Expose Prometheus metrics with Micrometer

Signed-off-by: nscuro <nscuro@protonmail.com>

alpine-common/pom.xml

@@ -39,6 +39,10 @@
             <groupId>com.fasterxml.jackson.core</groupId>
             <artifactId>jackson-annotations</artifactId>
         </dependency>
+        <dependency>
+            <groupId>io.micrometer</groupId>
+            <artifactId>micrometer-registry-prometheus</artifactId>
+        </dependency>
         <!-- Test Dependencies -->
         <dependency>
             <groupId>junit</groupId>

alpine-common/src/main/java/alpine/Config.java

@@ -129,7 +129,8 @@ public enum AlpineKey implements Key {
         LDAP_USERS_SEARCH_FILTER  ("alpine.ldap.users.search.filter",   null),
         LDAP_USER_PROVISIONING    ("alpine.ldap.user.provisioning",     false),
         LDAP_TEAM_SYNCHRONIZATION ("alpine.ldap.team.synchronization",  false),
-        OIDC_ENABLED              ("alpine.oidc.enabled",              false),
+        METRICS_ENABLED           ("alpine.metrics.enabled",            false),
+        OIDC_ENABLED              ("alpine.oidc.enabled",               false),
         OIDC_ISSUER               ("alpine.oidc.issuer",                null),
         OIDC_CLIENT_ID            ("alpine.oidc.client.id",             null),
         OIDC_USERNAME_CLAIM       ("alpine.oidc.username.claim",       "sub"),

alpine-common/src/main/java/alpine/common/metrics/Metrics.java

@@ -0,0 +1,45 @@
+/*
+ * This file is part of Alpine.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ * Copyright (c) Steve Springett. All Rights Reserved.
+ */
+package alpine.common.metrics;
+
+import alpine.Config;
+import io.micrometer.core.instrument.binder.jvm.ExecutorServiceMetrics;
+import io.micrometer.prometheus.PrometheusConfig;
+import io.micrometer.prometheus.PrometheusMeterRegistry;
+
+import java.util.concurrent.ExecutorService;
+
+/**
+ * @since 2.1.0
+ */
+public final class Metrics {
+
+    private static final PrometheusMeterRegistry registry = new PrometheusMeterRegistry(PrometheusConfig.DEFAULT);
+
+    public static PrometheusMeterRegistry getRegistry() {
+        return registry;
+    }
+
+    public static void registerExecutorService(final ExecutorService executorService, final String name) {
+        if (Config.getInstance().getPropertyAsBoolean(Config.AlpineKey.METRICS_ENABLED)) {
+            new ExecutorServiceMetrics(executorService, name, null).bindTo(registry);
+        }
+    }
+
+}

alpine-infra/src/main/java/alpine/event/framework/BaseEventService.java

@@ -19,8 +19,10 @@
 package alpine.event.framework;
 
 import alpine.common.logging.Logger;
+import alpine.common.metrics.Metrics;
 import alpine.model.EventServiceLog;
 import alpine.persistence.AlpineQueryManager;
+import io.micrometer.core.instrument.Counter;
 import org.apache.commons.lang3.concurrent.BasicThreadFactory;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
@@ -86,7 +88,7 @@ public void publish(Event event) {
             if (event instanceof ChainableEvent) {
                 if (! addTrackedEvent((ChainableEvent)event)) {
                     return;
-                };
+                }
             }
 
             // Check to see if the Event is Unblocked. If so, use a separate executor pool from normal events
@@ -138,6 +140,7 @@ public void publish(Event event) {
 
             });
         }
+        recordPublishedMetric(event);
     }
 
     /**
@@ -189,6 +192,14 @@ private synchronized void removeTrackedEvent(ChainableEvent event) {
         }
     }
 
