使用librdkafka的C++接口实现简单的生产者和消费者

一.编译librdkafka

环境：Fedora 20，32位

依赖：pthreads（必选），zlib（可选），libssl-dev（可选），libsasl2-dev（可选）

先查看自己的linux上是否安装了pthreads，指令如下：

# locate libpthread

因为我之前安过了，所以可以直接编译librdkafka，没有安的下个pthreads的源码——configure、make、make install。

开始编译librdkafka，指令如下：

# ./configure
# make
# make install

lib库会被默认安装到/usr/local/lib目录

头文件被默认安装到/usr/local/include/librdkafka目录

二.生产者

新建Qt控制台工程KafkaProducer，Pro文件如下：

#-------------------------------------------------
#
# Project created by QtCreator 2018-03-27T19:45:09
#
#-------------------------------------------------
QT       -= gui core

TARGET = KafkaProducer
CONFIG   += console
CONFIG   -= app_bundle

TEMPLATE = app

SOURCES += main.cpp
INCLUDEPATH += /usr/local/include/librdkafka
LIBS += -L/usr/local/lib -lrdkafka
LIBS += -L/usr/local/lib -lrdkafka++

main.cpp文件如下：

#include 
#include 
#include 
#include 
#include 
#include 

#include 

#include "rdkafkacpp.h"

static bool run = true;

static void sigterm (int sig) {
    run = false;
}

class ExampleDeliveryReportCb : public RdKafka::DeliveryReportCb {
public:
    void dr_cb (RdKafka::Message &message) {
        std::cout << "Message delivery for (" << message.len() << " bytes): " <<
                     message.errstr() << std::endl;
        if (message.key())
            std::cout << "Key: " << *(message.key()) << ";" << std::endl;
    }
};

class ExampleEventCb : public RdKafka::EventCb {
public:
    void event_cb (RdKafka::Event &event) {
        switch (event.type())
        {
        case RdKafka::Event::EVENT_ERROR:
            std::cerr << "ERROR (" << RdKafka::err2str(event.err()) << "): " <<
                         event.str() << std::endl;
            if (event.err() == RdKafka::ERR__ALL_BROKERS_DOWN)
                run = false;
            break;

        case RdKafka::Event::EVENT_STATS:
            std::cerr << "\"STATS\": " << event.str() << std::endl;
            break;

        case RdKafka::Event::EVENT_LOG:
            fprintf(stderr, "LOG-%i-%s: %s\n",
                    event.severity(), event.fac().c_str(), event.str().c_str());
            break;

        default:
            std::cerr << "EVENT " << event.type() <<
                         " (" << RdKafka::err2str(event.err()) << "): " <<
                         event.str() << std::endl;
            break;
        }
    }
};

int main ()
{
    std::string brokers = "localhost";
    std::string errstr;
    std::string topic_str="test";
    int32_t partition = RdKafka::Topic::PARTITION_UA;

    RdKafka::Conf *conf = RdKafka::Conf::create(RdKafka::Conf::CONF_GLOBAL);
    RdKafka::Conf *tconf = RdKafka::Conf::create(RdKafka::Conf::CONF_TOPIC);

    conf->set("bootstrap.servers", brokers, errstr);

    ExampleEventCb ex_event_cb;
    conf->set("event_cb", &ex_event_cb, errstr);

    signal(SIGINT, sigterm);
    signal(SIGTERM, sigterm);

    ExampleDeliveryReportCb ex_dr_cb;
    conf->set("dr_cb", &ex_dr_cb, errstr);

    RdKafka::Producer *producer = RdKafka::Producer::create(conf, errstr);
    if (!producer) {
        std::cerr << "Failed to create producer: " << errstr << std::endl;
        exit(1);
    }
    std::cout << "% Created producer " << producer->name() << std::endl;

