src/clientpaho.cpp

/* ****************************************************************************
 * Copyright 2019 Open Systems Development BV                                 *
 *                                                                            *
 * Permission is hereby granted, free of charge, to any person obtaining a    *
 * copy of this software and associated documentation files (the "Software"), *
 * to deal in the Software without restriction, including without limitation  *
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,   *
 * and/or sell copies of the Software, and to permit persons to whom the      *
 * Software is furnished to do so, subject to the following conditions:       *
 *                                                                            *
 * The above copyright notice and this permission notice shall be included in *
 * all copies or substantial portions of the Software.                        *
 *                                                                            *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR *
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,   *
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL    *
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER *
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING    *
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER        *
 * DEALINGS IN THE SOFTWARE.                                                  *
 * ***************************************************************************/
#include "clientpaho.h"
#include "errorcode.h"
#include "mqttutil.h"
#include "lockguard.h"
#include "log.h"
#include "metaprogrammingdefs.h"
#include "mqttstream.h"
#include "scopeguard.h"
#include "uriparser.h"
// std::chrono
#include "compat-chrono.h"
// std
#include <algorithm>
#include <iterator>
using namespace osdev::components::mqtt;
namespace {
#if defined(__clang__)
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wunused-template"
#endif
OSDEV_COMPONENTS_HASMEMBER_TRAIT(onSuccess5)
template <typename TRet>
inline typename std::enable_if<!has_onSuccess5<TRet>::value, TRet>::type initializeMqttStruct(TRet*)
{
    return MQTTAsync_disconnectOptions_initializer;
}
template <typename TRet>
inline typename std::enable_if<has_onSuccess5<TRet>::value, TRet>::type initializeMqttStruct(TRet*)
{
// For some reason g++ on centos7 evaluates the function body even when it is discarded by SFINAE.
// This leads to a compile error on an undefined symbol. We will use the old initializer macro, but this
// method should not be chosen when the struct does not contain member onSuccess5!
// On yocto warrior mqtt-paho-c 1.3.0 the macro MQTTAsync_disconnectOptions_initializer5 is not defined.
// while the struct does have an onSuccess5 member. In that case we do need correct initializer code.
// We fall back to the MQTTAsync_disconnectOptions_initializer macro and initialize
// additional fields ourself (which unfortunately results in a pesky compiler warning about missing field initializers).
#ifndef MQTTAsync_disconnectOptions_initializer5
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wmissing-field-initializers"
    TRet ret = MQTTAsync_disconnectOptions_initializer;
    ret.struct_version = 1;
    ret.onSuccess5 = nullptr;
    ret.onFailure5 = nullptr;
    return ret;
#pragma GCC diagnostic pop
#else
    return MQTTAsync_disconnectOptions_initializer5;
#endif
}
template <typename TRet>
struct Init
{
    static TRet initialize()
    {
        return initializeMqttStruct<TRet>(static_cast<TRet*>(nullptr));
    }
};
#if defined(__clang__)
#pragma GCC diagnostic pop
#endif
} // namespace
std::atomic_int ClientPaho::s_numberOfInstances(0);
ClientPaho::ClientPaho( const std::string& _endpoint,
    const std::string& _id,
    const std::function<void( const std::string&, ConnectionStatus )>& connectionStatusCallback,
    const std::function<void( const std::string& clientId, std::int32_t pubMsgToken )>& deliveryCompleteCallback )
    : m_mutex()
    , m_endpoint()
    , m_username()
    , m_password()
    , m_clientId(_id)
    , m_pendingOperations()
    , m_operationResult()
    , m_operationsCompleteCV()
    , m_subscriptions()
    , m_pendingSubscriptions()
    , m_subscribeTokenToTopic()
    , m_unsubscribeTokenToTopic()
    , m_pendingPublishes()
    , m_processPendingPublishes(false)
    , m_pendingPublishesReadyCV()
    , m_client()
    , m_connectionStatus(ConnectionStatus::Disconnected)
    , m_connectionStatusCallback(connectionStatusCallback)
    , m_deliveryCompleteCallback(deliveryCompleteCallback)
    , m_lastUnsubscribe(-1)
    , m_connectPromise()
    , m_disconnectPromise()
    , m_callbackEventQueue(m_clientId)
    , m_workerThread()
{
    if( 0 == s_numberOfInstances++ )
    {
        MQTTAsync_setTraceCallback( &ClientPaho::onLogPaho );
    }
    LogDebug( "[ClientPaho::ClientPaho]", std::string( " " + m_clientId + " - ctor ClientPaho " ) );
    parseEndpoint(_endpoint);
    auto rc = MQTTAsync_create( &m_client, m_endpoint.c_str(), m_clientId.c_str(), MQTTCLIENT_PERSISTENCE_NONE, nullptr );
    if( MQTTASYNC_SUCCESS == rc )
    {
        MQTTAsync_setCallbacks( m_client, reinterpret_cast<void*>(this), ClientPaho::onConnectionLost, ClientPaho::onMessageArrived, ClientPaho::onDeliveryComplete );
        m_workerThread = std::thread( &ClientPaho::callbackEventHandler, this );
    }
    else
    {
        LogError( "[ClientPaho::ClientPaho]", std::string( m_clientId + " - Failed to create client for endpoint " + m_endpoint + ", return code " + pahoAsyncErrorCodeToString( rc ) ) );
    }
}
ClientPaho::~ClientPaho()
{
    LogDebug( "[ClientPaho::~ClientPaho]", std::string( m_clientId + " - destructor ClientPaho" ) );
    if( MQTTAsync_isConnected( m_client ) )
    {
        this->unsubscribeAll();
        this->waitForCompletion( std::chrono::milliseconds(2000), std::set<int32_t>{} );
        this->disconnect( true, 5000 );
    }
    else
    {
        // If the status was already disconnected this call does nothing
        setConnectionStatus( ConnectionStatus::Disconnected );
    }
    if( 0 == --s_numberOfInstances )
    {
        // encountered a case where termination of the logging system within paho led to a segfault.
        // This was a paho thread that was cleaned while at the same time the logging system was terminated.
        // Removing the trace callback will not solve the underlying problem but hopefully will trigger it less
        // frequently.
