set-headers-element.md

Set Headers Element

The Set Headers Element constructs a list of all the HTTP response header values that other Elements in the Pipeline want to be set. Usually, this is done in order to request more Evidence from the client (For example User-Agent Client Hints).

This relies on a Property naming convention whereby any Property values containing data that needs to be sent in a response header are named according to the following format:

SetHeader[Identifier][HeaderName]

• The SetHeader prefix indicates that this Property is intended for setting HTTP response headers.
• [Identifier] is some string that relates to what this value is for. It MUST NOT have upper-case characters after the first character.
• [HeaderName] is the name of the HTTP header to set in the response.

Accepted Evidence

This element uses no Evidence, it works on Property values in Element Data in the Flow Data.

Start-up activity

For performance reasons, it is usually best to construct a list of Properties with the SetHeader prefix on start-up, rather than doing so for each request.

Element Data

Name	Type	Description
response-header-dictionary	IReadOnlyDictionary<string, string>	A collection of key value pairs where the key is the HTTP response header name and the value is the value to set that response header to.

Process

• Get all Properties in Flow Data with SetHeader at the start of the name.
• For each Property
  • If Property value is set and is not Unknown
    • Extract the header name from the Property name using the convention outlined above. Use this as the key to the output key value pair collection.
    • Split the Property value using , and add each individual segment to the output collection if it has not yet been added for that key.

Configuration options

None