    RdKafka::Topic *topic = RdKafka::Topic::create(producer, topic_str,
                                                   tconf, errstr);
    if (!topic) {
        std::cerr << "Failed to create topic: " << errstr << std::endl;
        exit(1);
    }

    for (std::string line; run && std::getline(std::cin, line);) {
        if (line.empty()) {
            producer->poll(0);
            continue;
        }

        RdKafka::ErrorCode resp =
                producer->produce(topic, partition,
                                  RdKafka::Producer::RK_MSG_COPY /* Copy payload */,
                                  const_cast(line.c_str()), line.size(),
                                  NULL, NULL);
        if (resp != RdKafka::ERR_NO_ERROR)
            std::cerr << "% Produce failed: " <<
                         RdKafka::err2str(resp) << std::endl;
        else
            std::cerr << "% Produced message (" << line.size() << " bytes)" <<
                         std::endl;

        producer->poll(0);
    }

    run = true;
   // 退出前处理完输出队列中的消息
    while (run && producer->outq_len() > 0) {
        std::cerr << "Waiting for " << producer->outq_len() << std::endl;
        producer->poll(1000);
    }

    delete conf;
    delete tconf;
    delete topic;
    delete producer;

    RdKafka::wait_destroyed(5000);

    return 0;
}

三.消费者

新建Qt控制台工程KafkaConsumer，Pro文件如下：

#-------------------------------------------------
#
# Project created by QtCreator 2018-03-28T16:27:54
#
#-------------------------------------------------
QT       -= gui core

TARGET = KafkaConsumer
CONFIG   += console
CONFIG   -= app_bundle

TEMPLATE = app

SOURCES += main.cpp
INCLUDEPATH += /usr/local/include/librdkafka
LIBS += -L/usr/local/lib -lrdkafka
LIBS += -L/usr/local/lib -lrdkafka++

main.cpp文件如下：

#include 
#include 
#include 
#include 
#include 
#include 

#include 
#include 
#include 

#include "rdkafkacpp.h"

static bool run = true;
static bool exit_eof = true;
static int eof_cnt = 0;
static int partition_cnt = 0;
static int verbosity = 1;
static long msg_cnt = 0;
static int64_t msg_bytes = 0;

static void sigterm (int sig) {
    run = false;
}

class ExampleEventCb : public RdKafka::EventCb {
public:
    void event_cb (RdKafka::Event &event) {
        switch (event.type())
        {
        case RdKafka::Event::EVENT_ERROR:
            std::cerr << "ERROR (" << RdKafka::err2str(event.err()) << "): " <<
                         event.str() << std::endl;
            if (event.err() == RdKafka::ERR__ALL_BROKERS_DOWN)
                run = false;
            break;

        case RdKafka::Event::EVENT_STATS:
            std::cerr << "\"STATS\": " << event.str() << std::endl;
            break;

        case RdKafka::Event::EVENT_LOG:
            fprintf(stderr, "LOG-%i-%s: %s\n",
                    event.severity(), event.fac().c_str(), event.str().c_str());
            break;

        case RdKafka::Event::EVENT_THROTTLE:
            std::cerr << "THROTTLED: " << event.throttle_time() << "ms by " <<
                         event.broker_name() << " id " << (int)event.broker_id() << std::endl;
            break;

        default:
            std::cerr << "EVENT " << event.type() <<
                         " (" << RdKafka::err2str(event.err()) << "): " <<
                         event.str() << std::endl;
            break;
        }
    }
};

void msg_consume(RdKafka::Message* message, void* opaque) {
    switch (message->err()) {
    case RdKafka::ERR__TIMED_OUT:
        //std::cerr << "RdKafka::ERR__TIMED_OUT"<len();
        if (verbosity >= 3)
            std::cerr << "Read msg at offset " << message->offset() << std::endl;
        RdKafka::MessageTimestamp ts;
        ts = message->timestamp();
        if (verbosity >= 2 &&
                ts.type != RdKafka::MessageTimestamp::MSG_TIMESTAMP_NOT_AVAILABLE) {
            std::string tsname = "?";
            if (ts.type == RdKafka::MessageTimestamp::MSG_TIMESTAMP_CREATE_TIME)
                tsname = "create time";
            else if (ts.type == RdKafka::MessageTimestamp::MSG_TIMESTAMP_LOG_APPEND_TIME)
                tsname = "log append time";
            std::cout << "Timestamp: " << tsname << " " << ts.timestamp << std::endl;
        }
        if (verbosity >= 2 && message->key()) {
            std::cout << "Key: " << *message->key() << std::endl;
        }
        if (verbosity >= 1) {
            printf("%.*s\n",
                   static_cast(message->len()),
                   static_cast(message->payload()));
        }
        break;

