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Posted to users@activemq.apache.org by t-watana <wa...@jp.fujitsu.com> on 2018/06/15 09:59:02 UTC

Abount "KahaDB Cleanup" of durable subscribers including pending messages

My understanding is that, KahaDB rewrite the KAHA_SUBSCRIPTION_COMMAND to 
latest journal file for ease of deletion the oldeset jorunal log, 
when the durable subscriber has no pending message. 

But, in the following case, "Durable Subscriber C and D" aren't rewritten 
to latest journal despite they have no pending message, because 
"Durable Subscriber B" has pending messages. 
I think that it's becoming difficult to delete the oldest journal. 

- Durable Subscriber A, B, C, D 
- Validation order of cleanup is "A, B, C, D" 
- "Durable Subscriber A" has no pending message 
- "Durable Subscriber B" has some pending messages 
- "Durable Subscriber C" has no pending message 
- "Durable Subscriber D" has no pending message 

the following code is partial cleanup routine, pasted from ActiveMQ 5.13.1
(MessageDatabase.java 
line.1705-1732) 
Why is the condition "gcCandidateSet.first() == dataFileId" necessary? 

It seem that it's blocking the KahaDB cleanup routine. 





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