What's this NetKernel Thing Anyway?

What Is This NetKernel Thing

Anyway?

Darren CruseAugust 5, 2010

(for the Lambda Lounge of St. Louis)Wednesday, August 11, 2010

Preface(one slide answers all)

Wednesday, August 11, 2010

What’s This NetKernel Thing?• A “REST Based Microkernel”

• Written in Java

• Originally developed at HP Labs over 10 years ago

• Started life as an XML framework ala Cocoon

• Generalized over 4 versions into a general purpose “Resource Oriented Computing” framework (though it maintains esp. strong XML support).

• The main guys split off from HP and formed their own company called 1060 Research Limited

• It’s sold under a dual source license - i.e. free for open source projects, paid for commercial projects.


(that was the short answer - now the longer one)


Chapter 1:Lots of Computers

(macro)


In the Beginning There Was One Computer

• Plus a 300 baud modem

• I had hair

• Things were simple then (BASIC built in the ROM!)


State Of The Art

• 0.89 MHz Processor

• 4K RAM

• 192 x 128 Screen Resolution

• Audio Cassette Storage


And That Computer Begat Other Computers


And They Begat Some More...


And so on...


And so on...


And The World Became Awash(in computers)


They Climbed Into Our Pockets


And A Lot Had Changed.(Since The Time That I Had Hair)


But Not So Much AboutThe Way We Program


Chapter 2:Lots of Computers

(micro)


Dude -What Happened To 4 GHz?http://www.drdobbs.com/architecture-and-design/184405990


http://www.drdobbs.com/architecture-and-design/184405990


Moore No More?(nope - but it’s a different world)


“The Multi-Core Problem”

(http://www.drdobbs.com/architecture-and-design/184405990)

What This Means For Software: The Next RevolutionThe revolution in mainstream software development from structured programming to object-oriented programming was the greatest such change in the past 20 years, and arguably in the past 30 years. There have been other changes, including the most recent (and genuinely interesting) naissance of web services, but nothing that most of us have seen during our careers has been as fundamental and as far-reaching a change in the way we write software as the object revolution.

Until now.

Starting today, the performance lunch isn’t free any more. [...] But if you want your application to benefit from the continued exponential throughput advances in new processors, it will need to be a well-written concurrent (usually multithreaded) application. And that’s easier said than done, because not all problems are inherently parallelizable and because concurrent programming is hard.

Edited from: “The Free Lunch is Over”, Herb Sutter





Postscript to Chapters 1 & 2(in case it’s not obvious)

What’s the connection between “lots of computers on the network” (chapter 1) and “lots of cores on a cpu die” (chapter 2)?

The answer: Stuff running in Parallel


Chapter 3a:The Web


Chapter 3a:The Web

(of Lies and Deceit)


Actual made up conversationbetween Product Managers, Circa 2003

Lie #1

“Oh yeah the guys are using this new thing Service Oriented Architecture.

They put their software on a whole bunch of servers. That means it’s guaranteed to scale and have good performance and be like super super reliable.

It’s really simple it uses this new thing called SOAP. That stands for simple something or other. All they have to do is connect up these “service” things how hard could that be.

And they said something called REST I don’t what that is but it sounds easy too I guess it’s so easy the developers get to rest.

It’s going to save us lots of time and money it really sounds great.”


Chapter 3b:The Web

(for real this time)


The Web is a Very Successful “Distributed System” (with some very nice qualities)

✓ Flexibility★ It's fairly easy to rearrange things at the server/network level, e.g.

move a document (or dynamic “service”) from one node to another.

✓ Heterogenous Technologies★ Different servers can easily use different technologies (e.g. different

languages).

✓ Scalability★ In general, services scale easily, if they're stateless and placed behind

multiple machine clusters with load balancers.

✓ Availability / Ease of Deployment★ As long as you have at least two servers running the service, you can

hot deploy services leaving the old service running for a time while you're starting the new service ("rolling restart").


