cos-generic-metadata

Generic cloud-init generator for Container Optimized OS

This helper module manages a cloud-config configuration that can start a container on Container Optimized OS (COS). Either a complete cloud-config template can be provided via the cloud_config variable with optional template variables via the config_variables, or a generic cloud-config can be generated based on typical parameters needed to start a container.

Logging can be enabled via the Google Cloud Logging docker driver using the gcp_logging variable. This is enabled by default, but requires that the service account running the COS instance have the roles/logging.logWriter IAM role or equivalent permissions on the project. If it doesn't, the container will fail to start unless this is disabled.

The module renders the generated cloud config in the cloud_config output, which can be directly used in instances or instance templates via the user-data metadata attribute.

Examples

Default configuration

This example will create a cloud-config that starts Envoy Proxy and expose it on port 80. For a complete example, look at the sibling envoy-traffic-director module that uses this module to start Envoy Proxy and connect it to Traffic Director.

module "cos-envoy" {
  source = "./fabric/modules/cos-generic-metadata"

  container_image = "envoyproxy/envoy:v1.14.1"
  container_name  = "envoy"
  container_args  = "-c /etc/envoy/envoy.yaml --log-level info --allow-unknown-static-fields"

  container_volumes = [
    { host = "/etc/envoy/envoy.yaml", container = "/etc/envoy/envoy.yaml" }
  ]

  docker_args = "--network host --pid host"

  files = {
    "/var/run/envoy/customize.sh" = {
      content     = file("customize.sh")
      owner       = "root"
      permissions = "0744"
    }
    "/etc/envoy/envoy.yaml" = {
      content     = file("envoy.yaml")
      owner       = "root"
      permissions = "0644"
    }
  }

  run_commands = [
    "iptables -t nat -N ENVOY_IN_REDIRECT",
    "iptables -t nat -A ENVOY_IN_REDIRECT -p tcp -j REDIRECT --to-port 15001",
    "iptables -t nat -A PREROUTING -p tcp -m tcp --dport 80 -j ENVOY_IN_REDIRECT",
    "iptables -t filter -A INPUT -p tcp -m tcp --dport 15001 -m state --state NEW,ESTABLISHED -j ACCEPT",
    "/var/run/envoy/customize.sh",
    "systemctl daemon-reload",
    "systemctl start envoy",
  ]

  users = [
    {
      username = "envoy",
      uid      = 1337
    }
  ]
}

Variables

name	description	type	required	default
container_image	Container image.	string	✓
authenticate_gcr	Setup docker to pull images from private GCR. Requires at least one user since the token is stored in the home of the first user defined.	bool		false
boot_commands	List of cloud-init bootcmds.	list(string)		[]
cloud_config	Cloud config template path. If provided, takes precedence over all other arguments.	string		null
config_variables	Additional variables used to render the template passed via cloud_config.	map(any)		{}
container_args	Arguments for container.	string		""
container_name	Name of the container to be run.	string		"container"
container_volumes	List of volumes.	list(object({…}))		[]
docker_args	Extra arguments to be passed for docker.	string		null
docker_logging	Log via the Docker gcplogs driver. Disable if you use the legacy Logging Agent instead.	bool		true
file_defaults	Default owner and permissions for files.	object({…})		{…}
files	Map of extra files to create on the instance, path as key. Owner and permissions will use defaults if null.	map(object({…}))		{}
gcp_logging	Should container logs be sent to Google Cloud Logging.	bool		true
run_commands	List of cloud-init runcmds.	list(string)		[]
users	List of usernames to be created. If provided, first user will be used to run the container.	list(object({…}))		[…]

Outputs

name	description	sensitive
cloud_config	Rendered cloud-config file to be passed as user-data instance metadata.