+    private void recordPublishedMetric(final Event event) {
+        Counter.builder("alpine_events_published_total")
+                .description("Total number of published events")
+                .tags("event", event.getClass().getName(), "publisher", this.getClass().getName())
+                .register(Metrics.getRegistry())
+                .increment();
+    }
+
     /**
      * {@inheritDoc}
      * @since 1.0.0

alpine-infra/src/main/java/alpine/event/framework/EventService.java

@@ -20,6 +20,7 @@
 
 import alpine.common.logging.Logger;
 import alpine.common.util.ThreadUtil;
+import alpine.common.metrics.Metrics;
 import org.apache.commons.lang3.concurrent.BasicThreadFactory;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
@@ -42,15 +43,17 @@ public final class EventService extends BaseEventService {
     private static final EventService INSTANCE = new EventService();
     private static final Logger LOGGER = Logger.getLogger(EventService.class);
     private static final ExecutorService EXECUTOR;
+    private static final String EXECUTOR_NAME = "Alpine-EventService";
 
     static {
         BasicThreadFactory factory = new BasicThreadFactory.Builder()
-                .namingPattern("Alpine-EventService-%d")
+                .namingPattern(EXECUTOR_NAME + "-%d")
                 .uncaughtExceptionHandler(new LoggableUncaughtExceptionHandler())
                 .build();
         EXECUTOR = Executors.newFixedThreadPool(ThreadUtil.determineNumberOfWorkerThreads(), factory);
         INSTANCE.setExecutorService(EXECUTOR);
         INSTANCE.setLogger(LOGGER);
+        Metrics.registerExecutorService(EXECUTOR, EXECUTOR_NAME);
     }
 
     /**

alpine-infra/src/main/java/alpine/event/framework/SingleThreadedEventService.java

@@ -19,6 +19,7 @@
 package alpine.event.framework;
 
 import alpine.common.logging.Logger;
+import alpine.common.metrics.Metrics;
 import org.apache.commons.lang3.concurrent.BasicThreadFactory;
 
 import java.util.concurrent.ExecutorService;
@@ -40,15 +41,17 @@ public final class SingleThreadedEventService extends BaseEventService {
     private static final SingleThreadedEventService INSTANCE = new SingleThreadedEventService();
     private static final Logger LOGGER = Logger.getLogger(EventService.class);
     private static final ExecutorService EXECUTOR;
+    private static final String EXECUTOR_NAME = "Alpine-SingleThreadedEventService";
 
     static {
         BasicThreadFactory factory = new BasicThreadFactory.Builder()
-                .namingPattern("Alpine-SingleThreadedEventService")
+                .namingPattern(EXECUTOR_NAME)
                 .uncaughtExceptionHandler(new LoggableUncaughtExceptionHandler())
                 .build();
         EXECUTOR = Executors.newSingleThreadExecutor(factory);
         INSTANCE.setExecutorService(EXECUTOR);
         INSTANCE.setLogger(LOGGER);
+        Metrics.registerExecutorService(EXECUTOR, EXECUTOR_NAME);
     }
 
     /**

alpine-infra/src/main/java/alpine/notification/NotificationService.java

@@ -18,9 +18,12 @@
  */
 package alpine.notification;
 
-import alpine.event.framework.LoggableUncaughtExceptionHandler;
 import alpine.common.logging.Logger;
+import alpine.common.metrics.Metrics;
+import alpine.event.framework.LoggableUncaughtExceptionHandler;
+import io.micrometer.core.instrument.Counter;
 import org.apache.commons.lang3.concurrent.BasicThreadFactory;
+
 import java.lang.reflect.InvocationTargetException;
 import java.util.ArrayList;
 import java.util.Map;
@@ -42,12 +45,18 @@ public final class NotificationService implements INotificationService {
     private static final NotificationService INSTANCE = new NotificationService();
     private static final Logger LOGGER = Logger.getLogger(NotificationService.class);
     private static final Map<Class<? extends Notification>, ArrayList<Subscription>> SUBSCRIPTION_MAP = new ConcurrentHashMap<>();
-    private static final ExecutorService EXECUTOR_SERVICE = Executors.newFixedThreadPool(4,
-            new BasicThreadFactory.Builder()
-                    .namingPattern("Alpine-NotificationService-%d")
-                    .uncaughtExceptionHandler(new LoggableUncaughtExceptionHandler())
-                    .build()
-    );
+    private static final ExecutorService EXECUTOR_SERVICE;
+    private static final String EXECUTOR_SERVICE_NAME = "Alpine-NotificationService";
+
+    static {
+        EXECUTOR_SERVICE = Executors.newFixedThreadPool(4,
+                new BasicThreadFactory.Builder()
+                        .namingPattern(EXECUTOR_SERVICE_NAME + "-%d")
+                        .uncaughtExceptionHandler(new LoggableUncaughtExceptionHandler())
+                        .build()
+        );
+        Metrics.registerExecutorService(EXECUTOR_SERVICE, EXECUTOR_SERVICE_NAME);
+    }
 
