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From "Jaliya Ekanayake" <jnekanay...@gmail.com>
Subject Re: WSRM handling
Date Fri, 05 May 2006 14:57:48 GMT
Hi Paul,

Please see my comments below.

Thanks,
Jaliya
----- Original Message ----- 
From: "Paul Fremantle" <paul@wso2.com>
To: "Jaliya Ekanayake" <jaliya@apache.org>
Cc: <synapse-dev@ws.apache.org>
Sent: Friday, May 05, 2006 10:21 AM
Subject: Re: WSRM handling


> Jaliya
>
> I'm not clear I understand. In the case that the Axis server pauses a 
> message no thread should be used.

I might have not expressed it correctly, this is what I have in mind; 
Pausing does not cause any threading issue, however the handler which call 
pause should keep track of the messages it has been paused. (e.g. in RM case 
we need to send the an ack after the Acknowledgement Interval  (we have to 
either wait or have to incorporate a thread to do that)

>We could decouple the input of messages from the processing (that model is 
>called SEDA http://www.eecs.harvard.edu/~mdw/proj/seda/).

This is what I had in my mind. If you see the Figure 6 of article 
http://www.eecs.harvard.edu/~mdw/papers/seda-sosp01.pdf that is what I had 
in my mind and I think we should start synapse as the EventHandler in the 
figure.


 However, studies have
> shown that the overhead of thread switching is not always valuable. If the 
> Axis2 front-end is being saturated the first aim is to fix that.
> Queueing can be a good model but shouldn't be essential in this model - 
> the Axis2 front-end should gracefully cope with many thousands of requests 
> and should be able to "queue" at the TCP/IP socket level.

Could not figure out a way to do this in a container based model. Could you 
please explain a bit about it?

>
> Paul
>
>
> Jaliya Ekanayake wrote:
>> Hi Paul,
>>  Here are some of my thoughts about this.
>>  When we support RM from Synapse IMHO we need to support all the three 
>> scenarios.  It should have the full capabilities of an RM Endpoint if we 
>> decided to support RM.
>>  The major hurdle that I find in the architecture is the lack of Queuing. 
>> It is true that Axis2 can pause the messages but there should be some 
>> thread keeping track of this paused message and since we are inside a 
>> container we always have the limitation from the container's thread 
>> models. I tested this scenario and found that it quickly exhaust the 
>> container's thread pool.
>>  Scalability requirement of synapse is very high and we should go for a 
>> model where the incoming messages does not cause limitations to the 
>> performance. IMHO a standalone server (Standalone Synapse Server) with 
>> front end queue will provide this capability and then we can easily 
>> handle these QoSs. I even tested this scenario and found that it does not 
>> load the container in the case of Asynchronous Invocations. (I used Axis 
>> servlet just to inject messages to a broker(Naradabroker 
>> http://www.naradabrokering.org/)  and Synapse "pulls" the messages from a 
>> Queue instead of getting invoked.)
>>  Any thoughts?
>>  Thanks,
>> Jaliya
>>
>>     ----- Original Message -----
>>     *From:* Paul Fremantle <mailto:pzfreo@gmail.com>
>>     *To:* synapse-dev@ws.apache.org <mailto:synapse-dev@ws.apache.org>
>>     *Sent:* Friday, May 05, 2006 7:56 AM
>>     *Subject:* WSRM handling
>>
>>     I'd like to start a discussion on handling WSRM in Synapse.
>>
>>     There are three aspects:
>>
>>     1. passthrough. In this model the sequence is from one endpoint to
>>     the other, and Synapse doesn't really get involved.
>>     2. Synapse as an RM client. The message comes into Synapse, maybe
>>     over JMS or SMTP. We send it on with a sequence. Synapse is acting
>>     as an RM client (probably two-way).
>>     3. Synapse is acting as an RM server and passing messages on
>>     without RM, perhaps to a "pre-RM" SOAP server, or via JMS.
>>
>>     1 isn't very interesting to us, tho we could do some special logging.
>>     2 should be fairly straightforward. We need to be able to
>>     configure some aspects of the RM infrastructure - timeouts, the
>>     assignment of messages to sequences etc. I will propose a config
>>     model and syntax for this.
>>     3 is a little tricky. The problem comes with "in-order" delivery.
>>     If this is enabled then synapse may need to hold up further
>>     processing of this  message until earlier messages have been
>>     delivered. Sandesha can take care of the "holding up", but we have
>>     no way currently of pausing a mediator or re-injecting a message
>>     partway through a mediator chain.
>>
>>     There are a few solutions to this I can think of:
>>     A) Don't support inorder delivery - at least to start with. I
>>     think this might be a worthwhile first step, but it isn't a good
>>     long term solution as in-order is one of the main requirements
>>     people have for RM.
>>     B) Add pausing or re-injection into Synapse. This would be some
>>     re-architecture. My main issue with this is that this is already
>>     built into Axis2 so I'm not keen on re-building it in Synapse as
>>     well if we can re-use the Axis2 capability instead.
>>     C) This is a limited proposal but might be a reasonable model to
>>     start with. The idea is to split processing into two halves. The
>>     first half happens before RM "delivery" (i.e. before the inorder
>>     constraint is applied). The second half takes place after
>>     delivery. A simple syntax to handle this might look like:
>>
>>     <sequence>
>>        <reliableTerminate> <!-- i.e. we are terminating the RM
>>     connection in Synapse and passing on without RM -->
>>            <pre-delivery>
>>               mediators here
>>            </pre-delivery>
>>            <deliver/>
>>        </reliableTerminate>
>>        <mediator...> Any mediators here get called post delivery </med>
>>     </sequence>
>>
>>     Paul
>>
>>
>>     -- 
>>     Paul Fremantle
>>     VP/Technology, WSO2 and OASIS WS-RX TC Co-chair
>>
>>     http://bloglines.com/blog/paulfremantle
>>     paul@wso2.com <mailto:paul@wso2.com>
>>
>>     "Oxygenating the Web Service Platform", www.wso2.com
>>     <http://www.wso2.com>
>>
>
> -- 
>
> Paul Fremantle
> VP/Technology, WSO2 and OASIS WS-RX TC Co-chair
>
> http://feeds.feedburner.com/bloglines/pzf
> paul@wso2.com
>
> "Oxygenating the Web Service Platform", www.wso2.com
> 


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