Bytes #2: An introduction to Consul as a Key Value (KV) Store

If you have not heard of Hashicorp Consul before, then this bytes (short) post is going to be interesting!

Consul is an interesting software that has a lot of features, which is a boon and a bane I guess. One of the features it has is - it has a Key Value (KV) store

A Key Value (KV) store is a kind of data storage software that helps you store data in the form of key value pairs. In the programming languages world, if you are familiar with objects, hashes, hash tables or dictionary, it’s similar to that.

What are the use cases for key value stores? There are many, one that Consul mentions as an example for Consul KV store is - storing configuration and metadata.

Note that Consul KV store is a simple one, there are many complicated fully featured KV stores out there. You will have to choose your KV Store based on your use case if you are looking to use KV Stores in a production environment

A basic KV store visualization will look like a table like this -

When you store information, you store it in key-value pairs, where value is kind of like the main data and key is to find the data and retrieve the data. So, to retrieve data, you would provide the key as input to the system and get the value as the output

Let’s look at this in action using Consul KV store!

To run Consul in your local or any non production environment, simply download the Consul binary from here - https://www.consul.io/downloads

And then run it in your terminal

$ # check if it's installed
$ consul version
Consul v1.9.4
Revision 10bb6cb3b
Protocol 2 spoken by default, understands 2 to 3 (agent will automatically use protocol >2 when speaking to compatible agents)

$ # run it!
$ consul agent -dev

There will be a lot of logs from the program, you can ignore that as of now or else it can be overwhelming to understand it in the beginning itself. Consul is a long running program, it’s a server software, which provides Key Value (KV) store feature. Since it’s long running server software, the program will keep running until you stop it with Control + C or whatever keyboard shortcut is needed to kill foreground processes / programs

Now in another terminal use the consul program as a client software and try out the Consul KV store!

$ consul kv put redis_connections 5
Success! Data written to: redis_connections

$ consul kv get redis_connections 
5

In the above example redis_connections is an example configuration in an application that’s connecting to redis and has a maximum limit to the number of connections to a database called Redis.

This is just the surface of the Consul KV store features. I’ll talk about other features in another bytes post! :) Feel free to meddle around with the consul program, check it’s help and play with it! :D