On 22 Jan 2013, at 20:11, Paul Robinson <[email protected]> wrote:

>> I learnt to love observers on the biggest project I've ever been involved 
>> with (Python, with no web stuff in sight), which was very SOA, with 7 
>> different services sending messages to each other over a home grown message 
>> bus.
> 
> How synchronous did this message passing need to be? That sounds like for our 
> application a deep dive into latency hell if not managed carefully.

It varied. Some services didn't really need to handle their work and spit 
messages onto the message bus particularly quickly, while others needed to act 
fast as the consequences of their actions were reflected immediately in the UI 
of a desktop app (which was itself one of the 7 services).

Where latency was an issue we had the option to take an RPC approach 
(essentially the observer pattern again, but over the network), but because 
resilience and the need to keep processing incoming data was important 
(irrespective of whether the GUI was able to keep up), we used it very 
sparingly.

> I'm already fighting that on one part of the setup with some controller 
> actions on the website needing tens of seconds to do their thing.

That sounds like it needs re-doing; is the task suitable for a background job?

>> Would it be easy to flesh out what the system does, and what the various 
>> services involved are responsible for?
> 
> It might be difficult to do that on a public list and to maintain commercial 
> confidences. Are you likely to be at an LRUG or NWRUG any time soon?

I'll be at the next NWRUG (21st Feb). Not planning on being in London again for 
at least a few weeks, but I am due a trip in a month or so. It's unlikely to 
coincide with LRUG though.

If you're up in Manchester feel free to drop into the office for half an hour. 
An off list email is also fine, but it's not the most likely route to me making 
relevant suggestions!

Graham

--
Graham Ashton
Founder, The Agile Planner
http://www.theagileplanner.com | @agileplanner | @grahamashton




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