threshold/website/content/docs/configuration/worker/index.mdx

---
layout: docs
page_title: Worker configuration overview
description: >-
  Learn about worker configuration for proxies, storage, and tags. Understand how multi-hop configurations let you chain workers together in private networks.
---

# Worker stanza

The `worker` stanza configures Boundary worker-specific parameters.

All workers within Boundary use certificates and encryption keys to identify
themselves and protect data in transit. However, there are three different
ways to register them so that registration of workers can fit into any workflow: controller-led, worker-led, and via external KMS.

The sub-pages linked at the bottom of this page explain the differences in their configuration.

You must register workers using the worker-led or controller-led methods in the system with an API call. These workers require storage on disk to store the current set of credentials. Workers using an external KMS auto-register after authenticating. This makes them an easy mechanism to use for automatic scaling.
This also means they do not need to store
credentials locally; the KMS re-authenticates them each time they connect.

<Note title="Important">

Before version 0.15 of Boundary, there were two different types of workers, PKI & KMS workers.
If you are using pre-0.15 workers with pre-0.15 upstream configurations, please switch the documentation version to `0.13.x` - `0.14.x`. This will ensure you have the correct information.

</Note>

## Common worker parameters
The following fields apply to all registration mechanisms.

```hcl
worker {
  public_addr = "5.1.23.198"

  # Local storage path required if session recording is enabled
  recording_storage_path = "tmp/boundary/"

  # Minimum available disk space required in the local storage path if session recording is enabled
  recording_storage_minimum_available_capacity = "500MB"

  # Mutually exclusive with hcp_boundary_cluster_id
  initial_upstreams = [
    "10.0.0.1",
    "10.0.0.2",
  ]

  tags {
    type   = ["prod", "webservers"]
    region = ["us-east-1"]
  }

  # HCP Boundary only
  # hcp_boundary_cluster_id = "....."
}
```

- `public_addr` - Specifies the public host or IP address (and optionally port)
   where clients can reach the worker for proxying. By default, it uses the
   address of the listener marked for `proxy` purpose. This is useful for cloud
   environments that do not bind a publicly accessible IP directly to a NIC on
   the host, such as an Amazon EIP.

   You should omit this parameter in multi-hop configurations if this self-managed worker connects to an upstream HCP-managed worker.

   This value can reference any of the following:
   - a direct address string
   - read an address from a file on disk (file://)
   - read an address from an environment variable (env://)

- `initial_upstreams` - A list of hosts/IP addresses and optionally ports for
  reaching the Boundary cluster. The port will default to `:9201` if not
  specified. This value can be a direct access string array with the addresses,
  or it can refer to a file on disk (`file://`) from which the addresses will be
  read, or an environment variable (`env://`) from which to read the addresses. When
  using environment variable or file, their contents must formatted as a JSON array:
  `["127.0.0.1", "192.168.0.1", "10.0.0.1"]`

  Self-managed workers connecting to HCP Boundary require the [`hcp_boundary_cluster_id`](/boundary/docs/configuration/worker/#hcp_boundary_cluster_id) parameter instead of `initial upstreams`, unless you are configuring an HCP-managed worker as an ingress worker.
  If you configure a self-managed worker with both `initial_upstreams` and `hcp_boundary_cluster_id`, the worker configuration fails.

- `hcp_boundary_cluster_id` - A string required to configure workers using worker-led or controller-led registration
  to connect to your HCP Boundary cluster rather than specifying
`initial_upstreams`. This parameter is valid only for workers using the worker-led or controller-led
  registration method and for workers directly connected to HCP Boundary.

- `recording_storage_path` - A path to the local storage for recorded sessions.
   Boundary stores session recordings in the local storage while they are in progress.
   When the session is complete, Boundary moves the local session recording to remote storage and deletes the local copy.

- `recording_storage_minimum_available_capacity` - A value measured in bytes that
   defines the worker's local storage state.  Boundary compares this value to the available local disk space found in the `recording_storage_path` and determines if a worker can perform session recording operations.
   The supported suffixes are kb, kib, mb, mib, gb, gib, tb, tib, which are not case sensitive. Example: 2GB, 2gb, 2GiB, 2gib.
   The possible storage states based on the `recording_storage_minimum_available_capacity` are:
    - Available - The worker has storage above the threshold and can proxy sessions that have session recording enabled.
    - Low storage - The worker has storage below the threshold. It allows existing sessions to continue without interruption but prevents proxying new sessions that have session recording enabled. The worker cannot record new sessions or play back existing recordings.
    - Critically low storage - The worker falls below half the storage threshold. It forcefully closes existing sessions with session recording. The worker cannot record new sessions or play back existing recordings.
    - Out of storage - The worker is out of local disk space. It cannot record new sessions or play back existing recordings. The worker enters an unrecoverable state, requiring an administrator to intervene and resolve the issue.
    - Not configured - The worker lacks a configured local storage path.
    - Unknown - The worker starts with this default local storage state. This state indicates that the worker's local storage state is not yet known.