    case RdKafka::ERR__PARTITION_EOF:
        /* Last message */
        if (exit_eof && ++eof_cnt == partition_cnt) {
            std::cerr << "%% EOF reached for all " << partition_cnt <<
                         " partition(s)" << std::endl;
            run = false;
        }
        break;

    case RdKafka::ERR__UNKNOWN_TOPIC:
    case RdKafka::ERR__UNKNOWN_PARTITION:
        std::cerr << "Consume failed: " << message->errstr() << std::endl;
        run = false;
        break;

    default:
        /* Errors */
        std::cerr << "Consume failed: " << message->errstr() << std::endl;
        run = false;
    }
}

class ExampleConsumeCb : public RdKafka::ConsumeCb {
public:
    void consume_cb (RdKafka::Message &msg, void *opaque) {
        msg_consume(&msg, opaque);
    }
};

int main () {
    std::string brokers = "localhost";
    std::string errstr;
    std::string topic_str="test";
    std::vector topics;
    std::string group_id="101";

    RdKafka::Conf *conf = RdKafka::Conf::create(RdKafka::Conf::CONF_GLOBAL);
    RdKafka::Conf *tconf = RdKafka::Conf::create(RdKafka::Conf::CONF_TOPIC);
    //group.id必须设置
    if (conf->set("group.id", group_id, errstr) != RdKafka::Conf::CONF_OK) {
           std::cerr << errstr << std::endl;
           exit(1);
         }

    topics.push_back(topic_str);
   //bootstrap.servers可以替换为metadata.broker.list
    conf->set("bootstrap.servers", brokers, errstr);

    ExampleConsumeCb ex_consume_cb;
    conf->set("consume_cb", &ex_consume_cb, errstr);

    ExampleEventCb ex_event_cb;
    conf->set("event_cb", &ex_event_cb, errstr);
    conf->set("default_topic_conf", tconf, errstr);

    signal(SIGINT, sigterm);
    signal(SIGTERM, sigterm);

    RdKafka::KafkaConsumer *consumer = RdKafka::KafkaConsumer::create(conf, errstr);
    if (!consumer) {
        std::cerr << "Failed to create consumer: " << errstr << std::endl;
        exit(1);
    }
    std::cout << "% Created consumer " << consumer->name() << std::endl;

    RdKafka::ErrorCode err = consumer->subscribe(topics);
    if (err) {
        std::cerr << "Failed to subscribe to " << topics.size() << " topics: "
                  << RdKafka::err2str(err) << std::endl;
        exit(1);
    }

    while (run) {
        //5000毫秒未订阅到消息，触发RdKafka::ERR__TIMED_OUT
        RdKafka::Message *msg = consumer->consume(5000);
        msg_consume(msg, NULL);
        delete msg;
    }

    consumer->close();

    delete conf;
    delete tconf;
    delete consumer;

    std::cerr << "% Consumed " << msg_cnt << " messages ("
              << msg_bytes << " bytes)" << std::endl;

    //应用退出之前等待rdkafka清理资源
    RdKafka::wait_destroyed(5000);

    return 0;
}

四.测试

先启动zookeeper服务和kafka服务，详见：kafka的编译和使用，然后再启动生产者和消费者。

生产者循环等待用户输入，输入后回车，消息就发布出去了，此时消费者显示订阅到的内容。