Blocking

A function that blocks its thread, such as one writing a projection or checking a uniqueness over JDBC. A synchronous function is otherwise taken for pure computation and runs inline on a shared worker; the generated call runs this one on the blocking dispatcher, a virtual thread per call. It applies to command functions (@OnCommand), after hooks (@AfterCommand), subscription handlers (@OnEvent, @OnRejected, @OnCommitted) and scheduled jobs (@OnSchedule), also when it is on the function an override overrides. Sourcing functions, @Upgrade functions and @Access members do no I/O, so it is a compile error on them; on a function returning a Reactor publisher it is a warning, since a publisher should not block.