c语言使用librdkafka库实现kafka生产和消费的实例
使用librdkafka库实现kafka生产和消费的实例
关于librdkafka库的介绍，可以参考kafka的c/c++高性能客户端librdkafka简介，本文使用librdkafka库来进行kafka的简单的生产、消费
一、producer
librdkafka进行kafka生产操作的大致步骤如下：
1、创建kafka配置
rd_kafka_conf_t *rd_kafka_conf_new (void)
2、配置kafka各项参数
rd_kafka_conf_res_t rd_kafka_conf_set (rd_kafka_conf_t *conf,
const char *name,
const char *value,
char *errstr, size_t errstr_size)
3、设置发送回调函数
void rd_kafka_conf_set_dr_msg_cb (rd_kafka_conf_t *conf,
void (*dr_msg_cb) (rd_kafka_t *rk,
const rd_kafka_message_t *
rkmessage,
void *opaque))
4、创建producer实例
rd_kafka_t *rd_kafka_new (rd_kafka_type_t type, rd_kafka_conf_t *conf,char *errstr, size_t errstr_size)
5、实例化topic
rd_kafka_topic_t *rd_kafka_topic_new (rd_kafka_t *rk, const char *topic, rd_kafka_topic_conf_t *conf)
6、异步调用将消息发送到指定的topic
int rd_kafka_produce (rd_kafka_topic_t *rkt, int32_t partition,
int msgflags,
void *payload, size_t len,
const void *key, size_t keylen,
void *msg_opaque)
7、阻塞等待消息发送完成
int rd_kafka_poll (rd_kafka_t *rk, int timeout_ms)
8、等待完成producer请求完成
rd_kafka_resp_err_t rd_kafka_flush (rd_kafka_t *rk, int timeout_ms)
9、销毁topic
void rd_kafka_topic_destroy (rd_kafka_topic_t *app_rkt)
10、销毁producer实例
void rd_kafka_destroy (rd_kafka_t *rk)
完整代码如下my_producer.c：
#include
#include
#include
#include "../src/rdkafka.h"
static int run = 1;
static void stop(int sig){
run = 0;
fclose(stdin);
}
/*
每条消息调用一次该回调函数，说明消息是传递成功(rkmessage->err == rd_kafka_resp_err_no_error)
还是传递失败(rkmessage->err != rd_kafka_resp_err_no_error)
该回调函数由rd_kafka_poll()触发，在应用程序的线程上执行
*/
static void dr_msg_cb(rd_kafka_t *rk,
const rd_kafka_message_t *rkmessage, void *opaque){
if(rkmessage->err)
fprintf(stderr, "%% message delivery failed: %s\n",
rd_kafka_err2str(rkmessage->err));
else
fprintf(stderr,
"%% message delivered (%zd bytes, "
"partition %"prid32")\n",
rkmessage->len, rkmessage->partition);
/* rkmessage被librdkafka自动销毁*/
}
int main(int argc, char **argv){
rd_kafka_t *rk; /*producer instance handle*/
rd_kafka_topic_t *rkt; /*topic对象*/
rd_kafka_conf_t *conf; /*临时配置对象*/
char errstr[512];
char buf[512];
const char *brokers;
const char *topic;
if(argc != 3){
fprintf(stderr, "%% usage: %s
return 1;
}
brokers = argv[1];
topic = argv[2];
/* 创建一个kafka配置占位 */
conf = rd_kafka_conf_new();
/*创建broker集群*/
if (rd_kafka_conf_set(conf, "bootstrap.servers", brokers, errstr,
sizeof(errstr)) != rd_kafka_conf_ok){
fprintf(stderr, "%s\n", errstr);
return 1;
}
/*设置发送报告回调函数，rd_kafka_produce()接收的每条消息都会调用一次该回调函数
*应用程序需要定期调用rd_kafka_poll()来服务排队的发送报告回调函数*/
rd_kafka_conf_set_dr_msg_cb(conf, dr_msg_cb);
/*创建producer实例
rd_kafka_new()获取conf对象的所有权,应用程序在此调用之后不得再次引用它*/
rk = rd_kafka_new(rd_kafka_producer, conf, errstr, sizeof(errstr));
if(!rk){
fprintf(stderr, "%% failed to create new producer:%s\n", errstr);
return 1;
}
/*实例化一个或多个topics(`rd_kafka_topic_t`)来提供生产或消费，topic
对象保存topic特定的配置，并在内部填充所有可用分区和leader brokers，*/
rkt = rd_kafka_topic_new(rk, topic, null);
if (!rkt){
fprintf(stderr, "%% failed to create topic object: %s\n",
rd_kafka_err2str(rd_kafka_last_error()));
rd_kafka_destroy(rk);
return 1;
}
/*用于中断的信号*/
signal(sigint, stop);
fprintf(stderr,
"%% type some text and hit enter to produce message\n"
"%% or just hit enter to only serve delivery reports\n"
"%% press ctrl-c or ctrl-d to exit\n");
while(run && fgets(buf, sizeof(buf), stdin)){
size_t len = strlen(buf);
if(buf[len-1] == '\n')
buf[--len] = '\0';
if(len == 0){
/*轮询用于事件的kafka handle，
事件将导致应用程序提供的回调函数被调用
第二个参数是最大阻塞时间，如果设为0，将会是非阻塞的调用*/
rd_kafka_poll(rk, 0);
continue;
}
retry:
/*send/produce message.
