In the context of pulsar, when a consumer acks a message, it doesn’t remove
entries from bookkeeper. Instead, for each subscription at pulsar, pulsar
brokers use a separate ledger for storing the acknowledgments for each
subscription. When a broker receives individual acks, it writes an entry to
the cursor ledger marking that message as acknowledged, when the cursor
ledgers move beyond the data ledger, broker deletes the data ledger.

If ack failed, brokers will try to redeliver the unacked messages after
acks timeout. This is configured as ackTimeout when you construct a
consumer instance.

Hope this helps.


On Wed, Jul 11, 2018 at 2:38 AM li.peng...@zhaopin.com.cn <
li.peng...@zhaopin.com.cn> wrote:

> In introduce of pulsar, i interest in ack mode of individual.
> I know that pulsar use bookkeeper to store messages, and entries in
> bookkeeper write only once.
> so i want to know how pulsar server do message ack in individual mode. if
> ack failed, how long will i receive the message again.

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