---
layout: "docs"
page_title: "parameterized Stanza - Job Specification"
sidebar_current: "docs-job-specification-parameterized"
description: |-
A parameterized job is used to encapsulate a set of work that can be carried
out on various inputs much like a function definition. When the
`parameterized` stanza is added to a job, the job acts as a function to the
cluster as a whole.
---
# `parameterized` Stanza
Placement |
job -> **parameterized**
|
A parameterized job is used to encapsulate a set of work that can be carried out
on various inputs much like a function definition. When the `parameterized`
stanza is added to a job, the job acts as a function to the cluster as a whole.
The `parameterized` stanza allows job operators to configure a job that carries
out a particular action, define its resource requirements and configure how
inputs and configuration are retrieved by the tasks within the job.
To invoke a parameterized job, [`nomad job
dispatch`][dispatch command] or the equivalent HTTP APIs are
used. When dispatching against a parameterized job, an opaque payload and
metadata may be injected into the job. These inputs to the parameterized job act
like arguments to a function. The job consumes them to change its behavior,
without exposing the implementation details to the caller.
To that end, tasks within the job can add a
[`dispatch_payload`][dispatch_payload] stanza that
defines where on the filesystem this payload gets written to. An example payload
would be a task's JSON configuration.
Further, certain metadata may be marked as required when dispatching a job so it
can be used to inject configuration directly into a task's arguments using
[interpolation]. An example of this would be to require a run ID key that
could be used to lookup the work the job is suppose to do from a management
service or database.
Each time a job is dispatched, a unique job ID is generated. This allows a
caller to track the status of the job, much like a future or promise in some
programming languages.
```hcl
job "docs" {
parameterized {
payload = "required"
meta_required = ["dispatcher_email"]
meta_optional = ["pager_email"]
}
}
```
## `parameterized` Requirements
- The job's [scheduler type][batch-type] must be `batch`.
## `parameterized` Parameters
- `meta_optional` `(array: nil)` - Specifies the set of metadata keys that
may be provided when dispatching against the job.
- `meta_required` `(array: nil)` - Specifies the set of metadata keys that
must be provided when dispatching against the job.
- `payload` `(string: "optional")` - Specifies the requirement of providing a
payload when dispatching against the parameterized job. The **maximum size of a
`payload` is 16 KiB**. The options for this
field are:
- `"optional"` - A payload is optional when dispatching against the job.
- `"required"` - A payload must be provided when dispatching against the job.
- `"forbidden"` - A payload is forbidden when dispatching against the job.
## `parameterized` Examples
The following examples show non-runnable example parameterized jobs:
### Required Inputs
This example shows a parameterized job that requires both a payload and
metadata:
```hcl
job "video-encode" {
# ...
type = "batch"
parameterized {
payload = "required"
meta_required = ["dispatcher_email"]
}
group "encode" {
# ...
task "ffmpeg" {
driver = "exec"
config {
command = "ffmpeg-wrapper"
# When dispatched, the payload is written to a file that is then read by
# the created task upon startup
args = ["-config=${NOMAD_TASK_DIR}/config.json"]
}
dispatch_payload {
file = "config.json"
}
}
}
}
```
### Metadata Interpolation
```hcl
job "email-blast" {
# ...
type = "batch"
parameterized {
payload = "forbidden"
meta_required = ["CAMPAIGN_ID"]
}
group "emails" {
# ...
task "emailer" {
driver = "exec"
config {
command = "emailer"
# The campaign ID is interpolated and injected into the task's
# arguments
args = ["-campaign=${NOMAD_META_CAMPAIGN_ID}"]
}
}
}
}
```
[batch-type]: /docs/job-specification/job.html#type "Batch scheduler type"
[dispatch command]: /docs/commands/job/dispatch.html "Nomad Job Dispatch Command"
[resources]: /docs/job-specification/resources.html "Nomad resources Job Specification"
[interpolation]: /docs/runtime/interpolation.html "Nomad Runtime Interpolation"
[dispatch_payload]: /docs/job-specification/dispatch_payload.html "Nomad dispatch_payload Job Specification"