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WS-Eventing
WOW , I got a very polite response from an issue I reported ( see earlier article in Blog) with WS-Eventing. I wish work related bugs reports were handled so nicely.
I do disagree however it would have been nice to at least add this as Optional to the standard , though hope is not lost for a standard fast WS-Eventing as they may introduce it for WS-Topics. All it needs is a comment and then vendors will implement it as at the moment they do their own thing.
Here is the transcript.
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Can EDA SOA eventing systems be fast
A lot of traditional eventing systems use C++ and are dubious about whether the Lego block style SOA can provide sufficient performance.
Again it boils down to design
WCF C# can process over 22000 small messeges per second on an average 2 year old quad server. http://msdn.microsoft.com/en-us/library/bb310550.aspx#wcfperform_topic4.
This is more than sufficient for most applications especially as with eventing systems you can add servers relatively simply , the algorithms which manage the propogation of subscriptions and the path are far more important . ( Distributed Event-Based Systems (Muhl , Fiege and Pietzuch) is a good book which covers the theory here...
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EDAM -What is EDAM trying to do.
Just been working on EDAM ( my event driven architecture product) and wanted to note down and restate the long term goal (in addition to being a great eventing system).
The goal of EDAM is for people to be able to quickly add programs to the enterprise and to provide a fast event driven service to make this happen . Note i avoided the term framework as i want this to be usable with no dll linked though we will provide one later to make it even easier.
Remember when we used UNIX commands such as
cat file* | tr...
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Why should you use an Event Driven Architecture (EDA)?
There is a lot of documentation on EDA and people working with SOA and call backs will naturally gravitate to EDA , but i have often wanted a simple reason why. Here i will attempt this and focus on service based EDA's.
1. It Naturally mirrors organisations.
High level EDA events are business events. With EDA anybody may receive these events and act accordingly. This means extending events to new applications is a trivial excercise.
2. Low integration costs
Integration expenses are massive, EDA makes it really easy for systems to communicate even more so than SOA's which require writing a...
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EDA vs Cloud storage
Cloud storage promises a lot of the things that EDA does namely almost unlimited scaling however EDA implemented in the Cloud has significant advantages.
Firstly while Cloud storage Data may scale extremely well , it does so by using masses amounts of caching or disk spindles. In itself this is not an issue but if you have say 1,000,000 users querying/polling a 10 Gig Table While the performance is likely to be good the CPU usage will be massive and this is where cloud computing bites you - in the pocket. And the situations will get worse as data increases.
However EDA...
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Eventing with and without Topics
While WS-Eventing has no support for Topics ( see last post) it is almost essential for efficient processing of messages if you have a large amount of subscriptions.
Consider the case of 10,000 Subscriptions for 10,000 Notification you are looking at 10^8 expensive xPath comparisons which will bring many servers down to its knees.
With EDA we can easily solve this problem ( compare to an overloaded DB) .
Lets say we have a Topicless share pricing feed something like
<Trades>
<Trade>
<Symbol>BHP</Symbol>
<Price>38.12</Price>
<Volume>10000</Volume>
<Exchange>ASX</Exchange>
</Trade>
</Trades>
Now WS-Eventing has a really nice feature in that subscriptions can force notifications to contain a header this header can...