AgentManagerImpl.java

// 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 com.cloud.agent.manager;

import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.nio.channels.ClosedChannelException;
import java.util.ArrayList;
import java.util.Date;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Random;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

import javax.ejb.Local;
import javax.naming.ConfigurationException;

import org.apache.log4j.Logger;

import com.cloud.agent.AgentManager;
import com.cloud.agent.Listener;
import com.cloud.agent.StartupCommandProcessor;
import com.cloud.agent.api.AgentControlAnswer;
import com.cloud.agent.api.AgentControlCommand;
import com.cloud.agent.api.Answer;
import com.cloud.agent.api.CheckHealthCommand;
import com.cloud.agent.api.Command;
import com.cloud.agent.api.PingAnswer;
import com.cloud.agent.api.PingCommand;
import com.cloud.agent.api.PingRoutingCommand;
import com.cloud.agent.api.ReadyAnswer;
import com.cloud.agent.api.ReadyCommand;
import com.cloud.agent.api.ShutdownCommand;
import com.cloud.agent.api.StartupAnswer;
import com.cloud.agent.api.StartupCommand;
import com.cloud.agent.api.StartupProxyCommand;
import com.cloud.agent.api.StartupRoutingCommand;
import com.cloud.agent.api.StartupSecondaryStorageCommand;
import com.cloud.agent.api.StartupStorageCommand;
import com.cloud.agent.api.UnsupportedAnswer;
import com.cloud.agent.transport.Request;
import com.cloud.agent.transport.Response;
import com.cloud.alert.AlertManager;
import com.cloud.capacity.dao.CapacityDao;
import com.cloud.cluster.ManagementServerNode;
import com.cloud.cluster.StackMaid;
import com.cloud.configuration.Config;
import com.cloud.configuration.dao.ConfigurationDao;
import com.cloud.dc.ClusterDetailsDao;
import com.cloud.dc.ClusterVO;
import com.cloud.dc.DataCenterVO;
import com.cloud.dc.HostPodVO;
import com.cloud.dc.dao.ClusterDao;
import com.cloud.dc.dao.DataCenterDao;
import com.cloud.dc.dao.DataCenterIpAddressDao;
import com.cloud.dc.dao.HostPodDao;
import com.cloud.exception.AgentUnavailableException;
import com.cloud.exception.ConnectionException;
import com.cloud.exception.OperationTimedoutException;
import com.cloud.exception.UnsupportedVersionException;
import com.cloud.ha.HighAvailabilityManager;
import com.cloud.host.Host;
import com.cloud.host.HostVO;
import com.cloud.host.Status;
import com.cloud.host.Status.Event;
import com.cloud.host.dao.HostDao;
import com.cloud.host.dao.HostTagsDao;
import com.cloud.hypervisor.Hypervisor.HypervisorType;
import com.cloud.hypervisor.HypervisorGuruManager;
import com.cloud.hypervisor.kvm.discoverer.KvmDummyResourceBase;
import com.cloud.network.dao.IPAddressDao;
import com.cloud.resource.Discoverer;
import com.cloud.resource.ResourceManager;
import com.cloud.resource.ResourceState;
import com.cloud.resource.ServerResource;
import com.cloud.storage.StorageManager;
import com.cloud.storage.StorageService;
import com.cloud.storage.dao.StoragePoolDao;
import com.cloud.storage.dao.StoragePoolHostDao;
import com.cloud.storage.dao.VolumeDao;
import com.cloud.storage.resource.DummySecondaryStorageResource;
import com.cloud.storage.secondary.SecondaryStorageVmManager;
import com.cloud.user.AccountManager;
import com.cloud.utils.ActionDelegate;
import com.cloud.utils.NumbersUtil;
import com.cloud.utils.Pair;
import com.cloud.utils.component.ComponentLocator;
import com.cloud.utils.component.Inject;
import com.cloud.utils.component.Manager;
import com.cloud.utils.concurrency.NamedThreadFactory;
import com.cloud.utils.db.DB;
import com.cloud.utils.db.Transaction;
import com.cloud.utils.exception.CloudRuntimeException;
import com.cloud.utils.exception.HypervisorVersionChangedException;
import com.cloud.utils.fsm.NoTransitionException;
import com.cloud.utils.fsm.StateMachine2;
import com.cloud.utils.nio.HandlerFactory;
import com.cloud.utils.nio.Link;
import com.cloud.utils.nio.NioServer;
import com.cloud.utils.nio.Task;
import com.cloud.vm.VirtualMachineManager;
import com.cloud.vm.dao.VMInstanceDao;

import edu.emory.mathcs.backport.java.util.Collections;

