为什么不能将 Kafka 偏移量设置为主题的开头？

如何解决为什么不能将 Kafka 偏移量设置为主题的开头？

我想将具有 1 个分区和给定组 ID mytopic 的主题 testgroup1 的偏移量设置为 0。但是这并不总是可行的。如果我想将偏移量设置为 0，我会收到以下消息：

bash-4.4# kafka-consumer-groups.sh --bootstrap-server localhost:9092 --topic mytopic --group testgroup1 --reset-offsets --to-offset 0 --execute
[2021-06-04 09:23:30,854] WARN New offset (0) is lower than earliest offset for topic partition mytopic-0. Value will be set to 1365671 (kafka.admin.ConsumerGroupCommand$)

bash-4.4# kafka-topics.sh --bootstrap-server localhost:9092 --topic mytopic --describe 
Topic: mytopic  PartitionCount: 1   ReplicationFactor: 1    Configs: segment.bytes=1073741824
    Topic: mytopic  Partition: 0    leader: 1001    Replicas: 1001  Isr: 1001

bash-4.4# kafka-configs.sh --bootstrap-server localhost:9092 --describe --entity-name mytopic --entity-type topics
Dynamic configs for topic mytopic are:
bash-4.4#

在 Kafka 日志中，我可以在整个主题被消费后看到这一点；不确定它是否真的相关：

[2021-06-04 10:18:36,130] INFO [Log partition=__consumer_offsets-19,dir=/kafka/logs] Deleting segment files LogSegment(baSEOffset=0,size=634,lastModifiedTime=1598954190000,largestRecordTimestamp=Some(1585909899136)) (kafka.log.Log)
[2021-06-04 10:18:36,131] INFO Deleted log /kafka/logs/__consumer_offsets-19/00000000000000000000.log.deleted. (kafka.log.LogSegment)
[2021-06-04 10:18:36,132] INFO Deleted offset index /kafka/logs/__consumer_offsets-19/00000000000000000000.index.deleted. (kafka.log.LogSegment)
[2021-06-04 10:18:36,132] INFO Deleted time index /kafka/logs/__consumer_offsets-19/00000000000000000000.timeindex.deleted. (kafka.log.LogSegment)

使用此命令甚至无法再次使用主题：

kafka-console-consumer.sh --bootstrap-server localhost:9092 --from-beginning --group testgroup1 --topic mytopic

我读过其他问题，例如：

但是我还没有找到 Kafka 会出现这种行为的原因，即最早的偏移量设置为不同的值，并且不可能再次返回到偏移量 0。也许它与数据保留有关，但我尝试将日志保留设置为 3 年：

log.cleaner.backoff.ms = 15000
log.cleaner.dedupe.buffer.size = 134217728
log.cleaner.delete.retention.ms = 86400000
log.cleaner.enable = true
log.cleaner.io.buffer.load.factor = 0.9
log.cleaner.io.buffer.size = 524288
log.cleaner.io.max.bytes.per.second = 1.7976931348623157E308
log.cleaner.max.compaction.lag.ms = 9223372036854775807
log.cleaner.min.cleanable.ratio = 0.5
log.cleaner.min.compaction.lag.ms = 0
log.cleaner.threads = 1
log.cleanup.policy = [delete]
log.dir = /tmp/kafka-logs
log.dirs = /kafka/logs
log.flush.interval.messages = 9223372036854775807
log.flush.interval.ms = null
log.flush.offset.checkpoint.interval.ms = 60000
log.flush.scheduler.interval.ms = 9223372036854775807
log.flush.start.offset.checkpoint.interval.ms = 60000
log.index.interval.bytes = 4096
log.index.size.max.bytes = 10485760
log.message.downconversion.enable = true
log.message.format.version = 2.7-IV2
log.message.timestamp.difference.max.ms = 9223372036854775807
log.message.timestamp.type = CreateTime
log.preallocate = false
log.retention.bytes = -1
log.retention.check.interval.ms = 300000
log.retention.hours = 26280
log.retention.minutes = null
log.retention.ms = null
log.roll.hours = 168
log.roll.jitter.hours = 0
log.roll.jitter.ms = null
log.roll.ms = null
log.segment.bytes = 1073741824
log.segment.delete.delay.ms = 6000

解决方法

带有清除策略 DELETE 的 Kafka 主题，主题的默认“类型”会修剪其数据（基于配置-大小/时间保留），因此在您的情况下，主题中不再存在数据，偏移计数器始终为继续前进，所以像 0 这样的旧偏移量在主题中没有数据，希望能解决问题

检查您的主题配置是否内部配置了不同的保留配置