The hcloud-server target plugin allows for the scaling of the Nomad cluster clients via manipulating Hetzner Cloud Servers.

To use the hcloud-server target plugin, the agent configuration needs to be populated with the appropriate target block.

target "hcloud-server" {
  driver = "hcloud-server"
  config = {
    hcloud_token = "YOUR_HCLOUD_TOKEN"
  }
}

• hcloud_token (string: required) - The Hetzner Cloud token used to authenticate to connect to and where resources should be managed.

• hcloud_random_suffix_len (string: "10") - Random Server name suffix length

• hcloud_retry_interval (string: "1m") - Hetzner Cloud API retry interval

• hcloud_retry_limit (string: "5") - Hetzner Cloud API retry limit

• hcloud_items_per_page (string: "50") - Hetzner Cloud API request page size

• hcloud_group_id_label_selector (string: "group-id") - Server group id label selector

• hcloud_node_attr_id (string: "unique.hostname") - Nomad Node attribute id

When using a Nomad cluster with ACLs enabled, the plugin will require an ACL token which provides the following permissions:

node {
  policy = "write"
}

check "hashistack-allocated-cpu" {
  # ...
  target "hcloud-server" {
    datacenter                   = "XXX"
    node_class                   = "XXX"
    node_drain_deadline          = "5m"
    node_purge                   = "true"
    node_selector_strategy       = "newest_create_index"
    hcloud_location              = "XXX"
    hcloud_image                 = "XXX"
    hcloud_user_data             = "#cloud-config\npackages:\n - jq"
    hcloud_b64_user_data_encoded = "false"
    hcloud_ssh_keys              = "XXX"
    hcloud_server_type           = "cx11"
    hcloud_group_id              = "XXX"
    hcloud_labels                = "XXX_node=true"
    hcloud_networks              = "XXX"
  }
  # ...
}

• hcloud_location (string: "") - ID or name of Location to create Server in (must not be used together with hcloud_datacenter).

• hcloud_datacenter (string: "") - ID or name of Datacenter to create Server in (must not be used together with hcloud_location).

• hcloud_firewalls (string: "") - Comma-separated list of Firewall IDs

• hcloud_placement_group (string: "") - Placement Group ID

• hcloud_image (string: required) - ID or name of the Image the Server is created from.

• hcloud_group_id (string: required) - Server group name used for filtering targeted HCloud hosts. group-id label is attached to a server during creation.

• hcloud_user_data (string: required) - Cloud-Init user data to use during Server creation. This field is limited to 32KiB (must not be used together with hcloud_user_data_file).

• hcloud_b64_user_data_encoded (string: "false") - Identifies if hcloud_user_data (or the content of the file specified in hcloud_user_data_file) is base64 encoded or not.

• hcloud_user_data_file (string: required) - Cloud-Init user data file to use during Server creation (must not be used together with hcloud_user_data).

• hcloud_ssh_keys (string: required) - Comma-separated IDs or names of SSH keys which should be injected into the server at creation time.

• hcloud_labels (string: "") - User-defined labels (key-value pairs) string in a format key1=value1,key2=value2,...,keyN=valueN.

• hcloud_networks (string: "") - Network IDs which should be attached to the server private network interface at the creation time.

• hcloud_public_net_enable_ipv4 (bool: "true") - Enable IPV4 address for HCloud instances

• hcloud_public_net_enable_ipv6 (bool: "false") - Enable IPV6 address for HCloud instances

• datacenter (string: "") - The Nomad client datacenter identifier used to group nodes into a pool of resource.

• node_class (string: "") - The Nomad client node class identifier used to group nodes into a pool of resource.

• node_drain_deadline (duration: "15m") The Nomad drain deadline to use when performing node draining actions.

• node_drain_ignore_system_jobs (bool: "false") A boolean flag used to control if system jobs should be stopped when performing node draining actions.

• node_purge (bool: "false") A boolean flag to determine whether Nomad clients should be purged when performing scale in actions.

• node_selector_strategy (string: "least_busy") The strategy to use when selecting nodes for termination. Refer to the node selector strategy documentation for more information.

Run terraform apply in demo folder to create:

• nomad server which runs services for:
  • nomad-autoscaler
  • prometheus
  • redis

Autoscaler scales hcloud nodes for redis. After successful run both Nomad and Consul are wide-world open and credentials for both you can find in terraform output and in creds.json file