WireTap/Detour:

Using Cloud Events as messages

Use Cases/Definition:

• WireTap: Inspect a Message on a channel without modifying the producer/consumer

• Detour: Route a message through additional intermediary steps dynamically include and exclude additional steps

  • Context-based router with additional output channels:
    • First channel passes unmodified message directly to original destination
    • Other channels passes unmodified message to different destination (Will be routed back to orginal destination afterwards)

• Mostly used for debugging/validation

• In theory, producer/consumer of messages shouldnt be touched

Discussion:

• Both of these patterns are designed for MOMs that support queues. Since we use Kafka, they have limited application.

  • Messages in Kafka can not be consumed without deserializing them first. This means that messages must be consumed and deserialized and then produced again.
    • Re-publishing of messages will change header-fields like message-id -> may be problematic in the future
    • Should be part of another pattern to avoid unnecessary transformations and traffic

• Both patterns require a Dynamic Router (See Router) that requires a configuration that can be changed externally

  • A Configuration should include:
    • See Cloud Events Format

• The actual implementation should be part of another service/pattern. It doesn't make much sense to just implement a service that basically just duplicates a message. Depending on further decisions.

Usage: Not advised

The Prototype is only kept as part of the current documentation for the prototyping phase and will not be updated any further.