Stream Ports

Stream Ports are structures used to describe the parts of incoming and outgoing Stream Messages. For an introduction to Ports, please see Ports.

Input Ports

Input Ports specify fields to be extracted from an incoming stream message or HTTP request.

Stream Input Port struct tags must use the in prefix.

Each field with an in struct tag will be automatically populated before being passed to your Message Subscriber. The full syntax of the in struct tag is as follows:

in:"<fieldGroup>[=<peerName>]"

The in struct tag contains the following subcomponents:

<fieldGroup> : (Required) The name of the message part from which the value will be extracted. Valid field groups for streaming operations are:

• header - Message metadata/headers (string-keyed map of strings).
• body - Message payload (JSON request body). Max one per port struct.
• messageId - Unique id of the message (typically a random uuid)

[=<peerName>] : (Optional) A peer is the index within the field group of the data for each port field in the original message. Currently, only header fieldGroup has indexed content (individual header values). When not specified, the default peer in the metadata is the lowerCamelCase inflection of the field name: eg the EventType struct field points to the header eventType.

Output Ports

Output ports specify parts of the published message to be populated from the port struct.

Stream Output Port struct tags must use the out prefix.

Each field with an out struct tag will be automatically applied to the message before the message is published. The full syntax of the out struct tag is as follows:

out:"<fieldGroup>[=peerName]"

The subcomponents of the out struct tag are the same as in struct tag, above.

Data Transfer Objects (DTOs)

Fields in a port specifying the body component will typically have a DTO struct as their underlying type (eg. api.DriftCheckRequest above).

By default, these are serialized using the Content-Type of the stream (currently defaults to application/json).