This document provides an overview of getting started with Consul, including: 1. Consul is a tool for discovering and configuring services that is built on Golang and uses 3 basic ports for RPC, HTTP, and DNS. 2. It features service discovery, health checking, key/value storage, and multi-datacenter support. 3. Setup involves downloading the Consul binary, running the agent, and using commands like "consul members" and "consul join" to manage nodes.

1. Getting Started with Consul
Ramit Surana @ramitsurana /in/ramitsurana

2. Agenda
• Introduction
• Consul Architecture
• Raft Algorithm
• Comparisons
• Setup
• How to use it ?
• Bootstrapping and DNS
• Jespen Testing
• Consul on AWS

3. Introduction
• Tool for discovering and
configuring a variety of different
services in your infrastructure.
• Built on Golang.
• 3 basic ports:
8400 - RPC
8500 - HTTP
8600 - DNS

4. Features
• Service Discovery − Using either DNS or HTTP, applications can easily find the
services they depend upon.
• Health Check Status − It can provide any number of health checks. It is used
by the service discovery components to route traffic away from unhealthy
hosts.
• Key/Value Store − It can make use of Consul's hierarchical key/value store for
any number of purposes, including dynamic configuration, feature flagging,
coordination, leader election, etc.
• Multi Datacenter Deployment − Consul supports multiple datacenters. It is
used for building additional layers of abstraction to grow to multiple regions.
• 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.

5. Consul Architecture

6. Raft Algorithm

7. Comparison between etcd, zookeeper & consul

8. Setup
• Download consul from https://www.consul.io/downloads.html
• Extract binary package from the downloaded folder.
$ cd Downloads
$ chmod +x consul
$ sudo mv consul /usr/bin/

9. Consul-Template
• Daemon that queries the Consul instance and updates any number of
specified templates on the file system.
• Download & Extract from https://releases.hashicorp.com/consul-
template/.
$ cd Downloads
$ chmod +x consul-template
$ sudo mv consul-template /usr/share/bin/

10. Consul-UI
• Divided into three important parts, which are −
ACL − Set of Rules to easily lock your clusters easily
Datacenter − Enables you to easily manage datacenters and work out with your cluster.
Nodes − Quick update on the nodes that Consul cluster is using
$ mkdir /opt/consul-ui
$ cd /opt/consul-ui
$ wget https://releases.hashicorp.com/consul/0.7.2/consul_0.7.2_web_ui.zip
$ unzip consul_0.7.2_web_ui.zip
$ sudo consul agent -dev -ui -data-dir /tmp/consul

11. How to use it ?
• //Running Consul
$ sudo consul agent –dev –data-dir=/tmp/consul
• // Listing members
$ consul members
• // Joining Nodes
$ consul join <Node1><Node2>
• // Using Docker
$ docker run –p 8400:8400–p 8500:8500–p 8600:53/udp-h node1 progrium/consul -
server -bootstrap

12. How to use it ?
• //Running Consul UI
$ docker run –p 8400:8400–p 8500:8500–p 8600:53/udp-h node1 progrium/consul -
server –bootstrap –ui-dir /ui
• // Digging
$ dig @127.0.0.1-p 8600 web.service.consul
• // Monitor
$ consul monitor
• // Watch
$ consul watch –type=service –service=consul

13. How to use it ?
• //Registering External Services on Consul
$ sudo curl -X PUT -d '{"Datacenter": "dc1", "Node": "amazon",
"Address": "www.amazon.com",
"Service": {"Service": "shop", "Port": 80}}'
http://127.0.0.1:8500/v1/catalog/register
• // Removing External Service
$ curl -X PUT -d '{"Datacenter": "dc1", "Node": "amazon"}'
http://127.0.0.1:8500/v1/catalog/deregister
• // Info
$ sudo consul info

14. Bootstrapping & DNS
• Bootstrapping can be divided into 2 parts:
Automatic Bootstrapping - Automatically configured to detect, identify and join
nodes.
Manual Bootstrapping – Manual addition of Nodes using below cmd
$ consul join <Node B Address> <Node C Address>
• DNS is served from port 53. The DNS forwarding can be done using BIND,
dnsmasq and iptables.
• Consul DNS interface makes the port information for a service available via
the SRV records.
• If Dnsmasq is installed - $ dig web.service.consul

15. Jespen Testing
• Tool written to test the partial tolerance and networking in any system.
• Written in Clojure.
• Tests the system by creating some random operations on the system.
• For demo, Jepsen testing requires a huge level of cluster formation
with database systems and hence is out of scope for demo

16. Consul on AWS
• URL: https://aws.amazon.com/quickstart/archit
ecture/consul/
• create the following components −
• A VPC with public and private subnets across
three Availability Zones.
• A Seed Consul server and a Seed client along
with two Auto Scaling groups.
• You can choose to create 3, 5, or 7 servers. The
number of clients is set to three by default, but
it is user-configurable.
• Dnsmasq, which is installed and configured for
Consul as part of the installation.
• A Consul cluster
using bootstrap_expect option.

17. Thank You :)