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From Imesh Gunaratne <im...@apache.org>
Subject Re: Concern regarding the "ping" topic used in Stratos
Date Fri, 08 Aug 2014 20:45:33 GMT
Hi Amila,

Yes it shouldn't be a problem. The only concern is that we need to define a
time interval which is less than the time it takes to restart the message
broker. Otherwise the health check won't notice the unavailability of the
message broker and as a result message subscribers will not get
re-connected. Consequently messages won't get received thereafter.

Thanks


On Wed, Aug 6, 2014 at 1:54 AM, Amila Maha Arachchi <amilam@wso2.com> wrote:

> Re-igniting this thread:
>
> Yes, this message is discarded since there are no subscribers to the
> topic. So, it does not seems harmful.
>
> Yet, since WSO2 MB uses Apache Cassandra, this seems to cause problems
> when keep running for few days. Because of that, we are considering about
> reducing the frequency of this ping message.
>
> Imesh,
>
> What are the cons of reducing the frequency to 5 seconds or so (default
> seems to be one second) to send the ping message? I believe it is the delay
> to detect any connection drop? Can this end up in a message loss? I think
> it won't because the mms client should retry. Isn't it?
>
> Regards,
> Amila.
>
>
> On Wed, May 21, 2014 at 2:43 PM, Udara Liyanage <udara@wso2.com> wrote:
>
>> Hi,
>>
>>   MESSAGE DISCARDED: No routes for message - Messag..
>>
>> I see above log in the logs Amila has pasted. The messages
>> are discarded since there is no subscriber ? Unless the topic is a durable
>> topic the messages are discarded when there are no subscriber I guess.
>>
>>
>>
>> On Mon, May 19, 2014 at 6:43 PM, Nirmal Fernando <nirmal070125@gmail.com>
>> wrote:
>>
>>> We have to stop persisting and set a expiration time may be. Is the time
>>> interval of this topic is configurable?
>>>
>>>
>>> On Mon, May 19, 2014 at 1:40 PM, Udara Liyanage <udara@wso2.com> wrote:
>>>
>>>> Hi,
>>>>
>>>> Is there any way that we can specify to discard the messages after
>>>> sometime if they are not consumed? If so we can let the ping messages to
>>>> automatically discard after sometime.
>>>>
>>>>
>>>> On Mon, May 12, 2014 at 9:46 PM, Imesh Gunaratne <imesh@apache.org>
>>>> wrote:
>>>>
>>>>> Thanks Amila for bringing this up. The idea of this implementation was
>>>>> to introduce a generic implementation for any AMQP based message broker
to
>>>>> detect a connection drop and re-connect. The problem was with the message
>>>>> subscribers. Yes we need to have a message consumer for the ping topic
to
>>>>> avoid the message broker being overloaded.
>>>>>
>>>>> I started a discussion on this topic here [1] with respective to
>>>>> ActiveMQ. It seems like ActiveMQ provides a solution for this problem.
The
>>>>> concern we have here is that whether this is something the message broker
>>>>> should handle. If so we could simply ignore this functionality in Stratos.
>>>>>
>>>>> [1]
>>>>> http://stackoverflow.com/questions/23503720/how-to-detect-a-connection-drop-in-an-activemq-subscriber
>>>>>
>>>>> Thanks
>>>>>
>>>>>
>>>>> On Sun, May 11, 2014 at 10:37 PM, Udara Liyanage <udara@wso2.com>
>>>>> wrote:
>>>>>
>>>>>> Hi,
>>>>>>
>>>>>> Yes it might cause problems in long run. Some cleanup process to
