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操作场景

本文介绍使用 C++ 客户端连接 CKafka 弹性 Topic 并收发消息的操作步骤。

前提条件

操作步骤

步骤1:准备环境

1. 安装 C/C++ 依赖库 安装 librdkafka
2. 安装 SSL/SASL 依赖。
yum install openssl openssl-devel
yum install cyrus-sasl{,-plain}

步骤2:创建 Topic 和订阅关系

1. 在控制台的弹性 Topic 列表页面创建一个 Topic。


2. 单击 Topic 的 “ID” 进入基本信息页面,获取用户名、密码和地址信息。


3. 订阅关系页签,新建一个订阅关系(消费组)。



步骤3:生产消息

1. 创建 producer.c 文件。
/*
* librdkafka - Apache Kafka C library
*
* Copyright (c) 2017, 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.
*/

/**
* Simple Apache Kafka producer
* using the Kafka driver from librdkafka
* (https://github.com/edenhill/librdkafka)
*/

#include <stdio.h>
#include <signal.h>
#include <string.h>


#include <librdkafka/rdkafka.h>


static volatile sig_atomic_t run = 1;

/**
* @brief Signal termination of program
*/
static void stop (int sig) {
run = 0;
fclose(stdin); /* abort fgets() */
}


/**
* @brief Message delivery report callback.
*
* This callback is called exactly once per message, indicating if
* the message was succesfully delivered
* (rkmessage->err == RD_KAFKA_RESP_ERR_NO_ERROR) or permanently
* failed delivery (rkmessage->err != RD_KAFKA_RESP_ERR_NO_ERROR).
*
* The callback is triggered from rd_kafka_poll() and executes on
* the application's thread.
*/
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);

/* The rkmessage is destroyed automatically by librdkafka */
}



int main (int argc, char **argv) {
rd_kafka_t *rk; /* Producer instance handle */
rd_kafka_conf_t *conf; /* Temporary configuration object */
char errstr[512]; /* librdkafka API error reporting buffer */
char buf[512]; /* Message value temporary buffer */
const char *brokers; /* Argument: broker list */
const char *topic; /* Argument: topic to produce to */
const char *user; /* Argument: sasl username */
const char *passwd; /* Argument: sasl password */

/*
* Argument validation
*/
if (argc < 3) {
fprintf(stderr, "%% Usage: %s <broker> <topic> <username> <password> \\n Optional:username password\\n", argv[0]);
return 1;
}

brokers = argv[1];
topic = argv[2];

if(argc == 5) {
user = argv[3];
passwd = argv[4];
}


/*
* Create Kafka client configuration place-holder
*/
conf = rd_kafka_conf_new();

/* Set bootstrap broker(s) as a comma-separated list of
* host or host:port (default port 9092).
* librdkafka will use the bootstrap brokers to acquire the full
* set of brokers from the cluster. */
if (rd_kafka_conf_set(conf, "bootstrap.servers", brokers,
errstr, sizeof(errstr)) != RD_KAFKA_CONF_OK) {
fprintf(stderr, "%s\\n", errstr);
return 1;
}

/* Set sasl config*/
if( user && passwd ) {
if(rd_kafka_conf_set(conf,"security.protocol","sasl_plaintext",errstr,sizeof(errstr)) !=RD_KAFKA_CONF_OK) {
fprintf(stderr,"%s\\n",errstr);
return 1;
}
if(rd_kafka_conf_set(conf, "sasl.mechanisms", "PLAIN", errstr, sizeof(errstr)) != RD_KAFKA_CONF_OK) {
fprintf(stderr,"%s\\n",errstr);
return 1;
}
if(rd_kafka_conf_set(conf,"sasl.username",user,errstr,sizeof(errstr)) !=RD_KAFKA_CONF_OK) {
fprintf(stderr,"%s\\n",errstr);
return 1;

}
if(rd_kafka_conf_set(conf,"sasl.password",passwd,errstr,sizeof(errstr)) !=RD_KAFKA_CONF_OK) {
fprintf(stderr,"%s\\n",errstr);
return 1;
}

}
/* Tencent Cloud recommended configuration parameters
* https://cloud.tencent.com/document/product/597/30203
*/
//if(rd_kafka_conf_set(conf,"debug","none",errstr,sizeof(errstr))!= RD_KAFKA_CONF_OK) { // 注意 线上环境需要谨慎评估开启debug。
// fprintf(stderr,"%s\\n",errstr);
// return 1;
// }

if(rd_kafka_conf_set(conf,"acks","1",errstr,sizeof(errstr)) != RD_KAFKA_CONF_OK) {
fprintf(stderr,"%s\\n",errstr);
return 1;
}
if(rd_kafka_conf_set(conf,"request.timeout.ms","30000",errstr,sizeof(errstr)) != RD_KAFKA_CONF_OK) {
fprintf(stderr,"%s\\n",errstr);
return 1;
}
if(rd_kafka_conf_set(conf,"retries","3",errstr,sizeof(errstr)) != RD_KAFKA_CONF_OK) {
fprintf(stderr,"%s\\n",errstr);
return 1;
}

if(rd_kafka_conf_set(conf,"retry.backoff.ms","1000",errstr,sizeof(errstr)) != RD_KAFKA_CONF_OK) {
fprintf(stderr,"%s\\n",errstr);
return 1;
}

