[GitHub] merlimat commented on issue #654: Do not delete inactive topics if they have retention policy

[gi...@git.apache.org]

merlimat commented on issue #654: Do not delete inactive topics if they have retention policy
URL: https://github.com/apache/incubator-pulsar/pull/654#issuecomment-320966051
 
 
   > change LGTM. But quick question: if topic doesn't have subscribers and publishers, then why do we want to keep inactive topic till message-retention time?
   
   I can see multiple reasons : 
    * Consistency & semantic: If I configure the retention for 3h, I should have the data stored for (at least) 3h, irrespective of other conditions 
    * Retention is used primarily to be able to roll-back a consumer. Right now it's possible to create a subscription (at the end of the stream) and then roll it back to a earlier point in time, but only if there are already other subscriptions, otherwise the topic would have been deleted before.
    * Using the Reader API, the broker doesn't control the reader position, so, when a reader is gone it doesn't retain anything on the broker side. The reader relies on the retention for the data to be available and it's vital to not delete the topic before that time expires.
   
   
 
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