWord = HELLO_LIST.get(rand);
        wordCount.getAndAdd(hitWord.length());
        sleep(rand); // レスポンスタイムをバラつかせる
        return hitWord;
    }
    private void sleep(long t) {
        try {
            Thread.sleep(t * 100);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        }
    }
}

@GET
@Produces(MediaType.TEXT_PLAIN)
@Counted(name = "helloCallCounter", absolute = true)
public String randomHello() {
	...
}

curl localhost:7001/hello
アンニョンハセヨ
curl -H 'Accept:application/json' localhost:7001/metrics/application/helloCallCounter
{"helloCallCounter":1}

curl localhost:7001/hello
Hello
curl -H 'Accept:application/json' localhost:7001/metrics/application/helloCallCounter
{"helloCallCounter":2}

curl localhost:7001/hello
ニイハオ
curl -H 'Accept:application/json' localhost:7001/metrics/application/helloCallCounter
{"helloCallCounter":3}

@GET
@Produces(MediaType.TEXT_PLAIN)
@Gauge(name = "wordCountGauge", absolute = true, unit = MetricUnits.NONE)
public int getWordCount() {
    return wordCount.get();
}

curl -H 'Accept:application/json' localhost:7001/metrics/application/wordCountGauge
{"wordCountGauge":10}

curl localhost:7001/hello
ニイハオ
curl -H 'Accept:application/json' localhost:7001/metrics/application/wordCountGauge
{"wordCountGauge":14}

curl localhost:7001/hello
アンニョンハセヨ
curl -H 'Accept:application/json' localhost:7001/metrics/application/wordCountGauge
{"wordCountGauge":22}

@GET
@Produces(MediaType.TEXT_PLAIN)
@Metered(name = "helloCallMeter", absolute = true)
public String randomHello() {
	...
}

curl -H 'Accept:application/json' localhost:7001/metrics/application/helloCallCounter
{
  "helloCallMeter": {
    "count": 28, # 呼び出し回数
    "meanRate": 0.025484137734903035, # 1秒間あたりの平均呼び出し回数
    "oneMinRate": 0.3052050559284745,      # 1分間の指数加重移動平均呼び出し回数
    "fiveMinRate": 0.0818330403081332,     # 5分間の指数加重移動平均呼び出し回数
    "fifteenMinRate": 0.029416806974250087 # 15分間の指数加重移動平均呼び出し回数
  }
}

@GET
@Produces(MediaType.TEXT_PLAIN)
@Timed(name = "helloCallTimer", 
        absolute = true, 
        unit = MetricUnits.MILLISECONDS)
public String randomHello() {
	...
}

curl -H 'Accept:application/json' localhost:7001/metrics/application/helloCallTimer
{
  "helloCallTimer": {
    "count": 41, # 呼び出し回数
    "elapsedTime": 3046.8758, # 通算処理時間(ミリ秒)
    "meanRate": 2.4748045431061425,        # 1秒間あたりの平均呼び出し
    "oneMinRate": 0.9290031985612927,      # 1分間の指数加重移動平均呼び出し
    "fiveMinRate": 0.5143884976225771,     # 5分間の指数加重移動平均呼び出し
    "fifteenMinRate": 0.43863373620190443, # 15分間の指数加重移動平均呼び出し
    "min": 0,   # 最小処理時間(ミリ秒)
    "max": 406, # 最大処理時間(ミリ秒)
    "mean": 75.04309741315609,   # 平均処理時間(ミリ秒)
    "stddev": 85.41192334664485, # 標準偏差
    "p50": 76.027,    # 50パーセンタイル
    "p75": 110.7091,  # 75パーセンタイル
    "p95": 215.5179,  # 95パーセンタイル
    "p98": 406.0691,  # 98パーセンタイル
    "p99": 406.0691,  # 99パーセンタイル
    "p999": 406.0691  # 99.9パーセンタイル
  }
}

@GET
@Produces(MediaType.TEXT_PLAIN)
@SimplyTimed(name = "helloCallSimpleTimer", 
              absolute = true, 
              unit = MetricUnits.MILLISECONDS)
public String randomHello() {
	...
}

curl -H 'Accept:application/json' localhost:7001/metrics/application/helloCallSimpleTimer
{
  "helloCallSimpleTimer": {
    "count": 56, # 呼び出し回数
    "elapsedTime": 6610.1478, # 通算処理時間(ミリ秒)
    "maxTimeDuration": 313.3178, # 直前1分間の最大処理時間(ミリ秒)
    "minTimeDuration": 0.0666    # 直前1分間の最小処理時間(ミリ秒)
  }
}

