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https://issues.apache.org/jira/browse/QPID-3613?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Rajith Attapattu updated QPID-3613:
-----------------------------------
Fix Version/s: (was: 0.15)
Future
> Management of message credits should be on a per subscription basis (not on a
> per session basis)
> ------------------------------------------------------------------------------------------------
>
> Key: QPID-3613
> URL: https://issues.apache.org/jira/browse/QPID-3613
> Project: Qpid
> Issue Type: Bug
> Components: Java Client
> Affects Versions: 0.14
> Reporter: Rajith Attapattu
> Assignee: Rajith Attapattu
> Labels: message-credit
> Fix For: Future
>
>
> We currently calculate credit replenishment at the session level completely
> ignoring the capacity of each individual subscription. Further more as per
> QPID-3612 the completions are tied to message-acks further complicating the
> issue.
> The general formula used for calculating the replenishment rate is as
> follows.
> {code}
> if (unackedCount >= prefetch/2 || maxAckDelay <= 0 || _acknowledgeMode ==
> javax.jms.Session.AUTO_ACKNOWLEDGE)
> {
> flushAcknowledgments();
> }
> {code}
> There are several issues with this.
> 1. If the application doesn't ack (in CLIENT_ACK) or commit a transaction
> before it exhaust the credits, the consumer will starve. See QPID-3612. A
> recent change done in rev 1195213 fixes the TX case.
> 2. Ineffective flow control as the calculation happens globally at the
> session level instead at the subscription level. Due to this, slow consumers
> can affect fast consumers.
> Ex . Assume there are two fast consumers and a slow consumer each with an
> individual capacity of 20 and the max_prefetch for the connection to be 100.
> The threshold for sending acks (and therefore completions) is 50. If the fast
> consumers have already done with their 20 messages, they will have to wait
> for the slow consumer to do atleast 10 messages before the threshold is hit.
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