        MQTTAsync_setTraceCallback( nullptr );
    }
    MQTTAsync_destroy( &m_client );
    m_callbackEventQueue.stop();
    if( m_workerThread.joinable() )
    {
        m_workerThread.join();
    }
}
std::string ClientPaho::clientId() const
{
    return m_clientId;
}
ConnectionStatus ClientPaho::connectionStatus() const
{
    return m_connectionStatus;
}
std::int32_t ClientPaho::connect( bool wait, const mqtt_LWT &lwt )
{
    {
        OSDEV_COMPONENTS_LOCKGUARD(m_mutex);
        if( ConnectionStatus::Disconnected != m_connectionStatus )
        {
            return -1;
        }
        setConnectionStatus( ConnectionStatus::ConnectInProgress );
    }
    LogInfo( "[ClientPaho::connect]", std::string( m_clientId + " - start connect to endpoint " + m_endpoint ) );
    MQTTAsync_connectOptions conn_opts = MQTTAsync_connectOptions_initializer;
    conn_opts.keepAliveInterval = 5;
    conn_opts.cleansession = 1;
    conn_opts.onSuccess = nullptr;
    conn_opts.onFailure = &ClientPaho::onConnectFailure;
    conn_opts.context = this;
    conn_opts.automaticReconnect = 1;
    // Make sure we get a signal if the promise is fulfilled
    auto ccb = MQTTAsync_setConnected( m_client, reinterpret_cast<void*>(this), ClientPaho::onFirstConnect );
    if( MQTTASYNC_SUCCESS == ccb )
    {
        LogDebug( "[ClientPaho::connect]", std::string( m_clientId + " - Setting the extra onConnected callback SUCCEEDED.") );
    }
    else
    {
        LogDebug( "[ClientPaho::connect]", std::string( m_clientId + " - Setting the extra onConnected callback FAILED.") );
    }
    // Setup the last will and testament, if so desired.
    if( !lwt.topic().empty() )
    {
        MQTTAsync_willOptions will_opts = MQTTAsync_willOptions_initializer;
        will_opts.message = lwt.message().c_str();
        will_opts.topicName = lwt.topic().c_str();
        conn_opts.will = &will_opts;
        LogDebug( "[ClientPaho::connect]", std::string( m_clientId + " - Set Last will and testament. Topic : " + lwt.topic() + " => Message : " + lwt.message() ) );
    }
    else
    {
        conn_opts.will = nullptr;
    }
    if( !m_username.empty() )
    {
        conn_opts.username = m_username.c_str();
    }
    if( !m_password.empty() )
    {
        conn_opts.password = m_password.c_str();
    }
    std::promise<void> waitForConnectPromise{};
    auto waitForConnect = waitForConnectPromise.get_future();
    m_connectPromise.reset();
    if( wait )
    {
        m_connectPromise = std::make_unique<std::promise<void>>( std::move( waitForConnectPromise ) );
    }
    {
        OSDEV_COMPONENTS_LOCKGUARD( m_mutex );
        if( !m_pendingOperations.insert( -100 ).second )
        {
            // Write something
        }
        m_operationResult.erase( -100 );
    }
    int rc = MQTTAsync_connect( m_client, &conn_opts );
    if( MQTTASYNC_SUCCESS != rc )
    {
        setConnectionStatus( ConnectionStatus::Disconnected );
        OSDEV_COMPONENTS_LOCKGUARD( m_mutex );
        m_operationResult[-100] = false;
        m_pendingOperations.erase(-100);
    }
    if( wait )
    {
        waitForConnect.get();
        m_connectPromise.reset();
    }
    return -100;
}
std::int32_t ClientPaho::disconnect( bool wait, int timeoutMs )
{
    ConnectionStatus currentStatus = m_connectionStatus;
    {
        OSDEV_COMPONENTS_LOCKGUARD(m_mutex);
        if( ConnectionStatus::Disconnected == m_connectionStatus || ConnectionStatus::DisconnectInProgress == m_connectionStatus )
        {
            return -1;
        }
        currentStatus = m_connectionStatus;
        setConnectionStatus( ConnectionStatus::DisconnectInProgress );
    }
    MQTTAsync_disconnectOptions disconn_opts = Init<MQTTAsync_disconnectOptions>::initialize();
    disconn_opts.timeout = timeoutMs;
    disconn_opts.onSuccess = &ClientPaho::onDisconnectSuccess;
    disconn_opts.onFailure = &ClientPaho::onDisconnectFailure;
    disconn_opts.context = this;
    std::promise<void> waitForDisconnectPromise{};
    auto waitForDisconnect = waitForDisconnectPromise.get_future();
    m_disconnectPromise.reset();
    if( wait )
    {
        m_disconnectPromise = std::make_unique<std::promise<void>>(std::move(waitForDisconnectPromise));
    }
    {
        OSDEV_COMPONENTS_LOCKGUARD(m_mutex);
        if( !m_pendingOperations.insert( -200 ).second )
        {
            LogDebug( "[ClientPaho::disconnect]", std::string( m_clientId + " disconnect - token" + std::to_string( -200 ) + "already in use" ) );
        }
        m_operationResult.erase( -200 );
    }
    int rc = MQTTAsync_disconnect( m_client, &disconn_opts );
    if( MQTTASYNC_SUCCESS != rc )
    {
        if( MQTTASYNC_DISCONNECTED == rc )
        {
            currentStatus = ConnectionStatus::Disconnected;
        }
        setConnectionStatus( currentStatus );
        OSDEV_COMPONENTS_LOCKGUARD( m_mutex );
        m_operationResult[-200] = false;
        m_pendingOperations.erase( -200 );
        if( MQTTASYNC_DISCONNECTED == rc )
        {
            return -1;
        }
        LogDebug( "[ClientPaho::disconnect]", std::string( m_clientId + " - failed to disconnect - return code " + pahoAsyncErrorCodeToString( rc ) ) );
    }
    if( wait )
    {
        if (std::future_status::timeout == waitForDisconnect.wait_for(std::chrono::milliseconds(timeoutMs + 100)))
        {
            LogDebug( "[ClientPaho::disconnect]", std::string( m_clientId + " - timeout occurred on disconnect" ) );
        }
        waitForDisconnect.get();
        m_disconnectPromise.reset();
    }
    return -200;
}
std::int32_t ClientPaho::publish( const MqttMessage& message, int qos )
{
    if( ConnectionStatus::DisconnectInProgress == m_connectionStatus )
    {
        LogDebug( "[ClientPaho::publish]", std::string( m_clientId + " - disconnect in progress, ignoring publish with qos " + std::to_string( qos ) + " on topic " + message.topic() ) );
        return -1;
    }
    else if( ConnectionStatus::Disconnected == m_connectionStatus )
    {
        LogDebug( "[ClientPaho::disconnect]", std::string( m_clientId + " - unable to publish, not connected" ) );
