0x06. Consul

Introduction to Consul

What is Consul

Consul is a Hashicorp based tool for discovering and configuring a variety of different services in your infrastructure. It is based and built on Golang. One of the core reasons to build Consul was to maintain the services present in the distributed systems. Some of the significant features that Consul provides are as follows.

The key features of Consul are:

• Service Discovery

  Clients of Consul can register a service, such as api or mysql, and other clients can use Consul to discover providers of a given service. Using either DNS or HTTP, applications can easily find the services they depend upon.

• Health Checking

  Consul clients can provide any number of health checks, either associated with a given service ("is the webserver returning 200 OK"), or with the local node ("is memory utilization below 90%"). This information can be used by an operator to monitor cluster health, and it is used by the service discovery components to route traffic away from unhealthy hosts.

• KV Store

  Applications can make use of Consul's hierarchical key/value store for any number of purposes, including dynamic configuration, feature flagging, coordination, leader election, and more. The simple HTTP API makes it easy to use.

• Secure Service Communication

  Consul can generate and distribute TLS certificates for services to establish mutual TLS connections. Intentions can be used to define which services are allowed to communicate. Service segmentation can be easily managed with intentions that can be changed in real time instead of using complex network topologies and static firewall rules.

• Web UI

  Consul provides its users a beautiful web interface using which it can be easy to use and manage all of the features in consul.

• Multi Datacenter

  Consul supports multiple datacenters out of the box. This means users of Consul do not have to worry about building additional layers of abstraction to grow to multiple regions.

Service Discovery

Service discovery is one of the most important feature of Consul. It is defined as the detection of different services and network protocols using which a service is found. The usage of service discovery comes in as a boon for distributed systems. This is one of the main problems, which are faced by today's large-scale industries with the advancement of distributed systems in their environment.

Comparison with Etcd and Zookeeper

When we look at other service discovery tools in this domain, we have two popular options. Some major players in the software industry have been using it in the past. These tools are Etcd and Zookeeper.

Let us consider the following table for comparing different aspects of each tool. We will also understand what each one of them uses internally.

Properties	Consul	Etcd	Zoo Keeper
User Interface	Yes	No	No
RPC	Yes	Yes	No
Health Check	HTTP API	HTTP API	TCP
Key Value	Yes	Yes	Yes
Language	Go	Go	Java

Credits

• https://www.consul.io/intro/index.html
• https://www.tutorialspoint.com/consul/consul_introduction.htm