@GET
@Produces(MediaType.TEXT_PLAIN)
@ConcurrentGauge(name = "helloCallConcurrentGauge", absolute = true)
public String randomHello() {
	...
}

curl -H 'Accept:application/json' localhost:7001/metrics/application/helloCallConcurrentGauge
{
  "helloCallConcurrentGauge": {
    "current": 2, # 現時点のメソッド実行数
    "max": 3, # 直前1分間の最大同時メソッド実行数
    "min": 0  # 直前1分間の最小同時メソッド実行数
  }
}

@ApplicationScoped
@Path("/hello/antn")
public class HelloRandomResourceByAnnotation {
    @Inject
    @Metric(name = "helloCallCounter-antn", absolute = true)
    private Counter jaCounter;
    ...
    @GET
    @Path("/counter")
    @Produces(MediaType.TEXT_PLAIN)
    public String randomHelloWithCounter() {
        var hitWord = internalRandomHello();
        if (hitWord.equals("こんにちは")) {
            jaCounter.inc();
        }
        return hitWord;
    }
    ...
}

@ApplicationScoped
@Path("/hello/reg")
public class HelloRandomResourceByResistry {
    private MetricRegistry registry;
    ...
    @Inject
    public HelloRandomResourceByResistry(MetricRegistry registry) {
        this.registry = registry;
    }
    @GET
    @Path("/counter/ja")
    @Produces(MediaType.TEXT_PLAIN)
    public String randomHelloCounterWithJa() {
        var hitWord = internalRandomHello();
        if (hitWord.equals("こんにちは")) {
            Counter jaCounter = getOrCreateJaCounter();
            jaCounter.inc();
        }
        return hitWord;
    }
    ...
    private Counter getOrCreateJaCounter() {
        Metadata conterMetadata = new MetadataBuilder()
                .withName("helloCallCounter-reg")
                .withDisplayName("Counter Metrics By MetricRegistry")
                .withDescription("Number of hits on randomHello method")
                .withType(MetricType.COUNTER)
                .withUnit(MetricUnits.NONE)
                .build();
        return registry.counter(conterMetadata);
    }
    ...
}

@ApplicationScoped
@Path("/hello/reg")
public class HelloRandomResourceByResistry {
    private static final Tag JA_TAG = new Tag("lang", "ja");
    private static final Tag OTHER_TAG = new Tag("lang", "other");
    private MetricRegistry registry;
    ...
    @GET
    @Path("/counter/ja-and-other")
    @Produces(MediaType.TEXT_PLAIN)
    public String randomHelloCounterWithJaAndOthers() {
        var hitWord = internalRandomHello();
        if (hitWord.equals("こんにちは")) {
            Counter jaCounter = getOrCreateWithTagCounter(JA_TAG);
            jaCounter.inc();
        } else {
            Counter otherCounter = getOrCreateWithTagCounter(OTHER_TAG);
            otherCounter.inc();
        }
        return hitWord;
    }
    ...
    private Counter getOrCreateWithTagCounter(Tag tag) {
        Metadata withTagConterMetadata = new MetadataBuilder()
                .withName("withTagCounter-reg")
                .withType(MetricType.COUNTER)
                .withUnit(MetricUnits.NONE)
                .build();
        // tagを指定してメトリクスインスタンスを取得
        return registry.counter(withTagConterMetadata, tag);
    }
    ...
}

curl -H 'Accept:application/json' localhost:7001/metrics/application/withTagCounter-reg
{
  "withTagCounter-reg;lang=other": 21,
  "withTagCounter-reg;lang=ja": 1
}

curl localhost:7001/metrics/application/helloCallMeter
# TYPE application_helloCallMeter_total counter
# HELP application_helloCallMeter_total
application_helloCallMeter_total 17
# TYPE application_helloCallMeter_rate_per_second gauge
application_helloCallMeter_rate_per_second 0.6624877407617819
# TYPE application_helloCallMeter_one_min_rate_per_second gauge
application_helloCallMeter_one_min_rate_per_second 0.49306718323907406
# TYPE application_helloCallMeter_five_min_rate_per_second gauge
application_helloCallMeter_five_min_rate_per_second 0.4222801075419199
# TYPE application_helloCallMeter_fifteen_min_rate_per_second gauge
application_helloCallMeter_fifteen_min_rate_per_second 0.40765853729890883
# EOF