Node filters

A node filter is a search expression used to identify a set of nodes using SQL-like expressions on any namespace and attribute. You can create node filters that include or exclude nodes based on specific pattern sets.

When the filter is evaluated, Chef Courier creates a node list from the set of registered nodes at the time that the filter is evaluated.

Create a node filter

Create a node filter payload in a JSON file:
```
{
    "name": "<FILTER_NAME>",
    "constraints": {
        "attributes": [{
            "name": "<ATTRIBUTE_NAME>",
            "operator": "<OPERATOR>",
            "value": ["<ATTRIBUTE_VALUE>"],
            "namespace": ["<NAMESPACE_NAME>"]
        }]
    }
}
```
Replace:
- <FILTER_NAME> with a name for the filter
- <ATTRIBUTE_NAME> with an attribute to filter by
- <OPERATOR> with an filter operator. The supported operators are:
  - MATCHES
  - CONTAINS
  - =
  - !=
- <ATTRIBUTE_VALUE> with the attribute value filter operator matches against
- <NAMESPACE_NAME> with the namespace to search in. The following namespaces are supported:
  - agent for node attributes collected from the Node Management Agent
  - gohai for node attributes collected by the Gohai skill
  - aws for AWS-specific attributes collected by the Gohai skill
  - azure for Azure-specific attributes collected by the Gohai skill
  - tags for tags applied to nodes using Node Management

Create and save a node filter:

chef-node-management-cli management filter create-filter --body-file <FILTER_FILENAME>

The response is similar to the following:

{
    "item": {
    "filterId": "ab38aed7-f35a-4e44-90f5-ef9ea11e6464"
    }
}

Get nodes from a filter

To get nodes from an adhoc filter, use the filter run-adhocFilter subcommand:

chef-node-management-cli management filter run-adhocFilter --body-file <FILTER_FILENAME>

To get nodes from a saved filter, use the filter run-savedFilter subcommand:

chef-node-management-cli management filter run-savedFilter --filterId <FILTER_ID>