metrics examples

metrics/src/main/java/com/baeldung/metrics/core/ActiveUserCountGauge.java

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+package com.baeldung.metrics.core;
+
+import java.util.List;
+
+import com.codahale.metrics.DerivativeGauge;
+import com.codahale.metrics.Gauge;
+
+public class ActiveUserCountGauge extends DerivativeGauge<List<Long>, Integer> {
+    public ActiveUserCountGauge(Gauge<List<Long>> base) {
+        super(base);
+    }
+
+    @Override
+    protected Integer transform(List<Long> value) {
+        return value.size();
+    }
+}

metrics/src/main/java/com/baeldung/metrics/core/ActiveUsersGauge.java

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+package com.baeldung.metrics.core;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.TimeUnit;
+
+import com.codahale.metrics.CachedGauge;
+
+public class ActiveUsersGauge extends CachedGauge<List<Long>> {
+    public ActiveUsersGauge(long timeout, TimeUnit timeoutUnit) {
+        super(timeout, timeoutUnit);
+    }
+
+    @Override
+    protected List<Long> loadValue() {
+        return getActiveUserCount();
+    }
+
+    private List<Long> getActiveUserCount() {
+        // mock reading from database and count the active users, return a fixed value
+        List<Long> result = new ArrayList<Long>();
+        result.add(12L);
+        return result;
+    }
+}

metrics/src/main/java/com/baeldung/metrics/core/AttendanceRatioGauge.java

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+package com.baeldung.metrics.core;
+
+import com.codahale.metrics.RatioGauge;
+
+public class AttendanceRatioGauge extends RatioGauge {
+    private int attendanceCount;
+    private int courseCount;
+
+    public AttendanceRatioGauge(int attendanceCount, int courseCount) {
+        this.attendanceCount = attendanceCount;
+        this.courseCount = courseCount;
+    }
+
+    @Override
+    protected Ratio getRatio() {
+        return Ratio.of(attendanceCount, courseCount);
+    }
+}

metrics/src/main/java/com/baeldung/metrics/core/MetricsDemo.java

@@ -1,4 +0,0 @@
-package com.baeldung.metrics.core;
-
-public class MetricsDemo {
-}

metrics/src/main/java/com/baeldung/metrics/core/MetricsRegistryDemo.java

@@ -1,6 +0,0 @@
-package com.baeldung.metrics.core;
-
-public class MetricsRegistryDemo {
-    public static void main(String[] args) {
-    }
-}

metrics/src/main/java/com/baeldung/metrics/healthchecks/DatabaseHealthCheck.java

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+package com.baeldung.metrics.healthchecks;
+
+import com.codahale.metrics.health.HealthCheck;
+
+public class DatabaseHealthCheck extends HealthCheck {
+    @Override
+    protected Result check() throws Exception {
+        return HealthCheck.Result.healthy();
+    }
+}

metrics/src/main/java/com/baeldung/metrics/healthchecks/UserCenterHealthCheck.java

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+package com.baeldung.metrics.healthchecks;
+
+import com.codahale.metrics.health.HealthCheck;
+
+public class UserCenterHealthCheck extends HealthCheck {
+    @Override
+    protected Result check() throws Exception {
+        return Result.healthy();
+    }
+}

metrics/src/main/java/com/baeldung/metrics/servlet/MyInstrumentedFilterContextListener.java

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+package com.baeldung.metrics.servlet;
+
+import com.codahale.metrics.MetricRegistry;
+import com.codahale.metrics.servlet.InstrumentedFilterContextListener;
+
+public class MyInstrumentedFilterContextListener extends InstrumentedFilterContextListener {
+    public static final MetricRegistry REGISTRY = new MetricRegistry();
+
+    @Override
+    protected MetricRegistry getMetricRegistry() {
+        return REGISTRY;
+    }
+}

metrics/src/main/java/com/baeldung/metrics/servlets/MyHealthCheckServletContextListener.java

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+package com.baeldung.metrics.servlets;
+
+import com.baeldung.metrics.healthchecks.DatabaseHealthCheck;
+import com.codahale.metrics.health.HealthCheckRegistry;
+import com.codahale.metrics.servlets.HealthCheckServlet;
+
+public class MyHealthCheckServletContextListener extends HealthCheckServlet.ContextListener {
+    public static final HealthCheckRegistry HEALTH_CHECK_REGISTRY = new HealthCheckRegistry();
+
+    static {
+        HEALTH_CHECK_REGISTRY.register("db", new DatabaseHealthCheck());
+    }
+
+    @Override
+    protected HealthCheckRegistry getHealthCheckRegistry() {
+        return HEALTH_CHECK_REGISTRY;
+    }
+}

metrics/src/main/java/com/baeldung/metrics/servlets/MyMetricsServletContextListener.java

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+package com.baeldung.metrics.servlets;
+
+import com.codahale.metrics.Counter;
+import com.codahale.metrics.Histogram;
+import com.codahale.metrics.MetricRegistry;
+import com.codahale.metrics.servlets.MetricsServlet;
+
+public class MyMetricsServletContextListener extends MetricsServlet.ContextListener {
+    private static final MetricRegistry METRIC_REGISTRY = new MetricRegistry();
+
+    static {
+        Counter counter = METRIC_REGISTRY.counter("m01-counter");
+        counter.inc();
+
+        Histogram histogram = METRIC_REGISTRY.histogram("m02-histogram");
+        histogram.update(5);
+        histogram.update(20);
+        histogram.update(100);
+    }
+
+    @Override
+    protected MetricRegistry getMetricRegistry() {
+        return METRIC_REGISTRY;
+    }
+}