     /**
      * Private constructor
@@ -70,7 +79,7 @@ public void publish(final Notification notification) {
             LOGGER.debug("No subscribers to inform from notification: " + notification.getClass().getName());
             return;
         }
-        for (final Subscription subscription: subscriptions) {
+        for (final Subscription subscription : subscriptions) {
             if (subscription.getScope() != null && subscription.getGroup() != null && subscription.getLevel() != null) { // subscription was the most specific
                 if (subscription.getScope().equals(notification.getScope()) && subscription.getGroup().equals(notification.getGroup()) && subscription.getLevel() == notification.getLevel()) {
                     alertSubscriber(notification, subscription.getSubscriber());
@@ -91,19 +100,33 @@ public void publish(final Notification notification) {
                 alertSubscriber(notification, subscription.getSubscriber());
             }
         }
+        recordPublishedMetric(notification);
     }
 
     private void alertSubscriber(final Notification notification, final Class<? extends Subscriber> subscriberClass) {
         LOGGER.debug("Alerting subscriber " + subscriberClass.getName());
         EXECUTOR_SERVICE.execute(() -> {
             try {
                 subscriberClass.getDeclaredConstructor().newInstance().inform(notification);
-            } catch (NoSuchMethodException | InvocationTargetException | InstantiationException | IllegalAccessException | SecurityException e) {
+            } catch (NoSuchMethodException | InvocationTargetException | InstantiationException |
+                     IllegalAccessException | SecurityException e) {
                 LOGGER.error("An error occurred while informing subscriber: " + e);
             }
         });
     }
 
+    private void recordPublishedMetric(final Notification notification) {
+        Counter.builder("alpine_notifications_published_total")
+                .description("Total number of published notifications")
+                .tags(
+                        "group", notification.getGroup(),
+                        "level", notification.getLevel().name(),
+                        "scope", notification.getScope()
+                )
+                .register(Metrics.getRegistry())
+                .increment();
+    }
+
     /**
      * {@inheritDoc}
      * @since 1.3.0

alpine-server/src/main/java/alpine/server/metrics/MetricsInitializer.java

@@ -0,0 +1,58 @@
+/*
+ * This file is part of Alpine.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ * Copyright (c) Steve Springett. All Rights Reserved.
+ */
+package alpine.server.metrics;
+
+import alpine.Config;
+import alpine.common.logging.Logger;
+import alpine.common.metrics.Metrics;
+import io.micrometer.core.instrument.binder.jvm.ClassLoaderMetrics;
+import io.micrometer.core.instrument.binder.jvm.JvmGcMetrics;
+import io.micrometer.core.instrument.binder.jvm.JvmInfoMetrics;
+import io.micrometer.core.instrument.binder.jvm.JvmMemoryMetrics;
+import io.micrometer.core.instrument.binder.jvm.JvmThreadMetrics;
+import io.micrometer.core.instrument.binder.system.DiskSpaceMetrics;
+import io.micrometer.core.instrument.binder.system.ProcessorMetrics;
+import io.micrometer.core.instrument.binder.system.UptimeMetrics;
+
+import javax.servlet.ServletContextEvent;
+import javax.servlet.ServletContextListener;
+
+/**
+ * @since 2.1.0
+ */
+public class MetricsInitializer implements ServletContextListener {
+
+    private static final Logger LOGGER = Logger.getLogger(MetricsInitializer.class);
+
+    @Override
+    public void contextInitialized(final ServletContextEvent event) {
+        if (Config.getInstance().getPropertyAsBoolean(Config.AlpineKey.METRICS_ENABLED)) {
+            LOGGER.info("Registering system metrics");
+            new ClassLoaderMetrics().bindTo(Metrics.getRegistry());
+            new DiskSpaceMetrics(Config.getInstance().getDataDirectorty()).bindTo(Metrics.getRegistry());
+            new JvmGcMetrics().bindTo(Metrics.getRegistry());
+            new JvmInfoMetrics().bindTo(Metrics.getRegistry());
+            new JvmMemoryMetrics().bindTo(Metrics.getRegistry());
+            new JvmThreadMetrics().bindTo(Metrics.getRegistry());
+            new ProcessorMetrics().bindTo(Metrics.getRegistry());
+            new UptimeMetrics().bindTo(Metrics.getRegistry());
+        }
+    }
+
+}

