Implement health endpoint based on MicroProfile Health

alpine-server/pom.xml

@@ -189,6 +189,10 @@
             <groupId>com.fasterxml.jackson.jaxrs</groupId>
             <artifactId>jackson-jaxrs-json-provider</artifactId>
         </dependency>
+        <dependency>
+            <groupId>com.fasterxml.jackson.datatype</groupId>
+            <artifactId>jackson-datatype-jdk8</artifactId>
+        </dependency>
         <!-- Logging -->
         <!-- Overriding OWASP Security Logging dependencies with newer versions -->
         <dependency>
@@ -211,6 +215,11 @@
             <groupId>org.owasp</groupId>
             <artifactId>security-logging-logback</artifactId>
         </dependency>
+        <!-- Health -->
+        <dependency>
+            <groupId>org.eclipse.microprofile.health</groupId>
+            <artifactId>microprofile-health-api</artifactId>
+        </dependency>
         <!-- XSS prevention -->
         <dependency>
             <groupId>org.owasp.encoder</groupId>

alpine-server/src/main/java/alpine/server/health/HealthCheckResponseBuilder.java

@@ -0,0 +1,94 @@
+/*
+ * 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.health;
+
+import org.apache.commons.lang3.StringUtils;
+import org.eclipse.microprofile.health.HealthCheckResponse;
+import org.eclipse.microprofile.health.HealthCheckResponse.Status;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Optional;
+
+import static java.util.function.Predicate.not;
+
+/**
+ * Implementation of the MicroProfile Health SPI.
+ *
+ * @see <a href="https://download.eclipse.org/microprofile/microprofile-health-3.1/microprofile-health-spec-3.1.html#_spi_usage">MicroProfile Health SPI Usage</a>
+ * @since 2.3.0
+ */
+class HealthCheckResponseBuilder extends org.eclipse.microprofile.health.HealthCheckResponseBuilder {
+
+    private String name;
+    private Status status = Status.DOWN;
+    private final Map<String, Object> data = new HashMap<>();
+
+    @Override
+    public org.eclipse.microprofile.health.HealthCheckResponseBuilder name(final String name) {
+        this.name = name;
+        return this;
+    }
+
+    @Override
+    public org.eclipse.microprofile.health.HealthCheckResponseBuilder withData(final String key, final String value) {
+        data.put(key, value);
+        return this;
+    }
+
+    @Override
+    public org.eclipse.microprofile.health.HealthCheckResponseBuilder withData(final String key, final long value) {
+        data.put(key, value);
+        return this;
+    }
+
+    @Override
+    public org.eclipse.microprofile.health.HealthCheckResponseBuilder withData(final String key, final boolean value) {
+        data.put(key, value);
+        return this;
+    }
+
+    @Override
+    public org.eclipse.microprofile.health.HealthCheckResponseBuilder up() {
+        status = Status.UP;
+        return this;
+    }
+
+    @Override
+    public org.eclipse.microprofile.health.HealthCheckResponseBuilder down() {
+        status = Status.DOWN;
+        return this;
+    }
+
+    @Override
+    public org.eclipse.microprofile.health.HealthCheckResponseBuilder status(final boolean up) {
+        status = up ? Status.UP : Status.DOWN;
+        return this;
+    }
+
+    @Override
+    public HealthCheckResponse build() {
+        if (StringUtils.isBlank(name)) {
+            throw new IllegalArgumentException("Health check responses must provide a name");
+        }
+
+        return new HealthCheckResponse(name, status, Optional.of(data).filter(not(Map::isEmpty)));
+    }
+
+}

alpine-server/src/main/java/alpine/server/health/HealthCheckResponseProvider.java

@@ -0,0 +1,34 @@
+/*
+ * 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.health;
+
+/**
+ * Implementation of the MicroProfile Health SPI.
+ *
+ * @see <a href="https://download.eclipse.org/microprofile/microprofile-health-3.1/microprofile-health-spec-3.1.html#_spi_usage">MicroProfile Health SPI Usage</a>
+ * @since 2.3.0
+ */
+public class HealthCheckResponseProvider implements org.eclipse.microprofile.health.spi.HealthCheckResponseProvider {
+
+    @Override
+    public org.eclipse.microprofile.health.HealthCheckResponseBuilder createResponseBuilder() {
+        return new HealthCheckResponseBuilder();
+    }
+
+}