        connect( true );
    }
    if( !isValidTopic(message.topic() ) )
    {
        LogDebug( "[ClientPaho::disconnect]", std::string( m_clientId + " - topic " + message.topic() + " is invalid" ) );
    }
    if( qos > 2 )
    {
        qos = 2;
    }
    else if( qos < 0 )
    {
        qos = 0;
    }
    std::unique_lock<std::mutex> lck(m_mutex);
    if( ConnectionStatus::ReconnectInProgress == m_connectionStatus || m_processPendingPublishes )
    {
        m_pendingPublishesReadyCV.wait(lck, [this]() { return !m_processPendingPublishes; });
        if( ConnectionStatus::ReconnectInProgress == m_connectionStatus )
        {
            LogDebug( "[ClientPaho::publish]", "Adding publish to pending queue." );
            m_pendingPublishes.push_front( Publish{ qos, message } );
            return -1;
        }
    }
    return publishInternal( message, qos );
}
void ClientPaho::publishPending()
{
    {
        OSDEV_COMPONENTS_LOCKGUARD(m_mutex);
        if( !m_processPendingPublishes )
        {
            return;
        }
    }
    if( ConnectionStatus::Connected != m_connectionStatus )
    {
        LogInfo( "[ClientPaho::publishPending]", std::string( m_clientId + " - " ) )
    }
    while( !m_pendingPublishes.empty() )
    {
        const auto& pub = m_pendingPublishes.back();
        publishInternal( pub.data, pub.qos );
        m_pendingPublishes.pop_back();
    }
    {
        OSDEV_COMPONENTS_LOCKGUARD(m_mutex);
        m_processPendingPublishes = false;
    }
    m_pendingPublishesReadyCV.notify_all();
}
std::int32_t ClientPaho::subscribe( const std::string& topic, int qos, const std::function<void(MqttMessage msg)>& cb )
{
    if( ConnectionStatus::Connected != m_connectionStatus )
    {
        // MqttException, "Not connected"
    }
    if( !isValidTopic( topic ) )
    {
        // ("ClientPaho", "%1 - topic %2 is invalid", m_clientId, topic);
    }
    if( qos > 2 )
    {
        qos = 2;
    }
    else if( qos < 0 )
    {
        qos = 0;
    }
    {
        OSDEV_COMPONENTS_LOCKGUARD(m_mutex);
        auto itExisting = m_subscriptions.find(topic);
        if( m_subscriptions.end() != itExisting )
        {
            if( itExisting->second.qos == qos )
            {
                return -1;
            }
            // (OverlappingTopicException, "existing subscription with same topic, but different qos", topic);
        }
        auto itPending = m_pendingSubscriptions.find(topic);
        if( m_pendingSubscriptions.end() != itPending )
        {
            if( itPending->second.qos == qos )
            {
                auto itToken = std::find_if( m_subscribeTokenToTopic.begin(), m_subscribeTokenToTopic.end(), [&topic](const std::pair<MQTTAsync_token, std::string>& item) { return topic == item.second; } );
                if( m_subscribeTokenToTopic.end() != itToken )
                {
                    return itToken->first;
                }
                else
                {
                    return -1;
                }
            }
            // (OverlappingTopicException, "pending subscription with same topic, but different qos", topic);
        }
        std::string existingTopic{};
        if( isOverlappingInternal( topic, existingTopic ) )
        {
            // (OverlappingTopicException, "overlapping topic", existingTopic, topic);
        }
        LogDebug( "[ClientPaho::subscribe]", std::string( m_clientId + " -adding subscription on topic " + topic + " to the pending subscriptions" ) );
        m_pendingSubscriptions.emplace( std::make_pair( topic, Subscription{ qos, boost::regex( convertTopicToRegex( topic ) ), cb } ) );
    }
    return subscribeInternal( topic, qos );
}
void ClientPaho::resubscribe()
{
    decltype( m_pendingSubscriptions ) pendingSubscriptions{};
    {
        OSDEV_COMPONENTS_LOCKGUARD(m_mutex);
        std::copy( m_pendingSubscriptions.begin(), m_pendingSubscriptions.end(), std::inserter(pendingSubscriptions, pendingSubscriptions.end() ) );
    }
    for( const auto& s : pendingSubscriptions )
    {
        subscribeInternal( s.first, s.second.qos );
    }
}
std::int32_t ClientPaho::unsubscribe( const std::string& topic, int qos )
{
    {
        OSDEV_COMPONENTS_LOCKGUARD( m_mutex );
        bool found = false;
        for( const auto& s : m_subscriptions )
        {
            if( topic == s.first && qos == s.second.qos )
            {
                found = true;
                break;
            }
        }
        if( !found )
        {
            return -1;
        }
    }
    MQTTAsync_responseOptions opts = MQTTAsync_responseOptions_initializer;
    opts.onSuccess = &ClientPaho::onUnsubscribeSuccess;
    opts.onFailure = &ClientPaho::onUnsubscribeFailure;
    opts.context = this;
    {
        // Need to lock the mutex because it is possible that the callback is faster than
        // the insertion of the token into the pending operations.
        OSDEV_COMPONENTS_LOCKGUARD(m_mutex);
        auto rc = MQTTAsync_unsubscribe( m_client, topic.c_str(), &opts );
        if( MQTTASYNC_SUCCESS != rc )
        {
            LogDebug( "[ClientPaho::unsubscribe]", std::string( m_clientId + " - unsubscribe on topic " + topic + " failed with code " + pahoAsyncErrorCodeToString( rc ) ) );
        }
        if( !m_pendingOperations.insert( opts.token ).second )
        {
            LogDebug( "[ClientPaho::unsubscribe]", std::string( m_clientId + " unsubscribe - token " + std::to_string( opts.token )  + " already in use" ) );
        }
        m_operationResult.erase( opts.token );
        if( m_unsubscribeTokenToTopic.count( opts.token ) > 0 )
        {
            LogDebug( "[ClientPaho::unsubscribe]", std::string( m_clientId + " - token already in use, replacing unsubscribe from topic  " + m_unsubscribeTokenToTopic[opts.token] + " with " + topic ) );
        }
        m_lastUnsubscribe = opts.token; // centos7 workaround
        m_unsubscribeTokenToTopic[opts.token] = topic;
    }
    // Because of a bug in paho-c on centos7 the unsubscribes need to be sequential (best effort).
