open-nomad/website/source/api/json-jobs.html.md

---
layout: api
page_title: JSON Job Specification - HTTP API
sidebar_current: api-jobs
description: |-
  Jobs can also be specified via the HTTP API using a JSON format. This guide
  discusses the job specification in JSON format.
---

# JSON Job Specification

This guide covers the JSON syntax for submitting jobs to Nomad. A useful command
for generating valid JSON versions of HCL jobs is:

```shell
$ nomad run -output my-job.nomad
```

## Syntax

Below is the JSON representation of the job outputed by `$ nomad init`:

```json
{
    "Job": {
        "ID": "example",
        "Name": "example",
        "Type": "service",
        "Priority": 50,
        "Datacenters": [
            "dc1"
        ],
        "TaskGroups": [{
            "Name": "cache",
            "Count": 1,
            "Tasks": [{
                "Name": "redis",
                "Driver": "docker",
                "User": "",
                "Config": {
                    "image": "redis:3.2",
                    "port_map": [{
                        "db": 6379
                    }]
                },
                "Services": [{
                    "Id": "",
                    "Name": "global-redis-check",
                    "Tags": [
                        "global",
                        "cache"
                    ],
                    "PortLabel": "db",
                    "AddressMode": "",
                    "Checks": [{
                        "Id": "",
                        "Name": "alive",
                        "Type": "tcp",
                        "Command": "",
                        "Args": null,
                        "Path": "",
                        "Protocol": "",
                        "PortLabel": "",
                        "Interval": 10000000000,
                        "Timeout": 2000000000,
                        "InitialStatus": "",
                        "TLSSkipVerify": false
                    }]
                }],
                "Resources": {
                    "CPU": 500,
                    "MemoryMB": 256,
                    "Networks": [{
                        "Device": "",
                        "CIDR": "",
                        "IP": "",
                        "MBits": 10,
                        "DynamicPorts": [{
                            "Label": "db",
                            "Value": 0
                        }]
                    }]
                },
                "Leader": false
            }],
            "RestartPolicy": {
                "Interval": 300000000000,
                "Attempts": 10,
                "Delay": 25000000000,
                "Mode": "delay"
            },
            "EphemeralDisk": {
                "SizeMB": 300
            }
        }],
        "Update": {
            "MaxParallel": 1,
            "MinHealthyTime": 10000000000,
            "HealthyDeadline": 180000000000,
            "AutoRevert": false,
            "Canary": 0
        }
    }
}
```

The example JSON could be submitted as a job using the following:

```text
$ curl -XPUT @d example.json http://127.0.0.1:4646/v1/job/example
{
  "EvalID": "5d6ded54-0b2a-8858-6583-be5f476dec9d",
  "EvalCreateIndex": 12,
  "JobModifyIndex": 11,
  "Warnings": "",
  "Index": 12,
  "LastContact": 0,
  "KnownLeader": false
}
```

## Syntax Reference

Following is a syntax reference for the possible keys that are supported and
their default values if any for each type of object.

### Job

The `Job` object supports the following keys:

- `AllAtOnce` - Controls if the entire set of tasks in the job must
  be placed atomically or if they can be scheduled incrementally.
  This should only be used for special circumstances. Defaults to `false`.

- `Constraints` - A list to define additional constraints where a job can be
  run. See the constraint reference for more details.

- `Datacenters` - A list of datacenters in the region which are eligible
  for task placement. This must be provided, and does not have a default.

- `TaskGroups` - A list to define additional task groups. See the task group
  reference for more details.

- `Meta` - Annotates the job with opaque metadata.

- `ParameterizedJob` - Specifies the job as a parameterized job such that it can
  be dispatched against. The `ParamaterizedJob` object supports the following
  attributes:

  - `MetaOptional` - Specifies the set of metadata keys that may be provided
    when dispatching against the job as a string array.

  - `MetaRequired` - Specifies the set of metadata keys that must be provided
    when dispatching against the job as a string array.

  - `Payload` - Specifies the requirement of providing a payload when
    dispatching against the parameterized job. The options for this field are
    "optional", "required" and "forbidden". The default value is "optional".

