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Re: [paho-dev] [iot-wg] Questions regarding MQTT/Paho

Hi Marco,

thanks for the information. I've looked at the Kura interface, and it looks good. The thoughts that arise in my mind are:

1) How or if to make use of the Kura interface within Paho. Just tell people to use Kura, or some reuse within Paho?

2) Whether a very simple enhancement to the Paho Java client API would be suitable for some people, and whether it was worth doing that in addition to Kura.

2) Whether there is any advantage for "offline buffering" for each of the Paho clients (C, JavaScript, Python etc) to look similar. For the C asynchronous client, a whole new interface seems unnecessary (just allowing publish to be called when not connected might be enough).

Ian

On 07/31/2014 08:44 PM, Carrer, Marco wrote:
Hello.

FYI, configurable offline buffering over Paho is available in the Eclipse Kura project if you want to look into it.
You can look at the DataService implementation.

Thanks.
-Marco


On Jul 30, 2014, at 8:11 AM, Jens Reimann <jens.reimann@xxxxxxxxxxxxxxx> wrote:

Hello Ian,

oh I even was not aware of the fact that events are not sent when the
connections is broken. I thought thats what the persistence stuff was for.

The bug description looks good for me. Thanks for adding it!

Jens

On 07/30/2014 11:55 AM, Ian Craggs wrote:
Hi Jens,

thanks for the comments.  We are open to suggestions and contributions
to improve the clients of course.  A frequently asked for capability
is to send messages when the client is disconnected ("offline
buffering") - it seems to me that these two improvements are related.N

It seems to me what you are asking for is a simple reconnect using the
same connect options until the application calls disconnect. There
would be some parameters (reconnect interval/backoff).  I've raised a
bug (https://bugs.eclipse.org/bugs/show_bug.cgi?id=440734) to track
the suggestion.  Please feel free to add more information there.

Ian


On 07/30/2014 08:38 AM, Jens Reimann wrote:
Hello Ian,

thanks for the answer.

I totally understand the reason for passing through the protocol
specific to a simple API. And it is important to have this control.

However, now I fully understand when you bang your head on the table
;-), "I just want to push some data to MQTT".

No I would guess that there are some "common ways to do it" and which
get repeatedly implemented by users. So instead of everybody
re-implementing these common cases, it would simply be nice to have
these coming from the MQTT library.

Actually In Eclipse SCADA we have the some issue. Connections simply
inform you about the state, but the "AutoReconnectController" keeps the
session open as long as requested.

Anyway, thanks for the help. So I now know that I have to do it
myself ;)

Jens

On 07/29/2014 03:15 PM, Ian Craggs wrote:
Hi Jens,

what Benjamin says is correct.  It is a manual step to reconnect in
the callback.  This is for a number of reasons.

1.  MQTT is defined as a protocol rather than an API, so the APIs have
been written to be close to the behaviour of MQTT.  This makes it easy
to understand the APIs in the context of MQTT, and provides maximum
flexibility.

2. Depending on the connect options used, will message or clean
session for instance, disconnection and reconnection can have effects
which you need to know about and/or control.  You may want to change
connect options when you reconnect, or delay reconnection.  To allow
all these combinations on automatic reconnection would require a
complicated API.

Ian

On 07/25/2014 02:08 PM, Benjamin Cabé wrote:
Hi Jens,

I think you may want to post this question on the paho-dev mailing
list (I
cross-posted there)!
My understanding though is that when the MqttCallback#connectionLost()
method is called, it's up to you to decide whether you want to
reconnect
or not.

Benjamin.


Le 25/07/2014 14:47, « Jens Reimann » <jens.reimann@xxxxxxxxxxxxxxx> a
écrit :

Hi,

maybe somebody can give me a short hint about the MqttAsyncClient
from
Paho.

I found the javadoc, and know how to connect and disconnect. What I
don't know is, what will happen when the connection breaks. Does it
automatically re-connect, or is this a "manual" step?

Thanks for helping

Jens

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