rdkafka_example.cpp

/*
 * librdkafka - Apache Kafka C library
 *
 * Copyright (c) 2014-2022, Magnus Edenhill
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

/**
 * Apache Kafka consumer & producer example programs
 * using the Kafka driver from librdkafka
 * (https://github.com/confluentinc/librdkafka)
 */

#include <iostream>
#include <string>
#include <cstdlib>
#include <cstdio>
#include <csignal>
#include <cstring>

#ifdef _WIN32
#include "../win32/wingetopt.h"
#elif _AIX
#include <unistd.h>
#else
#include <getopt.h>
#endif

/*
 * Typically include path in a real application would be
 * #include <librdkafka/rdkafkacpp.h>
 */
#include "rdkafkacpp.h"


static void metadata_print(const std::string &topic,
                           const RdKafka::Metadata *metadata) {
  std::cout << "Metadata for " << (topic.empty() ? "" : "all topics")
            << "(from broker " << metadata->orig_broker_id() << ":"
            << metadata->orig_broker_name() << std::endl;

  /* Iterate brokers */
  std::cout << " " << metadata->brokers()->size() << " brokers:" << std::endl;
  RdKafka::Metadata::BrokerMetadataIterator ib;
  for (ib = metadata->brokers()->begin(); ib != metadata->brokers()->end();
       ++ib) {
    std::cout << "  broker " << (*ib)->id() << " at " << (*ib)->host() << ":"
              << (*ib)->port() << std::endl;
  }
  /* Iterate topics */
  std::cout << metadata->topics()->size() << " topics:" << std::endl;
  RdKafka::Metadata::TopicMetadataIterator it;
  for (it = metadata->topics()->begin(); it != metadata->topics()->end();
       ++it) {
    std::cout << "  topic \"" << (*it)->topic() << "\" with "
              << (*it)->partitions()->size() << " partitions:";

    if ((*it)->err() != RdKafka::ERR_NO_ERROR) {
      std::cout << " " << err2str((*it)->err());
      if ((*it)->err() == RdKafka::ERR_LEADER_NOT_AVAILABLE)
        std::cout << " (try again)";
    }
    std::cout << std::endl;

    /* Iterate topic's partitions */
    RdKafka::TopicMetadata::PartitionMetadataIterator ip;
    for (ip = (*it)->partitions()->begin(); ip != (*it)->partitions()->end();
         ++ip) {
      std::cout << "    partition " << (*ip)->id() << ", leader "
                << (*ip)->leader() << ", replicas: ";

      /* Iterate partition's replicas */
      RdKafka::PartitionMetadata::ReplicasIterator ir;
      for (ir = (*ip)->replicas()->begin(); ir != (*ip)->replicas()->end();
           ++ir) {
        std::cout << (ir == (*ip)->replicas()->begin() ? "" : ",") << *ir;
      }

      /* Iterate partition's ISRs */
      std::cout << ", isrs: ";
      RdKafka::PartitionMetadata::ISRSIterator iis;
      for (iis = (*ip)->isrs()->begin(); iis != (*ip)->isrs()->end(); ++iis)
        std::cout << (iis == (*ip)->isrs()->begin() ? "" : ",") << *iis;

      if ((*ip)->err() != RdKafka::ERR_NO_ERROR)
        std::cout << ", " << RdKafka::err2str((*ip)->err()) << std::endl;
      else
        std::cout << std::endl;
    }
  }
}

static volatile sig_atomic_t run = 1;
static bool exit_eof             = false;

static void sigterm(int sig) {
  run = 0;
}


class ExampleDeliveryReportCb : public RdKafka::DeliveryReportCb {
 public:
  void dr_cb(RdKafka::Message &message) {
    std::string status_name;
    switch (message.status()) {
    case RdKafka::Message::MSG_STATUS_NOT_PERSISTED:
      status_name = "NotPersisted";
      break;
    case RdKafka::Message::MSG_STATUS_POSSIBLY_PERSISTED:
      status_name = "PossiblyPersisted";
      break;
    case RdKafka::Message::MSG_STATUS_PERSISTED:
      status_name = "Persisted";
      break;
    default:
      status_name = "Unknown?";
      break;
    }
    std::cout << "Message delivery for (" << message.len()
              << " bytes): " << status_name << ": " << 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:
      if (event.fatal()) {
        std::cerr << "FATAL ";
        run = 0;
      }
      std::cerr << "ERROR (" << RdKafka::err2str(event.err())
                << "): " << event.str() << std::endl;
      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;
    }
  }
};