这是一个异步调用，在成功的情况下，只会将消息排入内部producer队列，
对broker的实际传递尝试由后台线程处理，之前注册的传递回调函数(dr_msg_cb)
用于在消息传递成功或失败时向应用程序发回信号*/
if (rd_kafka_produce(
/* topic object */
rkt,
/*使用内置的分区来选择分区*/
rd_kafka_partition_ua,
/*生成payload的副本*/
rd_kafka_msg_f_copy,
/*消息体和长度*/
buf, len,
/*可选键及其长度*/
null, 0,
null) == -1){
fprintf(stderr,
"%% failed to produce to topic %s: %s\n",
rd_kafka_topic_name(rkt),
rd_kafka_err2str(rd_kafka_last_error()));
if (rd_kafka_last_error() == rd_kafka_resp_err__queue_full){
/*如果内部队列满，等待消息传输完成并retry,
内部队列表示要发送的消息和已发送或失败的消息，
内部队列受限于queue.buffering.max.messages配置项*/
rd_kafka_poll(rk, 1000);
goto retry;
}
}else{
fprintf(stderr, "%% enqueued message (%zd bytes) for topic %s\n",
len, rd_kafka_topic_name(rkt));
}
/*producer应用程序应不断地通过以频繁的间隔调用rd_kafka_poll()来为
传送报告队列提供服务。在没有生成消息以确定先前生成的消息已发送了其
发送报告回调函数(和其他注册过的回调函数)期间，要确保rd_kafka_poll()
仍然被调用*/
rd_kafka_poll(rk, 0);
}
fprintf(stderr, "%% flushing final message.. \n");
/*rd_kafka_flush是rd_kafka_poll()的抽象化，
等待所有未完成的produce请求完成，通常在销毁producer实例前完成
以确保所有排列中和正在传输的produce请求在销毁前完成*/
rd_kafka_flush(rk, 10*1000);
/* destroy topic object */
rd_kafka_topic_destroy(rkt);
/* destroy the producer instance */
rd_kafka_destroy(rk);
return 0;
}
二、consumer
librdkafka进行kafka消费操作的大致步骤如下：
1、创建kafka配置
rd_kafka_conf_t *rd_kafka_conf_new (void)
2、创建kafka topic的配置
rd_kafka_topic_conf_t *rd_kafka_topic_conf_new (void)
3、配置kafka各项参数
rd_kafka_conf_res_t rd_kafka_conf_set (rd_kafka_conf_t *conf,
const char *name,
const char *value,
char *errstr, size_t errstr_size)
4、配置kafka topic各项参数
rd_kafka_conf_res_t rd_kafka_topic_conf_set (rd_kafka_topic_conf_t *conf,
const char *name,
const char *value,
char *errstr, size_t errstr_size)
5、创建consumer实例
rd_kafka_t *rd_kafka_new (rd_kafka_type_t type, rd_kafka_conf_t *conf, char *errstr, size_t errstr_size)
6、为consumer实例添加brokerlist
int rd_kafka_brokers_add (rd_kafka_t *rk, const char *brokerlist)
7、开启consumer订阅
rd_kafka_subscribe (rd_kafka_t *rk, const rd_kafka_topic_partition_list_t *topics)
8、轮询消息或事件，并调用回调函数
rd_kafka_message_t *rd_kafka_consumer_poll (rd_kafka_t *rk,int timeout_ms)
9、关闭consumer实例
rd_kafka_resp_err_t rd_kafka_consumer_close (rd_kafka_t *rk)
10、释放topic list资源
rd_kafka_topic_partition_list_destroy (rd_kafka_topic_partition_list_t *rktparlist)
11、销毁consumer实例
void rd_kafka_destroy (rd_kafka_t *rk)
12、等待consumer对象的销毁
int rd_kafka_wait_destroyed (int timeout_ms)
完整代码如下my_consumer.c
#include
#include
#include
#include
#include
#include
#include "../src/rdkafka.h"
static int run = 1;
//`rd_kafka_t`自带一个可选的配置api，如果没有调用api，librdkafka将会使用configuration.md中的默认配置。
static rd_kafka_t *rk;
