On 07/14/2016 01:55 PM, Flores, Paul A. wrote:
Ted,
Thanks for the reply.
Paul
Questions remain.
In the C++ API documentation it is unclear how to set up prefetching. Is it
related to setting the receiver capacity? Is there an example?
With prefetch setup does a fetch return more than one message at a time from a
specific queue?
Prefetch is controlled by setting the receiver's capacity. The capacity
is the maximum number of messages that may be delivered by the peer
(broker) and stored locally on the client awaiting a fetch.
Fetch will return at most one message per call.
Prefetch allows the broker to deliver multiple messages along the
receiver to the client in batches. A capacity of greater that one
allows the broker to operate more efficiently and improves message
throughput. The reason for this is that the broker's threading model
assigns a thread to process a single connection at a time. If the
connection is writable (i.e. not congested outbound from the broker), it
is more efficient to send a batch of messages from the same queue than
to send only one.
________________________________________
From: Ted Ross [[email protected]]
Sent: Thursday, July 14, 2016 12:25 PM
To: [email protected]
Subject: Re: C++ API Next Receiver Questions
On 07/14/2016 12:22 PM, Flores, Paul A. wrote:
Hi,
At client.
Basic questions that I have answered but want to double check.
Can I get some verification/clarification.
How does pre-fetch influence these questions/answers?
Thanks for the feedback it is appreciated.
Paul
Premise:
Given:
a Connection with a Session. (Connection to Session 1:1?)
a Session with more than 1 Receiver. (Session to Receiver 1:N)
Default configuration specifying pre-fetch
Each Receiver has a queue. (Receiver to Queue 1:1)
Questions:
1) Does Next Receiver "cycle" through receivers?
Given:
Three Receivers: A,B and C
Receivers A and C have message on their respective queues (Alpha and
Charlie respectively)
After a fetch on Receiver A (messages remain on Alpha)
Will a call to Next Receiver return Receiver C?
NextReceiver is not directly concerned with whether there are messages
on the queue, but whether there are messages that have been delivered on
the receiver to the client (based on prefetch). So, yes, NextReceiver
will eventually return C even though messages remain on Alpha.
2) Does Next Receiver always return the Receiver with messages on its queue?
Given:
Three Receivers: A,B and C
Receiver B's queue (Bravo) has messages while the other Receiver queues
are empty
After a fetch on Receiver B (messages remain on Bravo)
Will a call to Next Receiver return Receiver B?
NextReceiver _only_ returns receivers on which messages have been
prefetched. So, yes, NextReceiver will return B in this case. Once all
the messages on Bravo are delivered (even if they remain), NextReceiver
will block because there is no receiver with prefetched deliveries to
return.
Note that if there is no prefetch on any of the receivers, NextReceiver
will never return a receiver.
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