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Nomad Autoscaler Agent

The Nomad Autoscaler agent has a variety of parameters that can be specified via configuration files or command-line flags. Configuration files are written in HCL. The Nomad Autoscaler can read and combine parameters from multiple configuration files or directories to configure the agent.

Nomad Namespaces

The Nomad Autoscaler currently has limited support for Nomad Namespaces. The nomad configuration below supports specifying a namespace; if configured with a namespace, the Autoscaler will retrieve scaling policies and perform autoscaling only for jobs in that namespace. A future version will include support for multiple namespaces.

Nomad ACLs

The Nomad Autoscaler can be configured to interact with an ACL-enabled Nomad cluster. Nomad 0.11 includes the scale ACL policy disposition specifically for supporting the operations of the Nomad Autoscaler. Therefore, the following policy is sufficient for creating an ACL token that can be used by the autoscaler for fetching scaling policies and scaling jobs:

namespace "default" {
  policy = "scale"
}

Other APM and target plugins may require additional ACLs; see the plugin documentation for more information.

Load Order and Merging

The Nomad Autoscaler agent supports multiple configuration files, which can be provided using the -config CLI flag. The flag can accept either a file or folder. In the case of a folder, any .hcl and .json files in the folder will be loaded and merged in lexicographical order. Directories are not loaded recursively.

For example:

$ nomad-autoscaler agent -config=autoscaler.conf -config=/etc/nomad-autoscaler -config=extra.json

This will load configuration from autoscaler.conf, from .hcl and .json files under /etc/nomad-autoscaler, and finally from extra.json. As each file is processed, its contents are merged into the existing configuration. When merging, any non-empty values from the latest config file will append or replace parameters in the current configuration. An empty value means "" for strings, 0 for integer or float values, and false for booleans.

SIGHUP Reload

The Nomad Autoscaler agent supports handling the SIGHUP signal for reloading without the need for restarting the agent. When sending a SIGHUP signal to the agent process, the agent will perform the following actions.

  • reload the contents of the scaling policy directory as defined by the -policy-dir parameter.

General Parameters

  • log_level (string: "INFO") - Specify the verbosity level of Nomad Autoscaler's logs. Valid values include DEBUG, INFO, and WARN, in decreasing order of verbosity.

  • log_json (bool: false) - Output logs in a JSON format.

  • plugin_dir (string: "./plugins") - The plugin directory is used to discover Nomad Autoscaler plugins.

http Block

The http block configures the Nomad Autoscaler's HTTP endpoint.

http {
  bind_address = "10.0.0.10"
  bind_port    = 9999
}

http Parameters

  • bind_address (string: "127.0.0.1") - The HTTP address that the server will bind to.

  • bind_port (int: 8080) - The port that the server will bind to.

nomad Block

The nomad block configures the Nomad Autoscaler's Nomad client.

nomad {
  address = "http://my-nomad.systems:4646"
  region  = "esp-vlc-1"
}

nomad Parameters

  • address (string: "http://127.0.0.1:4646") - The address of the Nomad server in the form of protocol://addr:port.

  • region (string: "global") - The region of the Nomad servers to connect with.

  • namespace (string: "") - The target namespace for queries and actions bound to a namespace.

  • token (string: "") - The SecretID of an ACL token to use to authenticate API requests with.

  • http_auth (string: "") - The authentication information to use when connecting to a Nomad API which is using HTTP authentication.

  • ca_cert (string: "") - Path to a PEM encoded CA cert file to use to verify the Nomad server SSL certificate.

  • ca_path (string: "") - Path to a directory of PEM encoded CA cert files to verify the Nomad server SSL certificate.

  • client_cert (string: "") - Path to a PEM encoded client certificate for TLS authentication to the Nomad server.

  • client_key (string: "") - Path to an unencrypted PEM encoded private key matching the client certificate.

  • tls_server_name (string: "") - The server name to use as the SNI host when connecting via TLS.

  • skip_verify (bool: false) - Do not verify TLS certificates. This is strongly discouraged.

policy Block

The policy block configures the Nomad Autoscaler's policy handling.

policy {
  dir              = "/opt/nomad-autoscaler/policies"
  default_cooldown = "2m"
}

policy Parameters

  • dir (string: "") - The path to a directory used to load scaling policies.

  • default_cooldown (string: "5m") - The default cooldown that will be applied to all scaling policies which do not specify a cooldown period.

  • default_evaluation_interval (string: "10s") - The default evaluation interval that will be applied to all scaling policies which do not specify an evaluation interval.

apm Block

The apm block is used to configure application performance metric (APM) plugins.

apm "example-apm-plugin" {
  driver = "example-apm-plugin"
  args   = ["-my-flag"]

  config = {
    address = "http://127.0.0.1:9090"
  }
}

apm Parameters

  • args (array<string>: []) - Specifies a set of arguments to pass to the plugin binary when it is executed.

  • driver (string: "") - The plugin's executable name relative to to the plugin_dir. If the plugin has a suffix, such as .exe, this should be omitted.

  • config (map<string><string>: nil) - Specifies configuration values for the plugin either as HCL or JSON. The accepted values are plugin specific. Please refer to the individual plugin's documentation.

target Block

The target block is used to configure scaling target plugins.

target "example-target-plugin" {
  driver = "example-target-plugin"
  args   = ["-my-flag"]

  config = {
    region = "esp-vlc-1"
  }
}

target Parameters

  • args (array<string>: []) - Specifies a set of arguments to pass to the plugin binary when it is executed.

  • driver (string: "") - The plugin's executable name relative to to the plugin_dir. If the plugin has a suffix, such as .exe, this should be omitted.

  • config (map<string><string>: nil) - Specifies configuration values for the plugin either as HCL or JSON. The accepted values are plugin specific. Please refer to the individual plugin's documentation.

strategy Block

The strategy block is used to configure scaling strategy plugins.

strategy "example-strategy-plugin" {
  driver = "example-strategy-plugin"
  args   = ["-my-flag"]

  config = {
    algorithm = "complex"
  }
}

strategy Parameters

  • args (array<string>: []) - Specifies a set of arguments to pass to the plugin binary when it is executed.

  • driver (string: "") - The plugin's executable name relative to to the plugin_dir. If the plugin has a suffix, such as .exe, this should be omitted.

  • config (map<string><string>: nil) - Specifies configuration values for the plugin either as HCL or JSON. The accepted values are plugin specific. Please refer to the individual plugin's documentation.