- `Payload` - The payload may not be set when submitting a job but may appear in
  a dispatched job. The `Payload` will be a base64 encoded string containing the
  payload that the job was dispatched with. The `payload` has a **maximum size
  of 16 KiB**.

- `Priority` - Specifies the job priority which is used to prioritize
  scheduling and access to resources. Must be between 1 and 100 inclusively,
  and defaults to 50.

- `Region` - The region to run the job in, defaults to "global".

- `Type` - Specifies the job type and switches which scheduler
  is used. Nomad provides the `service`, `system` and `batch` schedulers,
  and defaults to `service`. To learn more about each scheduler type visit
  [here](/docs/runtime/schedulers.html)

- `Update` - Specifies an update strategy to be applied to all task groups
  within the job. When specified both at the job level and the task group level,
  the update blocks are merged with the task group's taking precedence. For more
  details on the update stanza, please see below.

-   `Periodic` - `Periodic` allows the job to be scheduled at fixed times, dates
    or intervals. The periodic expression is always evaluated in the UTC
    timezone to ensure consistent evaluation when Nomad Servers span multiple
    time zones. The `Periodic` object is optional and supports the following attributes:

    - `Enabled` - `Enabled` determines whether the periodic job will spawn child
    jobs.

    - `time_zone` - Specifies the time zone to evaluate the next launch interval
      against. This is useful when wanting to account for day light savings in
      various time zones. The time zone must be parsable by Golang's
      [LoadLocation](https://golang.org/pkg/time/#LoadLocation). The default is
      UTC.

    - `SpecType` - `SpecType` determines how Nomad is going to interpret the
      periodic expression. `cron` is the only supported `SpecType` currently.

    - `Spec` - A cron expression configuring the interval the job is launched
    at. Supports predefined expressions such as "@daily" and "@weekly" See
    [here](https://github.com/gorhill/cronexpr#implementation) for full
    documentation of supported cron specs and the predefined expressions.

    - <a id="prohibit_overlap">`ProhibitOverlap`</a> - `ProhibitOverlap` can
      be set to true to enforce that the periodic job doesn't spawn a new
      instance of the job if any of the previous jobs are still running. It is
      defaulted to false.

    An example `periodic` block:

    ```json
    {
      "Periodic": {
          "Spec": "*/15 - *"
          "SpecType": "cron",
          "Enabled": true,
          "ProhibitOverlap": true
      }
    }
    ```

### Task Group

`TaskGroups` is a list of `TaskGroup` objects, each supports the following
attributes:

- `Constraints` - This is a list of `Constraint` objects. See the constraint
  reference for more details.

- `Count` - Specifies the number of the task groups that should
  be running. Must be non-negative, defaults to one.

- `Meta` - A key-value map that annotates the task group with opaque metadata.

- `Name` - The name of the task group. Must be specified.

- `RestartPolicy` - Specifies the restart policy to be applied to tasks in this group.
  If omitted, a default policy for batch and non-batch jobs is used based on the
  job type. See the [restart policy reference](#restart_policy) for more details.

- `EphemeralDisk` - Specifies the group's ephemeral disk requirements. See the
  [ephemeral disk reference](#ephemeral_disk) for more details.

- `Update` - Specifies an update strategy to be applied to all task groups
  within the job. When specified both at the job level and the task group level,
  the update blocks are merged with the task group's taking precedence. For more
  details on the update stanza, please see below.

- `Tasks` - A list of `Task` object that are part of the task group.

### Task

The `Task` object supports the following keys:

- `Artifacts` - `Artifacts` is a list of `Artifact` objects which define
  artifacts to be downloaded before the task is run. See the artifacts
  reference for more details.

- `Config` - A map of key-value configuration passed into the driver
  to start the task. The details of configurations are specific to
  each driver.

- `Constraints` - This is a list of `Constraint` objects. See the constraint
  reference for more details.

- `DispatchPayload` - Configures the task to have access to dispatch payloads.
  The `DispatchPayload` object supports the following attributes:

  - `File` - Specifies the file name to write the content of dispatch payload
    to. The file is written relative to the task's local directory.