alpine-server/src/main/java/alpine/server/servlets/MetricsServlet.java

@@ -0,0 +1,51 @@
+/*
+ * This file is part of Alpine.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ * Copyright (c) Steve Springett. All Rights Reserved.
+ */
+package alpine.server.servlets;
+
+import alpine.Config;
+import alpine.common.metrics.Metrics;
+
+import javax.servlet.ServletException;
+import javax.servlet.http.HttpServlet;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+import java.io.IOException;
+
+/**
+ * @since 2.1.0
+ */
+public class MetricsServlet extends HttpServlet {
+
+    private boolean metricsEnabled;
+
+    @Override
+    public void init() throws ServletException {
+        metricsEnabled = Config.getInstance().getPropertyAsBoolean(Config.AlpineKey.METRICS_ENABLED);
+    }
+
+    @Override
+    protected void doGet(final HttpServletRequest req, final HttpServletResponse resp) throws IOException {
+        if (metricsEnabled) {
+            Metrics.getRegistry().scrape(resp.getWriter());
+        } else {
+            resp.setStatus(HttpServletResponse.SC_NO_CONTENT);
+        }
+    }
+
+}

example/src/main/webapp/WEB-INF/web.xml

@@ -35,4 +35,14 @@
         <url-pattern>/api/*</url-pattern>
     </servlet-mapping>
 
+    <servlet>
+        <servlet-name>Metrics</servlet-name>
+        <servlet-class>alpine.server.servlets.MetricsServlet</servlet-class>
+        <load-on-startup>1</load-on-startup>
+    </servlet>
+    <servlet-mapping>
+        <servlet-name>Metrics</servlet-name>
+        <url-pattern>/metrics</url-pattern>
+    </servlet-mapping>
+
 </web-app>

pom.xml

@@ -188,6 +188,7 @@
         <lib.jsr353-spec.version>1.1.4</lib.jsr353-spec.version>
         <lib.jstl.version>1.2.5</lib.jstl.version>
         <lib.logback.version>1.2.11</lib.logback.version>
+        <lib.micrometer.version>1.9.1</lib.micrometer.version>
         <lib.nimbus-oauth2-oidc-sdk.version>9.37</lib.nimbus-oauth2-oidc-sdk.version>
         <lib.owasp.encoder.version>1.2.3</lib.owasp.encoder.version>
         <lib.owasp.security-logging.version>1.1.7</lib.owasp.security-logging.version>
@@ -380,6 +381,12 @@
                 <artifactId>jackson-jaxrs-json-provider</artifactId>
                 <version>${lib.jackson.version}</version>
             </dependency>
+            <!-- Metrics -->
+            <dependency>
+                <groupId>io.micrometer</groupId>
+                <artifactId>micrometer-registry-prometheus</artifactId>
+                <version>${lib.micrometer.version}</version>
+            </dependency>
             <!-- Logging -->
             <!-- Overriding OWASP Security Logging dependencies with newer versions -->
             <dependency>