Sunday, 28th February 2010
kriszyp’s node-promise. Another elegant approach to managing asynchronous flows in Node, including running things both in parallel and serial.
ClearMaps: A Mapping Framework for Data Visualization. An open source library for map visualisations using ActionScript, with an Adobe AIR based encoding tool for translating data from shapefiles in to vector data suitable for use with the library.
Unit Testing Achievements. A plugin for Python’s nose test runner that adds achievements—“Night Shift: Make a failing suite pass between 12am and 5am.”
Johnny Cache. Clever twist on ORM-level caching for Django. Johnny Cache (great name) monkey-patches Django’s QuerySet classes and caches the result of every single SELECT query in memcached with an infinite expiry time. The cache key includes a “generation” ID for each dependent database table, and the generation is changed every single time a table is updated. For apps with infrequent writes, this strategy should work really well—but if a popular table is being updated constantly the cache will be all but useless. Impressively, the system is transaction-aware—cache entries created during a transaction are held in local memory and only pushed to memcached should the transaction complete successfully.
Node.js, redis, and resque (via) Paul Gross has been experimenting with Node.js proxies for allowing web applications to be upgraded without missing any requests. Here he places all incoming HTTP requests in a redis queue, then has his backend Rails servers consume requests from the queue and push the responses back on to a queue for Node to deliver. When the backend application is upgraded, requests remain in the queue and users see a few seconds of delay before their request is handled. It’s not production ready yet (POST requests aren’t handled, for example) but it’s a very interesting approach.
Notes from a production MongoDB deployment. Notes from running MongoDB for 8 months in production, with 664 million documents spread across 72 GB master and slave servers located in two different data centers.