76 lines
3.6 KiB
Markdown
76 lines
3.6 KiB
Markdown
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---
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layout: "intro"
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page_title: "Introduction"
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sidebar_current: "what"
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---
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# Introduction to Terraform
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Welcome to the intro guide to Terraform! This guide is the best place to start
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with Terraform. We cover what Terraform is, what problems it can solve, how it compares
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to existing software, and a quick start for using Terraform. If you are already familiar
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with the basics of Terraform, the [documentation](/docs/index.html) provides more
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of a reference for all available features.
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## What is Terraform?
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Terraform 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 Terraform can _provide_ a service, such as
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`api` or `mysql`, and other clients can use Terraform 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**: Terraform 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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* **Key/Value Store**: Applications can make use of Terraform'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, etc. The simple HTTP API makes it easy to use.
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* **Multi Datacenter**: Terraform supports multiple datacenters out of the box. This
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means users of Terraform do not have to worry about building additional layers of
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abstraction to grow to multiple regions.
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Terraform 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 Terraform
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Terraform is a distributed, highly available system. There is an
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[in-depth architecture overview](/docs/internals/architecture.html) available,
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but this section will cover the basics so you can get an understanding
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of how Terraform works. This section will purposely omit details to quickly
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provide an overview of the architecture.
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Every node that provides services to Terraform runs a _Terraform 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 _Terraform servers_. The Terraform servers are
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where data is stored and replicated. The servers themselves elect a leader.
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While Terraform can function with one server, 3 to 5 is recommended to avoid
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data loss scenarios. A cluster of Terraform servers is recommended for each
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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 Terraform servers _or_ any of the Terraform agents.
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The agents forward queries to the servers automatically.
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Each datacenter runs a cluster of Terraform servers. When a cross-datacenter
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service discovery or configuration request is made, the local Terraform 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 the page on [how Terraform compares to other software](/intro/vs/index.html)
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to see how it fits into your existing infrastructure. Or continue onwards with
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the [getting started guide](/intro/getting-started/install.html) to get
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Terraform up and running and see how it works.
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