Templates

Templates

Templates are written in standard Terraform and describe the infrastructure for workspaces (e.g., aws_instance, kubernetes_pod, or both).

In most cases, a small group of users (Coder admins) manage templates. Then, other users provision their development workspaces from templates.

Add a template

Before users can create workspaces, you'll need at least one template in Coder.

# create a local directory to store templates
mkdir -p $HOME/coder/templates
cd $HOME/coder/templates

# start from an example
coder templates init

# optional: modify the template
vim <template-name>/main.tf

# add the template to Coder deployment
coder templates <create/update> <template-name>

See the documentation and source code for each example in the examples/ directory in the repo.

Customize templates

Example templates are not designed to support every use (e.g examples/aws-linux does not support custom VPCs). You can add these features by editing the Terraform code once you run coder templates init (new) or coder templates pull (existing).

Concepts in templates

While templates are written with standard Terraform, the Coder Terraform Provider is used to define the workspace lifecycle and establish a connection from resources to Coder.

Below is an overview of some key concepts in templates (and workspaces). For all template options, reference Coder Terraform provider docs.

Resource

Resources in Coder are simply Terraform resources. If a Coder agent is attached to a resource, users can connect directly to the resource over SSH or web apps.

Coder agent

Once a Coder workspace is created, the Coder agent establishes a connection between a resource (docker_container) and Coder, so that a user can connect to their workspace from the web UI or CLI. A template can have multiple agents to allow users to connect to multiple resources in their workspace.

Resources must download and start the Coder agent binary to connect to Coder. This means the resource must be able to reach your Coder URL.

Use the Coder agent's init script to

data "coder_workspace" "me" {
}

resource "coder_agent" "pod1" {
  os   = "linux"
  arch = "amd64"
}

resource "kubernetes_pod" "pod1" {
  spec {
    ...
    container {
      command = ["sh", "-c", coder_agent.pod1.init_script]
      env {
        name  = "CODER_AGENT_TOKEN"
        value = coder_agent.dev.token
      }
    }
  }
}

Parameters

Templates often contain parameters. These are defined by variable blocks in Terraform. There are two types of parameters:

  • Admin/template-wide parameters are set when a template is created/updated. These values are often cloud configuration, such as a VPC, and are annotated with sensitive = true in the template code.
  • User/workspace parameters are set when a user creates a workspace. These values are often personalization settings such as "preferred region" or "workspace image".

The template sample below uses admin and user parameters to allow developers to create workspaces from any image as long as it is in the proper registry:

variable "image_registry_url" {
  description = "The image registry developers can sele"
  default     = "artifactory1.organization.com`
  sensitive   = true # admin (template-wide) parameter
}

variable "docker_image_name" {
  description = "The image your workspace will start from"
  default     = "base_image"
  sensitive   = false # user (workspace) parameter
}

resource "docker_image" "workspace" {
  # ... other config
  name = "${var.image_registry_url}/${var.docker_image_name}"
}

Persistent vs. ephemeral resources

You can use the workspace state to ensure some resources in Coder can are persistent, while others are ephemeral.

Start/stop

Coder workspaces can be started/stopped. This is often used to save on cloud costs or enforce ephemeral workflows. When a workspace is started or stopped, the Coder server runs an additional terraform apply, informing the Coder provider that the workspace has a new transition state.

This template sample has one persistent resource (docker image) and one ephemeral resource (docker volume).

data "coder_workspace" "me" {
}

resource "docker_volume" "home_volume" {
  # persistent resource (remains a workspace is stopped)
  count = 1
  name  = "coder-${data.coder_workspace.me.owner}-${data.coder_workspace.me.name}-root"
}

resource "docker_container" "workspace" {
  # ephemeral resource (deleted when workspace is stopped, created when started)
  count = data.coder_workspace.me.start_count # 0 (stopped), 1 (started)
  volumes {
    container_path = "/home/coder/"
    volume_name    = docker_volume.home_volume.name
    read_only      = false
  }
  # ... other config
}

Delete workspaces

When a workspace is deleted, the Coder server essentially runs a terraform destroy to remove all resources associated with the workspace.

Terraform's prevent-destroy and ignore-changes meta-arguments can be used to accidental data loss.

Coder apps

By default, all templates allow developers to connect over SSH and a web terminal. See Configuring Web IDEs to learn how to give users access to additional web applications.

Creating & troubleshooting templates

You can use any Terraform resources or modules with Coder! When working on templates, we recommend you refer to the following resources:

Occasionally, you may run into scenarios where the agent is not able to connect. This means the start script has failed.

$ coder ssh myworkspace
Waiting for [agent] to connect...

While troubleshooting steps vary by resource, here are some general best practices:

  • Ensure the resource has curl installed
  • Ensure the resource can reach your Coder URL
  • Manually connect to the resource (e.g., docker exec or AWS console)
    • The Coder agent logs are typically stored in (/var/log/coder-agent.log)

Change Management

We recommend source controlling your templates as you would other code.

CI is as simple as running coder templates update with the appropriate credentials.


Next: Authentication & Secrets and Workspaces

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