/* Use of this partitioner is pretty pointless since no key is provided
 * in the produce() call. */
class MyHashPartitionerCb : public RdKafka::PartitionerCb {
 public:
  int32_t partitioner_cb(const RdKafka::Topic *topic,
                         const std::string *key,
                         int32_t partition_cnt,
                         void *msg_opaque) {
    return djb_hash(key->c_str(), key->size()) % partition_cnt;
  }

 private:
  static inline unsigned int djb_hash(const char *str, size_t len) {
    unsigned int hash = 5381;
    for (size_t i = 0; i < len; i++)
      hash = ((hash << 5) + hash) + str[i];
    return hash;
  }
};

void msg_consume(RdKafka::Message *message, void *opaque) {
  const RdKafka::Headers *headers;

  switch (message->err()) {
  case RdKafka::ERR__TIMED_OUT:
    break;

  case RdKafka::ERR_NO_ERROR:
    /* Real message */
    std::cout << "Read msg at offset " << message->offset() << std::endl;
    if (message->key()) {
      std::cout << "Key: " << *message->key() << std::endl;
    }
    headers = message->headers();
    if (headers) {
      std::vector<RdKafka::Headers::Header> hdrs = headers->get_all();
      for (size_t i = 0; i < hdrs.size(); i++) {
        const RdKafka::Headers::Header hdr = hdrs[i];

        if (hdr.value() != NULL)
          printf(" Header: %s = \"%.*s\"\n", hdr.key().c_str(),
                 (int)hdr.value_size(), (const char *)hdr.value());
        else
          printf(" Header:  %s = NULL\n", hdr.key().c_str());
      }
    }
    printf("%.*s\n", static_cast<int>(message->len()),
           static_cast<const char *>(message->payload()));
    break;

  case RdKafka::ERR__PARTITION_EOF:
    /* Last message */
    if (exit_eof) {
      run = 0;
    }
    break;

  case RdKafka::ERR__UNKNOWN_TOPIC:
  case RdKafka::ERR__UNKNOWN_PARTITION:
    std::cerr << "Consume failed: " << message->errstr() << std::endl;
    run = 0;
    break;

  default:
    /* Errors */
    std::cerr << "Consume failed: " << message->errstr() << std::endl;
    run = 0;
  }
}


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



int main(int argc, char **argv) {
  std::string brokers = "localhost";
  std::string errstr;
  std::string topic_str;
  std::string mode;
  std::string debug;
  int32_t partition    = RdKafka::Topic::PARTITION_UA;
  int64_t start_offset = RdKafka::Topic::OFFSET_BEGINNING;
  bool do_conf_dump    = false;
  int opt;
  MyHashPartitionerCb hash_partitioner;
  int use_ccb = 0;

  /*
   * Create configuration objects
   */
  RdKafka::Conf *conf  = RdKafka::Conf::create(RdKafka::Conf::CONF_GLOBAL);
  RdKafka::Conf *tconf = RdKafka::Conf::create(RdKafka::Conf::CONF_TOPIC);


  while ((opt = getopt(argc, argv, "PCLt:p:b:z:qd:o:eX:AM:f:")) != -1) {
    switch (opt) {
    case 'P':
    case 'C':
    case 'L':
      mode = opt;
      break;
    case 't':
      topic_str = optarg;
      break;
    case 'p':
      if (!strcmp(optarg, "random"))
        /* default */;
      else if (!strcmp(optarg, "hash")) {
        if (tconf->set("partitioner_cb", &hash_partitioner, errstr) !=
            RdKafka::Conf::CONF_OK) {
          std::cerr << errstr << std::endl;
          exit(1);
        }
      } else
        partition = std::atoi(optarg);
      break;
    case 'b':
      brokers = optarg;
      break;
    case 'z':
      if (conf->set("compression.codec", optarg, errstr) !=
          RdKafka::Conf::CONF_OK) {
        std::cerr << errstr << std::endl;
        exit(1);
      }
      break;
    case 'o':
      if (!strcmp(optarg, "end"))
        start_offset = RdKafka::Topic::OFFSET_END;
      else if (!strcmp(optarg, "beginning"))
        start_offset = RdKafka::Topic::OFFSET_BEGINNING;
      else if (!strcmp(optarg, "stored"))
        start_offset = RdKafka::Topic::OFFSET_STORED;
      else
        start_offset = strtoll(optarg, NULL, 10);
      break;
    case 'e':
      exit_eof = true;
      break;
    case 'd':
      debug = optarg;
      break;
    case 'M':
      if (conf->set("statistics.interval.ms", optarg, errstr) !=
          RdKafka::Conf::CONF_OK) {
        std::cerr << errstr << std::endl;
        exit(1);
      }
      break;
    case 'X': {
      char *name, *val;