    this->waitForCompletion(std::chrono::seconds(1), std::set<int32_t>{ opts.token });
    return opts.token;
}
void ClientPaho::unsubscribeAll()
{
    decltype( m_subscriptions ) subscriptions{};
    {
        OSDEV_COMPONENTS_LOCKGUARD(m_mutex);
        subscriptions = m_subscriptions;
    }
    for( const auto& s : subscriptions )
    {
        this->unsubscribe( s.first, s.second.qos );
    }
}
std::chrono::milliseconds ClientPaho::waitForCompletion(std::chrono::milliseconds waitFor, const std::set<std::int32_t>& tokens) const
{
    if( waitFor <= std::chrono::milliseconds( 0 ) )
    {
        return std::chrono::milliseconds( 0 );
    }
    std::chrono::milliseconds timeElapsed{};
    {
        osdev::components::mqtt::measurement::TimeMeasurement msr( "waitForCompletion", [&timeElapsed](const std::string&, std::chrono::steady_clock::time_point, std::chrono::microseconds sinceStart, std::chrono::microseconds )
        {
            timeElapsed = std::chrono::ceil<std::chrono::milliseconds>( sinceStart );
        });
        std::unique_lock<std::mutex> lck(m_mutex);
        // ("ClientPaho", "%1 waitForCompletion - pending operations : %2", m_clientId, m_pendingOperations);
        m_operationsCompleteCV.wait_for(lck, waitFor, [this, &tokens]()
        {
            if( tokens.empty() )
            { // wait for all operations to end
                return m_pendingOperations.empty();
            }
            else if( tokens.size() == 1 )
            {
                return m_pendingOperations.find( *tokens.cbegin() ) == m_pendingOperations.end();
            }
            std::vector<std::int32_t> intersect{};
            std::set_intersection(m_pendingOperations.begin(), m_pendingOperations.end(), tokens.begin(), tokens.end(), std::back_inserter(intersect));
            return intersect.empty();
        } );
    }
    return timeElapsed;
}
bool ClientPaho::isOverlapping( const std::string& topic ) const
{
    std::string existingTopic{};
    return isOverlapping( topic, existingTopic );
}
bool ClientPaho::isOverlapping( const std::string& topic, std::string& existingTopic ) const
{
    OSDEV_COMPONENTS_LOCKGUARD(m_mutex);
    return isOverlappingInternal( topic, existingTopic );
}
std::vector<std::int32_t> ClientPaho::pendingOperations() const
{
    OSDEV_COMPONENTS_LOCKGUARD(m_mutex);
    std::vector<std::int32_t> retval{};
    retval.resize(m_pendingOperations.size());
    std::copy( m_pendingOperations.begin(), m_pendingOperations.end(), retval.begin() );
    return retval;
}
bool ClientPaho::hasPendingSubscriptions() const
{
    OSDEV_COMPONENTS_LOCKGUARD(m_mutex);
    return !m_pendingSubscriptions.empty();
}
boost::optional<bool> ClientPaho::operationResult( std::int32_t token ) const
{
    OSDEV_COMPONENTS_LOCKGUARD(m_mutex);
    boost::optional<bool> ret{};
    auto cit = m_operationResult.find( token );
    if( m_operationResult.end() != cit )
    {
        ret = cit->second;
    }
    return ret;
}
void ClientPaho::parseEndpoint( const std::string& _endpoint )
{
    auto ep = UriParser::parse( _endpoint );
    if( ep.find( "user" ) != ep.end() )
    {
        m_username = ep["user"];
        ep["user"].clear();
    }
    if( ep.find( "password" ) != ep.end() )
    {
        m_password = ep["password"];
        ep["password"].clear();
    }
    m_endpoint = UriParser::toString( ep );
}
std::int32_t ClientPaho::publishInternal( const MqttMessage& message, int qos )
{
    MQTTAsync_responseOptions opts = MQTTAsync_responseOptions_initializer;
    opts.onSuccess = &ClientPaho::onPublishSuccess;
    opts.onFailure = &ClientPaho::onPublishFailure;
    opts.context = this;
    auto msg = message.toAsyncMessage();
    msg.qos = qos;
    // Need to lock the mutex because it is possible that the callback is faster than
    // the insertion of the token into the pending operations.
    // OSDEV_COMPONENTS_LOCKGUARD(m_mutex);
    auto rc = MQTTAsync_sendMessage( m_client, message.topic().c_str(), &msg, &opts );
    if( MQTTASYNC_SUCCESS != rc )
    {
        LogDebug( "[ClientPaho::publishInterval]", std::string( m_clientId + " - publish on topic " + message.topic() + " failed with code " + pahoAsyncErrorCodeToString( rc ) ) );
    }
    if( !m_pendingOperations.insert( opts.token ).second )
    {
        LogDebug( "[ClientPaho::publishInterval]", std::string( m_clientId + " publishInternal - token " + std::to_string( opts.token ) + " already in use" ) );
    }
    m_operationResult.erase( opts.token );
    return opts.token;
}
std::int32_t ClientPaho::subscribeInternal( const std::string& topic, int qos )
{
    MQTTAsync_responseOptions opts = MQTTAsync_responseOptions_initializer;
    opts.onSuccess = &ClientPaho::onSubscribeSuccess;
    opts.onFailure = &ClientPaho::onSubscribeFailure;
    opts.context = this;
    // Need to lock the mutex because it is possible that the callback is faster than
    // the insertion of the token into the pending operations.
    OSDEV_COMPONENTS_LOCKGUARD(m_mutex);
    auto rc = MQTTAsync_subscribe( m_client, topic.c_str(), qos, &opts );
    if (MQTTASYNC_SUCCESS != rc)
    {
        m_pendingSubscriptions.erase( topic );
        LogDebug( "[ClientPaho::subscribeInterval]", std::string( m_clientId + " subscribtion on topic " + topic + " failed with code " + pahoAsyncErrorCodeToString( rc ) ) );
    }
    if( !m_pendingOperations.insert( opts.token ).second )
    {
        LogDebug( "[ClientPaho::subscribeInterval]", std::string( m_clientId + " subscribe - token " + std::to_string( opts.token ) + " already in use" ) );
    }
    m_operationResult.erase( opts.token );
    if( m_subscribeTokenToTopic.count( opts.token ) > 0 )
    {
        LogDebug( "[ClientPaho::subscribeInterval]", std::string( m_clientId + " - overwriting pending subscription on topic " + m_subscribeTokenToTopic[opts.token] + " with topic " + topic ) );
    }
    m_subscribeTokenToTopic[opts.token] = topic;
    return opts.token;
}
void ClientPaho::setConnectionStatus( ConnectionStatus status )
{
    ConnectionStatus curStatus = m_connectionStatus;
    m_connectionStatus = status;
    if( status != curStatus && m_connectionStatusCallback )
    {
        m_connectionStatusCallback( m_clientId, status );
    }
}
bool ClientPaho::isOverlappingInternal( const std::string& topic, std::string& existingTopic ) const
{
    existingTopic.clear();
    for( const auto& s : m_pendingSubscriptions )
    {
        if( testForOverlap( s.first, topic ) )
        {
            existingTopic = s.first;
            return true;
        }
    }
    for( const auto& s : m_subscriptions )
    {
        if( testForOverlap( s.first, topic ) )
        {
            existingTopic = s.first;
            return true;
        }
    }
    return false;
}
void ClientPaho::pushIncomingEvent( std::function<void()> ev )
{
    m_callbackEventQueue.push( ev );
}
void ClientPaho::callbackEventHandler()
{
    LogDebug( "[ClientPaho::callbackEventHandler]", std::string( m_clientId + " - starting callback event handler" ) );
    for( ;; )
    {
        std::vector<std::function<void()>> events;
        if( !m_callbackEventQueue.pop(events) )
        {
            break;
        }
        for( const auto& ev : events )
        {
            ev();
        }
    }
    LogDebug( "[ClientPaho::callbackEventHandler]", std::string( m_clientId + " - leaving callback event handler" ) );
}
void ClientPaho::onConnectOnInstance( const std::string& cause )
{
    (void) cause;
    {
        OSDEV_COMPONENTS_LOCKGUARD(m_mutex);
        std::copy( m_subscriptions.begin(), m_subscriptions.end(), std::inserter( m_pendingSubscriptions, m_pendingSubscriptions.end() ) );
        m_subscriptions.clear();
        m_processPendingPublishes = true; // all publishes are on hold until publishPending is called.
