mirror of https://github.com/hashicorp/consul
77 lines
3.8 KiB
Markdown
77 lines
3.8 KiB
Markdown
---
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layout: "intro"
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page_title: "Introduction"
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sidebar_current: "what"
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description: |-
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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 how you can get started using it. If you are familiar with the basics of Consul, the documentation provides a more detailed reference of available features.
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---
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# Introduction to Consul
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Welcome to the intro guide to Consul! This guide is the best place to start
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with Consul. We cover what Consul is, what problems it can solve, how it compares
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to existing software, and how you can get started using it. If you are familiar
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with the basics of Consul, the [documentation](/docs/index.html) provides a more
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detailed reference of available features.
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## What is Consul?
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Consul has multiple components, but as a whole, it is a tool for discovering
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and configuring services in your infrastructure. It provides several
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key features:
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* **Service Discovery**: Clients of Consul can _provide_ a service, such as
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`api` or `mysql`, and other clients can use Consul to _discover_ providers
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of a given service. Using either DNS or HTTP, applications can easily find
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the services they depend upon.
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* **Health Checking**: Consul clients can provide any number of health checks,
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either associated with a given service ("is the webserver returning 200 OK"), or
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with the local node ("is memory utilization below 90%"). This information can be
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used by an operator to monitor cluster health, and it is used by the service
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discovery components to route traffic away from unhealthy hosts.
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* **KV Store**: Applications can make use of Consul's hierarchical key/value
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store for any number of purposes, including dynamic configuration, feature flagging,
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coordination, leader election, and more. The simple HTTP API makes it easy to use.
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* **Multi Datacenter**: Consul supports multiple datacenters out of the box. This
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means users of Consul do not have to worry about building additional layers of
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abstraction to grow to multiple regions.
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Consul is designed to be friendly to both the DevOps community and
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application developers, making it perfect for modern, elastic infrastructures.
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## Basic Architecture of Consul
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Consul is a distributed, highly available system. This section will cover the
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basics, purposely omitting some unnecessary detail, so you can get a quick
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understanding of how Consul works. For more detail, please refer to the
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[in-depth architecture overview](/docs/internals/architecture.html).
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Every node that provides services to Consul runs a _Consul agent_. Running
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an agent is not required for discovering other services or getting/setting
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key/value data. The agent is responsible for health checking the services
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on the node as well as the node itself.
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The agents talk to one or more _Consul servers_. The Consul servers are
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where data is stored and replicated. The servers themselves elect a leader.
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While Consul can function with one server, 3 to 5 is recommended to avoid
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failure scenarios leading to data loss. A cluster of Consul servers is recommended
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for each datacenter.
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Components of your infrastructure that need to discover other services
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or nodes can query any of the Consul servers _or_ any of the Consul agents.
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The agents forward queries to the servers automatically.
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Each datacenter runs a cluster of Consul servers. When a cross-datacenter
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service discovery or configuration request is made, the local Consul servers
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forward the request to the remote datacenter and return the result.
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## Next Steps
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* See [how Consul compares to other software](/intro/vs/index.html) to assess how it fits into your
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existing infrastructure.
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* Continue onwards with the [getting started guide](/intro/getting-started/install.html)
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to get Consul up and running.
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