/**
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you 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.apache.hadoop.hbase;
  
  import com.fasterxml.jackson.databind.JsonNode;
  import com.fasterxml.jackson.databind.ObjectMapper;
  import com.sun.jersey.api.client.Client;
  import com.sun.jersey.api.client.ClientResponse;
  import com.sun.jersey.api.client.filter.HTTPBasicAuthFilter;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.conf.Configured;
  import org.apache.hadoop.util.ReflectionUtils;
  
  import javax.ws.rs.core.MediaType;
  import javax.ws.rs.core.Response;
  import javax.ws.rs.core.UriBuilder;
  import javax.xml.ws.http.HTTPException;
  import java.io.IOException;
  import java.net.URI;
  import java.util.HashMap;
  import java.util.Locale;
  import java.util.Map;
  
  /**
   * A ClusterManager implementation designed to control Cloudera Manager (http://www.cloudera.com)
   * clusters via REST API. This API uses HTTP GET requests against the cluster manager server to
   * retrieve information and POST/PUT requests to perform actions. As a simple example, to retrieve a
   * list of hosts from a CM server with login credentials admin:admin, a simple curl command would be
   *     curl -X POST -H "Content-Type:application/json" -u admin:admin \
   *         "http://this.is.my.server.com:7180/api/v8/hosts"
   *
   * This command would return a JSON result, which would need to be parsed to retrieve relevant
   * information. This action and many others are covered by this class.
   *
   * A note on nomenclature: while the ClusterManager interface uses a ServiceType enum when
   * referring to things like RegionServers and DataNodes, cluster managers often use different
   * terminology. As an example, Cloudera Manager (http://www.cloudera.com) would refer to a
   * RegionServer as a "role" of the HBase "service." It would further refer to "hbase" as the
   * "serviceType." Apache Ambari (http://ambari.apache.org) would call the RegionServer a
   * "component" of the HBase "service."
   *
   * This class will defer to the ClusterManager terminology in methods that it implements from
   * that interface, but uses Cloudera Manager's terminology when dealing with its API directly.
   */
  public class RESTApiClusterManager extends Configured implements ClusterManager {
    // Properties that need to be in the Configuration object to interact with the REST API cluster
    // manager. Most easily defined in hbase-site.xml, but can also be passed on the command line.
    private static final String REST_API_CLUSTER_MANAGER_HOSTNAME =
        "hbase.it.clustermanager.restapi.hostname";
    private static final String REST_API_CLUSTER_MANAGER_USERNAME =
        "hbase.it.clustermanager.restapi.username";
    private static final String REST_API_CLUSTER_MANAGER_PASSWORD =
        "hbase.it.clustermanager.restapi.password";
    private static final String REST_API_CLUSTER_MANAGER_CLUSTER_NAME =
        "hbase.it.clustermanager.restapi.clustername";
    private static final String REST_API_DELEGATE_CLUSTER_MANAGER =
      "hbase.it.clustermanager.restapi.delegate";
  
    // Some default values for the above properties.
    private static final String DEFAULT_SERVER_HOSTNAME = "http://localhost:7180";
    private static final String DEFAULT_SERVER_USERNAME = "admin";
    private static final String DEFAULT_SERVER_PASSWORD = "admin";
    private static final String DEFAULT_CLUSTER_NAME = "Cluster 1";
  
    // Fields for the hostname, username, password, and cluster name of the cluster management server
    // to be used.
    private String serverHostname;
    private String clusterName;
  
    // Each version of Cloudera Manager supports a particular API versions. Version 6 of this API
    // provides all the features needed by this class.
    private static final String API_VERSION = "v6";
  
    // Client instances are expensive, so use the same one for all our REST queries.
    private Client client = Client.create();
  
    // An instance of HBaseClusterManager is used for methods like the kill, resume, and suspend
    // because cluster managers don't tend to implement these operations.
    private ClusterManager hBaseClusterManager;
  
   private static final Log LOG = LogFactory.getLog(RESTApiClusterManager.class);
 
   RESTApiClusterManager() { }
 
   @Override
   public void setConf(Configuration conf) {
     super.setConf(conf);
     if (conf == null) {
       // Configured gets passed null before real conf. Why? I don't know.
       return;
     }
 
     final Class<? extends ClusterManager> clazz = conf.getClass(REST_API_DELEGATE_CLUSTER_MANAGER,
       HBaseClusterManager.class, ClusterManager.class);
     hBaseClusterManager = ReflectionUtils.newInstance(clazz, conf);
 
     serverHostname = conf.get(REST_API_CLUSTER_MANAGER_HOSTNAME, DEFAULT_SERVER_HOSTNAME);
     clusterName = conf.get(REST_API_CLUSTER_MANAGER_CLUSTER_NAME, DEFAULT_CLUSTER_NAME);
     String serverUsername = conf.get(REST_API_CLUSTER_MANAGER_USERNAME, DEFAULT_SERVER_USERNAME);
     String serverPassword = conf.get(REST_API_CLUSTER_MANAGER_PASSWORD, DEFAULT_SERVER_PASSWORD);
 
