mirror of https://github.com/hashicorp/consul
76 lines
3.5 KiB
Markdown
76 lines
3.5 KiB
Markdown
---
|
|
layout: "intro"
|
|
page_title: "Introduction"
|
|
sidebar_current: "what"
|
|
---
|
|
|
|
# Introduction to Consul
|
|
|
|
Welcome to the intro guide to Consul! This guide is the best place to start
|
|
with Consul. We cover what Consul is, what problems it can solve, how it compares
|
|
to existing software, and a quick start for using Consul. If you are already familiar
|
|
with the basics of Consul, the [documentation](/docs/index.html) provides more
|
|
of a reference for all available features.
|
|
|
|
## What is Consul?
|
|
|
|
Consul has multiple components, but as a whole, it is a tool for discovering
|
|
and configuring services in your infrastructure. It provides several
|
|
key features:
|
|
|
|
* **Service Discovery**: Clients of Consul can _provide_ 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.
|
|
|
|
* **Key/Value 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, etc. The simple HTTP API makes it easy to use.
|
|
|
|
* **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.
|
|
|
|
Consul is designed to be friendly to both the DevOps community and
|
|
application developers, making it perfect for modern, elastic infrastructures.
|
|
|
|
## Basic Architecture of Consul
|
|
|
|
Consul is a distributed, highly available system. There is an
|
|
[in-depth architecture overview](/docs/internals/architecture.html) available,
|
|
but this section will cover the basics so you can get an understanding
|
|
of how Consul works. This section will purposely omit details to quickly
|
|
provide an overview of the architecture.
|
|
|
|
Every node that provides services to Consul runs a _Consul agent_. Running
|
|
an agent is not required for discovering other services or getting/setting
|
|
key/value data. The agent is responsible for health checking the services
|
|
on the node as well as the node itself.
|
|
|
|
The agents talk to one or more _Consul servers_. The Consul servers are
|
|
where data is stored and replicated. The servers themselves elect a leader.
|
|
While Consul can function with one server, 3 to 5 is recommended to avoid
|
|
data loss scenarios. A cluster of Consul servers is recommended for each
|
|
datacenter.
|
|
|
|
Components of your infrastructure that need to discover other services
|
|
or nodes can query any of the Consul servers _or_ any of the Consul agents.
|
|
The agents forward queries to the servers automatically.
|
|
|
|
Each datacenter runs a cluster of Consul servers. When a cross-datacenter
|
|
service discovery or configuration request is made, the local Consul servers
|
|
forward the request to the remote datacenter and return the result.
|
|
|
|
## Next Steps
|
|
|
|
See the page on [how Consul compares to other software](/intro/vs/index.html)
|
|
to see how it fits into your existing infrastructure. Or continue onwards with
|
|
the [getting started guide](/intro/getting-started/install.html) to get
|
|
Consul up and running and see how it works.
|