Add spring-geode-actuator module.

Add abstract base class for all Apache Geode, Spring Boot HealthIndicators.

Add ServerLoadProbe wrapper implementation to extract CacheServer load and metrics.

spring-geode-actuator/spring-geode-actuator.gradle

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+apply plugin: 'io.spring.convention.spring-module'
+
+description = "Spring Boot for Apache Geode Actuator"
+
+dependencies {
+
+    compile project(":spring-geode")
+
+    compile 'org.springframework.boot:spring-boot-starter-actuator'
+
+    testCompile "org.assertj:assertj-core"
+    testCompile "junit:junit"
+    testCompile "org.mockito:mockito-core"
+    testCompile "org.projectlombok:lombok"
+    testCompile "edu.umd.cs.mtc:multithreadedtc"
+
+    testCompile("org.springframework.boot:spring-boot-starter-test") {
+        exclude group: "org.springframework.boot", module: "spring-boot-starter-logging"
+    }
+
+    testCompile "org.springframework.data:spring-data-geode-test"
+    testCompile slf4jDependencies
+
+}

spring-geode-actuator/src/main/java/org/springframework/geode/boot/actuate/health/AbstractGeodeHealthIndicator.java

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+/*
+ * Copyright 2018 the original author or authors.
+ *
+ * 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.
+ */
+
+package org.springframework.geode.boot.actuate.health;
+
+import java.util.Optional;
+
+import org.apache.geode.cache.GemFireCache;
+import org.springframework.boot.actuate.health.AbstractHealthIndicator;
+import org.springframework.boot.actuate.health.HealthIndicator;
+import org.springframework.util.Assert;
+
+/**
+ * The {@link AbstractGeodeHealthIndicator} class is an abstract base class encapsulating functionality common to all
+ * Apache Geode {@link HealthIndicator} objects.
+ *
+ * @author John Blum
+ * @see org.apache.geode.cache.GemFireCache
+ * @see org.springframework.boot.actuate.health.AbstractHealthIndicator
+ * @see org.springframework.boot.actuate.health.HealthIndicator
+ * @since 1.0.0
+ */
+@SuppressWarnings("unused")
+public abstract class AbstractGeodeHealthIndicator extends AbstractHealthIndicator {
+
+	protected static final String UNKNOWN = "unknown";
+
+	private final GemFireCache gemfireCache;
+
+	/**
+	 * Default constructor to construct an uninitialized instance of {@link AbstractGeodeHealthIndicator},
+	 * which will not provide any health information.
+	 */
+	public AbstractGeodeHealthIndicator(String healthCheckedFailedMessage) {
+		super(healthCheckedFailedMessage);
+		this.gemfireCache = null;
+	}
+
+	/**
+	 * Constructs an instance of the {@link AbstractGeodeHealthIndicator} initialized with a reference to
+	 * the {@link GemFireCache} instance.
+	 *
+	 * @param gemfireCache reference to the {@link GemFireCache} instance used to collect health information.
+	 * @throws IllegalArgumentException if {@link GemFireCache} is {@literal null}.
+	 * @see org.apache.geode.cache.GemFireCache
+	 */
+	public AbstractGeodeHealthIndicator(GemFireCache gemfireCache) {
+
+		Assert.notNull(gemfireCache, "GemFireCache must not be null");
+
+		this.gemfireCache = gemfireCache;
+	}
+
+	/**
+	 * Returns a reference to the {@link GemFireCache} instance.
+	 *
+	 * @return a reference to the {@link GemFireCache} instance.
+	 * @see org.apache.geode.cache.GemFireCache
+	 */
+	protected Optional<GemFireCache> getGemFireCache() {
+		return Optional.ofNullable(this.gemfireCache);
+	}
+
+	/**
+	 * Determines the {@link String name} of the {@link Class} type safely by handling {@literal null}.
+	 *
+	 * @param type {@link Class} type to evaluate.
+	 * @return the {@link String name} of the {@link Class} type.
+	 * @see java.lang.Class#getName()
+	 */
+	protected String nullSafeClassName(Class<?> type) {
+		return type != null ? type.getName() : "";
+	}
+
+	/**
+	 * Converts a {@link Boolean} value into a {@literal yes} / {@literal no} {@link String}.
+	 *
+	 * @param value {@link Boolean} value to convert.
+	 * @return a {@literal yes} / {@literal no} response for the given {@link Boolean} value.
+	 */
+	protected String toYesNoString(Boolean value) {
+		return Boolean.TRUE.equals(value) ? "Yes" : "No";
+	}
+}

spring-geode-actuator/src/main/java/org/springframework/geode/boot/actuate/health/support/ActuatorServerLoadProbeWrapper.java