RESTful HTTP Based Services(bring the web’s benefits between servers)

Browser

AppServer

AppServer

Service 1

Service 1

Service 1

Service 2

load

balancer

balancer

balancer


NetKernel Modules and “Micro-Services”(bring the web’s benefits inside servers, as well as between)

Browser

load

balancer

balancer

balancer


So what are these granular services doing “inside” my program?

(revisiting those nice web qualities)

✓ More Flexibility★ Now there’s more opportunities to easily change things (e.g. change your

persistance strategy for some resource), often with just a configuration change.

★ And more opportunities to rearrange things on the network, e.g. moving a module to a different server and talking to it with some remote protocol instead of NetKernel’s in memory protocol.

★ Partly this is possible because of NetKernel’s caching which replicates local representations of remote resources just like a browser would (the reason it’s called “REpresentational State Transfer”! :).




✓ More Heterogenous Technologies★ Easily use and intermix many of the popular JVM languages within a single

application. Java, Javascript, Groovy, JRuby, Scala, Clojure (experimental), Beanshell, XSLT, XQuery, etc.

★ Add support for other languages if you’d like. Each language is supported by a module called a “language runtime” and you can write your own as an “adapter” for an existing tool. e.g. I added support for the Jakarta Velocity templating language and it wasn’t hard.

★ Language runtimes follow the same REST principles which the rest of the system does. e.g. In NetKernel, an XML file transformed to an HTML file via an XSLT is much the same as a Groovy source file transformed to a class file by the Groovy compiler runtime. Your groovy code will automatically be recompiled when you modify it just as your html will be updated when you modify the xml. This applies to any and all of NetKernel’s supported scripting languages.

★ As a consequence, under the new NetKernel Protocol you can even execute code on a remote NetKernel server that physically resides on your local server. This is not a feature “added on” to NetKernel so much as a natural consequence of it’s design.




✓ More Scalability★ NetKernel’s internal multi-threaded scheduler is to internal requests, as a

load balancer is to a web or application server.

★ Resource “representations” are immutable.

★ Accessor methods should be coded to be thread safe i.e. stateless.

★ More cpu cores mean more throughput / more simultaneous requests processed.

★ For faster response times, developers incorporate asynchronous requests to run sub-requests in parallel.

★ Third party libraries that are not thread safe can be wrapped in a module marked as such - in which case NetKernel will single thread them.

★ Representations that are not immutable can be locked explicitly - but this is not typical usage of NetKernel (it’s more of an escape hatch for bad code :).




✓ More Availability / Easier Deployment★ Modules can be hot deployed via the “Apposite” tool while a system is live and

running.

★ If problems are encountered the deployed module can be rolled back leaving just the original module.

★ Modules are versioned and clients to services can indicate the version(s) they desire.

★ This allows that multiple versions of the same module can be deployed simultaneously. e.g. A “stable version” and a “release candidate” version.


NETKERNEL CACHE (IN-MEMORY)

CORE “N”CORE 1

BUS

“CLOUD OF RESOURCES”

NETKERNEL CACHE (IN-MEMORY)

CORE “N”CORE 1

BUS

NETWORK

(and URIs are a sort of “machine independent” memory address)

The network really is the computer...


You sound like a used car salesman.(is this some kind of infomercial?)

“Just a note that I was skeptical of NetKernel until I tried it and got used to it a little bit.

It helped me see some things I hadn’t realized before which is how many lost opportunities I’d created in my “service oriented” system design because of how different I was doing things inside my code from the way things are done between the services.

To give a simple example, if I need to read a file in a program in java I typically write some code and use the File object to read the file. I don't use "file://" like we do from our browser. As a result, if I want to change where that information comes from, say read it from a blob in Oracle, or read it from an XML database, or maybe a better example: read it from another machine RESTFully using HTTP - each of those feel like a fairly serious change, but not when everything has a URI like in NetKernel.”

Darren Cruse, NetKernel Advocate (seriously)

and inventor of the “Ultra-Toe” Toe Nail Brightening System,the only toe nail brightening system with Toe-nail-isol!!


Thanks for listening.Reach me at:

[email protected]

Watch me blab at:http://bangthekeyboard.wordpress.com


mailto:[email protected]






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What's this NetKernel Thing Anyway?