      if (!strcmp(optarg, "dump")) {
        do_conf_dump = true;
        continue;
      }

      name = optarg;
      if (!(val = strchr(name, '='))) {
        std::cerr << "%% Expected -X property=value, not " << name << std::endl;
        exit(1);
      }

      *val = '\0';
      val++;

      /* Try "topic." prefixed properties on topic
       * conf first, and then fall through to global if
       * it didnt match a topic configuration property. */
      RdKafka::Conf::ConfResult res;
      if (!strncmp(name, "topic.", strlen("topic.")))
        res = tconf->set(name + strlen("topic."), val, errstr);
      else
        res = conf->set(name, val, errstr);

      if (res != RdKafka::Conf::CONF_OK) {
        std::cerr << errstr << std::endl;
        exit(1);
      }
    } break;

    case 'f':
      if (!strcmp(optarg, "ccb"))
        use_ccb = 1;
      else {
        std::cerr << "Unknown option: " << optarg << std::endl;
        exit(1);
      }
      break;

    default:
      goto usage;
    }
  }

  if (mode.empty() || (topic_str.empty() && mode != "L") || optind != argc) {
  usage:
    std::string features;
    conf->get("builtin.features", features);
    fprintf(stderr,
            "Usage: %s [-C|-P] -t <topic> "
            "[-p <partition>] [-b <host1:port1,host2:port2,..>]\n"
            "\n"
            "librdkafka version %s (0x%08x, builtin.features \"%s\")\n"
            "\n"
            " Options:\n"
            "  -C | -P         Consumer or Producer mode\n"
            "  -L              Metadata list mode\n"
            "  -t <topic>      Topic to fetch / produce\n"
            "  -p <num>        Partition (random partitioner)\n"
            "  -p <func>       Use partitioner:\n"
            "                  random (default), hash\n"
            "  -b <brokers>    Broker address (localhost:9092)\n"
            "  -z <codec>      Enable compression:\n"
            "                  none|gzip|snappy|lz4|zstd\n"
            "  -o <offset>     Start offset (consumer)\n"
            "  -e              Exit consumer when last message\n"
            "                  in partition has been received.\n"
            "  -d [facs..]     Enable debugging contexts:\n"
            "                  %s\n"
            "  -M <intervalms> Enable statistics\n"
            "  -X <prop=name>  Set arbitrary librdkafka "
            "configuration property\n"
            "                  Properties prefixed with \"topic.\" "
            "will be set on topic object.\n"
            "                  Use '-X list' to see the full list\n"
            "                  of supported properties.\n"
            "  -f <flag>       Set option:\n"
            "                     ccb - use consume_callback\n"
            "\n"
            " In Consumer mode:\n"
            "  writes fetched messages to stdout\n"
            " In Producer mode:\n"
            "  reads messages from stdin and sends to broker\n"
            "\n"
            "\n"
            "\n",
            argv[0], RdKafka::version_str().c_str(), RdKafka::version(),
            features.c_str(), RdKafka::get_debug_contexts().c_str());
    exit(1);
  }


  /*
   * Set configuration properties
   */
  conf->set("metadata.broker.list", brokers, errstr);

  if (!debug.empty()) {
    if (conf->set("debug", debug, errstr) != RdKafka::Conf::CONF_OK) {
      std::cerr << errstr << std::endl;
      exit(1);
    }
  }

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

  if (do_conf_dump) {
    int pass;

    for (pass = 0; pass < 2; pass++) {
      std::list<std::string> *dump;
      if (pass == 0) {
        dump = conf->dump();
        std::cout << "# Global config" << std::endl;
      } else {
        dump = tconf->dump();
        std::cout << "# Topic config" << std::endl;
      }

      for (std::list<std::string>::iterator it = dump->begin();
           it != dump->end();) {
        std::cout << *it << " = ";
        it++;
        std::cout << *it << std::endl;
        it++;
      }
      std::cout << std::endl;
    }
    exit(0);
  }