>>>>>> subscribe to the ping topic and discard might be useful.
>>>>>>
>>>>>>
>>>>>>
>>>>>> Touched, not typed. Erroneous words are a feature, not a typo.
>>>>>> On May 11, 2014 8:55 AM, "Amila Maha Arachchi" <amilam@wso2.com>
>>>>>> wrote:
>>>>>>
>>>>>>> Hi Devs,
>>>>>>>
>>>>>>> I am working with a Stratos deployment these days. In our
>>>>>>> deployment, we are using WSO2 Message Broker as the message broker.
There I
>>>>>>> see the following log getting printed very frequently (every
second).
>>>>>>>
>>>>>>> TID: [0] [MB] [2014-05-05 08:31:52,352]  INFO
>>>>>>> {org.wso2.andes.server.exchange.TopicExchange} -  Message routing
key: ping
>>>>>>> No routes. {org.wso2.andes.server.exchange.TopicExchange}
>>>>>>>
>>>>>>> TID: [0] [MB] [2014-05-05 08:31:52,352]  WARN
>>>>>>> {org.wso2.andes.server.AMQChannel} -  MESSAGE DISCARDED: No routes
for
>>>>>>> message - Message[(HC:449176483 ID:366318838955900928 Ref:0)]:
>>>>>>> 366318838955900928; ref count: 0 {org.wso2.andes.server.AMQChannel}
>>>>>>>
>>>>>>> TID: [0] [MB] [2014-05-05 08:31:52,621]  INFO
>>>>>>> {org.wso2.andes.server.exchange.TopicExchange} -  Message routing
key: ping
>>>>>>> No routes. {org.wso2.andes.server.exchange.TopicExchange}
>>>>>>>
>>>>>>> TID: [0] [MB] [2014-05-05 08:31:52,621]  WARN
>>>>>>> {org.wso2.andes.server.AMQChannel} -  MESSAGE DISCARDED: No routes
for
>>>>>>> message - Message[(HC:1522105342 ID:366318839026417664 Ref:0)]:
>>>>>>> 366318839026417664; ref count: 0 {org.wso2.andes.server.AMQChannel}
>>>>>>>
>>>>>>> I came to know that this is due to a mechanism used to check
whether
>>>>>>> the Message Broker (MB) is alive. i.e. subscribers publish an
event to this
>>>>>>> "ping" topic to see whether the MB is alive, but no one is consuming
it.
>>>>>>> Thats why the above log is getting printed.
>>>>>>>
>>>>>>> Since no one is consuming this messages, is it possible that
MB gets
>>>>>>> loaded with this message and cause problems?
>>>>>>>
>>>>>>> Regards,
>>>>>>> Amila.
>>>>>>>
>>>>>>> --
>>>>>>> *Amila Maharachchi*
>>>>>>> Senior Technical Lead
>>>>>>> WSO2, Inc.; http://wso2.com
>>>>>>>
>>>>>>> Blog: http://maharachchi.blogspot.com
>>>>>>> Mobile: +94719371446
>>>>>>>
>>>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> Imesh Gunaratne
>>>>>
>>>>> Technical Lead, WSO2
>>>>> Committer & PPMC Member, Apache Stratos
>>>>>
>>>>
>>>>
>>>>
>>>> --
>>>>
>>>> Udara Liyanage
>>>> Software Engineer
>>>> WSO2, Inc.: http://wso2.com
>>>> lean. enterprise. middleware
>>>>
>>>> web: http://udaraliyanage.wordpress.com
>>>> phone: +94 71 443 6897
>>>>
>>>
>>>
>>>
>>> --
>>> Best Regards,
>>> Nirmal
>>>
>>> Nirmal Fernando.
>>> PPMC Member & Committer of Apache Stratos,
>>> Senior Software Engineer, WSO2 Inc.
>>>
>>> Blog: http://nirmalfdo.blogspot.com/
>>>
>>
>>
>>
>> --
>>
>> Udara Liyanage
>> Software Engineer
>> WSO2, Inc.: http://wso2.com
>> lean. enterprise. middleware
>>
>> web: http://udaraliyanage.wordpress.com
>> phone: +94 71 443 6897
>>
>
>
>
> --
> *Amila Maharachchi*
> Senior Technical Lead
> WSO2, Inc.; http://wso2.com
>
> Blog: http://maharachchi.blogspot.com
> Mobile: +94719371446
>
>


-- 
Imesh Gunaratne

Technical Lead, WSO2
Committer & PPMC Member, Apache Stratos

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