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8eaf176868
When the `client.servers` block is parsed, we split the port from the address. This does not correctly handle IPv6 addresses when they are in URL format (wrapped in brackets), which we require to disambiguate the port and address. Fix the parser to correctly split out the port and handle a missing port value for IPv6. Update the documentation to make the URL format requirement clear. Fixes: https://github.com/hashicorp/nomad/issues/20310
299 lines
10 KiB
Plaintext
299 lines
10 KiB
Plaintext
---
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layout: docs
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page_title: server_join Block - Agent Configuration
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description: >-
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The "server_join" block 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` Block
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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` block 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 Nomad server
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addresses and [Cloud Auto-join](#cloud-auto-join) configurations that are
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joined as cluster members. This is similar to [`start_join`](#start_join),
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but join attempts are retried up to [retry_max](#retry_max) times.
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Further, `retry_join` is available to both Nomad servers and clients, while
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`start_join` is only defined for Nomad servers. This is useful for cases where
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we know the address will become available eventually. Use `retry_join` with an
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array as a replacement for `start_join`, **do not use both options**.
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Server addresses must conform to the [server address format](#server-address-format).
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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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}
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```
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Auto-join configurations must conform to the [Cloud Auto-join format](#cloud-auto-join).
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Cloud-Auto join using `go-discover` to join an AWS EC2 cluster.
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```hcl
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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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Cloud-Auto join using `go-netaddrs` to join a Hetzner cluster of servers
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labeled with `nomad-server=true` using the `hcloud` CLI.
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```hcl
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server_join {
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retry_join = [ "exec=hcloud server list -o noheader -o columns=ipv4 -l nomad-server=true | tr '\n' ' '" ]
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}
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```
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Server addresses and Cloud Auto-join configurations may be used together.
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This is a mixed configuration containing a server address and Cloud Auto-join
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configuration.
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```hcl
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server_join {
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retry_join = [ "1.1.1.1", "provider=aws tag_key=..." ]
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}
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```
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See [server address format](#server-address-format) for more information
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about expected server address formats and [Cloud Auto-join](#cloud-auto-join)
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for more information on expected Cloud Auto-join 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 IP address is an IPv6 address, it must be in URL format surrounded by
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brackets. For example:
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```
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[2001:db8::1]: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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`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 provider 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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`retry_join`'s Cloud Auto-join allows Nomad to automatically discover cluster
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server addresses using cloud provider metadata. Cloud Auto-join allows both
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[go-discover](https://github.com/hashicorp/go-discover) and
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[go-netaddrs](https://github.com/hashicorp/go-netaddrs) formats.
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Configurations prefixed with `provider=` use `go-discover` whereas
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configurations prefixed with `exec=` use `go-netaddrs`. For cloud providers not
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supported by `go-discover`, use `go-netaddrs`.
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### `go-discover` Configurations
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`go-discover` configurations are prefixed with `provider=`.
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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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```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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### `go-netaddrs` Configurations
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`go-netaddrs` configurations are prefixed with `exec=`.
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What follows the `exec=` prefix may be any executable program and its arguments.
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Commands run by `go-netaddrs` must return a list of space-delimited IPv4 or IPv6
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addresses and exit with code `0` on success and non-zero on failure.
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You can refer to the executable by its absolute file system path, or by
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the executable's name if it can be found on the Nomad agent's PATH. See
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[executables in the current directory](https://pkg.go.dev/os/exec#hdr-Executables_in_the_current_directory)
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for more details on the lookup behavior.
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Example `go-netaddrs` configuration.
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```hcl
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server_join {
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retry_join = [ "exec=hcloud server list -o noheader -o columns=ipv4 -l nomad-server=true | tr '\n' ' '" ]
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}
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```
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Here, `hcloud`'s newline-delimited output has been re-formatted as space-
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delimited by piping its output into `tr`.
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Output of an example `go-netaddrs` executable
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```
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"1.1.1.1 2.2.2.2"
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```
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Visit [go-netaddrs](https://github.com/hashicorp/go-netaddrs) for more
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information on go-netaddrs configuration.
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