/* Set the delivery report callback.
* This callback will be called once per message to inform
* the application if delivery succeeded or failed.
* See dr_msg_cb() above.
* The callback is only triggered from rd_kafka_poll() and
* rd_kafka_flush(). */
rd_kafka_conf_set_dr_msg_cb(conf, dr_msg_cb);

/*
* Create producer instance.
*
* NOTE: rd_kafka_new() takes ownership of the conf object
* and the application must not reference it again after
* this call.
*/
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;
}

/* Signal handler for clean shutdown */
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);
rd_kafka_resp_err_t err;

if (buf[len-1] == '\\n') /* Remove newline */
buf[--len] = '\\0';

if (len == 0) {
/* Empty line: only serve delivery reports */
rd_kafka_poll(rk, 0/*non-blocking */);
continue;
}

/*
* Send/Produce message.
* This is an asynchronous call, on success it will only
* enqueue the message on the internal producer queue.
* The actual delivery attempts to the broker are handled
* by background threads.
* The previously registered delivery report callback
* (dr_msg_cb) is used to signal back to the application
* when the message has been delivered (or failed).
*/
retry:
err = rd_kafka_producev(
/* Producer handle */
rk,
/* Topic name */
RD_KAFKA_V_TOPIC(topic),
/* Make a copy of the payload. */
RD_KAFKA_V_MSGFLAGS(RD_KAFKA_MSG_F_COPY),
/* Message value and length */
RD_KAFKA_V_VALUE(buf, len),
/* Per-Message opaque, provided in
* delivery report callback as
* msg_opaque. */
RD_KAFKA_V_OPAQUE(NULL),
/* End sentinel */
RD_KAFKA_V_END);

if (err) {
/*
* Failed to *enqueue* message for producing.
*/
fprintf(stderr,
"%% Failed to produce to topic %s: %s\\n",
topic, rd_kafka_err2str(err));

if (err == RD_KAFKA_RESP_ERR__QUEUE_FULL) {
/* If the internal queue is full, wait for
* messages to be delivered and then retry.
* The internal queue represents both
* messages to be sent and messages that have
* been sent or failed, awaiting their
* delivery report callback to be called.
*
* The internal queue is limited by the
* configuration property
* queue.buffering.max.messages */
rd_kafka_poll(rk, 1000/*block for max 1000ms*/);
goto retry;
}
} else {
fprintf(stderr, "%% Enqueued message (%zd bytes) "
"for topic %s\\n",
len, topic);
}


/* A producer application should continually serve
* the delivery report queue by calling rd_kafka_poll()
* at frequent intervals.
* Either put the poll call in your main loop, or in a
* dedicated thread, or call it after every
* rd_kafka_produce() call.
* Just make sure that rd_kafka_poll() is still called
* during periods where you are not producing any messages
* to make sure previously produced messages have their
* delivery report callback served (and any other callbacks
* you register). */
rd_kafka_poll(rk, 0/*non-blocking*/);
}


/* Wait for final messages to be delivered or fail.
* rd_kafka_flush() is an abstraction over rd_kafka_poll() which
* waits for all messages to be delivered. */
fprintf(stderr, "%% Flushing final messages..\\n");
rd_kafka_flush(rk, 10*1000 /* wait for max 10 seconds */);

/* If the output queue is still not empty there is an issue
* with producing messages to the clusters. */
if (rd_kafka_outq_len(rk) > 0)
fprintf(stderr, "%% %d message(s) were not delivered\\n",
rd_kafka_outq_len(rk));

/* Destroy the producer instance */
rd_kafka_destroy(rk);

return 0;
}
参数
描述
broker
接入地址,在控制台的弹性 Topic 基本信息页面获取。


username
用户名,在控制台的弹性 Topic 基本信息页面获取。
password
用户密码,在控制台的弹性 Topic 基本信息页面获取。
topic
Topic 名称,在控制台的弹性 Topic 基本信息页面获取。
2. 执行以下命令编译 producer.c。
gcc -lrdkafka ./producer.c -o producer
3. 执行以下命令发送消息。
./produce <broker> <topic> <username> <password>
4. 运行结果如下:




步骤3:消费消息

1. 创建 consumer.c 文件。
/*
* librdkafka - Apache Kafka C library
*
* Copyright (c) 2019, 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.
*/

/**
* Simple high-level balanced Apache Kafka consumer
* using the Kafka driver from librdkafka
* (https://github.com/edenhill/librdkafka)
*/

#include <stdio.h>
#include <signal.h>
#include <string.h>
#include <ctype.h>
#include <librdkafka/rdkafka.h>


static volatile sig_atomic_t run = 1;

/**
* @brief Signal termination of program
*/
static void stop (int sig) {
run = 0;
}

/**
* @returns 1 if all bytes are printable, else 0.
*/
static int is_printable (const char *buf, size_t size) {
size_t i;

for (i = 0 ; i < size ; i++)
if (!isprint((int)buf[i]))
return 0;

return 1;
}


int main (int argc, char **argv) {
rd_kafka_t *rk; /* Consumer instance handle */
rd_kafka_conf_t *conf; /* Temporary configuration object */
rd_kafka_resp_err_t err; /* librdkafka API error code */
char errstr[512]; /* librdkafka API error reporting buffer */
const char * user; /*Argument: sasl username*/
const char * password; /*Argument: sasl password*/
const char *brokers; /* Argument: broker list */
const char *groupid; /* Argument: Consumer group id */
char **topics; /* Argument: list of topics to subscribe to */
int topic_cnt; /* Number of topics to subscribe to */
rd_kafka_topic_partition_list_t *subscription; /* Subscribed topics */
int i;

/*
* Argument validation
*/
if (argc < 6) {
fprintf(stderr,
"%% Usage: "
"%s <broker> <group.id> <username> <password> <topic1> <topic2>..\\n",
argv[0]);
return 1;
}

brokers = argv[1];
groupid = argv[2];
user = argv[3];
password = argv[4];
topics = &argv[5];
topic_cnt = argc - 5;


/*
* Create Kafka client configuration place-holder
*/
conf = rd_kafka_conf_new();

/* Set bootstrap broker(s) as a comma-separated list of
* host or host:port (default port 9092).
* librdkafka will use the bootstrap brokers to acquire the full
* set of brokers from the cluster. */
if (rd_kafka_conf_set(conf, "bootstrap.servers", brokers,
errstr, sizeof(errstr)) != RD_KAFKA_CONF_OK) {
fprintf(stderr, "%s\\n", errstr);
rd_kafka_conf_destroy(conf);
return 1;
}

/* Set the consumer group id.
* All consumers sharing the same group id will join the same
* group, and the subscribed topic' partitions will be assigned
* according to the partition.assignment.strategy
* (consumer config property) to the consumers in the group. */
if (rd_kafka_conf_set(conf, "group.id", groupid,
errstr, sizeof(errstr)) != RD_KAFKA_CONF_OK) {
fprintf(stderr, "%s\\n", errstr);
rd_kafka_conf_destroy(conf);
return 1;
}

/* If there is no previously committed offset for a partition
* the auto.offset.reset strategy will be used to decide where
* in the partition to start fetching messages.
* By setting this to earliest the consumer will read all messages
* in the partition if there was no previously committed offset. */
if (rd_kafka_conf_set(conf, "auto.offset.reset", "earliest",
errstr, sizeof(errstr)) != RD_KAFKA_CONF_OK) {
fprintf(stderr, "%s\\n", errstr);
rd_kafka_conf_destroy(conf);
return 1;
}
/* Tencent Cloud recommended configuration parameters
* https://cloud.tencent.com/document/product/597/30203
*/
if(rd_kafka_conf_set(conf,"debug","all",errstr,sizeof(errstr))!= RD_KAFKA_CONF_OK) {
fprintf(stderr,"%s\\n",errstr);
return 1;
}

if(rd_kafka_conf_set(conf,"session.timeout.ms","10000",errstr,sizeof(errstr)) != RD_KAFKA_CONF_OK) {
fprintf(stderr,"%s\\n",errstr);
return 1;
}
if(rd_kafka_conf_set(conf,"heartbeat.interval.ms","3000",errstr,sizeof(errstr)) != RD_KAFKA_CONF_OK) {
fprintf(stderr,"%s\\n",errstr);
return 1;
}