    }
    setConnectionStatus( ConnectionStatus::Connected );
}
void ClientPaho::onConnectSuccessOnInstance()
{
    {
        OSDEV_COMPONENTS_LOCKGUARD(m_mutex);
        // Register the connect callback that is used in reconnect scenarios.
        auto rc = MQTTAsync_setConnected( m_client, this, &ClientPaho::onConnect );
        if( MQTTASYNC_SUCCESS != rc )
        {
            LogError( "[ClientPaho::onConnectSuccessOnInstance]", std::string( "onConnectSuccesOnInstance " + m_clientId + " - registering the connected callback failed with code : " + pahoAsyncErrorCodeToString(rc) ) );
        }
        // For MQTTV5
        //rc = MQTTAsync_setDisconnected(m_client, this, &ClientPaho::onDisconnect);
        //if (MQTTASYNC_SUCCESS != rc) {
        //    // ("ClientPaho", "onConnectSuccessOnInstance %1 - registering the disconnected callback failed with code %2", m_clientId, pahoAsyncErrorCodeToString(rc));
        //}
        // ("ClientPaho", "onConnectSuccessOnInstance %1 - pending operations : %2, removing operation -100", m_clientId, m_pendingOperations);
        m_operationResult[-100] = true;
        m_pendingOperations.erase(-100);
    }
    setConnectionStatus( ConnectionStatus::Connected );
    if( m_connectPromise )
    {
        LogDebug( "[ClientPaho::onConnectSuccessOnInstance]", std::string("connectPromise still present. Resetting!" ) );
        m_connectPromise->set_value();
    }
    m_operationsCompleteCV.notify_all();
}
void ClientPaho::onConnectFailureOnInstance( const MqttFailure& response )
{
    (void) response;
    LogDebug( "[ClientPaho::onConnectFailureOnInstance]", std::string( "onConnectFailureOnInstance" + m_clientId + " - connection failed with code " + response.codeToString() + " (" + response.message() + ")"));
    {
        OSDEV_COMPONENTS_LOCKGUARD(m_mutex);
        // ("ClientPaho", "onConnectFailureOnInstance %1 - pending operations : %2, removing operation -100", m_clientId, m_pendingOperations);
        m_operationResult[-100] = false;
        m_pendingOperations.erase(-100);
    }
    if( ConnectionStatus::ConnectInProgress == m_connectionStatus )
    {
        setConnectionStatus( ConnectionStatus::Disconnected );
    }
    m_operationsCompleteCV.notify_all();
}
//void ClientPaho::onDisconnectOnInstance(enum MQTTReasonCodes reasonCode)
//{
//    MLOGIC_COMMON_INFO("ClientPaho", "onDisconnectOnInstance %1 - disconnect (reason %2)", MQTTReasonCode_toString(reasonCode));
//}
void ClientPaho::onDisconnectSuccessOnInstance( const MqttSuccess& )
{
    LogDebug( "[ClientPaho::onDisconnectSuccessOnInstance]", std::string( m_clientId + " - disconnected from endpoint " + m_endpoint ) );
    {
        OSDEV_COMPONENTS_LOCKGUARD(m_mutex);
        m_subscriptions.clear();
        m_pendingSubscriptions.clear();
        m_subscribeTokenToTopic.clear();
        m_unsubscribeTokenToTopic.clear();
        // ("ClientPaho", "onDisconnectSuccessOnInstance %1 - pending operations : %2, removing all operations", m_clientId, m_pendingOperations);
        m_operationResult[-200] = true;
        m_pendingOperations.clear();
    }
    setConnectionStatus( ConnectionStatus::Disconnected );
    if( m_disconnectPromise )
    {
        m_disconnectPromise->set_value();
    }
    m_operationsCompleteCV.notify_all();
}
void ClientPaho::onDisconnectFailureOnInstance( const MqttFailure& response )
{
    (void) response;
    LogDebug( "[ClientPaho::onDisconnectFailureOnInstance]", std::string( m_clientId + " - disconnect failed with code " + response.codeToString() + " ( " + response.message() + " ) " ) );
    {
        OSDEV_COMPONENTS_LOCKGUARD(m_mutex);        
        // ("ClientPaho", "onDisconnectFailureOnInstance %1 - pending operations : %2, removing operation -200", m_clientId, m_pendingOperations);
        m_operationResult[-200] = false;
        m_pendingOperations.erase(-200);
    }
    if( MQTTAsync_isConnected( m_client ) )
    {
        setConnectionStatus( ConnectionStatus::Connected );
    }
    else
    {
        setConnectionStatus( ConnectionStatus::Disconnected );
    }
    if( m_disconnectPromise )
    {
        m_disconnectPromise->set_value();
    }
    m_operationsCompleteCV.notify_all();
}
void ClientPaho::onPublishSuccessOnInstance( const MqttSuccess& response )
{
    auto pd = response.publishData();
    LogDebug( "[ClientPaho::onPublishSuccessOnInstance]", std::string( m_clientId + " - publish with token " + std::to_string( response.token() ) + " succeeded ( message was " + pd.payload() + " )" ) );
    {
        OSDEV_COMPONENTS_LOCKGUARD(m_mutex);
        // ("ClientPaho", "onPublishSuccessOnInstance %1 - pending operations : %2, removing operation %3", m_clientId, m_pendingOperations, response.token());
        m_operationResult[response.token()] = true;
        m_pendingOperations.erase(response.token());
    }
    m_operationsCompleteCV.notify_all();
}
void ClientPaho::onPublishFailureOnInstance( const MqttFailure& response )
{
    LogDebug( "[ClientPaho::onPublishFailureOnInstance]", std::string( m_clientId + " - publish with token " + std::to_string( response.token() ) + " failed with code " + response.codeToString() + " ( " + response.message() + " )" ) );