/**
 * Implementation of the Agent Manager. This class controls the connection to the agents.
 *
 * @config {@table || Param Name | Description | Values | Default || || port | port to listen on for agent connection. | Integer
 *         | 8250 || || workers | # of worker threads | Integer | 5 || || router.template.id | default id for template | Integer
 *         | 1 || || router.ram.size | default ram for router vm in mb | Integer | 128 || || router.ip.address | ip address for
 *         the router | ip | 10.1.1.1 || || wait | Time to wait for control commands to return | seconds | 1800 || || domain |
 *         domain for domain routers| String | foo.com || || alert.wait | time to wait before alerting on a disconnected agent |
 *         seconds | 1800 || || update.wait | time to wait before alerting on a updating agent | seconds | 600 || ||
 *         ping.interval | ping interval in seconds | seconds | 60 || || instance.name | Name of the deployment String |
 *         required || || start.retry | Number of times to retry start | Number | 2 || || ping.timeout | multiplier to
 *         ping.interval before announcing an agent has timed out | float | 2.0x || || router.stats.interval | interval to
 *         report router statistics | seconds | 300s || * }
 **/
@Local(value = { AgentManager.class })
public class AgentManagerImpl implements AgentManager, HandlerFactory, Manager {
    private static final Logger s_logger = Logger.getLogger(AgentManagerImpl.class);
    private static final Logger status_logger = Logger.getLogger(Status.class);

    protected ConcurrentHashMap<Long, AgentAttache> _agents = new ConcurrentHashMap<Long, AgentAttache>(10007);
    protected List<Pair<Integer, Listener>> _hostMonitors = new ArrayList<Pair<Integer, Listener>>(17);
    protected List<Pair<Integer, Listener>> _cmdMonitors = new ArrayList<Pair<Integer, Listener>>(17);
    protected List<Pair<Integer, StartupCommandProcessor>> _creationMonitors = new ArrayList<Pair<Integer, StartupCommandProcessor>>(17);
    protected List<Long> _loadingAgents = new ArrayList<Long>();
    protected int _monitorId = 0;
    private Lock _agentStatusLock = new ReentrantLock();

    protected NioServer _connection;
    @Inject
    protected HostDao _hostDao = null;
    @Inject
    protected DataCenterDao _dcDao = null;
    @Inject
    protected DataCenterIpAddressDao _privateIPAddressDao = null;
    @Inject
    protected IPAddressDao _publicIPAddressDao = null;
    @Inject
    protected HostPodDao _podDao = null;
    @Inject
    protected VMInstanceDao _vmDao = null;
    @Inject
    protected CapacityDao _capacityDao = null;
    @Inject
    protected ConfigurationDao _configDao = null;
    @Inject
    protected StoragePoolDao _storagePoolDao = null;
    @Inject
    protected StoragePoolHostDao _storagePoolHostDao = null;
    @Inject
    protected ClusterDao _clusterDao = null;
    @Inject
    protected ClusterDetailsDao _clusterDetailsDao = null;
    @Inject
    protected HostTagsDao _hostTagsDao = null;
    @Inject
    protected VolumeDao _volumeDao = null;

    protected int _port;

    @Inject
    protected HighAvailabilityManager _haMgr = null;
    @Inject
    protected AlertManager _alertMgr = null;

    @Inject
    protected AccountManager _accountMgr = null;

    @Inject
    protected VirtualMachineManager _vmMgr = null;
    
    @Inject StorageService _storageSvr = null;
    @Inject StorageManager _storageMgr = null;
    
    @Inject
    protected HypervisorGuruManager _hvGuruMgr;

    @Inject SecondaryStorageVmManager _ssvmMgr;

    protected int _retry = 2;

    protected String _name;
    protected String _instance;

    protected int _wait;
    protected int _updateWait;
    protected int _alertWait;
    protected long _nodeId = -1;

    protected Random _rand = new Random(System.currentTimeMillis());

    protected int _pingInterval;
    protected long _pingTimeout;
    protected AgentMonitor _monitor = null;

    protected ExecutorService _executor;
    
    protected StateMachine2<Status, Status.Event, Host> _statusStateMachine = Status.getStateMachine();
    
    @Inject ResourceManager _resourceMgr;
    
    @Override
    public boolean configure(final String name, final Map<String, Object> params) throws ConfigurationException {
        _name = name;

        final ComponentLocator locator = ComponentLocator.getCurrentLocator();
        ConfigurationDao configDao = locator.getDao(ConfigurationDao.class);
        if (configDao == null) {
            throw new ConfigurationException("Unable to get the configuration dao.");
        }

        final Map<String, String> configs = configDao.getConfiguration("AgentManager", params);
        _port = NumbersUtil.parseInt(configs.get("port"), 8250);
        final int workers = NumbersUtil.parseInt(configs.get("workers"), 5);

