Problem Statement
To determine the best solution to provision infrastructure in a multi-datacenter environment.
Possible Solutions
Use Terraform or Ansible for infrastructure provisioning.
Solution Evaluations
Ansible is a very popular configuration management tool which can also be used to create and manage infrastructure. While Terraform is a orchestration tool, whose specific purpose is to create and manage infrastructure.
The major difference between them is that Ansible encourages a procedural style where you have to write code that specifies, step-by-step, how to achieve some desired end state. While Terraform uses a declarative style where you write code that specifies just your desired end state and Terraform figures out how to achieve that.
I referenced several open-source Ansible playbooks and modified the ansible-auto-scaling-tutorial playbook to create an Airavata API-Server autoscaling infrastructure on AWS. My observation upon using Ansible is that we have to manually write code that evaluates every variable/value of the existing deployment against the variables present in the configuration file and decide whether the configuration has changed and make changes accordingly. Ansible places a lot of responsibilty on the developer to make sure there aren’t any major bugs in the playbook that may result in an unstable infrastructure.
Comparatively Terraform standardizes this process and crowd sources this responsibilty of finding and fixes any potential bugs to the open-source community and devolpers using Terraform as a whole.
Terraform was evaluated in detail by Anuj visit https://anujbhan.github.io/blogs/DevOps-tool-Comparison.
Conclusion
Terraform seems to be the best choice for creating immutable infrastructure.
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