- `tags` - A map of key-value pairs where values are an array of strings. Most
  commonly used for [filtering](/boundary/docs/concepts/filtering) targets a
  worker can proxy via [worker
  tags](/boundary/docs/concepts/filtering/worker-tags). On `SIGHUP`, the tags
  set here will be re-parsed and new values used. It can also be a string
  referring to a file on disk (`file://`) or an environment variable (`env://`).

## Signals

The `SIGHUP` signal causes a worker to reload its configuration file to pick up any updates for the `initial_upstreams` and `tags` values.
Boundary ignores other updated values.

The `SIGTERM` and `SIGINT` signals initiate a graceful shutdown on a worker. The worker waits for any sessions to drain
before shutting down. Workers in a graceful shutdown state do not receive any new work, including session proxying, from the control plane.

## Multi-hop worker capabilities

<EnterpriseAlert product="boundary">This feature requires <a href="https://www.hashicorp.com/products/boundary">HCP Boundary or Boundary Enterprise</a></EnterpriseAlert>

Multi-hop capabilities, including multi-hop sessions and Vault private access,
is when a session or Vault credential request goes through more than one worker.
To enable this, you must connect two or more workers to each other in some
configuration. There are no limits on the number of workers allowed in a
multi-hop session configuration.

It helps to think of “upstream” and “downstream” nodes in the context of
multi-hop. If you view controllers as the “top” node of a multi-hop chain, any
worker connected to a node is "downstream" of that node. The node that any
particular worker connects to (whether another worker or a controller) is the
"upstream" of that node. For example, in the diagram below, Worker 2’s upstream
is Worker 1, and its downstream is Worker 3.

![multi-hop workers](/img/multi-hop-workers.png)

You can deploy multi-hop workers in scenarios where inbound network traffic is
not allowed. A worker in a private network can send outbound communication to
its upstream worker, and create a reverse proxy to establish a session.

You can configure [target worker filters][] with multi-hop workers to allow for
fine-grained control on which workers handle ingress and egress for session
traffic to a [target][]. Ingress worker filters specify the workers you use to initiate a session, and egress worker filters specify the workers you use to access targets.

### Multi-hop worker requirements

When you configure multi-hop sessions, there is an "ingress" worker, an "egress"
worker, and any number of intermediary workers. Ingress, egress, and
intermediary workers have the following requirements.

#### Ingress worker requirements

To proxy target connections, ingress workers require outbound access to the
Boundary control plane and inbound access from clients.

#### Intermediary worker requirements

Intermediary workers require outbound access to an upstream worker. The upstream
worker may be an ingress worker or another intermediary worker. Intermediary
workers also require inbound access from a downstream worker. The downstream
worker may be an egress worker or another intermediary worker.

#### Egress worker requirements

To proxy target connections, egress workers require outbound access to an
upstream worker and outbound access to the destination host or service.

## Complete configuration example

```hcl
listener "tcp" {
	purpose = "proxy"
	tls_disable = true
	address = "127.0.0.1"
}

worker {
  # Path for worker storage, assuming worker-led or controller-led registration. Must be unique across workers
  auth_storage_path="/boundary/demo-worker-1"

  # Local storage path required if session recording is enabled
  recording_storage_path = "tmp/boundary/"

  # Minimum available disk space required in the local storage path if session recording is enabled
  recording_storage_minimum_available_capacity = "500MB"

  # Workers typically need to reach upstreams on :9201
  initial_upstreams = [
    "10.0.0.1",
    "10.0.0.2",
    "10.0.0.3",
  ]

  public_addr = "myhost.mycompany.com"

  tags {
    type   = ["prod", "webservers"]
    region = ["us-east-1"]
  }
}

# The following KMS config is an example only
# Use a production KMS such as AWS KMS for production installs
kms "aead" {
  purpose = "worker-auth-storage"
	aead_type = "aes-gcm"
	key = "X+IJMVT6OnsrIR6G/9OTcJSX+lM9FSPN"
	key_id = "worker-auth-storage"
}


```

## Tutorials

Refer to the [Self-Managed Worker Registration with HCP Boundary](/boundary/tutorials/hcp-administration/hcp-manage-workers) tutorial to learn how to register and manage Workers.

Refer to the [Manage Multi-Hop Sessions with HCP Boundary](/boundary/tutorials/hcp-administration/hcp-manage-multi-hop) tutorial to learn how to configure a multi-hop session.

[Worker Configuration Methods]: /boundary/docs/configuration/worker/worker-configuration
[target]: /boundary/docs/concepts/domain-model/targets
[target worker filters]: /boundary/docs/concepts/filtering/worker-tags#target-worker-filtering
[session recording]: /boundary/docs/configuration/session-recording