    {
        OSDEV_COMPONENTS_LOCKGUARD(m_mutex);
        // ("ClientPaho", "onPublishFailureOnInstance %1 - pending operations : %2, removing operation %3", m_clientId, m_pendingOperations, response.token());
        m_operationResult[response.token()] = false;
        m_pendingOperations.erase(response.token());
    }
    m_operationsCompleteCV.notify_all();
}
void ClientPaho::onSubscribeSuccessOnInstance( const MqttSuccess& response )
{
    LogDebug( "[ClientPaho::onSubscribeSuccessOnInstance]", std::string( m_clientId + " - subscribe with token " + std::to_string( response.token() ) + "succeeded" ) );
    OSDEV_COMPONENTS_SCOPEGUARD( m_operationsCompleteCV, [this]() { m_operationsCompleteCV.notify_all(); });
    OSDEV_COMPONENTS_LOCKGUARD(m_mutex);
    bool operationOk = false;
    OSDEV_COMPONENTS_SCOPEGUARD( m_pendingOperations, [this, &response, &operationOk]()
    {
        // ("ClientPaho", "onSubscribeSuccessOnInstance %1 - pending operations : %2, removing operation %3", m_clientId, m_pendingOperations, response.token());
        m_operationResult[response.token()] = operationOk;
        m_pendingOperations.erase( response.token() );
    });
    auto it = m_subscribeTokenToTopic.find( response.token() );
    if( m_subscribeTokenToTopic.end() == it )
    {
        LogDebug( "[ClientPaho::onSubscribeSuccessOnInstance]", std::string( m_clientId + " - unknown token " + std::to_string( response.token() ) ) );
        return;
    }
    auto topic = it->second;
    m_subscribeTokenToTopic.erase(it);
    auto pendingIt = m_pendingSubscriptions.find( topic );
    if( m_pendingSubscriptions.end() == pendingIt )
    {
        LogDebug( "[ClientPaho::onSubscribeSuccessOnInstance]", std::string( m_clientId + " - cannot find pending subscription for token " + std::to_string( response.token() ) ) );
        return;
    }
    if( response.qos() != pendingIt->second.qos )
    {
        LogDebug( "[ClientPaho::onSubscribeSuccessOnInstance]", std::string( m_clientId + " - subscription requested qos " + std::to_string( pendingIt->second.qos ) + " , endpoint assigned qos " + std::to_string( response.qos() ) ) );
    }
    LogDebug( "[ClientPaho::onSubscribeSuccessOnInstance]", std::string( m_clientId + " - move pending subscription on topic " + topic + " to the registered subscriptions" ) );
    m_subscriptions.emplace( std::make_pair( pendingIt->first, std::move( pendingIt->second ) ) );
    m_pendingSubscriptions.erase( pendingIt );
    operationOk = true;
}
void ClientPaho::onSubscribeFailureOnInstance( const MqttFailure& response )
{
    LogDebug( "[ClientPaho::onSubscribeFailureOnInstance]", std::string( m_clientId + " - subscription failed with code " + response.codeToString() + " ( " + response.message() + " )" ) );
    OSDEV_COMPONENTS_SCOPEGUARD( m_operationsCompleteCV, [this]() { m_operationsCompleteCV.notify_all(); } );
    OSDEV_COMPONENTS_LOCKGUARD(m_mutex);
    OSDEV_COMPONENTS_SCOPEGUARD( m_pendingOperations, [this, &response]()
    {
        // MLOGIC_COMMON_DEBUG("ClientPaho", "onSubscribeFailureOnInstance %1 - pending operations : %2, removing operation %3", m_clientId, m_pendingOperations, response.token());
        m_operationResult[response.token()] = false;
        m_pendingOperations.erase( response.token() );
    });
    auto it = m_subscribeTokenToTopic.find( response.token() );
    if( m_subscribeTokenToTopic.end() == it )
    {
        LogDebug( "[ClientPaho::onSubscribeFailureOnInstance]", std::string( m_clientId + " - unknown token " + std::to_string( response.token() ) ) );
        return;
    }
    auto topic = it->second;
    m_subscribeTokenToTopic.erase( it );
    auto pendingIt = m_pendingSubscriptions.find( topic );
    if( m_pendingSubscriptions.end() == pendingIt )
    {
        LogDebug( "[ClientPaho::onSubscribeFailureOnInstance]", std::string( m_clientId + " - cannot find pending subscription for token " + std::to_string( response.token() ) ) );
        return;
    }
    LogDebug( "[ClientPaho::onSubscribeFailureOnInstance]", std::string( m_clientId + " - remove pending subscription on topic " + topic ) );
    m_pendingSubscriptions.erase( pendingIt );
}
void ClientPaho::onUnsubscribeSuccessOnInstance( const MqttSuccess& response )
{
    LogDebug( "[ClientPaho::onSubscribeSuccessOnInstance]", std::string( m_clientId + " - unsubscribe with token " + std::to_string( response.token() ) + " succeeded " ) );
    OSDEV_COMPONENTS_SCOPEGUARD( m_operationsCompleteCV, [this]() { m_operationsCompleteCV.notify_all(); } );
    OSDEV_COMPONENTS_LOCKGUARD(m_mutex);
    // On centos7 the unsubscribe response is a nullptr, so we do not have a valid token.
    // As a workaround the last unsubscribe token is stored and is used when no valid token is available.
    // This is by no means bullet proof because rapid unsubscribes in succession will overwrite this member
    // before the callback on the earlier unsubscribe has arrived. On centos7 the unsubscribes have to be handled
    // sequentially (see ClientPaho::unsubscribe)!