- `Driver` - Specifies the task driver that should be used to run the
  task. See the [driver documentation](/docs/drivers/index.html) for what
  is available. Examples include `docker`, `qemu`, `java`, and `exec`.

-   `Env` - A map of key-value representing environment variables that
    will be passed along to the running process. Nomad variables are
    interpreted when set in the environment variable values. See the table of
    interpreted variables [here](/docs/runtime/interpolation.html).

    For example the below environment map will be reinterpreted:

    ```json
    {
      "Env": {
        "NODE_CLASS" : "${nomad.class}"
      }
    }
    ```

- `KillTimeout` - `KillTimeout` is a time duration in nanoseconds. It can be
  used to configure the time between signaling a task it will be killed and
  actually killing it. Drivers first sends a task the `SIGINT` signal and then
  sends `SIGTERM` if the task doesn't die after the `KillTimeout` duration has
  elapsed. The default `KillTimeout` is 5 seconds.

- `leader` - Specifies whether the task is the leader task of the task group. If
  set to true, when the leader task completes, all other tasks within the task
  group will be gracefully shutdown.

- `LogConfig` - This allows configuring log rotation for the `stdout` and `stderr`
  buffers of a Task. See the log rotation reference below for more details.

- `Meta` - Annotates the task group with opaque metadata.

- `Name` - The name of the task. This field is required.

- `Resources` - Provides the resource requirements of the task.
  See the resources reference for more details.

- `Services` - `Services` is a list of `Service` objects. Nomad integrates with
  Consul for service discovery. A `Service` object represents a routable and
  discoverable service on the network. Nomad automatically registers when a task
  is started and de-registers it when the task transitions to the dead state.
  [Click here](/docs/service-discovery/index.html) to learn more about
  services. Below is the fields in the `Service` object:

     - `Name`: An explicit name for the Service. Nomad will replace `${JOB}`,
       `${TASKGROUP}` and `${TASK}` by the name of the job, task group or task,
       respectively. `${BASE}` expands to the equivalent of
       `${JOB}-${TASKGROUP}-${TASK}`, and is the default name for a Service.
       Each service defined for a given task must have a distinct name, so if
       a task has multiple services only one of them can use the default name
       and the others must be explicitly named. Names must adhere to
       [RFC-1123 §2.1](https://tools.ietf.org/html/rfc1123#section-2) and are
       limited to alphanumeric and hyphen characters (i.e. `[a-z0-9\-]`), and be
       less than 64 characters in length.

     - `Tags`: A list of string tags associated with this Service. String
       interpolation is supported in tags.

     - `PortLabel`: `PortLabel` is an optional string and is used to associate
       a port with the service.  If specified, the port label must match one
       defined in the resources block.  This could be a label of either a
       dynamic or a static port.

     - `Checks`: `Checks` is an array of check objects. A check object defines a
       health check associated with the service. Nomad supports the `script`,
       `http` and `tcp` Consul Checks. Script checks are not supported for the
       qemu driver since the Nomad client doesn't have access to the file system
       of a task using the Qemu driver.

         - `Type`:  This indicates the check types supported by Nomad. Valid
           options are currently `script`, `http` and `tcp`.

         - `Name`: The name of the health check.

         - `Interval`: This indicates the frequency of the health checks that
           Consul will perform.

         - `Timeout`: This indicates how long Consul will wait for a health
           check query to succeed.

         - `Path`: The path of the HTTP endpoint which Consul will query to query
           the health of a service if the type of the check is `http`. Nomad
           will add the IP of the service and the port, users are only required
           to add the relative URL of the health check endpoint.

         - `Protocol`: This indicates the protocol for the HTTP checks. Valid
           options are `http` and `https`. We default it to `http`.

         - `Command`: This is the command that the Nomad client runs for doing
           script based health check.

         - `Args`: Additional arguments to the `command` for script based health
           checks.

	 - `TLSSkipVerify`: If true, Consul will not attempt to verify the
	   certificate when performing HTTPS checks. Requires Consul >= 0.7.2.

- `Templates` - Specifies the set of [`Template`](#template) objects to render for the task.
  Templates can be used to inject both static and dynamic configuration with
  data populated from environment variables, Consul and Vault.

