卡夫卡用时间戳索引消息用c语言如何编写
时间: 2023-08-06 14:09:04 浏览: 64
使用Kafka C语言API可以通过设置`rd_kafka_topic_partition_t`结构体的`offset`字段为`RD_KAFKA_OFFSET_TIMESTAMP`来使用时间戳索引消息。以下是一个示例程序:
```c
#include <stdio.h>
#include <stdlib.h>
#include <librdkafka/rdkafka.h>
int main(int argc, char **argv) {
rd_kafka_t *rk;
rd_kafka_conf_t *conf;
char errstr[512];
rd_kafka_resp_err_t err;
rd_kafka_topic_partition_list_t *topics;
rd_kafka_topic_partition_t *topic;
rd_kafka_message_t *msg;
int64_t timestamp = 1620167042000; // Timestamp to use as index
/* Create Kafka configuration object */
conf = rd_kafka_conf_new();
/* Set bootstrap server */
if (rd_kafka_conf_set(conf, "bootstrap.servers", "localhost:9092", errstr, sizeof(errstr)) != RD_KAFKA_CONF_OK) {
fprintf(stderr, "Failed to set broker list: %s\n", errstr);
exit(1);
}
/* Create Kafka consumer instance */
rk = rd_kafka_new(RD_KAFKA_CONSUMER, conf, errstr, sizeof(errstr));
if (rk == NULL) {
fprintf(stderr, "Failed to create consumer: %s\n", errstr);
exit(1);
}
/* Create topic partition list */
topics = rd_kafka_topic_partition_list_new(1);
/* Add topic partition to list */
topic = rd_kafka_topic_partition_list_add(topics, "my-topic", RD_KAFKA_PARTITION_UA);
if (topic == NULL) {
fprintf(stderr, "Failed to add topic: %s\n", rd_kafka_err2str(err));
rd_kafka_topic_partition_list_destroy(topics);
rd_kafka_destroy(rk);
exit(1);
}
/* Set offset to timestamp */
topic->offset = rd_kafka_timestamp_to_offset(rk, topic->topic, topic->partition, timestamp, 1000);
/* Subscribe to topic */
err = rd_kafka_subscribe(rk, topics);
if (err != RD_KAFKA_RESP_ERR_NO_ERROR) {
fprintf(stderr, "Failed to subscribe to topic: %s\n", rd_kafka_err2str(err));
rd_kafka_topic_partition_list_destroy(topics);
rd_kafka_destroy(rk);
exit(1);
}
/* Consume messages */
while (1) {
msg = rd_kafka_consumer_poll(rk, 1000); // Wait up to 1000ms for a message
if (msg == NULL) {
continue;
}
if (msg->err == RD_KAFKA_RESP_ERR_NO_ERROR) {
printf("Received message: %.*s\n", (int)msg->len, (char *)msg->payload);
rd_kafka_message_destroy(msg);
}
}
/* Cleanup */
rd_kafka_topic_partition_list_destroy(topics);
rd_kafka_destroy(rk);
return 0;
}
```
在这个示例程序中,我们首先使用`rd_kafka_timestamp_to_offset()`函数将时间戳转换为偏移量,然后将这个偏移量赋值给`rd_kafka_topic_partition_t`结构体的`offset`字段。使用`rd_kafka_subscribe()`函数订阅主题时,Kafka会从指定的时间戳开始消费消息。
需要注意的是,`rd_kafka_timestamp_to_offset()`函数的最后一个参数是超时时间(以毫秒为单位),如果在指定时间内无法获取到偏移量,函数将返回错误。在示例程序中,我们将超时时间设置为1000ms,即1秒。根据实际情况可以调整这个值。
另外,如果订阅的主题中没有指定时间戳的消息,程序将会一直等待,直到有新的消息到达或者超时。在使用时间戳索引消息时,需要注意这一点。