---
layout: docs
page_title: Agent
sidebar_title: Agent
description: The Nomad Autoscaler is a long lived process which coordinates scaling activates.
---

# 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][hcl_v2]. 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][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:

```hcl
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`][autoscaler_cli_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:

```shell-session
$ 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`][autoscaler_cli_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.

```hcl
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.

```hcl
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.

```hcl
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.

## `policy_eval` Block

The `policy_eval` block holds the configuration related to the policy evaluation
process.

```hcl
policy_eval {
  ack_timeout    = "10m"
  delivery_limit = 4

  workers = {
    cluster    = 2
    horizontal = 2
  }
}
```

### `policy_eval` Parameters

- `ack_timeout` `(string: "5m")` - The time limit that an eval must be ACK'd
  before being considered NACK'd.

- `delivery_limit` `(int: 1)` - The maximum number of times a policy evaluation
  can be dequeued from the broker.

- `workers` `(map<string|int>: [cluster:10,horizontal:10])` - The number of workers
  to initialize for each queue. Nomad Autoscaler supports `cluster` and `horizontal`
  map keys. Nomad Autoscaler Enterprise supports additional `vertical_mem` and
  `vertical_cpu` entries.

## `telemetry` Block

The `telemetry` block configures the Nomad Autoscaler's publication of metrics
and telemetry to third-party systems.

```hcl
telemetry {
  disable_hostname = true
}
```

### `telemetry` Parameters

Due to the number of provider-specific parameters to the `telemetry` block, parameters
in this section are grouped by the telemetry provider.

### Common

The following options are available on all telemetry configurations.

- `disable_hostname` `(bool: false)` - Specifies if gauge values should be
  prefixed with the local hostname.

- `enable_hostname_label` `(bool: false)` - Enable adding hostname to metric
  labels.

- `collection_interval` `(duration: "1s")` - Specifies the time interval at which
  the Nomad agent collects telemetry data.

### `statsite`

These `telemetry` parameters apply to [Statsite][statsite].

- `statsite_address` `(string: "")` - Specifies the address of a statsite server
  to forward metrics data to.

```hcl
telemetry {
  statsite_address = "statsite.company.local:8125"
}
```

### `statsd`

These `telemetry` parameters apply to [StatsD][statsd].

- `statsd_address` `(string: "")` - Specifies the address of a statsd server to
  forward metrics to.

```hcl
telemetry {
  statsd_address = "statsd.company.local:8125"
}
```

### `datadog`

These `telemetry` parameters apply to [DataDog statsd][datadog_statsd].

- `dogstatsd_address` `(string: "")` - Specifies the address of a DataDog statsd
  server to forward metrics to.

- `dogstatsd_tags` `(list: [])` - Specifies a list of global tags that will be
  added to all telemetry packets sent to DogStatsD. It is a list of strings,
  where each string looks like `my_tag_name:my_tag_value`.

```hcl
telemetry {
  dogstatsd_address = "dogstatsd.company.local:8125"
  dogstatsd_tags    = ["my_tag_name:my_tag_value"]
}
```

### `prometheus`

These `telemetry` parameters apply to [Prometheus][prometheus].

- `prometheus_metrics` `(bool: false)` - Specifies whether the agent should
  make Prometheus formatted metrics available at `/v1/metrics?format=prometheus`.

- `prometheus_retention_time` `(string: "24h")` - Specifies the amount of time that Prometheus
  metrics are retained in memory.

### `circonus`

These `telemetry` parameters apply to [Circonus][circonus].

- `circonus_api_token` `(string: "")` - Specifies a valid Circonus API Token
  used to create/manage check. If provided, metric management is enabled.

- `circonus_api_app` `(string: "nomad-autoscaler")` - Specifies a valid app name
  associated with the API token.

- `circonus_api_url` `(string: "https://api.circonus.com/v2")` - Specifies the
  base URL to use for contacting the Circonus API.

- `circonus_submission_interval` `(string: "10s")` - Specifies the interval at
  which metrics are submitted to Circonus.

- `circonus_submission_url` `(string: "")` - Specifies the
  `check.config.submission_url` field, of a Check API object, from a previously
  created HTTPTRAP check.

- `circonus_check_id` `(string: "")` - Specifies the Check ID (**not check
  bundle**) from a previously created HTTPTrap check. The numeric portion of the
  `check._cid` field in the Check API object.

- `circonus_check_force_metric_activation` `(bool: false)` - Specifies if force
  activation of metrics which already exist and are not currently active. If
  check management is enabled, the default behavior is to add new metrics as
  they are encountered. If the metric already exists in the check, it will
  not be activated. This setting overrides that behavior.

- `circonus_check_instance_id` `(string: "<hostname>:<application>")` - Serves
  to uniquely identify the metrics coming from this _instance_. It can be used
  to maintain metric continuity with transient or ephemeral instances as they
  move around within an infrastructure. By default, this is set to
  "hostname:application name" (e.g. `host123:nomad-autoscaler`).

- `circonus_check_search_tag` `(string: <service>:<application>)` - Specifies a
  special tag which, when coupled with the instance id, helps to narrow down the
  search results when neither a Submission URL or Check ID is provided. By
  default, this is set to "service:app" (e.g. `service:nomad-autoscaler`).

- `circonus_check_display_name` `(string: "")` - Specifies a name to give a
  check when it is created. This name is displayed in the Circonus UI Checks
  list.

- `circonus_check_tags` `(string: "")` - Comma separated list of additional
  tags to add to a check when it is created.

- `circonus_broker_id` `(string: "")` - Specifies the ID of a specific Circonus
  Broker to use when creating a new check. The numeric portion of `broker._cid`
  field in a Broker API object. If metric management is enabled and neither a
  Submission URL nor Check ID is provided, an attempt will be made to search for
  an existing check using Instance ID and Search Tag. If one is not found, a new
  HTTPTrap check will be created. By default, this is a random
  Enterprise Broker is selected, or, the default Circonus Public Broker.

- `circonus_broker_select_tag` `(string: "")` - Specifies a special tag which
  will be used to select a Circonus Broker when a Broker ID is not provided. The
  best use of this is to as a hint for which broker should be used based on
  _where_ this particular instance is running (e.g., a specific geographic location or
  datacenter, dc:sfo).

## `apm` Block

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

```hcl
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.

```hcl
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.

```hcl
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.

[hcl_v2]: https://github.com/hashicorp/hcl/tree/hcl2
[nomad_namespaces]: https://learn.hashicorp.com/tutorials/nomad/namespaces
[nomad_acls]: https://learn.hashicorp.com/collections/nomad/access-control
[autoscaler_cli_config]: /docs/autoscaling/cli#config
[autoscaler_cli_policy_dir]: /docs/autoscaling/cli#policy-dir
[statsite]: https://github.com/armon/statsite
[statsd]: https://github.com/etsy/statsd
[datadog_statsd]: https://github.com/DataDog/datadog-agent
[prometheus]: https://prometheus.io
[circonus]: http://circonus.com/