    auto token = response.token();
    if( -1 == token )
    {
        token = m_lastUnsubscribe;
        m_lastUnsubscribe = -1;
    }
    bool operationOk = false;
    OSDEV_COMPONENTS_SCOPEGUARD( m_pendingOperations, [this, token, &operationOk]()
    {
        // ("ClientPaho", "onUnsubscribeSuccessOnInstance %1 - pending operations : %2, removing operation %3", m_clientId, m_pendingOperations, token);
        m_operationResult[token] = operationOk;
        m_pendingOperations.erase( token );
    });
    auto it = m_unsubscribeTokenToTopic.find( token );
    if( m_unsubscribeTokenToTopic.end() == it )
    {
        LogDebug( "[ClientPaho::onSubscribeSuccessOnInstance]", std::string( m_clientId + " - unknown token " + std::to_string( token ) ) );
        return;
    }
    auto topic = it->second;
    m_unsubscribeTokenToTopic.erase( it );
    auto registeredIt = m_subscriptions.find( topic );
    if( m_subscriptions.end() == registeredIt )
    {
        LogDebug( "[ClientPaho::onSubscribeSuccessOnInstance]", std::string( m_clientId + " - cannot find subscription for token " + std::to_string( response.token() ) ) );
        return;
    }
    LogDebug( "[ClientPaho::onSubscribeSuccessOnInstance]", std::string( m_clientId + " - remove subscription on topic " + topic + " from the registered subscriptions" ) );
    m_subscriptions.erase( registeredIt );
    operationOk = true;
}
void ClientPaho::onUnsubscribeFailureOnInstance( const MqttFailure& response )
{
    LogDebug( "[ClientPaho::onUnsubscribeFailureOnInstance]", std::string( m_clientId + " - subscription failed with code " + response.codeToString() + " ( " + response.message() + " )" ) );
    OSDEV_COMPONENTS_SCOPEGUARD( m_operationsCompleteCV, [this]() { m_operationsCompleteCV.notify_all(); } );
    OSDEV_COMPONENTS_LOCKGUARD(m_mutex);
    OSDEV_COMPONENTS_SCOPEGUARD( m_pendingOperations, [this, &response]()
    {
        // ("ClientPaho", "onUnsubscribeFailureOnInstance %1 - pending operations : %2, removing operation %3", m_clientId, m_pendingOperations, response.token());
        m_operationResult[response.token()] = false;
        m_pendingOperations.erase( response.token() );
    });
    auto it = m_unsubscribeTokenToTopic.find( response.token() );
    if( m_unsubscribeTokenToTopic.end() == it )
    {
        LogDebug( "[ClientPaho::onUnsubscribeFailureOnInstance]", std::string( m_clientId + " - unknown token " + std::to_string( response.token() ) ) );
        return;
    }
    auto topic = it->second;
    m_unsubscribeTokenToTopic.erase( it );
}
int ClientPaho::onMessageArrivedOnInstance( const MqttMessage& message )
{
    LogDebug( "[ClientPaho::onMessageArrivedOnInstance]", std::string( m_clientId + " - received message on topic " + message.topic() + ", retained : " + std::to_string( message.retained() ) + ", dup : " + std::to_string( message.duplicate() ) ) );
    std::function<void( MqttMessage )> cb;
    {
        OSDEV_COMPONENTS_LOCKGUARD(m_mutex);
        for( const auto& s : m_subscriptions )
        {
            if( boost::regex_match( message.topic(), s.second.topicRegex ) )
            {
                cb = s.second.callback;
            }
        }
    }
    if( cb )
    {
        cb( message );
    }
    else
    {
        LogDebug( "[ClientPaho::onMessageArrivedOnInstance]", std::string( m_clientId + " - no tpic filter found for message received on topic " + message.topic() ) );
    }
    return 1;
}
void ClientPaho::onDeliveryCompleteOnInstance( MQTTAsync_token token )
{
    LogDebug( "[ClientPaho::onDeliveryCompleteOnInstance]", std::string( m_clientId + " - message with token " + std::to_string( token ) + " is delivered" ) );
    if( m_deliveryCompleteCallback )
    {
        m_deliveryCompleteCallback( m_clientId, static_cast<std::int32_t>( token ) );
    }
}
void ClientPaho::onConnectionLostOnInstance( const std::string& cause )
{
    (void) cause;
    // ("ClientPaho", "onConnectionLostOnInstance %1 - connection lost (%2)", m_clientId, cause);
    setConnectionStatus( ConnectionStatus::ReconnectInProgress );
    OSDEV_COMPONENTS_LOCKGUARD(m_mutex);
    // Remove all tokens related to subscriptions from the active operations.
    for( const auto& p : m_subscribeTokenToTopic )
    {
        // ("ClientPaho", "onConnectionLostOnInstance %1 - pending operations : %2, removing operation %3", m_clientId, m_pendingOperations, p.first);
        m_pendingOperations.erase( p.first );
    }
    for( const auto& p : m_unsubscribeTokenToTopic )
    {
        // ("ClientPaho", "onConnectionLostOnInstance %1 - pending operations : %2, removing operation %3", m_clientId, m_pendingOperations, p.first);
        m_pendingOperations.erase( p.first );
    }
    // Clear the administration used in the subscribe process.
    m_subscribeTokenToTopic.clear();
    m_unsubscribeTokenToTopic.clear();
}
// static
void ClientPaho::onFirstConnect( void* context, char* cause )
{
    LogInfo( "[ClientPaho::onFirstConnect]", "onFirstConnect triggered.." );
    if( context )
    {
        auto *cl = reinterpret_cast<ClientPaho*>( context );
        std::string reason( nullptr == cause ? "Unknown cause" : cause );
        cl->pushIncomingEvent( [cl, reason]() { cl->onConnectSuccessOnInstance(); } );
    }
}
void ClientPaho::onConnect( void* context, char* cause )
{
    LogInfo( "[ClientPaho::onConnect]", "onConnect triggered.." );
    if( context )
    {
        auto* cl = reinterpret_cast<ClientPaho*>( context );
        std::string reason( nullptr == cause ? "unknown cause" : cause );
        cl->pushIncomingEvent( [cl, reason]() { cl->onConnectOnInstance( reason ); } );
    }
}
// static
void ClientPaho::onConnectSuccess( void* context, MQTTAsync_successData* response )
{
    LogInfo( "[ClientPaho::onConnectSuccess]", "onConnectSuccess triggered.." );
    if( context )
    {
        auto* cl = reinterpret_cast<ClientPaho*>( context );
        if( !response )
        {
            // connect should always have a valid response struct.
