Specs

prepare_messages(messages :: [Broadway.Message.t()], context :: term()) :: [
  Broadway.Message.t()
]

Invoked for preparing messages before handling (if defined).

It expects:

• message is the Broadway.Message struct to be processed.
• context is the user defined data structure passed to start_link/2.

This is the place to prepare and preload any information that will be used by handle_message/3. For example, if you need to query the database, instead of doing it once per message, you can do it on this callback.

The length of the list of messages received by this callback is based on the min_demand/max_demand configuration in the processor. This callback must always return all messages it receives, as handle_message/3 is still called individually for each message afterwards.