Terraform vs.Ansible : Key Differences and Comparison of Tools
BothTerraform andAnsible are DevOps tools, but how do these DevOps tools differ? In short,Terraform is an open-source, Infrastructure as Code platform, whileAnsible is an open-source configuration management tool focused on the configuration of that infrastructure.
It is often a topic of discussion about whether one should useTerraform orAnsible for infrastructure management Fortunately, there is an answer that lies in the Grey area This answer seems the same when asked to people who have working experience on both the tools
This post highlights similarities betweenTerraform andAnsible, explores the differences and concludes with the best way to manage infrastructure
Similarities
At a very high level, given the capabilities of both the products,Terraform andAnsible come across as similar tools Both of them are capable of provisioning the new cloud infrastructure and configuring the same with required application components.
BothTerraform andAnsible are capable of executing remote commands on the virtual machine that is newly created This means, both the tools are agentless There is no need to deploy agents on the machines for operational purposes.
Terraform uses cloud providerAPIs to create infrastructure and basic configuration tasks are achieved using SSH The same goes withAnsible – it uses SSH to perform all the required configuration tasks.The “state” information for both does not require a separate set of infrastructure to manage, thus both the tools are masterless
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Differences
The previous section gives an overview of the two tools in their broadest similarities.At a high level, it sounds like bothTerraform andAnsible are capable of provisioning and configuration management However, a deeper dive into them makes us realize the benefits of one over the other in certain areas
In general, both the tools are great in their own ways They have an overlap of functions when it comes to infrastructure management Infrastructure management broadly encompasses 2 aspects – orchestration and configuration management.
Terraform andAnsible have their own ways of managing both – with strong and weak points when it comes to overlaps Thus, it is important to delve into some details of both the tools to make a “perfect” choice or a combination with boundaries.
1) Orchestration vs. Configuration Management
Orchestration/provisioning is a process where we create the infrastructure – virtual machines, network components, databases, etc Whereas, on the other hand, configuration management is a process of automating versioned software component installation, OS configuration tasks, network and firewall configuration, etc
BothTerraform andAnsible are capable of performing both tasks However,Terraform offers a comprehensive solution to manage infrastructure Terraform uses cloud providerAPIs to provision and de-provision the infrastructure based on declared resources.
Ansible, on the other hand, is also capable of provisioning the cloud infrastructure but it is not comprehensive enough It is mainly geared towards configuration management Configuration management is a process of keeping the applications and dependencies up to date This is whereAnsible really shines as compared toTerraform
Both the tools can perform both kinds of activities. However, there are limitations when implementing configuration management usingTerraform, and infrastructure automation usingAnsible They are not flexible enough when it comes to complex infrastructure management
Logically, we can identify orchestration as Day 0 activity and configuration management as Day 1 activity Terraform works best for Day 0 activities andAnsible for Day 1 and onwards activities
2) Declarative vs. Procedural
Terraform is used to write Infrastructure as Code (IaC) It uses HCL(Hashicorp Configuration Language) which is declarative in nature It doesn’t matter in which sequence the code is written.The code could also be dispersed in multiple files.
No matter how you write the code,Terraform identifies the dependencies, and provisions infrastructure Writing or translating existing infrastructure to code is easy inTerraform Check thisTerraform import tutorial if you would like to know more about importing infrastructure underTerraform management
Ansible usesYAMLsyntax to define the procedure to perform on the target infrastructure. AnsibleYAMLscripts are procedural in nature – meaning when you write the script, it will be executed from top to bottom
Ansible scripts are called “ansible playbooks“. When you have to perform certain series of tasks, you define the same in the playbook The tasks will be performed in the sequence they are written For example, to install anApache server on the given virtual machine as a root user, you would have to write the user creation step before defining the task for installation.
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3) Mutable vs. Immutable
Application deployment workflow involves provisioning of the infrastructure and installing the right version of source code and dependencies on the provisioned infrastructure.
Mutability is an attribute associated with the underlying infrastructure that defines the way newer versions of applications and services are deployed. Deployment either takes place on existing infrastructure, or we can provision a completely new set of infrastructure for the same
The deployment practices typically determine whether the infrastructure is mutable or immutable When newer versions of applications are released on the same infrastructure, it is called mutable However, if the deployment happens on completely new infrastructure during releases, it is said to be immutable
Mutability seems convenient, but the risk of failure associated with it is higher When application configurations are re-applied on the same infrastructure, there are additional steps of uninstalling the previous version and then installing the desired version. More steps also introduce more chances of failure Doing this for a fleet of servers can result in uneven configurations and unpredictable behavior
Instead, if we focus on reducing these number of steps by ignoring the uninstallation procedure and performing the installation on new infrastructure resources – we get a chance
to test and revert the new deployment in case of failure Treating infrastructure as immutable in this way provides greater control over introducing changes.
However, there is no golden rule defined that advocates one approach over the other
SinceTerraform’s strength lies in handling the infrastructure lifecycle, it supports infrastructure immutability better It is easier to provision a completely new set of infrastructure and deprovision the older set usingTerraform However, handling configuration changes are not something that can be done in the most efficient manner
As far as the configuration changes are concerned,Ansible wins the race since it is primarily a configuration management tool Ansible supports infrastructure immutability by offering VM image creation. However, maintaining these additional images requires additional efforts.
It is recommended to follow the immutable infrastructure approach, whereTerraform takes care of the infrastructure management, andAnsible helps apply the changed configuration This is also known as the Blue/Green deployment strategy, where the risk of configuration failure is reduced
4) State Management
Terraform manages the entire lifecycle of the resources under its management It maintains the mapping of infrastructure resources with the current configuration in state files State management plays a very important role inTerraform.
States are used to track changes to the configuration and provision the same It is also possible to import existing resources underTerraform management by importing the real-world infrastructure in state files.
At any given time, it is possible to query theTerraform state files to understand the infrastructure component and their attributes currently available.
As opposed to this,Ansible does not support any lifecycle management SinceAnsible mainly deals with configuration management and considering it defaults to immutable infrastructure, any changes introduced in the configuration are executed automatically on the target resource
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