        String value = configs.get(Config.PingInterval.toString());
        _pingInterval = NumbersUtil.parseInt(value, 60);

        value = configs.get(Config.Wait.toString());
        _wait = NumbersUtil.parseInt(value, 1800);

        value = configs.get(Config.AlertWait.toString());
        _alertWait = NumbersUtil.parseInt(value, 1800);

        value = configs.get(Config.UpdateWait.toString());
        _updateWait = NumbersUtil.parseInt(value, 600);

        value = configs.get(Config.PingTimeout.toString());
        final float multiplier = value != null ? Float.parseFloat(value) : 2.5f;
        _pingTimeout = (long) (multiplier * _pingInterval);

        s_logger.info("Ping Timeout is " + _pingTimeout);

        value = configs.get(Config.DirectAgentLoadSize.key());
        int threads = NumbersUtil.parseInt(value, 16);

        _instance = configs.get("instance.name");
        if (_instance == null) {
            _instance = "DEFAULT";
        }

        _nodeId = ManagementServerNode.getManagementServerId();
        s_logger.info("Configuring AgentManagerImpl. management server node id(msid): " + _nodeId);
        
        long lastPing = (System.currentTimeMillis() >> 10) - _pingTimeout;
        _hostDao.markHostsAsDisconnected(_nodeId, lastPing);

        _monitor = ComponentLocator.inject(AgentMonitor.class, _nodeId, _hostDao, _vmDao, _dcDao, _podDao, this, _alertMgr, _pingTimeout);
        registerForHostEvents(_monitor, true, true, false);

        _executor = new ThreadPoolExecutor(threads, threads, 60l, TimeUnit.SECONDS, new LinkedBlockingQueue<Runnable>(), new NamedThreadFactory("AgentTaskPool"));

        _connection = new NioServer("AgentManager", _port, workers + 10, this);

        s_logger.info("Listening on " + _port + " with " + workers + " workers");
        return true;
    }

    @Override
    public Task create(Task.Type type, Link link, byte[] data) {
        return new AgentHandler(type, link, data);
    }

    @Override
    public int registerForHostEvents(final Listener listener, boolean connections, boolean commands, boolean priority) {
        synchronized (_hostMonitors) {
            _monitorId++;
            if (connections) {
                if (priority) {
                    _hostMonitors.add(0, new Pair<Integer, Listener>(_monitorId, listener));
                } else {
                    _hostMonitors.add(new Pair<Integer, Listener>(_monitorId, listener));
                }
            }
            if (commands) {
                if (priority) {
                    _cmdMonitors.add(0, new Pair<Integer, Listener>(_monitorId, listener));
                } else {
                    _cmdMonitors.add(new Pair<Integer, Listener>(_monitorId, listener));
                }
            }
            if (s_logger.isDebugEnabled()) {
                s_logger.debug("Registering listener " + listener.getClass().getSimpleName() + " with id " + _monitorId);
            }
            return _monitorId;
        }
    }

    @Override
    public int registerForInitialConnects(final StartupCommandProcessor creator,boolean priority) {
        synchronized (_hostMonitors) {
            _monitorId++;

            if (priority) {
                _creationMonitors.add(0, new Pair<Integer, StartupCommandProcessor>(
                        _monitorId, creator));
            } else {
                _creationMonitors.add(0, new Pair<Integer, StartupCommandProcessor>(
                        _monitorId, creator));
            }
        }

        return _monitorId;
    }

    @Override
    public void unregisterForHostEvents(final int id) {
        s_logger.debug("Deregistering " + id);
        _hostMonitors.remove(id);
    }

    private AgentControlAnswer handleControlCommand(AgentAttache attache, final AgentControlCommand cmd) {
        AgentControlAnswer answer = null;

        for (Pair<Integer, Listener> listener : _cmdMonitors) {
            answer = listener.second().processControlCommand(attache.getId(), cmd);

            if (answer != null) {
                return answer;
            }
        }

        s_logger.warn("No handling of agent control command: " + cmd + " sent from " + attache.getId());
        return new AgentControlAnswer(cmd);
    }

    public void handleCommands(AgentAttache attache, final long sequence, final Command[] cmds) {
        for (Pair<Integer, Listener> listener : _cmdMonitors) {
            boolean processed = listener.second().processCommands(attache.getId(), sequence, cmds);
            if (s_logger.isTraceEnabled()) {
                s_logger.trace("SeqA " + attache.getId() + "-" + sequence + ": " + (processed ? "processed" : "not processed") + " by " + listener.getClass());
            }
        }
    }

    public void notifyAnswersToMonitors(long agentId, long seq, Answer[] answers) {
        for (Pair<Integer, Listener> listener : _cmdMonitors) {
            listener.second().processAnswers(agentId, seq, answers);
        }
    }

    @Override
    public AgentAttache findAttache(long hostId) {
        AgentAttache attache = null;
        synchronized (_agents) {
            attache = _agents.get(hostId);
        }
        return attache;
    }

