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132 lines
4.0 KiB
Markdown
132 lines
4.0 KiB
Markdown
---
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layout: "docs"
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page_title: "server_join Stanza - Agent Configuration"
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sidebar_current: "docs-agent-configuration--server-join"
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description: |-
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The "server_join" stanza specifies how the Nomad agent will discover and connect to Nomad servers.
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---
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# `server_join` Stanza
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<table class="table table-bordered table-striped">
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<tr>
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<th width="120">Placement</th>
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<td>
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<code>server -> **server_join**</code>
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<br>
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<code>client -> **server_join**</code>
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</td>
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</tr>
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</table>
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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 [Cloud
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Auto-join][cloud_auto_join] 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
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about expected 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]: /docs/agent/cloud_auto_join.html "Nomad Cloud Auto-join"
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