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


  if (mode == "P") {
    /*
     * Producer mode
     */

    if (topic_str.empty())
      goto usage;

    ExampleDeliveryReportCb ex_dr_cb;

    /* Set delivery report callback */
    conf->set("dr_cb", &ex_dr_cb, errstr);

    conf->set("default_topic_conf", tconf, errstr);

    /*
     * Create producer using accumulated global configuration.
     */
    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;


    /*
     * Read messages from stdin and produce to broker.
     */
    for (std::string line; run && std::getline(std::cin, line);) {
      if (line.empty()) {
        producer->poll(0);
        continue;
      }

      RdKafka::Headers *headers = RdKafka::Headers::create();
      headers->add("my header", "header value");
      headers->add("other header", "yes");

      /*
       * Produce message
       */
      RdKafka::ErrorCode resp =
          producer->produce(topic_str, partition,
                            RdKafka::Producer::RK_MSG_COPY /* Copy payload */,
                            /* Value */
                            const_cast<char *>(line.c_str()), line.size(),
                            /* Key */
                            NULL, 0,
                            /* Timestamp (defaults to now) */
                            0,
                            /* Message headers, if any */
                            headers,
                            /* Per-message opaque value passed to
                             * delivery report */
                            NULL);
      if (resp != RdKafka::ERR_NO_ERROR) {
        std::cerr << "% Produce failed: " << RdKafka::err2str(resp)
                  << std::endl;
        delete headers; /* Headers are automatically deleted on produce()
                         * success. */
      } else {
        std::cerr << "% Produced message (" << line.size() << " bytes)"
                  << std::endl;
      }

      producer->poll(0);
    }
    run = 1;

    while (run && producer->outq_len() > 0) {
      std::cerr << "Waiting for " << producer->outq_len() << std::endl;
      producer->poll(1000);
    }

    delete producer;


  } else if (mode == "C") {
    /*
     * Consumer mode
     */

    conf->set("enable.partition.eof", "true", errstr);

    if (topic_str.empty())
      goto usage;

    /*
     * Create consumer using accumulated global configuration.
     */
    RdKafka::Consumer *consumer = RdKafka::Consumer::create(conf, errstr);
    if (!consumer) {
      std::cerr << "Failed to create consumer: " << errstr << std::endl;
      exit(1);
    }

    std::cout << "% Created consumer " << consumer->name() << std::endl;

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

    /*
     * Start consumer for topic+partition at start offset
     */
    RdKafka::ErrorCode resp = consumer->start(topic, partition, start_offset);
    if (resp != RdKafka::ERR_NO_ERROR) {
      std::cerr << "Failed to start consumer: " << RdKafka::err2str(resp)
                << std::endl;
      exit(1);
    }

    ExampleConsumeCb ex_consume_cb;

    /*
     * Consume messages
     */
    while (run) {
      if (use_ccb) {
        consumer->consume_callback(topic, partition, 1000, &ex_consume_cb,
                                   &use_ccb);
      } else {
        RdKafka::Message *msg = consumer->consume(topic, partition, 1000);
        msg_consume(msg, NULL);
        delete msg;
      }
      consumer->poll(0);
    }

    /*
     * Stop consumer
     */
    consumer->stop(topic, partition);

    consumer->poll(1000);

    delete topic;
    delete consumer;
  } else {
    /* Metadata mode */

    /*
     * Create producer using accumulated global configuration.
     */
    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;

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

    while (run) {
      class RdKafka::Metadata *metadata;

      /* Fetch metadata */
      RdKafka::ErrorCode err =
          producer->metadata(!topic, topic, &metadata, 5000);
      if (err != RdKafka::ERR_NO_ERROR) {
        std::cerr << "%% Failed to acquire metadata: " << RdKafka::err2str(err)
                  << std::endl;
        run = 0;
        break;
      }

      metadata_print(topic_str, metadata);

      delete metadata;
      run = 0;
    }
  }

  delete conf;
  delete tconf;

  /*
   * Wait for RdKafka to decommission.
   * This is not strictly needed (when check outq_len() above), but
   * allows RdKafka to clean up all its resources before the application
   * exits so that memory profilers such as valgrind wont complain about
   * memory leaks.
   */
  RdKafka::wait_destroyed(5000);

  return 0;
}