    @Override
    public Answer sendToSecStorage(HostVO ssHost, Command cmd) {
        if( ssHost.getType() == Host.Type.LocalSecondaryStorage ) {
            return  easySend(ssHost.getId(), cmd);
        } else if ( ssHost.getType() == Host.Type.SecondaryStorage) {
            return  sendToSSVM(ssHost.getDataCenterId(), cmd);
        } else {
            String msg = "do not support Secondary Storage type " + ssHost.getType();
            s_logger.warn(msg);
            return new Answer(cmd, false, msg);
        }
    }

    @Override
    public void sendToSecStorage(HostVO ssHost, Command cmd, Listener listener) throws AgentUnavailableException {
        if( ssHost.getType() == Host.Type.LocalSecondaryStorage ) {
            send(ssHost.getId(), new Commands(cmd), listener);
        } else if ( ssHost.getType() == Host.Type.SecondaryStorage) {
            sendToSSVM(ssHost.getDataCenterId(), cmd, listener);
        } else {
        	String err = "do not support Secondary Storage type " + ssHost.getType();
            s_logger.warn(err);
            throw new CloudRuntimeException(err);
        }
    }


    private void sendToSSVM(final long dcId, final Command cmd, final Listener listener) throws AgentUnavailableException {
        List<HostVO> ssAHosts = _ssvmMgr.listUpAndConnectingSecondaryStorageVmHost(dcId);
        if (ssAHosts == null || ssAHosts.isEmpty() ) {
            throw new AgentUnavailableException("No ssvm host found", -1);
        }
        Collections.shuffle(ssAHosts);
        HostVO ssAhost = ssAHosts.get(0);
        send(ssAhost.getId(), new Commands(cmd), listener);
    }

    @Override
    public Answer sendToSSVM(final Long dcId, final Command cmd) {
        List<HostVO> ssAHosts = _ssvmMgr.listUpAndConnectingSecondaryStorageVmHost(dcId);
        if (ssAHosts == null || ssAHosts.isEmpty() ) {
            return new Answer(cmd, false, "can not find secondary storage VM agent for data center " + dcId);
        }
        Collections.shuffle(ssAHosts);
        HostVO ssAhost = ssAHosts.get(0);
        return easySend(ssAhost.getId(), cmd);
    }

    @Override
    public Answer sendTo(Long dcId, HypervisorType type, Command cmd) {
        List<ClusterVO> clusters = _clusterDao.listByDcHyType(dcId, type.toString());
        int retry = 0;
        for (ClusterVO cluster : clusters) {
            List<HostVO> hosts = _resourceMgr.listAllUpAndEnabledHosts(Host.Type.Routing, cluster.getId(), null, dcId);
            for (HostVO host : hosts) {
                retry++;
                if (retry > _retry) {
                    return null;
                }
                Answer answer = null;
                try {
                	
                    long targetHostId = _hvGuruMgr.getGuruProcessedCommandTargetHost(host.getId(), cmd);
                    answer = easySend(targetHostId, cmd);
                } catch (Exception e) {
                }
                if (answer != null) {
                    return answer;
                }
            }
        }
        return null;
    }

    protected int getPingInterval() {
        return _pingInterval;
    }

    @Override
    public Answer send(Long hostId, Command cmd) throws AgentUnavailableException, OperationTimedoutException {
        Commands cmds = new Commands(OnError.Stop);
        cmds.addCommand(cmd);
        send(hostId, cmds, cmd.getWait());
        Answer[] answers = cmds.getAnswers();
        if (answers != null && !(answers[0] instanceof UnsupportedAnswer)) {
            return answers[0];
        }

        if (answers != null && (answers[0] instanceof UnsupportedAnswer)) {
            s_logger.warn("Unsupported Command: " + answers[0].getDetails());
            return answers[0];
        }

        return null;
    }

    @DB
    protected boolean noDbTxn() {
        Transaction txn = Transaction.currentTxn();
        return !txn.dbTxnStarted();
    }

    @Override
    public Answer[] send(Long hostId, Commands commands, int timeout) throws AgentUnavailableException, OperationTimedoutException {
        assert hostId != null : "Who's not checking the agent id before sending?  ... (finger wagging)";
        if (hostId == null) {
            throw new AgentUnavailableException(-1);
        }

        if (timeout <= 0) {
            timeout = _wait;
        }
        assert noDbTxn() : "I know, I know.  Why are we so strict as to not allow txn across an agent call?  ...  Why are we so cruel ... Why are we such a dictator .... Too bad... Sorry...but NO AGENT COMMANDS WRAPPED WITHIN DB TRANSACTIONS!";

