Building a Real-time SMS Voting App Part 1: Node.js and CouchDB | Hacker News Reader

Building a Real-time SMS Voting App Part 1: Node.js and CouchDB

twilio.com

44 pointscrabasa9 comments

Carter, you are a bad ass for putting your code up on Hacker News.

I'm not sure I'm a badass, but I think it's hard for many developers to subject their code to public scrutiny, especially when it's with a language that's outside of their wheelhouse.

I wrote this app to teach myself Node.js, CouchDB, Socket.io, HighCharts.js and bunch of other things that I really wanted to learn. I hope it's useful for people new to these things, and definitely appreciate all the feedback I'm getting from the community.

I'm anxiously waiting for the remaining parts. :)

Good article on building the node.js stack.

does the vote counter get incremented atomically?

Good question. Incoming votes get added to an in-memory array, which is then periodically flushed to the DB. During the flush, incoming votes are queued-up and aren't processed until the flush to the DB is complete.

Does that mean that when you implement visualization of voting data (in Part 2), there will be a small delay between the votes that have been cast and the votes that are being visualized? I have no experience with socket.io, so I am just asking out of curiosity.

<<I really wish I could edit my comments>>

Scratch my comment above, the caching and flushing is introduced in a future blog post. In this iteration of the code base, an attempt is made to save a vote to the DB. If it fails, it fails, there is no attempt to retry.

https://github.com/crabasa/votr-part1/blob/master/events.js#...

A comment was made about whether the vote persistence would be considered ACID. Most likely not! Each vote that comes in fetches a copy of the event document. If votes came in fast enough, this would create a problem.

However, rather than corrupting the data, I think the votes would simply fails since CouchDB uses a revision property to prevent this:

http://wiki.apache.org/couchdb/Document_revisions?action=sho...

Wow you are a brilliant hacker. How did you get so goods?

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