- `User` - Set the user that will run the task. It defaults to the same user
  the Nomad client is being run as. This can only be set on Linux platforms.

### Resources

The `Resources` object supports the following keys:

- `CPU` - The CPU required in MHz.

- `IOPS` - The number of IOPS required given as a weight between 10-1000.

- `MemoryMB` - The memory required in MB.

- `Networks` - A list of network objects.

The Network object supports the following keys:

- `MBits` - The number of MBits in bandwidth required.

Nomad can allocate two types of ports to a task - Dynamic and Static/Reserved
ports. A network object allows the user to specify a list of `DynamicPorts` and
`ReservedPorts`. Each object supports the following attributes:

- `Value` - The port number for static ports. If the port is dynamic, then this
  attribute is ignored.
- `Label` - The label to annotate a port so that it can be referred in the
  service discovery block or environment variables.

<a id="ephemeral_disk"></a>

### Ephemeral Disk

The `EphemeralDisk` object supports the following keys:

- `Migrate` - Specifies that the Nomad client should make a best-effort attempt
  to migrate the data from a remote machine if placement cannot be made on the
  original node. During data migration, the task will block starting until the
  data migration has completed. Value is a boolean and the default is false.

- `SizeMB` - Specifies the size of the ephemeral disk in MB. Default is 300.

- `Sticky` - Specifies that Nomad should make a best-effort attempt to place the
  updated allocation on the same machine. This will move the `local/` and
  `alloc/data` directories to the new allocation. Value is a boolean and the
  default is false.

<a id="restart_policy"></a>

### Restart Policy

The `RestartPolicy` object supports the following keys:

- `Attempts` - `Attempts` is the number of restarts allowed in an `Interval`.

- `Interval` - `Interval` is a time duration that is specified in nanoseconds.
  The `Interval` begins when the first task starts and ensures that only
  `Attempts` number of restarts happens within it. If more than `Attempts`
  number of failures happen, behavior is controlled by `Mode`.

- `Delay` - A duration to wait before restarting a task. It is specified in
  nanoseconds. A random jitter of up to 25% is added to the delay.

-   `Mode` - `Mode` is given as a string and controls the behavior when the task
    fails more than `Attempts` times in an `Interval`. Possible values are listed
    below:

    - `delay` - `delay` will delay the next restart until the next `Interval` is
      reached.

    - `fail` - `fail` will not restart the task again.

### Update

Specifies the task group update strategy. When omitted, rolling updates are
disabled. The update stanza can be specified at the job or task group level.
When specified at the job, the update stanza is inherited by all task groups.
When specified in both the job and in a task group, the stanzas are merged with
the task group's taking precedence. The `Update` object supports the following
attributes:

- `MaxParallel` - `MaxParallel` is given as an integer value and specifies
the number of tasks that can be updated at the same time.

- `HealthCheck` - Specifies the mechanism in which allocations health is
determined. The potential values are:

  - "checks" - Specifies that the allocation should be considered healthy when
    all of its tasks are running and their associated [checks][] are healthy,
    and unhealthy if any of the tasks fail or not all checks become healthy.
    This is a superset of "task_states" mode.

  - "task_states" - Specifies that the allocation should be considered healthy
    when all its tasks are running and unhealthy if tasks fail.

  - "manual" - Specifies that Nomad should not automatically determine health
    and that the operator will specify allocation health using the [HTTP
    API](/api/deployments.html#set-allocation-health-in-deployment).

- `MinHealthyTime` - 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. This is specified using a label suffix like "30s" or
  "15m".

- `HealthyDeadline` - Specifies the deadline in which the allocation must be
  marked as healthy after which the allocation is automatically transitioned to
  unhealthy. This is specified using a label suffix like "2m" or "1h".

- `AutoRevert` - 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.

- `Canary` - 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`.

- `Stagger` - Specifies the delay between migrating allocations off nodes marked
  for draining. This is specified using a label suffix like "30s" or "1h".

An example `Update` block:

```json
{
  "Update": {
        "MaxParallel": 3,
        "HealthCheck": "checks",
        "MinHealthyTime": 15000000000,
        "HealthyDeadline": 180000000000,
        "AutoRevert": false,
        "Canary": 1
  }
}
```

### Constraint

The `Constraint` object supports the following keys:

- `LTarget` - Specifies the attribute to examine for the
  constraint. See the table of attributes [here](/docs/runtime/interpolation.html#interpreted_node_vars).

- `RTarget` - Specifies the value to compare the attribute against.
  This can be a literal value, another attribute or a regular expression if
  the `Operator` is in "regexp" mode.

- `Operand` - Specifies the test to be performed on the two targets. It takes on the
  following values:

  - `regexp` - Allows the `RTarget` to be a regular expression to be matched.

  - `set_contains` - Allows the `RTarget` to be a comma separated list of values
    that should be contained in the LTarget's value.

  - `distinct_host` - If set, the scheduler will not co-locate any task groups on the same
        machine. This can be specified as a job constraint which applies the
        constraint to all task groups in the job, or as a task group constraint which
        scopes the effect to just that group. The constraint may not be
        specified at the task level.

        Placing the constraint at both the job level and at the task group level is
        redundant since when placed at the job level, the constraint will be applied
        to all task groups. When specified, `LTarget` and `RTarget` should be
        omitted.

  - `distinct_property` - If set, the scheduler selects nodes that have a
        distinct value of the specified property. The `RTarget` specifies how
        many allocations are allowed to share the value of a property. The
        `RTarget` must be 1 or greater and if omitted, defaults to 1. This can
        be specified as a job constraint which applies the constraint to all
        task groups in the job, or as a task group constraint which scopes the
        effect to just that group. The constraint may not be specified at the
        task level.

        Placing the constraint at both the job level and at the task group level is
        redundant since when placed at the job level, the constraint will be applied
        to all task groups. When specified, `LTarget` should be the property
        that should be distinct and and `RTarget` should be omitted.

  - Comparison Operators - `=`, `==`, `is`, `!=`, `not`, `>`, `>=`, `<`, `<=`. The
    ordering is compared lexically.

### Log Rotation

The `LogConfig` object configures the log rotation policy for a task's `stdout` and
`stderr`. The `LogConfig` object supports the following attributes:

- `MaxFiles` - The maximum number of rotated files Nomad will retain for
  `stdout` and `stderr`, each tracked individually.

- `MaxFileSizeMB` - The size of each rotated file. The size is specified in
  `MB`.

If the amount of disk resource requested for the task is less than the total
amount of disk space needed to retain the rotated set of files, Nomad will return
a validation error when a job is submitted.

```json
{
  "LogConfig": {
    "MaxFiles": 3,
    "MaxFileSizeMB": 10
  }
}
```

In the above example we have asked Nomad to retain 3 rotated files for both
`stderr` and `stdout` and size of each file is 10 MB. The minimum disk space that
would be required for the task would be 60 MB.

### Artifact

Nomad downloads artifacts using
[`go-getter`](https://github.com/hashicorp/go-getter). The `go-getter` library
allows downloading of artifacts from various sources using a URL as the input
source. The key-value pairs given in the `options` block map directly to
parameters appended to the supplied `source` URL. These are then used by
`go-getter` to appropriately download the artifact. `go-getter` also has a CLI
tool to validate its URL and can be used to check if the Nomad `artifact` is
valid.

Nomad allows downloading `http`, `https`, and `S3` artifacts. If these artifacts
are archives (zip, tar.gz, bz2, etc.), these will be unarchived before the task
is started.

The `Artifact` object supports the following keys:

- `GetterSource` - The path to the artifact to download.

- `RelativeDest` - An optional path to download the artifact into relative to the
  root of the task's directory. If omitted, it will default to `local/`.

- `GetterOptions` - A `map[string]string` block of options for `go-getter`.
  Full documentation of supported options are available
  [here](https://github.com/hashicorp/go-getter/tree/ef5edd3d8f6f482b775199be2f3734fd20e04d4a#protocol-specific-options-1).
  An example is given below:

```json
{
  "GetterOptions": {
    "checksum": "md5:c4aa853ad2215426eb7d70a21922e794",

    "aws_access_key_id": "<id>",
    "aws_access_key_secret": "<secret>",
    "aws_access_token": "<token>"
  }
}
```

An example of downloading and unzipping an archive is as simple as:

```json
{
  "Artifacts": [
    {
      "GetterSource": "https://example.com/my.zip",
      "GetterOptions": {
        "checksum": "md5:7f4b3e3b4dd5150d4e5aaaa5efada4c3"
      }
    }
  ]
}
```

#### S3 examples

S3 has several different types of addressing and more detail can be found
[here](http://docs.aws.amazon.com/AmazonS3/latest/dev/UsingBucket.html#access-bucket-intro)

S3 region specific endpoints can be found
[here](http://docs.aws.amazon.com/general/latest/gr/rande.html#s3_region)

Path based style:

```json
{
  "Artifacts": [
    {
      "GetterSource": "https://s3-us-west-2.amazonaws.com/my-bucket-example/my_app.tar.gz",
    }
  ]
}
```

or to override automatic detection in the URL, use the S3-specific syntax

```json
{
  "Artifacts": [
    {
      "GetterSource": "s3::https://s3-eu-west-1.amazonaws.com/my-bucket-example/my_app.tar.gz",
    }
  ]
}
```

Virtual hosted based style

```json
{
  "Artifacts": [
    {
      "GetterSource": "my-bucket-example.s3-eu-west-1.amazonaws.com/my_app.tar.gz",
    }
  ]
}
```

### Template

The `Template` block instantiates an instance of a template renderer. This
creates a convenient way to ship configuration files that are populated from
environment variables, Consul data, Vault secrets, or just general
configurations within a Nomad task.

Nomad utilizes a tool called [Consul Template][ct]. Since Nomad v0.5.3, the
template can reference [Nomad's runtime environment variables][env]. For a full
list of the API template functions, please refer to the [Consul Template
README][ct].


`Template` object supports following attributes:

- `ChangeMode` - Specifies the behavior Nomad should take if the rendered
  template changes. The default value is `"restart"`. The possible values are:

  - `"noop"` - take no action (continue running the task)
  - `"restart"` - restart the task
  - `"signal"` - send a configurable signal to the task

- `ChangeSignal` - Specifies the signal to send to the task as a string like
  "SIGUSR1" or "SIGINT". This option is required if the `ChangeMode` is
  `signal`.

- `DestPath` - Specifies the location where the resulting template should be
  rendered, relative to the task directory.

- `EmbeddedTmpl` -  Specifies the raw template to execute. One of `SourcePath`
  or `EmbeddedTmpl` must be specified, but not both. This is useful for smaller
  templates, but we recommend using `SourcePath` for larger templates.

- `Envvars` - Specifies the template should be read back as environment
  variables for the task.

- `LeftDelim` - Specifies the left delimiter to use in the template. The default
  is "{{" for some templates, it may be easier to use a different delimiter that
  does not conflict with the output file itself.

- `Perms` - Specifies the rendered template's permissions. File permissions are
  given as octal of the Unix file permissions rwxrwxrwx.

- `RightDelim` - Specifies the right delimiter to use in the template. The default
  is "}}" for some templates, it may be easier to use a different delimiter that
  does not conflict with the output file itself.

- `SourcePath` - Specifies the path to the template to be rendered. `SourcePath`
  is mutually exclusive with `EmbeddedTmpl` attribute. The source can be fetched
  using an [`Artifact`](#artifact) resource. The template must exist on the
  machine prior to starting the task; it is not possible to reference a template
  inside of a Docker container, for example.

- `Splay` - Specifies a random amount of time to wait between 0 ms and the given
  splay value before invoking the change mode. Should be specified in
  nanoseconds.


```json
{
  "Templates": [
    {
      "SourcePath": "local/config.conf.tpl",
      "DestPath": "local/config.conf",
      "EmbeddedTmpl": "",
      "ChangeMode": "signal",
      "ChangeSignal": "SIGUSR1",
      "Splay": 5000000000
    }
  ]
}
```

[ct]: https://github.com/hashicorp/consul-template "Consul Template by HashiCorp"
[env]: /docs/runtime/environment.html "Nomad Runtime Environment"