231 lines
8.2 KiB
Plaintext
231 lines
8.2 KiB
Plaintext
---
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layout: docs
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page_title: server_join Stanza - Agent Configuration
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sidebar_title: server_join
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description: >-
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The "server_join" stanza specifies how the Nomad agent will discover and
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connect to Nomad servers.
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---
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# `server_join` Stanza
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<Placement
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groups={[
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['server', 'server_join'],
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['client', 'server_join']
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]}
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/>
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The `server_join` stanza specifies how the Nomad agent will discover and connect
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to Nomad servers.
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```hcl
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server_join {
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retry_join = [ "1.1.1.1", "2.2.2.2" ]
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retry_max = 3
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retry_interval = "15s"
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}
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```
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## `server_join` Parameters
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- `retry_join` `(array<string>: [])` - Specifies a list of server addresses to
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join. This is similar to [`start_join`](#start_join), but will continue to
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be attempted even if the initial join attempt fails, up to
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[retry_max](#retry_max). Further, `retry_join` is available to
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both Nomad servers and clients, while `start_join` is only defined for Nomad
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servers. This is useful for cases where we know the address will become
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available eventually. Use `retry_join` with an array as a replacement for
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`start_join`, **do not use both options**.
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Address format includes both using IP addresses as well as an interface to the
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[go-discover](https://github.com/hashicorp/go-discover) library for doing
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automated cluster joining using cloud metadata. See the [Cloud Auto-join](#cloud-auto-join)
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section below for more information.
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```
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server_join {
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retry_join = [ "1.1.1.1", "2.2.2.2" ]
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}
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```
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Using the `go-discover` interface, this can be defined both in a client or
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server configuration as well as provided as a command-line argument.
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```
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server_join {
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retry_join = [ "provider=aws tag_key=..." ]
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}
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```
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See the [server address format](#server-address-format) for more information about expected
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server address formats.
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- `retry_interval` `(string: "30s")` - Specifies the time to wait between retry
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join attempts.
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- `retry_max` `(int: 0)` - Specifies the maximum number of join attempts to be
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made before exiting with a return code of 1. By default, this is set to 0
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which is interpreted as infinite retries.
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- `start_join` `(array<string>: [])` - Specifies a list of server addresses to
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join on startup. If Nomad is unable to join with any of the specified
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addresses, agent startup will fail. See the
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[server address format](#server-address-format) section for more information
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on the format of the string. This field is defined only for Nomad servers and
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will result in a configuration parse error if included in a client
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configuration.
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## Server Address Format
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This section describes the acceptable syntax and format for describing the
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location of a Nomad server. There are many ways to reference a Nomad server,
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including directly by IP address and resolving through DNS.
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### Directly via IP Address
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It is possible to address another Nomad server using its IP address. This is
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done in the `ip:port` format, such as:
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```
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1.2.3.4:5678
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```
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If the port option is omitted, it defaults to the Serf port, which is 4648
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unless configured otherwise:
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```
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1.2.3.4 => 1.2.3.4:4648
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```
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### Via Domains or DNS
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It is possible to address another Nomad server using its DNS address. This is
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done in the `address:port` format, such as:
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```
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nomad-01.company.local:5678
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```
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If the port option is omitted, it defaults to the Serf port, which is 4648
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unless configured otherwise:
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```
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nomad-01.company.local => nomad-01.company.local:4648
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```
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### Via the go-discover interface
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As of Nomad 0.8.4, `retry_join` accepts a unified interface using the
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[go-discover](https://github.com/hashicorp/go-discover) library for doing
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automated cluster joining using cloud metadata. See [Cloud
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Auto-join](#cloud_auto_join) for more information.
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```
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"provider=aws tag_key=..." => 1.2.3.4:4648
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```
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## Cloud Auto-join
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The following sections describe the Cloud Auto-join `retry_join` options that are specific
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to a subset of supported cloud providers. For information on all providers, see further
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documentation in [go-discover](https://github.com/hashicorp/go-discover).
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### Amazon EC2
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This returns the first private IP address of all servers in the given
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region which have the given `tag_key` and `tag_value`.
