Architecture

Agents

An agent is the Coder service that runs within a user's remote workspace. It provides a consistent interface for coderd and clients to communicate with workspaces regardless of operating system, architecture, or cloud.

It offers the following services along with much more:

• SSH
• Port forwarding
• Liveness checks
• startup_script automation

Service Bundling

While coderd, provisionerd and Postgres can be orchestrated independently, our default installation paths bundle them all together into one system service. It's perfectly fine to run a production deployment this way, but there are certain situations that necessitate decomposition:

• Reducing global client latency (distribute coderd and centralize database)
• Running untrusted provisioners (separate provisionerd from nodes with DB access)
• Achieving greater availability and efficiency (horizontally scale individual services)

coderd

coderd is the service created by running coder server. It is a thin API that connects workspaces, provisioners and users. coderd stores its state in Postgres and is the only service that communicates with Postgres.

It offers:

• Dashboard
• HTTP API
• Dev URLs (HTTP reverse proxy to workspaces)
• Workspace Web Applications (e.g easily access code-server)
• Agent registration

provisionerd

provisionerd is the execution context for infrastructure modifying providers. At the moment, the only provider is Terraform (running terraform).

Since the provisionerd can be separated from coderd, it can run the provider in a myriad of ways on the same Coder deployment. For example, provisioners can have different terraform versions to satisfy the requirements of different templates.

Separability is also advantageous for security. Since provisionerd has no database access, infrastructure admins that are not necessarily Coder admins can be safely given access to the provisionerd node. As Coder scales and multiple infrastructure teams appear, each can be given access to their own set of provisionerd nodes, with each set of nodes having their own cloud credentials.

Workspaces

At the highest level, a workspace is a set of cloud resources. These resources can be VMs, Kubernetes clusters, storage buckets, or whatever else Terraform lets you dream up.

The resources that run the agent are described as computational resources, while those that don't are called peripheral resources.

Each resource may also be persistent or ephemeral depending on whether they're destroyed on workspace stop.