Skip to main content

Asyncronous Database Records

Through persistance systems, notably Divmod's Axiom project, i have been experimenting with the idea of asyncronous request of items which may or may not exist for some time. The idea is an abstraction of a terrible first idea for "persistant deferreds," which my very suggestion of lead to horrible responses over in #twisted, but well deserved, I now believe.

The concept is similar but perhaps simplified for the limitations and complications involved. Operations may return an "asyncronous item," which in my implementation is done by an Item implementing the IAsyncronousOperation ("operation" may be replaced with "Item") interface. This is akin to returning a deferred. The item allows the caller to control the response to the availability of the item, but in a way that can survive server crashes and reboots, and is otherwise a persistant record, and not an emphemeral object.

Borrowing additionally from Twisted, the asyncronous results can support both positive and negative handlers, set for managing the result as success or error. The creation of these handlers constitutes an additional asyncronous result, which can be used to chain handlers, akin to the callback chains of Twisted. In the event that the requested item is ready, which is either immediately or in the future, the appropriate handler is called and the asyncronous result handlers are cleaned up.

I will release the code soon, when the rest of the unittests are complete and an example usecase can demonstrate the usefulness. I have gotten some negative reaction from this one, and I really hope it can be attributed to misconceptions of my intent and failure to consider the right usecases. Hopefully I can remedy this.

Comments

mrshoe said…
Shouldn't everything persist through server crashes, power outages, and restarts? Check out http://www.capros.org/.
Josiah Carlson said…
That sounds a bit like a trigger plus a stored procedure in a database with callback registration. But maybe I'm over-thinking it.

Popular posts from this blog

On Pruning Your Passions

We live in a hobby-rich world. There is no shortage of pastimes to grow a passion for. There is a shortage of one thing: time to indulge those passions. If you're someone who pours your heart into that one thing that makes your life worthwhile, that's a great deal. But, what if you've got no shortage of interests that draw your attention and you realize you will never have the time for all of them?

If I look at all the things I'd love to do with my life as a rose bush I'm tending, I realize that careful pruning is essential for the best outcome. This is a hard lesson to learn, because it can mean cutting beautiful flowers and watching the petals fall to the ground to wither. It has to be done.

I have a full time job that takes a lot of my mental energy. I have a wife and a son and family time is very important in my house. I try to read more, and I want to keep up with new developments in my career, and I'm trying to make time for simple, intentional relaxing t…

The Insidiousness of The Slow Solution

In software development, slow solutions can be worse than no progress at all. I'll even say its usually worse and if you find yourself making slow progress on a problem, consider stopping while you're a head.

Its easy to see why fast progress is better: either you solve the problem or you prove a proposed solution wrong and find a better one. Even a total standstill in pushing forward on a task or a bug or a request can force you to seek out new information or a second opinion.

Slow solutions, on the other hand, is kind of sneaky. Its insidious. Slow solution is related the Sunk Cost Fallacy, but maybe worse. Slow solutions have you constantly dripping more of your time, energy, and hope into a path that's still unproven, constantly digging a hole. Slow solutions are deceptive, because they still do offer real progress. It is hard to justify abandoning it or trying another route, because it is "working", technically.

We tend to romanticize the late night hacking…

Why I Switched From Git to Microsoft OneDrive

I made the unexpected move with a string of recent projects to drop Git to sync between my different computers in favor of OneDrive, the file sync offering from Microsoft. Its like Dropbox, but "enterprise."

Feeling a little ashamed at what I previously would have scoffed at should I hear of it from another developer, I felt a little write up of the why and the experience could be a good idea. Now, I should emphasize that I'm not dropping Git for all my projects, just specific kinds of projects. I've been making this change in habit for projects that are just for me, not shared with anyone else. It has been especially helpful in projects I work on sporadically. More on why a little later.

So, what drove me away from Git, exactly?

On the smallest projects, like game jam hacks, I just wanted to code. I didn't want to think about revisions and commit messages. I didn't need branching or merges. I didn't even need to rollback to another version, ever. I just …