Learning to Relax - CouchDB for beginners

In his presentation, Alan Hoffman, Co-Founder of Cloudant (hosted CouchDB) gives us an introduction to CouchDB. So what is CouchDB?

• Apache Project
• Written in Erlang
• Schema-free document database management system (like MongoDB)
• Robust, Concurrent and Fault-Tolerant
• RESTful JSON API
• Custom Persistent Views using MapReduce
• Bi-directional Increment Replication

So a couple of tidbits about CouchDB that I found interesting.

• Each document has a revision and under certain replication environments conflicts can occur
• Documents can have binary attachments
• Unlike some other RDBMS systems there is nothing to repair if the server crashes, just restart the server and you are back up and online
• Replication can be performed with one-click
• Multiple replication setups are available: Master-Slave, Master-Master and Robust Multi-Master
• Does not support ad-hoc queries, this is by design
• 1.0 is just around the corner

CouchDB Lounge is an open source proxy-based partitioning and clustering solution. It uses a combinatino of a smart and dumb proxy to add partitioning and cluster to CouchDB. Another option, which is being developed by Cloudant, is Open Cloudant which essentially tries to duplicate ring clustering like what is found in Amazon's Dynamo. According the slides this solution is "Coming soon to github near you" so keep a look out.

Polyglot Persistence, is it the future of application persistence?

In yesterday's post John Nunmaker discussed the future of persistence as it related to NoSQL. His thoughts were that application persistence would be hosted and would employ polyglot persistence. In today's post we are going to explore that last piece, polyglot persistence.

In his presentation at WindyCityDB, John P. Wood discusses polyglot persistence, what it is and how does it help?

Key points from the presentation:

• RDBMS is no longer the default choice, but it's not dead either
• We now have several choices in the NoSQL arena. Having choices is great. However, it means we must do the work to validate our tool of choice as the right one for the job. 

So what exactly is polyglot persistence?

The continued or prolonged existence of something using several databases.

Scott Lebnerknight is quoted in the presentation to reinforce this point:

Polyglot Persistence, like polyglot programming, is all about choosing the right persistence option for the task at hand.

One could assume this would be like using Grails for the UI portion of a web application and perhaps Java for other backed processes. So what does this mean? It means you that the default mode of large organizations will be to support multiple data stores.

Some organizations like Facebook and Twitter are already doing this. Specifically in both cases you see these organizations using MySQL, Cassandra and HBase for various aspects of there applications.

As John Wood beautifully summarizes why we do this:

Right tool for the job

Why is NoSQL so popular?

John Nunmaker, from Ordered List, presented the following presentation at WindyCityDB in Chicago a couple of days ago. After providing us with a reminder of the databases history he dives into NoSQL. Couple of highlights from that section:

• NoSQL technologies are development and operations friendly
• Moving from "How do we store?" to "How do we use"

What about the future? Well John sees two things:

• Hosted
• Polyglot Persistence

Unfortunately, we don't get to see John detail his thoughts on polyglot persistence. However, the idea is simple that applications will no longer use a single persistence layer. In theory and in my opinion this is what should be done right? Use the right tool for the job. It will be interesting as more applications adopt this strategy the issues it poses. We will explore ployglot persistence more in depth tomorrow.

Update: Here is the actual presenation on Vimeo (thanks to Ryan Briones for the link).