     // Add filter to Client instance to enable server authentication.
     client.addFilter(new HTTPBasicAuthFilter(serverUsername, serverPassword));
   }
 
   @Override
   public void start(ServiceType service, String hostname, int port) throws IOException {
     performClusterManagerCommand(service, hostname, RoleCommand.START);
   }
 
   @Override
   public void stop(ServiceType service, String hostname, int port) throws IOException {
     performClusterManagerCommand(service, hostname, RoleCommand.STOP);
   }
 
   @Override
   public void restart(ServiceType service, String hostname, int port) throws IOException {
     performClusterManagerCommand(service, hostname, RoleCommand.RESTART);
   }
 
   @Override
   public boolean isRunning(ServiceType service, String hostname, int port) throws IOException {
     String serviceName = getServiceName(roleServiceType.get(service));
     String hostId = getHostId(hostname);
     String roleState = getRoleState(serviceName, service.toString(), hostId);
     String healthSummary = getHealthSummary(serviceName, service.toString(), hostId);
     boolean isRunning = false;
 
     // Use Yoda condition to prevent NullPointerException. roleState will be null if the "service
     // type" does not exist on the specified hostname.
     if ("STARTED".equals(roleState) && "GOOD".equals(healthSummary)) {
       isRunning = true;
     }
 
     return isRunning;
   }
 
   @Override
   public void kill(ServiceType service, String hostname, int port) throws IOException {
     hBaseClusterManager.kill(service, hostname, port);
   }
 
   @Override
   public void suspend(ServiceType service, String hostname, int port) throws IOException {
     hBaseClusterManager.suspend(service, hostname, port);
   }
 
   @Override
   public void resume(ServiceType service, String hostname, int port) throws IOException {
     hBaseClusterManager.resume(service, hostname, port);
   }
 
 
   // Convenience method to execute command against role on hostname. Only graceful commands are
   // supported since cluster management APIs don't tend to let you SIGKILL things.
   private void performClusterManagerCommand(ServiceType role, String hostname, RoleCommand command)
       throws IOException {
     LOG.info("Performing " + command + " command against " + role + " on " + hostname + "...");
     String serviceName = getServiceName(roleServiceType.get(role));
     String hostId = getHostId(hostname);
     String roleName = getRoleName(serviceName, role.toString(), hostId);
     doRoleCommand(serviceName, roleName, command);
   }
 
   // Performing a command (e.g. starting or stopping a role) requires a POST instead of a GET.
   private void doRoleCommand(String serviceName, String roleName, RoleCommand roleCommand) {
     URI uri = UriBuilder.fromUri(serverHostname)
         .path("api")
         .path(API_VERSION)
         .path("clusters")
         .path(clusterName)
         .path("services")
         .path(serviceName)
         .path("roleCommands")
         .path(roleCommand.toString())
         .build();
     String body = "{ \"items\": [ \"" + roleName + "\" ] }";
     LOG.info("Executing POST against " + uri + " with body " + body + "...");
     ClientResponse response = client.resource(uri)
         .type(MediaType.APPLICATION_JSON)
         .post(ClientResponse.class, body);
 
     int statusCode = response.getStatus();
     if (statusCode != Response.Status.OK.getStatusCode()) {
       throw new HTTPException(statusCode);
     }
   }
 
   // Possible healthSummary values include "GOOD" and "BAD."
   private String getHealthSummary(String serviceName, String roleType, String hostId)
       throws IOException {
     return getRolePropertyValue(serviceName, roleType, hostId, "healthSummary");
   }
 
   // This API uses a hostId to execute host-specific commands; get one from a hostname.
   private String getHostId(String hostname) throws IOException {
     String hostId = null;
 
