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From "Joe Luo (JIRA)" <j...@apache.org>
Subject [jira] [Created] (AMQ-5341) ActiveMQ documentation is inaccurate in describing Store-based Cursors for a Fast Consumer section
Date Tue, 02 Sep 2014 13:51:21 GMT
Joe Luo created AMQ-5341:
----------------------------

             Summary: ActiveMQ documentation is inaccurate in describing Store-based Cursors
for a Fast Consumer section
                 Key: AMQ-5341
                 URL: https://issues.apache.org/jira/browse/AMQ-5341
             Project: ActiveMQ
          Issue Type: Bug
          Components: Documentation
            Reporter: Joe Luo


The ActiveMQ documentation: http://activemq.apache.org/message-cursors.html says
{quote}
As shown in Figure 6, store-based cursors address the fast consumer case by skipping the message
cursor. When a message consumer is keeping pace with the message producers, persistent messages
are written to the message store and moved directly into a dispatch queue for the consumer.
{quote}
Basically the statement is inaccurate since fast consumers are dealt with the same for both
StoreCursor and VMCursor. It does not skip StoreCursor/Pending Cursor as the messages will
be held in memory and dispatched from the memory. In fast consumers situation, StoreCursor
will behave exactly the same as VMCursor but with a few differences that VMCursor will be
a snapshot of entire persistent message store in memory as it needs to hold all messages in
memory while StoreCursor will be a mapping of only a fraction of persistent message store
in memory since it can only hold limited messages in memory.

I'd suggest to replace the figure "Dispatching Messages for Fast Consumers" for StoreCursor
(the first figure on the page) with the "VMCursor" one (The third figure on the page). And
we should also replace original statement quoted above with something like below to point
out the difference:
{code}
In fast consumers situation, StoreCursor will behave exactly the same as VMCursor but with
a few differences that VMCursor will be a snapshot of entire persistent message store in memory
as it needs to hold all messages in memory while StoreCursor will be a mapping of only a fraction
of persistent message store in memory since it can only hold limited messages in memory.
{code}



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