static rd_kafka_topic_partition_list_t *topics;
static void stop (int sig) {
if (!run)
exit(1);
run = 0;
fclose(stdin); /* abort fgets() */
}
static void sig_usr1 (int sig) {
rd_kafka_dump(stdout, rk);
}
/**
* 处理并打印已消费的消息
*/
static void msg_consume (rd_kafka_message_t *rkmessage,
void *opaque) {
if (rkmessage->err) {
if (rkmessage->err == rd_kafka_resp_err__partition_eof) {
fprintf(stderr,
"%% consumer reached end of %s [%"prid32"] "
"message queue at offset %"prid64"\n",
rd_kafka_topic_name(rkmessage->rkt),
rkmessage->partition, rkmessage->offset);
return;
}
if (rkmessage->rkt)
fprintf(stderr, "%% consume error for "
"topic \"%s\" [%"prid32"] "
"offset %"prid64": %s\n",
rd_kafka_topic_name(rkmessage->rkt),
rkmessage->partition,
rkmessage->offset,
rd_kafka_message_errstr(rkmessage));
else
fprintf(stderr, "%% consumer error: %s: %s\n",
rd_kafka_err2str(rkmessage->err),
rd_kafka_message_errstr(rkmessage));
if (rkmessage->err == rd_kafka_resp_err__unknown_partition ||
rkmessage->err == rd_kafka_resp_err__unknown_topic)
run = 0;
return;
}
fprintf(stdout, "%% message (topic %s [%"prid32"], "
"offset %"prid64", %zd bytes):\n",
rd_kafka_topic_name(rkmessage->rkt),
rkmessage->partition,
rkmessage->offset, rkmessage->len);
if (rkmessage->key_len) {
printf("key: %.*s\n",
(int)rkmessage->key_len, (char *)rkmessage->key);
}
printf("%.*s\n",
(int)rkmessage->len, (char *)rkmessage->payload);
}
/*
init all configuration of kafka
*/
int initkafka(char *brokers, char *group,char *topic){
rd_kafka_conf_t *conf;
rd_kafka_topic_conf_t *topic_conf;
rd_kafka_resp_err_t err;
char tmp[16];
char errstr[512];
/* kafka configuration */
conf = rd_kafka_conf_new();
//quick termination
snprintf(tmp, sizeof(tmp), "%i", sigio);
rd_kafka_conf_set(conf, "internal.termination.signal", tmp, null, 0);
//topic configuration
topic_conf = rd_kafka_topic_conf_new();
/* consumer groups require a group id */
if (!group)
group = "rdkafka_consumer_example";
if (rd_kafka_conf_set(conf, "group.id", group,
errstr, sizeof(errstr)) !=
rd_kafka_conf_ok) {
fprintf(stderr, "%% %s\n", errstr);
return -1;
}
/* consumer groups always use broker based offset storage */
if (rd_kafka_topic_conf_set(topic_conf, "offset.store.method",
"broker",
errstr, sizeof(errstr)) !=
rd_kafka_conf_ok) {
fprintf(stderr, "%% %s\n", errstr);
return -1;
}
/* set default topic config for pattern-matched topics. */
rd_kafka_conf_set_default_topic_conf(conf, topic_conf);
//实例化一个*对象rd_kafka_t作为基础容器，提供全局配置和共享状态
rk = rd_kafka_new(rd_kafka_consumer, conf, errstr, sizeof(errstr));
if(!rk){