        Command[] cmds = commands.toCommands();

        assert cmds.length > 0 : "Ask yourself this about a hundred times.  Why am I  sending zero length commands?";

        if (cmds.length == 0) {
            commands.setAnswers(new Answer[0]);
        }

        final AgentAttache agent = getAttache(hostId);
        if (agent == null || agent.isClosed()) {
            throw new AgentUnavailableException("agent not logged into this management server", hostId);
        }

        Request req = new Request(hostId, _nodeId, cmds, commands.stopOnError(), true);
        req.setSequence(agent.getNextSequence());
        Answer[] answers = agent.send(req, timeout);
        notifyAnswersToMonitors(hostId, req.getSequence(), answers);
        commands.setAnswers(answers);
        return answers;
    }

    protected Status investigate(AgentAttache agent) {
        Long hostId = agent.getId();
        if (s_logger.isDebugEnabled()) {
            s_logger.debug("checking if agent (" + hostId + ") is alive");
        }

        Answer answer = easySend(hostId, new CheckHealthCommand());
        if (answer != null && answer.getResult()) {
            Status status = Status.Up;
            if (s_logger.isDebugEnabled()) {
                s_logger.debug("agent (" + hostId + ") responded to checkHeathCommand, reporting that agent is " + status);
            }
            return status;
        }

        return _haMgr.investigate(hostId);
    }

    protected AgentAttache getAttache(final Long hostId) throws AgentUnavailableException {
        assert (hostId != null) : "Who didn't check their id value?";
        if (hostId == null) {
            return null;
        }
        AgentAttache agent = findAttache(hostId);
        if (agent == null) {
            s_logger.debug("Unable to find agent for " + hostId);
            throw new AgentUnavailableException("Unable to find agent ", hostId);
        }

        return agent;
    }

    @Override
    public long send(Long hostId, Commands commands, Listener listener) throws AgentUnavailableException {
        final AgentAttache agent = getAttache(hostId);
        if (agent.isClosed()) {
            throw new AgentUnavailableException("Agent " + agent.getId() + " is closed", agent.getId());
        }

        Command[] cmds = commands.toCommands();

        assert cmds.length > 0 : "Why are you sending zero length commands?";
        if (cmds.length == 0) {
        	throw new AgentUnavailableException("Empty command set for agent " + agent.getId(), agent.getId());
        }
        Request req = new Request(hostId, _nodeId, cmds, commands.stopOnError(), true);
        req.setSequence(agent.getNextSequence());
        agent.send(req, listener);
        return req.getSequence();
    }


    public void removeAgent(AgentAttache attache, Status nextState) {
        if (attache == null) {
            return;
        }
        long hostId = attache.getId();
        if (s_logger.isDebugEnabled()) {
            s_logger.debug("Remove Agent : " + hostId);
        }
        AgentAttache removed = null;
        boolean conflict = false;
        synchronized (_agents) {
            removed = _agents.remove(hostId);
            if (removed != null && removed != attache) {
                conflict = true;
                _agents.put(hostId, removed);
                removed = attache;
            }
        }
        if (conflict) {
            s_logger.debug("Agent for host " + hostId + " is created when it is being disconnected");
        }
        if (removed != null) {
            removed.disconnect(nextState);
        }
        
        for (Pair<Integer, Listener> monitor : _hostMonitors) {
            if (s_logger.isDebugEnabled()) {
                s_logger.debug("Sending Disconnect to listener: " + monitor.second().getClass().getName());
            }
            monitor.second().processDisconnect(hostId, nextState);
        }
    }
    
    protected AgentAttache notifyMonitorsOfConnection(AgentAttache attache, final StartupCommand[] cmd, boolean forRebalance) throws ConnectionException {
        long hostId = attache.getId();
        HostVO host = _hostDao.findById(hostId);
        for (Pair<Integer, Listener> monitor : _hostMonitors) {
            if (s_logger.isDebugEnabled()) {
                s_logger.debug("Sending Connect to listener: " + monitor.second().getClass().getSimpleName());
            }
            for (int i = 0; i < cmd.length; i++) {
                try {
                    monitor.second().processConnect(host, cmd[i], forRebalance);
                } catch (Exception e) {
                    if (e instanceof ConnectionException) {
                        ConnectionException ce = (ConnectionException)e;
                        if (ce.isSetupError()) {
                            s_logger.warn("Monitor " + monitor.second().getClass().getSimpleName() + " says there is an error in the connect process for " + hostId + " due to " + e.getMessage());
                            handleDisconnectWithoutInvestigation(attache, Event.AgentDisconnected);
                            throw ce;
                        } else {
                            s_logger.info("Monitor " + monitor.second().getClass().getSimpleName() + " says not to continue the connect process for " + hostId + " due to " + e.getMessage());
                            handleDisconnectWithoutInvestigation(attache, Event.ShutdownRequested);
                            return attache;
                        }
                    } else if (e instanceof HypervisorVersionChangedException) {
                        handleDisconnectWithoutInvestigation(attache, Event.ShutdownRequested);
                        throw new CloudRuntimeException("Unable to connect " + attache.getId(), e);
                    } else {
                        s_logger.error("Monitor " + monitor.second().getClass().getSimpleName() + " says there is an error in the connect process for " + hostId + " due to " + e.getMessage(), e);
                        handleDisconnectWithoutInvestigation(attache, Event.AgentDisconnected);
                        throw new CloudRuntimeException("Unable to connect " + attache.getId(), e);
                    }
                }
            }
        }

