Imagine a construction site where workers rush to install windows before the walls are up. Chaos would follow—tasks overlapping, dependencies ignored, and the project collapsing under its own disorder. In infrastructure automation, Terraform faces a similar challenge. Without clear task sequencing, it might attempt to create, modify, or destroy resources in the wrong order. This is where the depends_on attribute steps in, acting as the project manager that ensures every component is built at the right time, in the right order.
Building Order in an Asynchronous World
Terraform operates on a principle of declarative infrastructure—users describe what they want, and Terraform figures out how to make it happen. However, some dependencies are too nuanced for Terraform to infer automatically.
Consider deploying a web application where the database must exist before the application server connects to it. Terraform’s implicit dependency recognition (through references in code) can handle many cases, but not all.
That’s when depends_on becomes essential, explicitly declaring the order of operations so resources are created logically and predictably.
For professionals learning to master this orchestration of cloud resources, enrolling in a DevOps training institute in Bangalore provides valuable exposure to real-world scenarios where dependency management directly impacts automation reliability.
Why “depends_on” Matters
At its core, Terraform is like an orchestra conductor—every resource is an instrument that must play in harmony. The depends_on attribute ensures this synchrony by controlling when and how certain resources execute. Without it, Terraform might build components concurrently, risking configuration drift or failed provisioning.
For example, a security group rule might reference a load balancer that hasn’t yet been deployed. By introducing depends_on, you tell Terraform, “Wait until the load balancer exists before adding these rules.”
This small directive prevents deployment chaos, ensuring infrastructure behaves as intended.
Such fine-grained control distinguishes efficient Terraform users from beginners, giving DevOps engineers confidence in large-scale, automated environments.
Implementing “depends_on” in Practice
The syntax of depends_on is deceptively simple—it accepts a list of resources that the current block relies upon. For instance:
resource “aws_instance” “app_server” {
depends_on = [aws_db_instance.main]
…
}
In this example, Terraform ensures that the database instance (aws_db_instance.main) is successfully created before the application server is provisioned.
Behind this simplicity lies a significant impact: Terraform uses this directive to adjust its internal dependency graph, orchestrating builds with precision.
This approach prevents errors caused by asynchronous creation and promotes predictable outcomes during both deployment and destruction phases.
The Balance Between Automation and Control
While depends_on is powerful, overusing it can backfire. Too many explicit dependencies make the code rigid, defeating Terraform’s strength—automation flexibility. The best practice is to rely primarily on implicit dependencies (via variable references) and use depends_on only when necessary.
In complex systems, dependency chains can become intricate, spanning across modules and resources. A skilled DevOps engineer learns when to trust Terraform’s default intelligence and when to step in manually.
Hands-on experience through a DevOps training institute in Bangalore can help learners understand these nuances—teaching them to strike the perfect balance between automated flow and manual control.
Maintaining Stability in Evolving Infrastructure
Infrastructure evolves—databases migrate, APIs deprecate, and services expand. With these changes come new dependencies that can disrupt existing flows. Terraform’s depends_on attribute allows teams to manage transitions gracefully, ensuring that new components are introduced or removed without destabilising the system.
When applied thoughtfully, it transforms infrastructure as code from a simple automation tool into a resilient ecosystem—one that adapts and grows without losing its core structure.
Conclusion
In the world of Terraform, depends_on is the invisible thread that weaves order into potential chaos. It provides clarity where automation alone might falter, ensuring every digital brick is laid in sequence.
Understanding when and how to use this attribute is a mark of maturity in DevOps engineering—it reflects not just coding skill but architectural foresight.
For professionals looking to deepen their understanding of such advanced practices, formal training can bridge the gap between theory and practical mastery, empowering them to build infrastructures that stand strong amid rapid technological evolution.
