Joe Luo created AMQ-5341:
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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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