alpine-server/src/main/java/alpine/server/health/HealthCheckType.java

@@ -0,0 +1,53 @@
+/*
+ * 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.health;
+
+/**
+ * Defines types of health checks supported by MicroProfile Health.
+ *
+ * @see <a href="https://download.eclipse.org/microprofile/microprofile-health-3.1/microprofile-health-spec-3.1.html#_different_kinds_of_health_checks">MicroProfile Health Specification</a>
+ * @see <a href="https://kubernetes.io/docs/tasks/configure-pod-container/configure-liveness-readiness-startup-probes/">Probes in Kubernetes</a>
+ * @since 2.3.0
+ */
+public enum HealthCheckType {
+
+    /**
+     * Liveness probes may be used by service orchestrators to evaluate
+     * whether a service instance needs to be restarted.
+     */
+    LIVENESS,
+
+    /**
+     * Readiness probes may be used by service orchestrators to evaluate
+     * whether a service instance is ready to accept traffic.
+     */
+    READINESS,
+
+    /**
+     * Startup probes may be used by service orchestrators to evaluate
+     * whether a service instance has started.
+     */
+    STARTUP,
+
+    /**
+     * Probes that either do not specify their type, or apply to all types.
+     */
+    ALL
+
+}

alpine-server/src/main/java/alpine/server/health/checks/DatabaseHealthCheck.java

@@ -0,0 +1,101 @@
+/*
+ * 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.health.checks;
+
+import alpine.common.logging.Logger;
+import alpine.server.persistence.PersistenceManagerFactory;
+import org.eclipse.microprofile.health.HealthCheck;
+import org.eclipse.microprofile.health.HealthCheckResponse;
+import org.eclipse.microprofile.health.HealthCheckResponse.Status;
+import org.eclipse.microprofile.health.Readiness;
+
+import javax.jdo.PersistenceManager;
+import javax.jdo.Query;
+import javax.jdo.Transaction;
+
+/**
+ * @since 2.3.0
+ */
+@Readiness
+public class DatabaseHealthCheck implements HealthCheck {
+
+    private static final Logger LOGGER = Logger.getLogger(DatabaseHealthCheck.class);
+
+    @Override
+    public HealthCheckResponse call() {
+        final var responseBuilder = HealthCheckResponse.named("database");
+
+        try (final PersistenceManager pm = PersistenceManagerFactory.createPersistenceManager()) {
+            // DataNucleus maintains different connection pools for transactional and
+            // non-transactional operations. Check both of them by executing a test query
+            // in a transactional and non-transactional context.
+            final Status nonTransactionalStatus = checkNonTransactionalConnectionPool(pm);
+            final Status transactionalStatus = checkTransactionalConnectionPool(pm);
+
+            responseBuilder
+                    .status(nonTransactionalStatus == Status.UP && transactionalStatus == Status.UP)
+                    .withData("nontx_connection_pool", nonTransactionalStatus.name())
+                    .withData("tx_connection_pool", transactionalStatus.name());
+        } catch (Exception e) {
+            LOGGER.error("Executing database health check failed", e);
+            responseBuilder.down()
+                    .withData("exception_message", e.getMessage());
+        }
+
+        return responseBuilder.build();
+    }
+
+    private Status checkNonTransactionalConnectionPool(final PersistenceManager pm) {
+        LOGGER.debug("Checking non-transactional connection pool");
+        try {
+            return executeQuery(pm);
+        } catch (Exception e) {
+            LOGGER.error("Checking non-transactional connection pool failed", e);
+            return Status.DOWN;
+        }
+    }
+
+    private Status checkTransactionalConnectionPool(final PersistenceManager pm) {
+        LOGGER.debug("Checking transactional connection pool");
+        final Transaction trx = pm.currentTransaction();
+        trx.setRollbackOnly();
+        try {
+            trx.begin();
+            return executeQuery(pm);
+        } catch (Exception e) {
+            LOGGER.error("Checking transactional connection pool failed", e);
+            return Status.DOWN;
+        } finally {
+            if (trx.isActive()) {
+                trx.rollback();
+            }
+        }
+    }
+
+    private Status executeQuery(final PersistenceManager pm) {
+        final Query<?> query = pm.newQuery(Query.SQL, "SELECT 1");
+        try {
+            query.executeResultUnique(Long.class);
+            return Status.UP;
+        } finally {
+            query.closeAll();
+        }
+    }
+
+}