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https://issues.apache.org/jira/browse/ARTEMIS-1803?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16435669#comment-16435669
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ASF GitHub Bot commented on ARTEMIS-1803:
-----------------------------------------
Github user franz1981 commented on the issue:
https://github.com/apache/activemq-artemis/pull/2012
@cshannon
Summarized:
```
org.apache.activemq.artemis.core.server.impl.MessageReferenceImpl:
Instance size: 72 bytes
Space losses: 2 bytes internal + 4 bytes external = 6 bytes total
org.apache.activemq.artemis.core.paging.cursor.PagedReferenceImpl:
Instance size: 104 bytes
Space losses: 1 bytes internal + 4 bytes external = 5 bytes total
org.apache.activemq.artemis.core.server.impl.LastValueQueue$HolderReference:
Instance size: 40 bytes
Space losses: 3 bytes internal + 0 bytes external = 3 bytes total
```
`Instance size` is the value you're searching for: I have attached the
`Space losses` as well, because it
is related to what @michaelandrepearce is saying: just adding that mere 4
bytes reference (with heap < 32 Gb the JVM uses compressed oops by default) has
added 4 bytes (external) of padding ie a total of 8 bytes of more space used.
TBH that's a difficult choice: we have done recently many changes to make
every protocol much GC "gentle" to allow scaling more easily, but @cshannon is
right that there are monitoring/telemetry reasons very important to be achieved
as well.
You both have very good points :O
> MessageReference should include sessionId
> -----------------------------------------
>
> Key: ARTEMIS-1803
> URL: https://issues.apache.org/jira/browse/ARTEMIS-1803
> Project: ActiveMQ Artemis
> Issue Type: Improvement
> Affects Versions: 2.5.0
> Reporter: Christopher L. Shannon
> Assignee: Christopher L. Shannon
> Priority: Minor
>
> Right now a MessageReference will track a consumerId (in certain scenarios)
> but the sessionId is not included. This is a problem because consumerIds are
> not unique and are duplicated across sessions. In order to find a unique
> consumer you need the sessionId and consumerId as well.
> A use case for when this is important is when writing custom plugins. Some
> of the callbacks pass a message reference and it would be good to be able to
> figure out which consumer the reference belonged to such as in the
> messageAcknowledged callback.
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