        Long dcId = host.getDataCenterId();
        ReadyCommand ready = new ReadyCommand(dcId);
        Answer answer = easySend(hostId, ready);
        if (answer == null || !answer.getResult()) {
            // this is tricky part for secondary storage
            // make it as disconnected, wait for secondary storage VM to be up
            // return the attache instead of null, even it is disconnectede
            handleDisconnectWithoutInvestigation(attache, Event.AgentDisconnected);
        }

        agentStatusTransitTo(host, Event.Ready, _nodeId);
        attache.ready();
        return attache;
    }

    protected boolean notifyCreatorsOfConnection(StartupCommand[] cmd) throws ConnectionException {
        boolean handled = false;
        for (Pair<Integer, StartupCommandProcessor> monitor : _creationMonitors) {
            if (s_logger.isDebugEnabled()) {
                s_logger.debug("Sending Connect to creator: "
                        + monitor.second().getClass().getSimpleName());
            }
            handled =  monitor.second().processInitialConnect(cmd);
            if (handled) {
                break;
            }
        }

        return handled;
    }

    @Override
    public boolean start() {
        startDirectlyConnectedHosts();
        if (_monitor != null) {
            _monitor.start();
        }
        if (_connection != null) {
            _connection.start();
        }

        return true;
    }

    public void startDirectlyConnectedHosts() {
        List<HostVO> hosts = _resourceMgr.findDirectlyConnectedHosts();
        for (HostVO host : hosts) {
            loadDirectlyConnectedHost(host, false);
        }
    }
    
    private ServerResource loadResourcesWithoutHypervisor(HostVO host){
        String resourceName = host.getResource();
        ServerResource resource = null;
        try {
            Class<?> clazz = Class.forName(resourceName);
            Constructor constructor = clazz.getConstructor();
            resource = (ServerResource) constructor.newInstance();
        } catch (ClassNotFoundException e) {
            s_logger.warn("Unable to find class " + host.getResource(), e);
        } catch (InstantiationException e) {
            s_logger.warn("Unablet to instantiate class " + host.getResource(), e);
        } catch (IllegalAccessException e) {
            s_logger.warn("Illegal access " + host.getResource(), e);
        } catch (SecurityException e) {
            s_logger.warn("Security error on " + host.getResource(), e);
        } catch (NoSuchMethodException e) {
            s_logger.warn("NoSuchMethodException error on " + host.getResource(), e);
        } catch (IllegalArgumentException e) {
            s_logger.warn("IllegalArgumentException error on " + host.getResource(), e);
        } catch (InvocationTargetException e) {
            s_logger.warn("InvocationTargetException error on " + host.getResource(), e);
        }

        if(resource != null){
            _hostDao.loadDetails(host);
    
            HashMap<String, Object> params = new HashMap<String, Object>(host.getDetails().size() + 5);
            params.putAll(host.getDetails());
    
            params.put("guid", host.getGuid());
            params.put("zone", Long.toString(host.getDataCenterId()));
            if (host.getPodId() != null) {
                params.put("pod", Long.toString(host.getPodId()));
            }
            if (host.getClusterId() != null) {
                params.put("cluster", Long.toString(host.getClusterId()));
                String guid = null;
                ClusterVO cluster = _clusterDao.findById(host.getClusterId());
                if (cluster.getGuid() == null) {
                    guid = host.getDetail("pool");
                } else {
                    guid = cluster.getGuid();
                }
                if (guid != null && !guid.isEmpty()) {
                    params.put("pool", guid);
                }
            }
    
            params.put("ipaddress", host.getPrivateIpAddress());
            params.put("secondary.storage.vm", "false");
            params.put("max.template.iso.size", _configDao.getValue(Config.MaxTemplateAndIsoSize.toString()));
            params.put("migratewait", _configDao.getValue(Config.MigrateWait.toString()));
    
            try {
                resource.configure(host.getName(), params);
            } catch (ConfigurationException e) {
                s_logger.warn("Unable to configure resource due to " + e.getMessage());
                return null;
            }
    
            if (!resource.start()) {
                s_logger.warn("Unable to start the resource");
                return null;
            }
        }
        return resource;
    }
    