/*Set sasl config*/
if(rd_kafka_conf_set(conf,"security.protocol","sasl_plaintext",errstr,sizeof(errstr)) !=RD_KAFKA_CONF_OK) {
fprintf(stderr,"%s\\n",errstr);
return 1;
}
if(rd_kafka_conf_set(conf, "sasl.mechanisms", "PLAIN", errstr, sizeof(errstr)) != RD_KAFKA_CONF_OK) {
fprintf(stderr,"%s\\n",errstr);
return 1;
}
if(rd_kafka_conf_set(conf,"sasl.username",user,errstr,sizeof(errstr)) !=RD_KAFKA_CONF_OK) {
fprintf(stderr,"%s\\n",errstr);
return 1;
}
if(rd_kafka_conf_set(conf,"sasl.password",password,errstr,sizeof(errstr)) !=RD_KAFKA_CONF_OK) {
fprintf(stderr,"%s\\n",errstr);
return 1;
}
/*
* Create consumer instance.
*
* NOTE: rd_kafka_new() takes ownership of the conf object
* and the application must not reference it again after
* this call.
*/
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;
}

conf = NULL; /* Configuration object is now owned, and freed,
* by the rd_kafka_t instance. */


/* Redirect all messages from per-partition queues to
* the main queue so that messages can be consumed with one
* call from all assigned partitions.
*
* The alternative is to poll the main queue (for events)
* and each partition queue separately, which requires setting
* up a rebalance callback and keeping track of the assignment:
* but that is more complex and typically not recommended. */
rd_kafka_poll_set_consumer(rk);


/* Convert the list of topics to a format suitable for librdkafka */
subscription = rd_kafka_topic_partition_list_new(topic_cnt);
for (i = 0 ; i < topic_cnt ; i++)
rd_kafka_topic_partition_list_add(subscription,
topics[i],
/* the partition is ignored
* by subscribe() */
RD_KAFKA_PARTITION_UA);

/* Subscribe to the list of topics */
err = rd_kafka_subscribe(rk, subscription);
if (err) {
fprintf(stderr,
"%% Failed to subscribe to %d topics: %s\\n",
subscription->cnt, rd_kafka_err2str(err));
rd_kafka_topic_partition_list_destroy(subscription);
rd_kafka_destroy(rk);
return 1;
}

fprintf(stderr,
"%% Subscribed to %d topic(s), "
"waiting for rebalance and messages...\\n",
subscription->cnt);

rd_kafka_topic_partition_list_destroy(subscription);


/* Signal handler for clean shutdown */
signal(SIGINT, stop);

/* Subscribing to topics will trigger a group rebalance
* which may take some time to finish, but there is no need
* for the application to handle this idle period in a special way
* since a rebalance may happen at any time.
* Start polling for messages. */

while (run) {
rd_kafka_message_t *rkm;

rkm = rd_kafka_consumer_poll(rk, 100);
if (!rkm)
continue; /* Timeout: no message within 100ms,
* try again. This short timeout allows
* checking for `run` at frequent intervals.
*/

/* consumer_poll() will return either a proper message
* or a consumer error (rkm->err is set). */
if (rkm->err) {
/* Consumer errors are generally to be considered
* informational as the consumer will automatically
* try to recover from all types of errors. */
fprintf(stderr,
"%% Consumer error: %s\\n",
rd_kafka_message_errstr(rkm));
rd_kafka_message_destroy(rkm);
continue;
}

/* Proper message. */
printf("Message on %s [%"PRId32"] at offset %"PRId64":\\n",
rd_kafka_topic_name(rkm->rkt), rkm->partition,
rkm->offset);

/* Print the message key. */
if (rkm->key && is_printable(rkm->key, rkm->key_len))
printf(" Key: %.*s\\n",
(int)rkm->key_len, (const char *)rkm->key);
else if (rkm->key)
printf(" Key: (%d bytes)\\n", (int)rkm->key_len);

/* Print the message value/payload. */
if (rkm->payload && is_printable(rkm->payload, rkm->len))
printf(" Value: %.*s\\n",
(int)rkm->len, (const char *)rkm->payload);
else if (rkm->payload)
printf(" Value: (%d bytes)\\n", (int)rkm->len);

rd_kafka_message_destroy(rkm);
}


/* Close the consumer: commit final offsets and leave the group. */
fprintf(stderr, "%% Closing consumer\\n");
rd_kafka_consumer_close(rk);


/* Destroy the consumer */
rd_kafka_destroy(rk);

return 0;
}
参数
描述
broker
接入地址,在控制台的弹性 Topic 基本信息页面获取。


username
用户名,在控制台的弹性 Topic 基本信息页面获取。
password
用户密码,在控制台的弹性 Topic 基本信息页面获取。
topic
Topic 名称,在控制台的弹性 Topic 基本信息页面获取。
group.id
消费组名称,在控制台的弹性 Topic 的订阅关系列表获取。


2. 执行以下命令编译 consumer.c。
gcc -lrdkafka ./consumer.c -o consumer
3. 执行以下命令发送消息。
./consumer <broker> <group.id> <username> <password> <topic>.
4. 运行结果如下: