open-nomad/command/init.go

package command

import (
	"fmt"
	"io/ioutil"
	"os"
	"strings"
)

const (
	// DefaultInitName is the default name we use when
	// initializing the example file
	DefaultInitName = "example.nomad"
)

// InitCommand generates a new job template that you can customize to your
// liking, like vagrant init
type InitCommand struct {
	Meta
}

func (c *InitCommand) Help() string {
	helpText := `
Usage: nomad init

  Creates an example job file that can be used as a starting
  point to customize further.
`
	return strings.TrimSpace(helpText)
}

func (c *InitCommand) Synopsis() string {
	return "Create an example job file"
}

func (c *InitCommand) Run(args []string) int {
	// Check for misuse
	if len(args) != 0 {
		c.Ui.Error(c.Help())
		return 1
	}

	// Check if the file already exists
	_, err := os.Stat(DefaultInitName)
	if err != nil && !os.IsNotExist(err) {
		c.Ui.Error(fmt.Sprintf("Failed to stat '%s': %v", DefaultInitName, err))
		return 1
	}
	if !os.IsNotExist(err) {
		c.Ui.Error(fmt.Sprintf("Job '%s' already exists", DefaultInitName))
		return 1
	}

	// Write out the example
	err = ioutil.WriteFile(DefaultInitName, []byte(defaultJob), 0660)
	if err != nil {
		c.Ui.Error(fmt.Sprintf("Failed to write '%s': %v", DefaultInitName, err))
		return 1
	}

	// Success
	c.Ui.Output(fmt.Sprintf("Example job file written to %s", DefaultInitName))
	return 0
}

var defaultJob = strings.TrimSpace(`
# There can only be a single job definition per file. This job is named
# "example" so it will create a job with the ID and Name "example".

# The "job" stanza is the top-most configuration option in the job
# specification. A job is a declarative specification of tasks that Nomad
# should run. Jobs have a globally unique name, one or many task groups, which
# are themselves collections of one or many tasks.
#
# For more information and examples on the "job" stanza, please see
# the online documentation at:
#
#     https://www.nomadproject.io/docs/job-specification/job.html
#
job "example" {
  # The "region" parameter specifies the region in which to execute the job. If
  # omitted, this inherits the default region name of "global".
  # region = "global"

  # The "datacenters" parameter specifies the list of datacenters which should
  # be considered when placing this task. This must be provided.
  datacenters = ["dc1"]

  # The "type" parameter controls the type of job, which impacts the scheduler's
  # decision on placement. This configuration is optional and defaults to
  # "service". For a full list of job types and their differences, please see
  # the online documentation.
  #
  # For more information, please see the online documentation at:
  #
  #     https://www.nomadproject.io/docs/jobspec/schedulers.html
  #
  type = "service"

  # The "constraint" stanza defines additional constraints for placing this job,
  # in addition to any resource or driver constraints. This stanza may be placed
  # at the "job", "group", or "task" level, and supports variable interpolation.
  #
  # For more information and examples on the "constraint" stanza, please see
  # the online documentation at:
  #
  #     https://www.nomadproject.io/docs/job-specification/constraint.html
  #
  # constraint {
  #   attribute = "${attr.kernel.name}"
  #   value     = "linux"
  # }

  # The "update" stanza specifies the update strategy of task groups. The update
  # strategy is used to control things like rolling upgrades, canaries, and
  # blue/green deployments. If omitted, no update strategy is enforced. The
  # "update" stanza may be placed at the job or task group. When placed at the
  # job, it applies to all groups within the job. When placed at both the job and
  # group level, the stanzas are merged with the group's taking precedence.
  #
  # For more information and examples on the "update" stanza, please see
  # the online documentation at:
  #
  #     https://www.nomadproject.io/docs/job-specification/update.html
  #
  update {
    # The "max_parallel" parameter specifies the maximum number of updates to
    # perform in parallel. In this case, this specifies to update a single task
    # at a time.
    max_parallel = 1
    
    # The "min_healthy_time" parameter specifies the minimum time the allocation
    # must be in the healthy state before it is marked as healthy and unblocks
    # further allocations from being updated.
    min_healthy_time = "10s"
    
    # The "healthy_deadline" parameter specifies the deadline in which the
    # allocation must be marked as healthy after which the allocation is
    # automatically transitioned to unhealthy. Transitioning to unhealthy will
    # fail the deployment and potentially roll back the job if "auto_revert" is
    # set to true.
    healthy_deadline = "3m"
    
    # The "auto_revert" parameter specifies if the job should auto-revert to the
    # last stable job on deployment failure. A job is marked as stable if all the
    # allocations as part of its deployment were marked healthy.
    auto_revert = false
    
    # The "canary" parameter specifies that changes to the job that would result
    # in destructive updates should create the specified number of canaries
    # without stopping any previous allocations. Once the operator determines the
    # canaries are healthy, they can be promoted which unblocks a rolling update
    # of the remaining allocations at a rate of "max_parallel".
    #
    # Further, setting "canary" equal to the count of the task group allows
    # blue/green deployments. When the job is updated, a full set of the new
    # version is deployed and upon promotion the old version is stopped.
    canary = 0
  }

  # The "group" stanza defines a series of tasks that should be co-located on
  # the same Nomad client. Any task within a group will be placed on the same
  # client.
  #
  # For more information and examples on the "group" stanza, please see
  # the online documentation at:
  #
  #     https://www.nomadproject.io/docs/job-specification/group.html
  #
  group "cache" {
    # The "count" parameter specifies the number of the task groups that should
    # be running under this group. This value must be non-negative and defaults
    # to 1.
    count = 1

    # The "restart" stanza configures a group's behavior on task failure. If
    # left unspecified, a default restart policy is used based on the job type.
    #
    # For more information and examples on the "restart" stanza, please see
    # the online documentation at:
    #
    #     https://www.nomadproject.io/docs/job-specification/restart.html
    #
    restart {
      # The number of attempts to run the job within the specified interval.
      attempts = 2
      interval = "30m"

      # The "delay" parameter specifies the duration to wait before restarting
      # a task after it has failed.
      delay = "15s"

     # The "mode" parameter controls what happens when a task has restarted
     # "attempts" times within the interval. "delay" mode delays the next
     # restart until the next interval. "fail" mode does not restart the task
     # if "attempts" has been hit within the interval.
      mode = "fail"
    }

    # The "ephemeral_disk" stanza instructs Nomad to utilize an ephemeral disk
    # instead of a hard disk requirement. Clients using this stanza should
    # not specify disk requirements in the resources stanza of the task. All
    # tasks in this group will share the same ephemeral disk.
    #
    # For more information and examples on the "ephemeral_disk" stanza, please
    # see the online documentation at:
    #
    #     https://www.nomadproject.io/docs/job-specification/ephemeral_disk.html
    #
    ephemeral_disk {
      # When sticky is true and the task group is updated, the scheduler
      # will prefer to place the updated allocation on the same node and
      # will migrate the data. This is useful for tasks that store data
      # that should persist across allocation updates.
      # sticky = true
      # 
      # Setting migrate to true results in the allocation directory of a
      # sticky allocation directory to be migrated.
      # migrate = true

      # The "size" parameter specifies the size in MB of shared ephemeral disk
      # between tasks in the group.
      size = 300
    }

    # The "task" stanza creates an individual unit of work, such as a Docker
    # container, web application, or batch processing.
    #
    # For more information and examples on the "task" stanza, please see
    # the online documentation at:
    #
    #     https://www.nomadproject.io/docs/job-specification/task.html
    #
    task "redis" {
      # The "driver" parameter specifies the task driver that should be used to
      # run the task.
      driver = "docker"

      # The "config" stanza specifies the driver configuration, which is passed
      # directly to the driver to start the task. The details of configurations
      # are specific to each driver, so please see specific driver
      # documentation for more information.
      config {
        image = "redis:3.2"
        port_map {
          db = 6379
        }
      }

      # The "artifact" stanza instructs Nomad to download an artifact from a
      # remote source prior to starting the task. This provides a convenient
      # mechanism for downloading configuration files or data needed to run the
      # task. It is possible to specify the "artifact" stanza multiple times to
      # download multiple artifacts.
      #
      # For more information and examples on the "artifact" stanza, please see
      # the online documentation at:
      #
      #     https://www.nomadproject.io/docs/job-specification/artifact.html
      #
      # artifact {
      #   source = "http://foo.com/artifact.tar.gz"
      #   options {
      #     checksum = "md5:c4aa853ad2215426eb7d70a21922e794"
      #   }
      # }

      # The "logs" stanza instructs the Nomad client on how many log files and
      # the maximum size of those logs files to retain. Logging is enabled by
      # default, but the "logs" stanza allows for finer-grained control over
      # the log rotation and storage configuration.
      #
      # For more information and examples on the "logs" stanza, please see
      # the online documentation at:
      #
      #     https://www.nomadproject.io/docs/job-specification/logs.html
      #
      # logs {
      #   max_files     = 10
      #   max_file_size = 15
      # }

      # The "resources" stanza describes the requirements a task needs to
      # execute. Resource requirements include memory, network, cpu, and more.
      # This ensures the task will execute on a machine that contains enough
      # resource capacity.
      #
      # For more information and examples on the "resources" stanza, please see
      # the online documentation at:
      #
      #     https://www.nomadproject.io/docs/job-specification/resources.html
      #
      resources {
        cpu    = 500 # 500 MHz
        memory = 256 # 256MB
        network {
          mbits = 10
          port "db" {}
        }
      }

      # The "service" stanza instructs Nomad to register this task as a service
      # in the service discovery engine, which is currently Consul. This will
      # make the service addressable after Nomad has placed it on a host and
      # port.
      #
      # For more information and examples on the "service" stanza, please see
      # the online documentation at:
      #
      #     https://www.nomadproject.io/docs/job-specification/service.html
      #
      service {
        name = "redis-cache"
        tags = ["global", "cache"]
        port = "db"
        check {
          name     = "alive"
          type     = "tcp"
          interval = "10s"
          timeout  = "2s"
        }
      }

      # The "template" stanza instructs Nomad to manage a template, such as
      # a configuration file or script. This template can optionally pull data
      # from Consul or Vault to populate runtime configuration data.
      #
      # For more information and examples on the "template" stanza, please see
      # the online documentation at:
      #
      #     https://www.nomadproject.io/docs/job-specification/template.html
      #
      # template {
      #   data          = "---\nkey: {{ key \"service/my-key\" }}"
      #   destination   = "local/file.yml"
      #   change_mode   = "signal"
      #   change_signal = "SIGHUP"
      # }

      # The "template" stanza can also be used to create environment variables
      # for tasks that prefer those to config files. The task will be restarted
      # when data pulled from Consul or Vault changes.
      #
      # template {
      #   data        = "KEY={{ key \"service/my-key\" }}"
      #   destination = "local/file.env"
      #   env         = true
      # }

      # The "vault" stanza instructs the Nomad client to acquire a token from
      # a HashiCorp Vault server. The Nomad servers must be configured and
      # authorized to communicate with Vault. By default, Nomad will inject
      # The token into the job via an environment variable and make the token
      # available to the "template" stanza. The Nomad client handles the renewal
      # and revocation of the Vault token.
      #
      # For more information and examples on the "vault" stanza, please see
      # the online documentation at:
      #
      #     https://www.nomadproject.io/docs/job-specification/vault.html
      #
      # vault {
      #   policies      = ["cdn", "frontend"]
      #   change_mode   = "signal"
      #   change_signal = "SIGHUP"
      # }

      # Controls the timeout between signalling a task it will be killed
      # and killing the task. If not set a default is used.
      # kill_timeout = "20s"
    }
  }
}
`)