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Re: [paho-dev] Message loss with higher load - eclipse paho mqtt client


There's nothing in MQTT 3.1.1 that doesn't allow servers or clients to just drop QoS 0 whenever they want to; loaded or unloaded. And for 1/2, there's nothing to stop a server doing TCP (or other layer) traffic shaping, reduced CPU time, removing from a epoll/poll/whatever schedule, not reading the tcp buffer, etc.

However, a server may disconnect a client. Sometimes there's very little else the spec permits. The great challenge is in dealing with out-of-resource scenarios - the spec as it stands has no way of communicating 'sorry, can't do this right now / or ever '.

Raphael Cohn
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Co-Chair, OASIS MQTT Standard
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On 8 November 2013 11:22, Paul Fremantle <paul.fremantle@xxxxxxxxxx> wrote:

Can you point me at the wording that would compel this? This seems a bad decision to me. Generally I'd like to see the following behaviour:

QOS0: the server could just drop messages when overloaded.
QOS1/2: I'd like the server to apply tcp back-pressure on the client until less loaded. Disconnecting seems a bit drastic.


On 8 November 2013 10:13, Ian Craggs <icraggs@xxxxxxxxxxxxxxxxxxxxxxx> wrote:
With the new standard, if this sort of limit is reached, I think we will be compelled to disconnect the client.


On 08/11/13 09:51, Roger Light wrote:
Hi Kasun,

My guess is that you're using mosquitto with QoS 1 or 2 messages.
Current versions of mosquitto limit the number of messages a client
can have inflight and queued in both directions. The default limit is
20 inflight and 100 queued. You may wish to increase these limits.
There is also a valid argument that the client should limit the
incoming message rate and the server should just accept what is being



On Fri, Nov 8, 2013 at 6:50 AM, Kasun Weranga
<kasungunathilake@xxxxxxxxx> wrote:
Hi all,

I am experience some message loss with high load when using eclipse paho
mqtt client. I have subscribed to a set of topics (clients/+) and I did some
load testing using eclipse paho mqtt client. I saw my subscriber only
receiving first 120 messages when I publish messages to (clients/+) topics -
Message publishing rate is above 400 messages per second.
Is there any configuration that I need to set for higher load. How can I
solve above issue.
Appreciate any help on solving this issue.

Thanks and Regards,

Kasun Weranga Gunathilake.
mobile: +6594230423

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Paul Fremantle
Part-time PhD student - School of Computing
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