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Michael Zucchi

 B.E. (Comp. Sys. Eng.)

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Monday, 06 July 2015, 19:00

the future is micro?

Although i haven't been terribly active on it i've still been regularly mulling over a few ideas about the future of the stuff i did on google code, and this blog.

My plan some time ago was to setup a personal server locally - it wouldn't handle much traffic but I never got terribly much - and this is still the plan. The devil is of course in the details. If it turns out to be inadequate I can always change to something else later but given the site history I find this unlikely.

This choice is also intentionally something of a political one. Centralised control of information is becoming a significant societal problem and with the cheap availability high speed internet, computing power, and storage provides a means to tackle it head on via decentralisation.

Micro-Server

So after a few small experiments and mostly in-head iterations i've settled on a implementing stand-alone micro-server with an embedded db. I was going to play with JAX-RS for it but the setup required turned me off it. I think the tech is great and the setup is necessary but I just don't need it here. I have the knowledge and skills to do almost everything myself but at least initially i'm going to use the JavaSE bundled http server with berkeley db je as the transactional indexing and storage layer.

After many iterations I have designed an almost trivial schema of 3 small core tables which sits atop JE which allows me to implement a complex revision history including branches and renames. Think more of a `fixed' cvs rather than subversion; copies aren't the basis of everything and therefore aren't `cheap', but branching and especially tagging is (revisions are global like svn). Earlier prototypes supported both cheap copies and branching but i felt they lead to unworkable cognitive complexity and I realised that since I think the subversion approach just isn't a good solution at all I should not even try to support it. The work I did on DEZ-1 was for this history database and revisions are stored using reverse deltas. Although this is not the aim or purpose it should be possible to import a full cvs or subversion revision tree and retrieve it correctly and accurately; actually I will likely implement some of this functionality as a basis of testing as this is the easiest way to obtain effectively unlimited test data.

Atop this will sit a wiki-like system where nodes are referenced by symbolic name and/or branch/revision. Having a branch-able revision tree may allow for some interesting things to be done: or it may just collapse in an unscalable heap. Binary data will be indexed by the db but storage may be external and/or non-delta where appropriate.

From very long ago I was keen on using texinfo as the wiki syntax; i'm still aiming for this although it will mean a good deal of work converting the blog and posts over even if automated. The syntax can be a bit verbose and unforgiving though so i'll have to see how it works in practice. There are some other reasons i'm going this route although it is unclear if they will prove useful or not yet; some potential examples include pdf export, response optimisation, and literate programming. Its likely i'll end up with pluggable syntax anyway.

The frontend will be mostly be html+css and perhaps small amounts of javascript; but it's not going to be anything too fancy initially because I want to focus on the backend systems. Authoring is likely to be through external command line and/or desktop tools because I find the browser UX of even the most sophisticated applications completely shithouse and the effort i can afford them would render any I made even more pathetic.

The project itself will also be a personal project: it will be Free Software (AGPL3) and maybe someone else will find it interesting but providing a reference product for others isn't a goal.

Living prototype

This project actually started years ago as everything from a C based bdb prototype to a JavaEE learning exercise. In the distant past I have ummed and ahhed over whether it should be absolute bare-bones C or full-blown JavaEE. I think it may well never get much beyond these experiments but unless I start it definitely will not. So I thought it's about time to put a stake in the ground and get moving beyond experimentation.

So my latest current plan is to begin with implementing my internode software pages. A read-only version covers the basic response construction, namespace and paths, and file and image serving mechanisms. Then moving on to authoring touches on revision and branch management. Adding a news system will allow this blog to be moved across. Comments would make sense at this stage but aren't trivial if moderated, as I would desire. This is most of the meat and would also allow some version of the google code stuff to make it across. Then I could think about what next ...

The idea would be to go live as soon as I get anything working and just continue working on it 'live'; availability not guaranteed. A system in constant pre-alpha, beta, production.

I'm pretty sure i've got the base of the revision systems working quite well. Object names (& other metadata) and object data history are tracked separately which allows for renames and version specific meta-data. It's actually so simple i'm not quite sure it will support everything I need but every use-case i've tried to test so far has been solvable once I determined the correct query. I've still to get a few basic things like delete implemented but these are quite simple and the hardest part now is just deciding on application level decisions like namespaces and path conventions. Other application level functionality like merging is something for later consideration and doesn't need implementing at the db layer. I still need to learn some JE details too.

Initially the architecture will be somewhat naive but once I see how things start to fall out I want to move to a more advanced split-tier architecture based on messaging middleware. This is a long term plan though. I will aim for scalability and performance but am not aiming for "mega"-scalability as that is simply out of scope. Things like searching (lucene) and comments can be tacked on later. Being a personal server authentication/authorisation and other identity related security systems aren't an initial focus.

I've done the texinfo parsing a few times and my current effort is still some way from completion but i will probably just start with the basics and grow it organically as I need more features and only worry about completeness or exporting later on. I will start with processing everything live but resort static snapshots if it proves too burdensome for the server. Actually the revision tree provides the perfect mechanism for efficiently implementing incremental snapshots so it will probably just fall out of testing stuff anyway.

The why of the what

I was prompted to think about this again by the only request about jjmpeg source i've had and i'm also in the middle of a 2-week break. I've spent a couple of those break days poking around but so far it hasn't really gotten it's teeth into me so it will continue to be a slow burn (and i really do just want a short break).

Apart from setting up the hardware and deciding on some `simple' decisions i'm quite close to having something running.

Tagged hacking, java, java ee.
Wednesday, 04 April 2012, 12:02

Web N Shit ... N Stuff.

Hmm, so i've been poking away at webifiying[sic] our client's application.

Overall i'm making pretty good progress: worked out the async ajax stuff / XMLHttpRequest, 'hidden' form submission, RESTful resource mapping, handling long-running tasks and so on. The Enterprise bean stuff is pretty good, and particularly things like JMS, all the bean types, jax-rs, and jaxb. The latter two helping to hide some of the horrible shit going on under the bonnet.

But I dunno ... it's just boring. I probably would've found this stuff neat 5 years ago, and had a puppy over it 15 years ago, but now it's still enough of a pain in the arse having to deal with that given a choice I wouldn't be doing it.

Probably help if i'd had more than 4 hours sleep each day this week ...

Tagged hacking, java, java ee.
Thursday, 29 March 2012, 15:48

Web N Shit

So, as inevitably happens, the client wants to look at some mobile interface to some of the application we have.

Which for various reasons at the moment, means: web/html5/all that jazz. Fortunately someone else is working on the browser stuff so I get to avoid javascript ...

I get to play on the backend, so that means Java EE 6 ... Boy it's been a long time since I used any of this. Well I had a play with a wiki/documentation system a couple of years ago for fun but the last time I was paid to work on it was around 12 years ago: you know back when CORBA was mentioned on the first page ...

Java EE 6 has a fairly sleep learning curve - and a lot of reading required - but so far i'm pretty impressed. As you might imagine, with a decade of maturity behind it, there is a good bit of polish in the design. Some of the errors you get from the implementations could be a bit more meaningful though - array index out of bounds exception because one didn't specify proper attributes on the class or method don't help much. So after a couple of days of swearing violently ... it starts to fall into place really well.

I knew this was coming so for the last month or so I'd been re-architecting the desktop application in a more tiered and re-usable fashion so much of the jax-rs interface just slotted straight over the top with only a couple of lines of code for each request type. But that's the easy stuff: I also need long-running async tasks, so thats another big chunk of api to get to grips with.

Tagged hacking, java, java ee.
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