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```json
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{
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"retry_join": ["provider=aws tag_key=... tag_value=..."]
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}
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```
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- `provider` (required) - the name of the provider ("aws" in this case).
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- `tag_key` (required) - the key of the tag to auto-join on.
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- `tag_value` (required) - the value of the tag to auto-join on.
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- `region` (optional) - the AWS region to authenticate in.
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- `addr_type` (optional) - the type of address to discover: `private_v4`, `public_v4`, `public_v6`. Default is `private_v4`. (>= 1.0)
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- `access_key_id` (optional) - the AWS access key for authentication (see below for more information about authenticating).
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- `secret_access_key` (optional) - the AWS secret access key for authentication (see below for more information about authenticating).
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#### Authentication & Precedence
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- Static credentials `access_key_id=... secret_access_key=...`
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- Environment variables (`AWS_ACCESS_KEY_ID` and `AWS_SECRET_ACCESS_KEY`)
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- Shared credentials file (`~/.aws/credentials` or the path specified by `AWS_SHARED_CREDENTIALS_FILE`)
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- ECS task role metadata (container-specific).
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- EC2 instance role metadata.
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The only required IAM permission is `ec2:DescribeInstances`, and it is
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recommended that you make a dedicated key used only for auto-joining. If the
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region is omitted it will be discovered through the local instance's [EC2
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metadata
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endpoint](http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/instance-identity-documents.html).
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### Microsoft Azure
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This returns the first private IP address of all servers in the given region
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which have the given `tag_key` and `tag_value` in the tenant and subscription, or in
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the given `resource_group` of a `vm_scale_set` for Virtual Machine Scale Sets.
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```json
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{
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"retry_join": [
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"provider=azure tag_name=... tag_value=... tenant_id=... client_id=... subscription_id=... secret_access_key=..."
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]
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}
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```
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- `provider` (required) - the name of the provider ("azure" in this case).
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- `tenant_id` (required) - the tenant to join machines in.
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- `client_id` (required) - the client to authenticate with.
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- `secret_access_key` (required) - the secret client key.
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Use these configuration parameters when using tags:
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- `tag_name` - the name of the tag to auto-join on.
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- `tag_value` - the value of the tag to auto-join on.
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Use these configuration parameters when using Virtual Machine Scale Sets (Consul 1.0.3 and later):
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- `resource_group` - the name of the resource group to filter on.
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- `vm_scale_set` - the name of the virtual machine scale set to filter on.
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When using tags the only permission needed is the `ListAll` method for `NetworkInterfaces`. When using
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Virtual Machine Scale Sets the only role action needed is `Microsoft.Compute/virtualMachineScaleSets/*/read`.
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### Google Compute Engine
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This returns the first private IP address of all servers in the given
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project which have the given `tag_value`.
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````
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```json
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{
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"retry_join": ["provider=gce project_name=... tag_value=..."]
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}
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````
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- `provider` (required) - the name of the provider ("gce" in this case).
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- `tag_value` (required) - the value of the tag to auto-join on.
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- `project_name` (optional) - the name of the project to auto-join on. Discovered if not set.
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- `zone_pattern` (optional) - the list of zones can be restricted through an RE2 compatible regular expression. If omitted, servers in all zones are returned.
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- `credentials_file` (optional) - the credentials file for authentication. See below for more information.
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#### Authentication & Precedence
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- Use credentials from `credentials_file`, if provided.
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- Use JSON file from `GOOGLE_APPLICATION_CREDENTIALS` environment variable.
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- Use JSON file in a location known to the gcloud command-line tool.
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- On Windows, this is `%APPDATA%/gcloud/application_default_credentials.json`.
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- On other systems, `$HOME/.config/gcloud/application_default_credentials.json`.
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- On Google Compute Engine, use credentials from the metadata
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server. In this final case any provided scopes are ignored.
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Discovery requires a [GCE Service
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Account](https://cloud.google.com/compute/docs/access/service-accounts).
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Credentials are searched using the following paths, in order of precedence.
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