118 lines
3.2 KiB
Markdown
118 lines
3.2 KiB
Markdown
---
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layout: "docs"
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page_title: "Nomad Networking"
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sidebar_current: "docs-jobspec-networking"
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description: |-
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Learn how to configure networking and ports for Nomad tasks.
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---
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# Networking
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When scheduling jobs in Nomad they are provisioned across your fleet of
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machines along with other jobs and services. Because you don't know in advance
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what host your job will be provisioned on, Nomad will provide your task with
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network configuration when they start up.
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Note that this document only applies to services that want to _listen_
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on a port. Batch jobs or services that only make outbound connections do not
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need to allocate ports, since they will use any available interface to make an
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outbound connection.
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## Ports
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In addition to allocating an interface, Nomad can allocate static or dynamic
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ports to your task.
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### Dynamic Ports
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Dynamic ports are allocated in a range from `20000` to `60000`.
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Most services run in your cluster should use dynamic ports. This means that the
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port will be allocated dynamically by the scheduler, and your service will have
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to read an environment variable (see below) to know which port to bind to at
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startup.
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```
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task "webservice" {
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...
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resources {
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...
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network {
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port "http" {}
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port "https" {}
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}
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}
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}
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```
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### Static Ports
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Static ports bind your job to a specific port on the host they're placed on.
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Since multiple services cannot share a port, the port must be open in order to
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place your task.
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```
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task "dnsservice" {
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...
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resources {
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...
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network {
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port "dns" {
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static = 53
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}
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}
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}
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}
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```
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We recommend _only_ using static ports for [system
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jobs](/docs/jobspec/schedulers.html) or specialized jobs like load balancers.
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### Labels and Environment Variables
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The label assigned to the port is used to identify the port in service
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discovery, and used for the name of the environment variable that indicates
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which port your application should bind to. For example, we've labeled this
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port `http`:
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```
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port "http" {}
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```
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When the task is started, it is passed the following environment variables:
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* `NOMAD_IP_http` - The IP to bind on for the given port label.
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* `NOMAD_PORT_http` - The port value for the given port label.
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* `NOMAD_ADDR_http` - A combined `IP:Port` that can be used for convenience.
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### Mapped Ports <a id="mapped_ports"></a>
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Some drivers (such as Docker and QEMU) allow you to map ports. A mapped port
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means that your application can listen on a fixed port (it does not need to
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read the environment variable) and the dynamic port will be mapped to the port
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in your container or VM.
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```
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driver = "docker"
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port "http" {}
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config {
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port_map = {
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http = 8080
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}
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}
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```
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The above example is for the Docker driver. The service is listening on port
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`8080` inside the container. The driver will automatically map the dynamic port
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to this service.
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When the task is started, it is passed an additional environment variable named
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`NOMAD_HOST_PORT_http` which indicates the host port that the http service is
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bound to.
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Please refer to the [Docker](/docs/drivers/docker.html) and [QEMU](/docs/drivers/qemu.html) drivers for additional information.
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