    @SuppressWarnings("rawtypes")
    protected boolean loadDirectlyConnectedHost(HostVO host, boolean forRebalance) {
    	boolean initialized = false;
        ServerResource resource = null;
    	try {
            //load the respective discoverer
            Discoverer discoverer = _resourceMgr.getMatchingDiscover(host.getHypervisorType());
            if(discoverer == null){
                s_logger.info("Could not to find a Discoverer to load the resource: "+ host.getId() +" for hypervisor type: "+host.getHypervisorType());
                resource = loadResourcesWithoutHypervisor(host);
            }else{
                resource = discoverer.reloadResource(host);
            }
            
            if(resource == null){
                s_logger.warn("Unable to load the resource: "+ host.getId());
                return false;
            }
        
	        initialized = true;
    	} finally {
    		if(!initialized) {
                if (host != null) {
                    agentStatusTransitTo(host, Event.AgentDisconnected, _nodeId);
                }
    		}	
    	}

        if (forRebalance) {
            Host h = _resourceMgr.createHostAndAgent(host.getId(), resource, host.getDetails(), false, null, true);
            return (h == null ? false : true);
        } else {
            _executor.execute(new SimulateStartTask(host.getId(), resource, host.getDetails(), null));
            return true;
        }
    }

    protected AgentAttache createAttacheForDirectConnect(HostVO host, ServerResource resource)
            throws ConnectionException {
        if (resource instanceof DummySecondaryStorageResource || resource instanceof KvmDummyResourceBase) {
            return new DummyAttache(this, host.getId(), false);
        }
        
        s_logger.debug("create DirectAgentAttache for " + host.getId());
        DirectAgentAttache attache = new DirectAgentAttache(this, host.getId(), resource, host.isInMaintenanceStates(), this);
        
        AgentAttache old = null;
        synchronized (_agents) {
            old = _agents.put(host.getId(), attache);
        }
        if (old != null) {
            old.disconnect(Status.Removed);
        }

        return attache;
    }
    
    @Override
    public boolean stop() {
        if (_monitor != null) {
            _monitor.signalStop();
        }
        if (_connection != null) {
            _connection.stop();
        }

        s_logger.info("Disconnecting agents: " + _agents.size());
        synchronized (_agents) {
            for (final AgentAttache agent : _agents.values()) {
                final HostVO host = _hostDao.findById(agent.getId());
                if (host == null) {
                    if (s_logger.isDebugEnabled()) {
                        s_logger.debug("Cant not find host " + agent.getId());
                    }
                } else {
                	if (!agent.forForward()) {
                		agentStatusTransitTo(host, Event.ManagementServerDown, _nodeId);
                	}
                }
            }
        }
        return true;
    }

    @Override
    public String getName() {
        return _name;
    }
   
    protected boolean handleDisconnectWithoutInvestigation(AgentAttache attache, Status.Event event) {
        long hostId = attache.getId();

        s_logger.info("Host " + hostId + " is disconnecting with event " + event);
        Status nextStatus = null;
        HostVO host = _hostDao.findById(hostId);
        if (host == null) {
            s_logger.warn("Can't find host with " + hostId);
            nextStatus = Status.Removed;
        } else {
            final Status currentStatus = host.getStatus();
            if (currentStatus == Status.Down || currentStatus == Status.Alert || currentStatus == Status.Removed) {
                if (s_logger.isDebugEnabled()) {
                    s_logger.debug("Host " + hostId + " is already " + currentStatus);
                }
                nextStatus = currentStatus;
            } else {
                try {
                    nextStatus = currentStatus.getNextStatus(event);
                } catch (NoTransitionException e) {
                    String err = "Cannot find next status for " + event + " as current status is " + currentStatus + " for agent " + hostId;
                    s_logger.debug(err);
                    throw new CloudRuntimeException(err);
                }
                
                if (s_logger.isDebugEnabled()) {
                    s_logger.debug("The next status of agent " + hostId + "is " + nextStatus + ", current status is " + currentStatus);
                }
            }
        }

        if (s_logger.isDebugEnabled()) {
            s_logger.debug("Deregistering link for " + hostId + " with state " + nextStatus);
        }

        removeAgent(attache, nextStatus);
        if (host != null) {
        	disconnectAgent(host, event, _nodeId);
        }

        return true;
    }
    
    protected boolean handleDisconnectWithInvestigation(AgentAttache attache, Status.Event event) {
        long hostId = attache.getId();
        HostVO host = _hostDao.findById(hostId);
        if (host != null) {
            Status nextStatus = null;
            try {
                nextStatus = host.getStatus().getNextStatus(event);
            } catch (NoTransitionException ne) {
                /* Agent may be currently in status of Down, Alert, Removed, namely there is no next status for some events.
                 * Why this can happen? Ask God not me. I hate there was no piece of comment for code handling race condition.
                 * God knew what race condition the code dealt with! 
                 */
            }
            
