Today I am announcing the first official version of EnnoDB, a new entry in the busy field of NoSQL databases. It’s goal is not to be a tool for Big Data problems, but more for the Medium to Small Data that fits into memory.
I originally wrote this software as an exercise, but it got out of hand and became actually useful. In other words, you may want to think twice before using this with mission-critical data. I wouldn’t, and I wrote the thing!
Source code is available on github under a BSD style license.
Core Features
- fast, in-memory database
- fastcgi interface
- accessible through HTTP API
- journaled database
EnnoDB is fast because it keeps the entire database in memory. It uses djb’s critbit trees as its internal data structure, which means that even though it only handles a single request at a time, each request is extremely short.
Example Usage
I set up a quick JavaScript example that reads and writes values from the database running on my home server, at http://enno.kn-bremen.de/keyval.html.
Much like the now defunct openkeyval.org, this means all keys in this example database are world writable. Though you could use this instance of EnnoDB for your own web projects, I do not recommend that anyone store any data here that they rely on.
Acknowledgements
This project would not have happened without the inspiration from openkeyval.
Daniel J Bernstein published the paper about the critbit tree data structure that makes all this happen so quickly.
Katelyn Gadd kept nagging me to finish this, when it was still just a pipe dream.
The Raspberry Pi that I used for developing and running the server is a fantastic little machine, and its specs encouraged the compact, memory-efficent design.
History
First of all, yes, the name is a pun. We were converting database tables from myISAM to InnoDB at IMVU one day, and I kept hearing my name come up in conversations around me, only to realize that it was not a mispronunciation of Enno (which I am used to), but the name of a MySQL table format. And so I made the joke that, if I were to one day create my own database, it would have to be called EnnoDB, as payback.
Some time later, I was reading djb’s paper on critbit tries, and decided to implement my own C version of his idea for fun. This worked out well, and in doing so I realized that it could not just be used for fast prefix searches, but fast string lookups in general. Anyone who ever wrote a std::map<std::string, int> and cringed when they thought of what was really going on when they looked up a customer id by name will understand why that was an exciting prospect.
These two ideas together, that I should some day write my own database, and that I knew how to do fast key-value lookups, combined when I learned about FastCGI. During a period of low-intensity work I sat down to teach myself libfcgi so I could put it all together, and here we are.