fprintf(stderr, "%% failed to create new consumer:%s\n", errstr);
return -1;
}
//librdkafka需要至少一个brokers的初始化list
if (rd_kafka_brokers_add(rk, brokers) == 0){
fprintf(stderr, "%% no valid brokers specified\n");
return -1;
}
//重定向 rd_kafka_poll()队列到consumer_poll()队列
rd_kafka_poll_set_consumer(rk);
//创建一个topic+partition的存储空间(list/vector)
topics = rd_kafka_topic_partition_list_new(1);
//把topic+partition加入list
rd_kafka_topic_partition_list_add(topics, topic, -1);
//开启consumer订阅，匹配的topic将被添加到订阅列表中
if((err = rd_kafka_subscribe(rk, topics))){
fprintf(stderr, "%% failed to start consuming topics: %s\n", rd_kafka_err2str(err));
return -1;
}
return 1;
}
int main(int argc, char **argv){
char *brokers = "localhost:9092";
char *group = null;
char *topic = null;
int opt;
rd_kafka_resp_err_t err;
while ((opt = getopt(argc, argv, "g:b:t:qd:ex:as:do")) != -1){
switch (opt) {
case 'b':
brokers = optarg;
break;
case 'g':
group = optarg;
break;
case 't':
topic = optarg;
break;
default:
break;
}
}
signal(sigint, stop);
signal(sigusr1, sig_usr1);
if(!initkafka(brokers, group, topic)){
fprintf(stderr, "kafka server initialize error\n");
}else{
while(run){
rd_kafka_message_t *rkmessage;
/*-轮询消费者的消息或事件，最多阻塞timeout_ms
-应用程序应该定期调用consumer_poll()，即使没有预期的消息，以服务
所有排队等待的回调函数，当注册过rebalance_cb，该操作尤为重要，
因为它需要被正确地调用和处理以同步内部消费者状态 */
rkmessage = rd_kafka_consumer_poll(rk, 1000);
if(rkmessage){
msg_consume(rkmessage, null);
/*释放rkmessage的资源，并把所有权还给rdkafka*/
rd_kafka_message_destroy(rkmessage);
}
}
}
done:
/*此调用将会阻塞，直到consumer撤销其分配，调用rebalance_cb(如果已设置)，
commit offset到broker,并离开consumer group
最大阻塞时间被设置为session.timeout.ms
*/
err = rd_kafka_consumer_close(rk);
if(err){
fprintf(stderr, "%% failed to close consumer: %s\n", rd_kafka_err2str(err));
}else{
fprintf(stderr, "%% consumer closed\n");
}
//释放topics list使用的所有资源和它自己
rd_kafka_topic_partition_list_destroy(topics);
//destroy kafka handle
rd_kafka_destroy(rk);
run = 5;
//等待所有rd_kafka_t对象销毁，所有kafka对象被销毁，返回0，超时返回-1
while(run-- > 0 && rd_kafka_wait_destroyed(1000) == -1){
printf("waiting for librdkafka to decommission\n");
}
if(run <= 0){
//dump rdkafka内部状态到stdout流
rd_kafka_dump(stdout, rk);
}
return 0;
}
在linux下编译producer和consumer的代码：
gcc my_producer.c -o my_producer -lrdkafka -lz -lpthread -lrt
gcc my_consumer.c -o my_consumer -lrdkafka -lz -lpthread -lrt
在运行my_producer或my_consumer时可能会报错"error while loading shared libraries xxx.so", 此时需要在/etc/ld.so.conf中加入xxx.so所在的目录
在本地启动一个简单的kafka服务，设置broker集群为localhost：9092并创建一个叫“test_topic”的topic
启动方式可参考kafka0.8.2集群的环境搭建并实现基本的生产消费
启动consumer：
启动producer，并发送一条数据“hello world”：
consumer处成功收到producer发送的“hello world”：