            if (nextStatus == Status.Alert) {
                /* OK, we are going to the bad status, let's see what happened */
                s_logger.info("Investigating why host " + hostId + " has disconnected with event " + event);

                final Status determinedState = investigate(attache);
                final Status currentStatus = host.getStatus();
                s_logger.info("The state determined is " + determinedState);

                if (determinedState == null || determinedState == Status.Down) {
                    s_logger.error("Host is down: " + host.getId() + "-" + host.getName() + ".  Starting HA on the VMs");
                    event = Status.Event.HostDown;
                } else if (determinedState == Status.Up) {
                    /* Got ping response from host, bring it back*/
                    s_logger.info("Agent is determined to be up and running");
                    agentStatusTransitTo(host, Status.Event.Ping, _nodeId);
                    return false;
                } else if (determinedState == Status.Disconnected) {
                    s_logger.warn("Agent is disconnected but the host is still up: " + host.getId() + "-" + host.getName());
                    if (currentStatus == Status.Disconnected) {
                        if (((System.currentTimeMillis() >> 10) - host.getLastPinged()) > _alertWait) {
                            s_logger.warn("Host " + host.getId() + " has been disconnected pass the time it should be disconnected.");
                            event = Status.Event.WaitedTooLong;
                        } else {
                            s_logger.debug("Host has been determined to be disconnected but it hasn't passed the wait time yet.");
                            return false;
                        }
                    } else if (currentStatus == Status.Up) {
                        DataCenterVO dcVO = _dcDao.findById(host.getDataCenterId());
                        HostPodVO podVO = _podDao.findById(host.getPodId());
                        String hostDesc = "name: " + host.getName() + " (id:" + host.getId() + "), availability zone: " + dcVO.getName() + ", pod: " + podVO.getName();
                        if ((host.getType() != Host.Type.SecondaryStorage) && (host.getType() != Host.Type.ConsoleProxy)) {
                            _alertMgr.sendAlert(AlertManager.ALERT_TYPE_HOST, host.getDataCenterId(), host.getPodId(), "Host disconnected, " + hostDesc, "If the agent for host [" + hostDesc
                                    + "] is not restarted within " + _alertWait + " seconds, HA will begin on the VMs");
                        }
                        event = Status.Event.AgentDisconnected;
                    }
                } else {
                    // if we end up here we are in alert state, send an alert
                    DataCenterVO dcVO = _dcDao.findById(host.getDataCenterId());
                    HostPodVO podVO = _podDao.findById(host.getPodId());
                    String hostDesc = "name: " + host.getName() + " (id:" + host.getId() + "), availability zone: " + dcVO.getName() + ", pod: " + podVO.getName();
                    _alertMgr.sendAlert(AlertManager.ALERT_TYPE_HOST, host.getDataCenterId(), host.getPodId(), "Host in ALERT state, " + hostDesc, "In availability zone " + host.getDataCenterId()
                            + ", host is in alert state: " + host.getId() + "-" + host.getName());
                }
            } else {
                s_logger.debug("The next status of Agent " + host.getId() + " is not Alert, no need to investigate what happened");
            }
        }
        
        handleDisconnectWithoutInvestigation(attache, event);
        host = _hostDao.findById(host.getId());
        if (host.getStatus() == Status.Alert || host.getStatus() == Status.Down) {
            _haMgr.scheduleRestartForVmsOnHost(host, true);
        }

        return true;
    }

    protected class DisconnectTask implements Runnable {
        AgentAttache _attache;
        Status.Event _event;
        boolean _investigate;

        DisconnectTask(final AgentAttache attache, final Status.Event event, final boolean investigate) {
            _attache = attache;
            _event = event;
            _investigate = investigate;
        }

        @Override
        public void run() {
        	try {
                if (_investigate == true) {
                    handleDisconnectWithInvestigation(_attache, _event);
                } else {
                	handleDisconnectWithoutInvestigation(_attache, _event);
                }
            } catch (final Exception e) {
                s_logger.error("Exception caught while handling disconnect: ", e);
            } finally {
                StackMaid.current().exitCleanup();
            }
        }
    }

    @Override
    public Answer easySend(final Long hostId, final Command cmd) {
        try {
            Host h = _hostDao.findById(hostId);
            if (h == null || h.getRemoved() != null) {
                s_logger.debug("Host with id " + hostId + " doesn't exist");
                return null;
            }
            Status status = h.getStatus();
            if (!status.equals(Status.Up) && !status.equals(Status.Connecting)) {
                s_logger.debug("Can not send command " + cmd + " due to Host " + hostId + " is not up");
                return null;
            }
            final Answer answer = send(hostId, cmd);
            if (answer == null) {
                s_logger.warn("send returns null answer");
                return null;
            }

            if (s_logger.isDebugEnabled() && answer.getDetails() != null) {