Revamp API and SPI

api/src/main/java/org/eclipse/microprofile/health/HealthStatus.java → api/src/main/java/org/eclipse/microprofile/health/HealthCheck.java

@@ -19,23 +19,18 @@
  * SPDX-License-Identifier: Apache-2.0
  *
  */
-
 package org.eclipse.microprofile.health;
 
-import java.util.Map;
-import java.util.Optional;
-
 /**
- * The health procedure response
+ * The health check procedure interface.
+ * Invoked by consumers to verify the healthiness of a computing node.
+ * Unhealthy nodes are expected to be terminated.
+ *
+ * @author Heiko Braun
+ * @since 13.06.17
  */
-public interface HealthStatus {
-
-    enum State { UP, DOWN }
-
-    String getName();
-
-    State getState();
-
-    Optional<Map<String, Object>> getAttributes();
-
+@FunctionalInterface
+public interface HealthCheck {
+
+    Response call();
 }

api/src/main/java/org/eclipse/microprofile/health/Response.java

@@ -0,0 +1,138 @@
+/*
+ * Copyright (c) 2017 Contributors to the Eclipse Foundation
+ *
+ * See the NOTICES file(s) distributed with this work for additional
+ * information regarding copyright ownership.
+ *
+ * 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
+ *
+ */
+
+package org.eclipse.microprofile.health;
+
+import org.eclipse.microprofile.health.spi.SPIFactory;
+
+import java.security.AccessController;
+import java.security.PrivilegedAction;
+import java.util.Map;
+import java.util.Optional;
+import java.util.ServiceLoader;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+/**
+ * The response to a health check invocation.
+ * <p>
+ * The Response class is reserved for an extension by implementation providers.
+ * An application should use one of the static methods to create a Response instance using a ResponseBuilder.
+ * </p>
+ *
+ */
+public abstract class Response {
+
+    private static final Logger LOGGER = Logger.getLogger(Response.class.getName());
+
+    private static volatile SPIFactory factory = null;
+
+    public static ResponseBuilder named(String name) {
+
+        if (factory == null) {
+            synchronized (Response.class) {
+                if (factory != null) {
+                    return factory.createResponseBuilder();
+                }
+
+                SPIFactory newInstance = find(SPIFactory.class);
+
+                if (newInstance == null) {
+                    throw new IllegalStateException("No SPIFactory implementation found!");
+                }
+
+                factory = newInstance;
+            }
+        }
+
+        return factory.createResponseBuilder().name(name);
+    }
+
+    // the actual contract
+
+    public enum State { UP, DOWN }
+
+    public abstract String getName();
+
+    public abstract State getState();
+
+    public abstract Optional<Map<String, Object>> getAttributes();
+
+    private static <T> T find(Class<T> service) {
+
+        T serviceInstance = find(service, Response.getContextClassLoader());
+
+        // alternate classloader
+        if(null==serviceInstance) {
+            serviceInstance = find(service, Response.class.getClassLoader());
+        }
+
+        // service cannot be found
+        if(null==serviceInstance) {
+            throw new IllegalStateException("Unable to find service " + service.getName());
+        }
+
+        return serviceInstance;
+    }
+
+    private static <T> T find(Class<T> service, ClassLoader cl) {
+
+        T serviceInstance = null;
+
+        try {
+            ServiceLoader<T> services = ServiceLoader.load(service, cl);
+
+            for (T spi : services) {
+                if (serviceInstance != null) {
+                    throw new IllegalStateException(
+                            "Multiple service implementations found: "
+                                    + spi.getClass().getName() + " and "
+                                    + serviceInstance.getClass().getName());
+                }
+                serviceInstance = spi;
+            }
+        }
+        catch (Throwable t) {
+            LOGGER.log(Level.SEVERE, "Error loading service " + service.getName() + ".", t);
+        }
+
+        return serviceInstance;
+    }
+
+
+
+    private static ClassLoader getContextClassLoader() {
+        return AccessController.doPrivileged((PrivilegedAction<ClassLoader>) () -> {
+            ClassLoader cl = null;
+            try {
+                cl = Thread.currentThread().getContextClassLoader();
+            }
+            catch (SecurityException ex) {
+                LOGGER.log(
+                        Level.WARNING,
+                        "Unable to get context classloader instance.",
+                        ex);
+            }
+            return cl;
+        });
+    }
+}

api/src/main/java/org/eclipse/microprofile/health/ResponseBuilder.java

@@ -0,0 +1,49 @@
+/*
+ * Copyright (c) 2017 Contributors to the Eclipse Foundation
+ *
+ * See the NOTICES file(s) distributed with this work for additional
+ * information regarding copyright ownership.
+ *
+ * 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
+ *
+ */
+
+package org.eclipse.microprofile.health;
+
+/**
+ * A builder to construct a health procedure response.
+ *
+ * <p>
+ * The ResponseBuilder class is reserved for an extension by implementation providers.
+ * </p>
+ */
+public abstract class ResponseBuilder {
+
+    public abstract ResponseBuilder name(String name);
+
+    public abstract ResponseBuilder withAttribute(String key, String value);
+
+    public abstract ResponseBuilder withAttribute(String key, long value);
+
+    public abstract ResponseBuilder withAttribute(String key, boolean value);
+
+    public abstract Response up();
+
+    public abstract Response down();
+
+    public abstract Response state(boolean up);
+
+
+}

api/src/main/java/org/eclipse/microprofile/health/HealthCheckProcedure.java → api/src/main/java/org/eclipse/microprofile/health/spi/SPIFactory.java

@@ -19,14 +19,16 @@
  * SPDX-License-Identifier: Apache-2.0
  *
  */
-package org.eclipse.microprofile.health;
+
+package org.eclipse.microprofile.health.spi;
+
+import org.eclipse.microprofile.health.ResponseBuilder;
 
 /**
- * The basic health check procedure interface
- *
- * @author Heiko Braun
- * @since 13.06.17
+ * Created by hbraun on 07.07.17.
  */
-public interface HealthCheckProcedure {
-    HealthStatus perform();
+public interface SPIFactory {
+
+    ResponseBuilder createResponseBuilder();
+
 }