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Documentation for interpreted variables
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| Original file line number | Diff line number | Diff line change |
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| --- | ||
| layout: "docs" | ||
| page_title: "Interpreted Variables" | ||
| sidebar_current: "docs-jobspec-interpreted" | ||
| description: |- | ||
| Learn about the Nomad's interpreted variables. | ||
| --- | ||
| # Interpreted Variables | ||
|
|
||
| Nomad support interpreting two classes of variables, node attributes and runtime | ||
| environment variables. Node attributes are interpretable in constraints, task | ||
| environment variables and certain driver fields. Runtime environment variables | ||
| are not interpretable in constraints because they are only defined once the | ||
| scheduler has placed them on a particular node. | ||
|
|
||
| The syntax for interpreting variables is `${variable}`. An example and a | ||
| comprehensive list of interpretable fields can be seen below: | ||
|
|
||
| ``` | ||
| task "demo" { | ||
| driver = "docker" | ||
| # Drivers support interpreting node attributes and runtime environment | ||
| # variables | ||
| config { | ||
| image = "my-app" | ||
| # Interpret runtime variables to inject the address to bind to and the | ||
| # location to write logs to. | ||
| args = ["--bind=${NOMAD_ADDR_RPC}", "--logs=${NOMAD_ALLOC_DIR}/logs"] | ||
| port_map { | ||
| RPC = 6379 | ||
| } | ||
| } | ||
| # Constraints only support node attributes as runtime environment variables | ||
| # are only defined after the task is placed on a node. | ||
| constraint { | ||
| attribute = "${attr.kernel.name}" | ||
| value = "linux" | ||
| } | ||
| # Environment variables are interpreted and can contain both runtime and | ||
| # node attributes. | ||
| env { | ||
| "DC" = "Running on datacenter ${node.datacenter}" | ||
| "VERSION" = "Version ${NOMAD_META_VERSION}" | ||
| } | ||
| # Meta keys are also interpretable. | ||
| meta { | ||
| VERSION = "v0.3" | ||
| } | ||
| } | ||
| ``` | ||
|
|
||
| ## Node Variables <a id="interpreted_node_vars"></a> | ||
|
|
||
| Below is a full listing of node attributes that are interpretable. These | ||
| attributes are Interpreted by __both__ constraints and within the task and | ||
| driver. | ||
|
|
||
| <table class="table table-bordered table-striped"> | ||
| <tr> | ||
| <th>Variable</th> | ||
| <th>Description</th> | ||
| </tr> | ||
| <tr> | ||
| <td>${node.unique.id}</td> | ||
| <td>The client node identifier</td> | ||
| </tr> | ||
| <tr> | ||
| <td>${node.datacenter}</td> | ||
| <td>The client node datacenter</td> | ||
| </tr> | ||
| <tr> | ||
| <td>${node.unique.name}</td> | ||
| <td>The client node name</td> | ||
| </tr> | ||
| <tr> | ||
| <td>${node.class}</td> | ||
| <td>The client node class</td> | ||
| </tr> | ||
| <tr> | ||
| <td>${attr.\<key\}></td> | ||
| <td>The attribute given by `key` on the client node.</td> | ||
| </tr> | ||
| <tr> | ||
| <td>${meta.\<key\>}</td> | ||
| <td>The metadata value given by `key` on the client node.</td> | ||
| </tr> | ||
| </table> | ||
|
|
||
| Below is a table documenting common node attributes: | ||
|
|
||
| <table class="table table-bordered table-striped"> | ||
| <tr> | ||
| <th>Attribute</th> | ||
| <th>Description</th> | ||
| </tr> | ||
| <tr> | ||
| <td>arch</td> | ||
| <td>CPU architecture of the client. Examples: `amd64`, `386`</td> | ||
| </tr> | ||
| <tr> | ||
| <td>consul.datacenter</td> | ||
| <td>The Consul datacenter of the client node if Consul found</td> | ||
| </tr> | ||
| <tr> | ||
| <td>cpu.numcores</td> | ||
| <td>Number of CPU cores on the client</td> | ||
| </tr> | ||
| <tr> | ||
| <td>driver.\<key\></td> | ||
| <td>See the [task drivers](/docs/drivers/index.html) for attribute documentation</td> | ||
| </tr> | ||
| <tr> | ||
| <td>hostname</td> | ||
| <td>Hostname of the client</td> | ||
| </tr> | ||
| <tr> | ||
| <td>kernel.name</td> | ||
| <td>Kernel of the client. Examples: `linux`, `darwin`</td> | ||
| </tr> | ||
| <tr> | ||
| <td>kernel.version</td> | ||
| <td>Version of the client kernel. Examples: `3.19.0-25-generic`, `15.0.0`</td> | ||
| </tr> | ||
| <tr> | ||
| <td>platform.aws.ami-id</td> | ||
| <td>On EC2, the AMI ID of the client node</td> | ||
| </tr> | ||
| <tr> | ||
| <td>platform.aws.instance-type</td> | ||
| <td>On EC2, the instance type of the client node</td> | ||
| </tr> | ||
| <tr> | ||
| <td>os.name</td> | ||
| <td>Operating system of the client. Examples: `ubuntu`, `windows`, `darwin`</td> | ||
| </tr> | ||
| <tr> | ||
| <td>os.version</td> | ||
| <td>Version of the client OS</td> | ||
| </tr> | ||
| </table> | ||
|
|
||
| ## Environment Variables <a id="interpreted_env_vars"></a> | ||
|
|
||
| The following are runtime environment variables that describe the environment | ||
| the task is running in. These are only defined once the task has been placed on | ||
| a particular node and as such can not be used in constraints. | ||
|
|
||
| <table class="table table-bordered table-striped"> | ||
| <tr> | ||
| <th>Variable</th> | ||
| <th>Description</th> | ||
| </tr> | ||
| <tr> | ||
| <td>${NOMAD_ALLOC_DIR}</td> | ||
| <td>The path to the shared `alloc/` directory. See | ||
| [here](/docs/jobspec/environment.html#task_dir) for more | ||
| information.</td> | ||
| </tr> | ||
| <tr> | ||
| <td>${NOMAD_TASK_DIR}</td> | ||
| <td>The path to the task `local/` directory. See | ||
| [here](/docs/jobspec/environment.html#task_dir) for more | ||
| information.</td> | ||
| </tr> | ||
| <tr> | ||
| <td>${NOMAD_MEMORY_LIMIT}</td> | ||
| <td>The memory limit in MBits for the task</td> | ||
| </tr> | ||
| <tr> | ||
| <td>${NOMAD_CPU_LIMIT}</td> | ||
| <td>The CPU limit in MHz for the task</td> | ||
| </tr> | ||
| <tr> | ||
| <td>${NOMAD_ADDR_"label"}></td> | ||
| <td>The `ip:port` pair for the given port `label`. See | ||
| [here](/docs/jobspec/networking.html) for more information.</td> | ||
| </tr> | ||
| <tr> | ||
| <td>${NOMAD_HOST_PORT_"label"}</td> | ||
| <td>The port on the host if port forwarding is being used for the port | ||
| `label`. See [here](/docs/jobspec/networking.html#mapped_ports) for more | ||
| information.</td> | ||
| </tr> | ||
| <tr> | ||
| <td>${NOMAD_META_"key"}</td> | ||
| <td>The metadata value given by `key` on the task's metadata</td> | ||
| </tr> | ||
| <tr> | ||
| <td>${"env_key"}</td> | ||
| <td>Interpret an environment variable with key `env_key` set on the task.</td> | ||
| </tr> | ||
| </table> | ||
|
|
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