Azure Virtual Machine Scale Set Target

The azure-vmss target plugin allows for the scaling of the Nomad cluster clients via manipulating Azure Virtual Machine Scale Sets.

Agent Configuration Options

To use the azure-vmss target plugin, the agent configuration needs to be populated with the appropriate target block. Authentication to the Azure API can be supplied in a number of ways.

Virtual Machine Identities

When using virtual machine identities you will need to provide a user-managed identity with the Contributor role and set the subscription_id in the Autoscaler configuration file:

target "azure-vmss" {
  driver = "azure-vmss"
  config = {
    subscription_id = "ee0886ab-5cc2-4583-a3f0-c4bfd044ee82"
  }
}

Configuration file

Credentials should be injected into the configuration via a template rather than as environment variables. This ensures the credentials are passed only to the plugin, rather than being available for all plugins and the agent process. It is recommended, if possible to use the Vault Azure Secrets engine for supplying access credentials to the plugin.

target "azure-vmss" {
  driver = "azure-vmss"
  config = {
    tenant_id         = "02e99e69-91b0-4d0a-bd61-bf5c08fbfbab"
    client_id         = "34c276fa-2a74-4cf9-9fce-4e60642274cb"
    secret_access_key = "ThisIrznTIS_~FAKEj4X93FTyAgilUC511"
    subscription_id   = "ee0886ab-5cc2-4583-a3f0-c4bfd044ee82"
  }
}

• tenant_id (string: "") - The ID of the tenant to authenticate to.

• client_id (string: "") - The app ID of the user-assigned identity in Azure Active Directory.

• secret_access_key (string: "") - The secret key ID used to authenticate with the Azure API.

• subscription_id (string: "") - The ID of the subscription to authenticate to.

Nomad ACL

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

node {
  policy = "write"
}

Policy Configuration Options

check "clients-azure-vmss" {
  # ...
  target "azure-vmss" {
    resource_group      = "prod"
    vm_scale_set        = "hashistack-client-set"
    node_class          = "hashistack"
    node_drain_deadline = "5m"
    node_purge          = "true"
  }
  # ...

• resource_group (string: <required>) - The name of the Azure resource group within which the virtual machine scale set resides.

• vm_scale_set (string: <required>) - The name of the Azure virtual machine scale set to interact with when performing scaling actions.

• 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_pool (string: "") - The Nomad client node pool 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. Note that the default value for this setting differs from Nomad's default of 1h.

• 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.

Client meta tag

The azure-vmss target plugin requires Nomad 1.0 for Azure fingerprinting. Alternatively, you can set a client meta tag called unique.platform.azure.name with the value being the Azure VMSS node name. This can be retrieved programatically via the Azure Instance Metadata service.