Hi,
I'm relatively new to ActiveMQ and currently I try to understand the various
information about persintence, Memory limit, Cursor memory limit, Cursur
percent usage and Producer Flow Control. (I' m sure I read almost all
available information, especially
http://blog.christianposta.com/activemq/activemq-understanding-memory-usage/
<http://blog.christianposta.com/activemq/activemq-understanding-memory-usage/>
)
I've built up a small test system and I see that the system behaviour is not
as I would expect.
Here is my configuration:
-ActiveMQ version 5.13.3
-broker persistence using KahaDB
-testing with persistent messages
-SystemUsage:
<systemUsage>
<systemUsage>
<memoryUsage>
<memoryUsage limit="256 mb" />
</memoryUsage>
<storeUsage>
<storeUsage limit="5 gb"/>
</storeUsage>
<tempUsage>
<tempUsage limit="64 mb"/>
</tempUsage>
</systemUsage>
</systemUsage>
-DestinationPolicy:
<destinationPolicy>
<policyMap>
<policyEntries>
<policyEntry queue=">" producerFlowControl="true"
cursorMemoryHighWaterMark="70" memoryLimit="10MB"/>
<policyEntry topic=">" >
<pendingMessageLimitStrategy>
<constantPendingMessageLimitStrategy
limit="1000"/>
</pendingMessageLimitStrategy>
</policyEntry>
</policyEntries>
</policyMap>
</destinationPolicy>
For testing, I have only one queue : queue://TEST
I produce 100 messages with size 1MB each.
>activemq producer --messageCount 100 --messageSize 1048576
As a result I would expect that the Cursors memory limit remains under 70%
of the destination memory limit (10MB)
because I use persistent messages and hence the store cursor per default.
But I see the following:
Cursor memory usage: 104960000
Cursor percent usage :1000
Memory Limit: 10485760
Memory percent usage: 1000
Memory usage byte count:104960000
Memory usage portion: 0
Store message size: 104887192
Broker Memory percent usage :39
Also from my understanding the PDC should never kicks in (as long as the
store memory limit is not reached). But after producing another 100
messages the PFC kicks in.
I don't understand why the cursor exceeds the memory limit of 10 MB for the
destination.
What is the base value of the CursorHighWaterMark?
Another observation:
If I first send 7 messages the Cursur usage percent value is 70%.
After that I' m able to send any amount without the PDC kicks in. The
Cursor usage percent remains at 70%
What do I missunderstand ? Any help is appreciated
Many Thanks
Joerg
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