Architecture and Data Blog

When trying to evaluate NoSQL databases, its usually better to try them out. While trying them out, its better to use them with multiple node configurations instead of running single node. Such as clusters in Riak or Replica-set in mongodb maybe even a sharded setup. On our project we evaluated a 10 node Riak cluster so that we could experiment with N, R and W values and decide which values where optimal for us. In Riak here is what N, R and W mean.

There are multiple ways to take backups of mongodb is different configuraitions, one of the configuration that I have been involved recently is replica-sets. When mongodb is running in replica-set configuration, there is a single primary node and multiple secondary nodes. To take backup of the replica-set we can either do a mongodump of one of the nodes or shutdown one of the secondary nodes and take file copies, since in a replica-set all nodes have the same data (except arbiter). Lets see how we could deal with mongodump method of taking backup.

Replica sets is a feature of MongoDB for Automatic Failover, in this setup there is a primary server and the rest are secondary servers. If the primary server goes down, the rest of the secondary servers choose a new primary via an election process, each server can also be assigned number of votes, so that you can decide the next primary based on data-center location, machine properties etc, you can also start mongo database processes that act only as election tie-breakers these are known as arbiters, these arbiters will never have data, but just act as agents that break the tie.

In the No-SQL land schema-less is a power full feature that is advertised a lot, schema-less basically means you don’t have to worry about column names and table names in a traditional sense, if you want to change the column name you just start saving the data using the new column name Lets say you have a document database like mongoDB and you have JSON document as shown below.

{
"_id":"4bc9157e201f254d204226bf",
"FIRST_NAME":"JOHN",
"MIDDLE_NAME":"D",
"LAST_NAME":"DOE",
"CREATED":"2010-10-12"
}

You have some corresponding code to read the documents from the database and lets say you lots of data in the database in the order of millions of documents. If you want to change the name of some attributes or columns at this point and the new JSON would look like

We are using MongoDB on our project, since mongo is document store, schema design is somewhat different, when you are using traditional RDBMS data stores, one thinks about tables and rows, while using a document database you have to think about the schema in a some what different way. Lets say, we want to save a customer object, when using a RDBMS we would come up with Customer, Address, Phone, Email. They are related to each other as shown below.