            LogError( "[ClientPaho::onConnectSuccess]", "onConnectSuccess - no response data" );
            return;
        }
        // MqttSuccess resp(response->token, ConnectionData(response->alt.connect.serverURI, response->alt.connect.MQTTVersion, response->alt.connect.sessionPresent));
        cl->pushIncomingEvent( [cl]() { cl->onConnectSuccessOnInstance(); } );
    }
}
// static
void ClientPaho::onConnectFailure( void* context, MQTTAsync_failureData* response )
{
    LogDebug("[ClientPaho::onConnectFailure]", std::string( "Connection Failure?" ) );
    if( context )
    {
        auto* cl = reinterpret_cast<ClientPaho*>( context );
        MqttFailure resp( response );
        cl->pushIncomingEvent( [cl, resp]() { cl->onConnectFailureOnInstance( resp ); } );
    }
}
//// static
//void ClientPaho::onDisconnect(void* context, MQTTProperties* properties, enum MQTTReasonCodes reasonCode)
//{
//    apply_unused_parameters(properties);
//    try {
//        if (context) {
//            auto* cl = reinterpret_cast<ClientPaho*>(context);
//            cl->pushIncomingEvent([cl, reasonCode]() { cl->onDisconnectOnInstance(reasonCode); });
//        }
//    }
//    catch (...) {
//    }
//    catch (const std::exception& e) {
//        MLOGIC_COMMON_ERROR("ClientPaho", "onDisconnect - exception : %1", e.what());
//    }
//    catch (...) {
//        MLOGIC_COMMON_ERROR("ClientPaho", "onDisconnect - unknown exception");
//    }
//}
// static
void ClientPaho::onDisconnectSuccess( void* context, MQTTAsync_successData* response )
{
    if( context )
    {
        auto* cl = reinterpret_cast<ClientPaho*>( context );
        MqttSuccess resp( response ? response->token : 0 );
        cl->pushIncomingEvent( [cl, resp]() { cl->onDisconnectSuccessOnInstance( resp ); } );
    }
}
// static
void ClientPaho::onDisconnectFailure( void* context, MQTTAsync_failureData* response )
{
    LogInfo( "[ClientPaho::onDisconnectFailure]", "onDisconnectFailure triggered.." );
    if( context )
    {
        auto* cl = reinterpret_cast<ClientPaho*>( context );
        MqttFailure resp( response );
        cl->pushIncomingEvent( [cl, resp]() { cl->onDisconnectFailureOnInstance( resp ); } );
    }
}
// static
void ClientPaho::onPublishSuccess( void* context, MQTTAsync_successData* response )
{
    if( context )
    {
        auto* cl = reinterpret_cast<ClientPaho*>( context );
        if( !response )
        {
            // publish should always have a valid response struct.
            // toLogFile ("ClientPaho", "onPublishSuccess - no response data");
        }
        MqttSuccess resp(response->token, MqttMessage(response->alt.pub.destinationName == nullptr ? "null" : response->alt.pub.destinationName, response->alt.pub.message));
        cl->pushIncomingEvent([cl, resp]() { cl->onPublishSuccessOnInstance(resp); });
    }
}
// static
void ClientPaho::onPublishFailure( void* context, MQTTAsync_failureData* response )
{
    (void) response;
    if( context )
    {
        auto* cl = reinterpret_cast<ClientPaho*>( context );
        MqttFailure resp( response );
        cl->pushIncomingEvent( [cl, resp]() { cl->onPublishFailureOnInstance( resp ); } );
    }
}
// static
void ClientPaho::onSubscribeSuccess( void* context, MQTTAsync_successData* response )
{
    if( context )
    {
        auto* cl = reinterpret_cast<ClientPaho*>( context );
        if( !response )
        {
            // subscribe should always have a valid response struct.
            // MLOGIC_COMMON_FATAL("ClientPaho", "onSubscribeSuccess - no response data");
        }
        MqttSuccess resp( response->token, response->alt.qos );
        cl->pushIncomingEvent( [cl, resp]() { cl->onSubscribeSuccessOnInstance( resp ); } );
    }
}
// static
void ClientPaho::onSubscribeFailure( void* context, MQTTAsync_failureData* response )
{
    if( context )
    {
        auto* cl = reinterpret_cast<ClientPaho*>( context );
        MqttFailure resp( response );
        cl->pushIncomingEvent( [cl, resp]() { cl->onSubscribeFailureOnInstance( resp ); } );
    }
}
// static
void ClientPaho::onUnsubscribeSuccess( void* context, MQTTAsync_successData* response )
{
    if( context )
    {
        auto* cl = reinterpret_cast<ClientPaho*>( context );
        MqttSuccess resp( response ? response->token : -1 );
        cl->pushIncomingEvent( [cl, resp]() { cl->onUnsubscribeSuccessOnInstance( resp ); } );
    }
}
// static
void ClientPaho::onUnsubscribeFailure( void* context, MQTTAsync_failureData* response )
{
    if( context )
    {
        auto* cl = reinterpret_cast<ClientPaho*>( context );
        MqttFailure resp( response );
        cl->pushIncomingEvent( [cl, resp]() { cl->onUnsubscribeFailureOnInstance( resp ); } );
    }
}
// static
int ClientPaho::onMessageArrived( void* context, char* topicName, int, MQTTAsync_message* message )
{
    OSDEV_COMPONENTS_SCOPEGUARD( freeMessage, [&topicName, &message]()
    {
        MQTTAsync_freeMessage( &message );
        MQTTAsync_free( topicName );
    });
    if( context )
    {
        auto* cl = reinterpret_cast<ClientPaho*>( context );
        MqttMessage msg( topicName, *message );
        cl->pushIncomingEvent( [cl, msg]() { cl->onMessageArrivedOnInstance( msg ); } );
    }
    return 1; // always return true. Otherwise this callback is triggered again.
}
// static
void ClientPaho::onDeliveryComplete( void* context, MQTTAsync_token token )
{
    if( context )
    {
        auto* cl = reinterpret_cast<ClientPaho*>( context );
        cl->pushIncomingEvent( [cl, token]() { cl->onDeliveryCompleteOnInstance( token ); } );
    }
}
// static
void ClientPaho::onConnectionLost( void* context, char* cause )
{
    OSDEV_COMPONENTS_SCOPEGUARD( freeCause, [&cause]()
    {
        if( cause )
        {
            MQTTAsync_free( cause );
        }
    });
    if( context )
    {
        auto* cl = reinterpret_cast<ClientPaho*>( context );
        std::string msg( nullptr == cause ? "cause unknown" : cause );
        cl->pushIncomingEvent( [cl, msg]() { cl->onConnectionLostOnInstance( msg ); } );
    }
}
// static
void ClientPaho::onLogPaho( enum MQTTASYNC_TRACE_LEVELS level, char* message )
{
    (void) message;
    switch( level )
    {
        case MQTTASYNC_TRACE_MAXIMUM:
        case MQTTASYNC_TRACE_MEDIUM:
        case MQTTASYNC_TRACE_MINIMUM:
        {
            // ("ClientPaho", "paho - %1", message)
            break;
        }
        case MQTTASYNC_TRACE_PROTOCOL:
        {
            // ("ClientPaho", "paho - %1", message)
            break;
        }
        case MQTTASYNC_TRACE_ERROR:
        case MQTTASYNC_TRACE_SEVERE:
        case MQTTASYNC_TRACE_FATAL:
        {
            // ("ClientPaho", "paho - %1", message)
            break;
        }
    }
}