Where does Ansible fit in a CI/CD pipeline?

In the CD (continuous delivery/deployment) part: after CI has built and tested the code, Ansible deploys it through review, staging and production.

* CI builds and tests the code; Ansible does the CD half, deploying through review, staging and production. *

A typical pipeline, for example with GitLab:

1. Code and commit: a developer pushes a change.
2. CI pipeline (continuous integration), e.g. GitLab + Docker: build the software, run unit tests and integration tests.
3. CD pipeline (continuous delivery/deployment), e.g. GitLab + Ansible: deploy to a review environment, then staging, then production.

Ansible is a natural fit for step 3 because deploying means configuring servers and rolling out software, which is what playbooks describe. GitLab triggers the playbook; Ansible does the actual work on the target machines.

Go deeper:

• CI/CD: Using GitLab + Docker + Ansible (Callr Tech Blog) — a worked pipeline where GitLab CI builds with Docker and Ansible deploys.
• What is CI/CD? (Red Hat) — separates continuous delivery from continuous deployment clearly.
• CI/CD (Wikipedia) — overview of the combined practice and its stages.