@@ -0,0 +1,107 @@
+/*
+ * Copyright 2018 the original author or authors.
+ *
+ * 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.
+ */
+
+package org.springframework.geode.boot.actuate.health.support;
+
+import java.util.Optional;
+import java.util.concurrent.atomic.AtomicReference;
+
+import org.apache.geode.cache.server.ServerLoad;
+import org.apache.geode.cache.server.ServerLoadProbe;
+import org.apache.geode.cache.server.ServerMetrics;
+import org.springframework.util.Assert;
+
+/**
+ * The ActuatorServerLoadProbeWrapper class is an implementation of Apache Geode's {@link ServerLoadProbe} interface
+ * used to capture the current {@link ServerMetrics} and access the latest {@link ServerLoad} details.
+ *
+ * @author John Blum
+ * @see org.apache.geode.cache.server.ServerLoad
+ * @see org.apache.geode.cache.server.ServerLoadProbe
+ * @see org.apache.geode.cache.server.ServerMetrics
+ * @since 1.0.0
+ */
+@SuppressWarnings("unused")
+public class ActuatorServerLoadProbeWrapper implements ServerLoadProbe {
+
+	private AtomicReference<ServerMetrics> currentServerMetrics = new AtomicReference<>(null);
+
+	private final ServerLoadProbe delegate;
+
+	/**
+	 * Constructs a new instance of {@link ActuatorServerLoadProbeWrapper} initialized with the required
+	 * {@link ServerLoadProbe} used as the delegate.
+	 *
+	 * @param serverLoadProbe required {@link ServerLoadProbe}.
+	 * @throws IllegalArgumentException if {@link ServerLoadProbe} is {@literal null}.
+	 * @see org.apache.geode.cache.server.ServerLoadProbe
+	 */
+	public ActuatorServerLoadProbeWrapper(ServerLoadProbe serverLoadProbe) {
+
+		Assert.notNull(serverLoadProbe, "ServerLoaderProbe is required");
+
+		this.delegate = serverLoadProbe;
+	}
+
+	/**
+	 * Returns the current, most up-to-date details on the {@link ServerLoad} if possible.
+	 *
+	 * @return the current {@link ServerLoad}.
+	 * @see org.apache.geode.cache.server.ServerLoad
+	 * @see #getCurrentServerMetrics()
+	 * @see java.util.Optional
+	 */
+	public Optional<ServerLoad> getCurrentServerLoad() {
+		return getCurrentServerMetrics().map(getDelegate()::getLoad);
+	}
+
+	/**
+	 * Returns the current, provided {@link ServerMetrics} if available.
+	 *
+	 * @return the current, provided {@link ServerMetrics} if available.
+	 */
+	public Optional<ServerMetrics> getCurrentServerMetrics() {
+		return Optional.ofNullable(this.currentServerMetrics.get());
+	}
+
+	/**
+	 * Returns the underlying, wrapped {@link ServerLoadProbe} backing this instance.
+	 *
+	 * @return the underlying, wrapped {@link ServerLoadProbe}.
+	 * @see org.apache.geode.cache.server.ServerLoadProbe
+	 */
+	protected ServerLoadProbe getDelegate() {
+		return this.delegate;
+	}
+
+	@Override
+	public ServerLoad getLoad(ServerMetrics metrics) {
+
+		this.currentServerMetrics.set(metrics);
+
+		return getDelegate().getLoad(metrics);
+	}
+
+	@Override
+	public void open() {
+		getDelegate().open();
+	}
+
+	@Override
+	public void close() {
+		getDelegate().close();
+	}
+}