set-vars

set-vars

Pulls values out of the request context and stores them in context.message, where every downstream node can read them as $msg_<name> (legacy $var interpolation) or {{message.<name>}} (universal templates). Each variable is derived by up to three steps: a source template, an optional JSONPath applied to the source parsed as JSON, and an optional regex capture. Featherbit-native (no APISIX equivalent); it replaces the small Lua script you would otherwise write to extract a path segment or a body field.

Configuration

Every regex and JSONPath is compiled at config load: a malformed one fails policy compilation, not requests. Unknown keys are rejected.

Key	Type	Default	Description
vars	array	required, non-empty	Evaluated in order; each entry stores one variable.
vars[].name	string	required	Message key. Letters, digits, _, -, .; unique within the node. Read it as $msg_<name> / {{message.<name>}}.
vars[].from	string	$request_body when json_path is set, else required	Source text: any $var ($uri, $http_<header>, $arg_<param>, $cookie_<name>, $msg_<key>, …) or {{namespace.path}} template, literal text allowed.
vars[].json_path	string	—	RFC 9535 JSONPath applied to from parsed as JSON. One scalar node → its text; one object/array → its JSON text; several nodes → a JSON array text; none → default.
vars[].regex	string	—	Regex applied to the text after json_path.
vars[].group	integer or string	1	Which capture becomes the value: an index (0 = whole match) or a named group. Needs regex.
vars[].default	string	—	Used when the source is empty, is not JSON, the path matches nothing, or the regex does not match. Without it the value is "".

type: set-vars
config:
  vars:
    - name: user                     # /hello/frenk → "frenk"
      from: $uri
      regex: '^/hello/([^/]+)'
      default: stranger
    - name: tenant                   # plain copy of a header
      from: $http_x_tenant
    - name: plan                     # query parameter with a fallback
      from: $arg_plan
      default: free
    - name: order_id                 # JSON body field (source defaults to the request body)
      json_path: $.order.id
    - name: minor                    # named capture group
      from: $http_x_api_version
      regex: '^(?P<major>\d+)\.(?P<minor>\d+)'
      group: minor
    - name: greeting                 # later entries see earlier ones
      from: 'hello $msg_user'

Behavior

For each entry, in order: render from against the current context (so an entry can use $msg_<name> set by a previous entry), then apply json_path, then regex/group. The result is stored as a string under context.message[name]; an empty result falls back to default (or ""). The node is always pass-through: it returns Ok in every case, the Context flows out the success port, and the error port is never taken.

Typical follow-ups: a mocking node answering hello $msg_user, a proxy-rewrite adding x-tenant: $msg_tenant to the upstream request, a condition branching on ["msg_plan", "==", "free"], or any logger's log_format including $msg_order_id. Values are visible in a debug trace as message.<name> in the step's changes.

Behavior notes

• JSONPath sources must be valid JSON; a non-JSON source resolves to default. Use from: $http_<header> with json_path to read a JSON-valued header.
• A regex without capture groups selects the whole match by default.
• Absent variables render as the empty string, so from: $arg_plan with no plan parameter yields default.
• Values are strings; a JSON number 42 is stored as "42".

Errors

This node never fails at execution time: it always returns through success, so its error port is never taken.