     URI uri = UriBuilder.fromUri(serverHostname)
         .path("api")
         .path(API_VERSION)
         .path("hosts")
         .build();
     JsonNode hosts = getJsonNodeFromURIGet(uri);
     if (hosts != null) {
       // Iterate through the list of hosts, stopping once you've reached the requested hostname.
       for (JsonNode host : hosts) {
         if (host.get("hostname").textValue().equals(hostname)) {
           hostId = host.get("hostId").textValue();
           break;
         }
       }
     } else {
       hostId = null;
     }
 
     return hostId;
   }
 
   // Execute GET against URI, returning a JsonNode object to be traversed.
   private JsonNode getJsonNodeFromURIGet(URI uri) throws IOException {
     LOG.info("Executing GET against " + uri + "...");
     ClientResponse response = client.resource(uri)
         .accept(MediaType.APPLICATION_JSON_TYPE)
         .get(ClientResponse.class);
 
     int statusCode = response.getStatus();
     if (statusCode != Response.Status.OK.getStatusCode()) {
       throw new HTTPException(statusCode);
     }
     // This API folds information as the value to an "items" attribute.
     return new ObjectMapper().readTree(response.getEntity(String.class)).get("items");
   }
 
   // This API assigns a unique role name to each host's instance of a role.
   private String getRoleName(String serviceName, String roleType, String hostId)
       throws IOException {
     return getRolePropertyValue(serviceName, roleType, hostId, "name");
   }
 
   // Get the value of a  property from a role on a particular host.
   private String getRolePropertyValue(String serviceName, String roleType, String hostId,
       String property) throws IOException {
     String roleValue = null;
     URI uri = UriBuilder.fromUri(serverHostname)
         .path("api")
         .path(API_VERSION)
         .path("clusters")
         .path(clusterName)
         .path("services")
         .path(serviceName)
         .path("roles")
         .build();
     JsonNode roles = getJsonNodeFromURIGet(uri);
     if (roles != null) {
       // Iterate through the list of roles, stopping once the requested one is found.
       for (JsonNode role : roles) {
         if (role.get("hostRef").get("hostId").textValue().equals(hostId) &&
             role.get("type")
                 .textValue()
                 .toLowerCase(Locale.ROOT)
                 .equals(roleType.toLowerCase(Locale.ROOT))) {
           roleValue = role.get(property).textValue();
           break;
         }
       }
     }
 
     return roleValue;
   }
 
   // Possible roleState values include "STARTED" and "STOPPED."
   private String getRoleState(String serviceName, String roleType, String hostId)
       throws IOException {
     return getRolePropertyValue(serviceName, roleType, hostId, "roleState");
   }
 
   // Convert a service (e.g. "HBASE," "HDFS") into a service name (e.g. "HBASE-1," "HDFS-1").
   private String getServiceName(Service service) throws IOException {
     String serviceName = null;
     URI uri = UriBuilder.fromUri(serverHostname)
         .path("api")
         .path(API_VERSION)
         .path("clusters")
         .path(clusterName)
         .path("services")
         .build();
     JsonNode services = getJsonNodeFromURIGet(uri);
     if (services != null) {
       // Iterate through the list of services, stopping once the requested one is found.
       for (JsonNode serviceEntry : services) {
         if (serviceEntry.get("type").textValue().equals(service.toString())) {
           serviceName = serviceEntry.get("name").textValue();
           break;
         }
       }
     }
 
     return serviceName;
   }
 
   /*
    * Some enums to guard against bad calls.
    */
 
   // The RoleCommand enum is used by the doRoleCommand method to guard against non-existent methods
   // being invoked on a given role.
   // TODO: Integrate zookeeper and hdfs related failure injections (Ref: HBASE-14261).
   private enum RoleCommand {
     START, STOP, RESTART;
 
     // APIs tend to take commands in lowercase, so convert them to save the trouble later.
     @Override
     public String toString() {
       return name().toLowerCase(Locale.ROOT);
     }
   }
 
   // ClusterManager methods take a "ServiceType" object (e.g. "HBASE_MASTER," "HADOOP_NAMENODE").
   // These "service types," which cluster managers call "roles" or "components," need to be mapped
   // to their corresponding service (e.g. "HBase," "HDFS") in order to be controlled.
   private static Map<ServiceType, Service> roleServiceType = new HashMap<ServiceType, Service>();
   static {
     roleServiceType.put(ServiceType.HADOOP_NAMENODE, Service.HDFS);
     roleServiceType.put(ServiceType.HADOOP_DATANODE, Service.HDFS);
     roleServiceType.put(ServiceType.HADOOP_JOBTRACKER, Service.MAPREDUCE);
     roleServiceType.put(ServiceType.HADOOP_TASKTRACKER, Service.MAPREDUCE);
     roleServiceType.put(ServiceType.HBASE_MASTER, Service.HBASE);
     roleServiceType.put(ServiceType.HBASE_REGIONSERVER, Service.HBASE);
   }
 
   private enum Service {
     HBASE, HDFS, MAPREDUCE
   }
 }