github.com/ranjib/nomad@v0.1.1-0.20160225204057-97751b02f70b/website/source/docs/jobspec/networking.html.md (about)

     1  ---
     2  layout: "docs"
     3  page_title: "Nomad Networking"
     4  sidebar_current: "docs-jobspec-networking"
     5  description: |-
     6    Learn how to configure networking and ports for Nomad tasks.
     7  ---
     8  
     9  # Networking
    10  
    11  When scheduling jobs in Nomad they are provisioned across your fleet of
    12  machines along with other jobs and services. Because you don't know in advance
    13  what host your job will be provisioned on, Nomad will provide your task with
    14  network configuration when they start up.
    15  
    16  Note that this document only applies to services that want to _listen_
    17  on a port. Batch jobs or services that only make outbound connections do not
    18  need to allocate ports, since they will use any available interface to make an
    19  outbound connection.
    20  
    21  ## Ports
    22  
    23  In addition to allocating an interface, Nomad can allocate static or dynamic
    24  ports to your task.
    25  
    26  ### Dynamic Ports
    27  
    28  Dynamic ports are allocated in a range from `20000` to `60000`.
    29  
    30  Most services run in your cluster should use dynamic ports. This means that the
    31  port will be allocated dynamically by the scheduler, and your service will have
    32  to read an environment variable (see below) to know which port to bind to at
    33  startup.
    34  
    35  ```
    36  task "webservice" {
    37      ...
    38      resources {
    39          ...
    40          network {
    41              port "http" {}
    42              port "https" {}
    43          }
    44      }
    45  }
    46  ```
    47  
    48  ### Static Ports
    49  
    50  Static ports bind your job to a specific port on the host they're placed on.
    51  Since multiple services cannot share a port, the port must be open in order to
    52  place your task.
    53  
    54  ```
    55  task "dnsservice" {
    56      ...
    57      resources {
    58          ...
    59          network {
    60              port "dns" {
    61                  static = 53
    62              }
    63          }
    64      }
    65  }
    66  ```
    67  
    68  We recommend _only_ using static ports for [system
    69  jobs](/docs/jobspec/schedulers.html) or specialized jobs like load balancers.
    70  
    71  ### Labels and Environment Variables
    72  
    73  The label assigned to the port is used to identify the port in service
    74  discovery, and used for the name of the environment variable that indicates
    75  which port your application should bind to. For example, we've labeled this
    76  port `http`:
    77  
    78  ```
    79  port "http" {}
    80  ```
    81  
    82  When the task is started, it is passed an environment variable named
    83  `NOMAD_ADDR_http` which indicates a combination of the interface IP and port.
    84  
    85  ```
    86  NOMAD_ADDR_http=127.0.0.1:53423 ./start-command
    87  ```
    88  
    89  ### Mapped Ports <a id="mapped_ports"></a>
    90  
    91  Some drivers (such as Docker and QEMU) allow you to map ports. A mapped port
    92  means that your application can listen on a fixed port (it does not need to
    93  read the environment variable) and the dynamic port will be mapped to the port
    94  in your container or VM.
    95  
    96  ```
    97  driver = "docker"
    98  
    99  port "http" {}
   100  
   101  config {
   102      port_map = {
   103          http = 8080
   104      }
   105  }
   106  ```
   107  
   108  The above example is for the Docker driver. The service is listening on port
   109  `8080` inside the container. The driver will automatically map the dynamic port
   110  to this service.
   111  
   112  When the task is started, it is passed an additional environment variable named
   113  `NOMAD_HOST_PORT_http` which indicates the host port that the http service is
   114  bound to.
   115  
   116  Please refer to the [Docker](/docs/drivers/docker.html) and [QEMU](/docs/drivers/qemu.html) drivers for additional information.