Fanout-sink-type

FanoutSink[A, B] is the public routing sink type used for duplicating each record to two underlying sinks. It is the concrete sink type returned by fanout_sink(...) and preserves both wrapped sink types in its type parameters.

Interface

pub struct FanoutSink[A, B] {
  left : A
  right : B
}

output

• FanoutSink[A, B] - Public synchronous sink type that forwards each record to both wrapped sinks.

Explanation

Detailed rules explaining key parameters and behaviors

• This is a public root struct, not a type alias.
• The current fields are left : A and right : B.
• fanout_sink(...) constructs this type directly from two sink values.
• The sink preserves both wrapped sink types in the public type, which is useful when typed composition still matters after duplication is introduced.

How to Use

Here are some specific examples provided.

When Need A Typed Dual-output Sink Value

When code should keep the concrete duplication sink type visible:

let sink : FanoutSink[ConsoleSink, JsonConsoleSink] = fanout_sink(console_sink(), json_console_sink())

In this example, the sink value stays explicit and preserves both destination sink types.

When Need A Typed Logger With Duplicated Delivery

When logging should preserve the fanout sink type in the logger:

let logger : Logger[FanoutSink[ConsoleSink, JsonConsoleSink]] = Logger::new(
  fanout_sink(console_sink(), json_console_sink()),
  target="dual",
)

In this example, the concrete duplication sink remains part of the logger type.

Error Case

e.g.:

• FanoutSink[A, B] itself does not have a runtime failure mode.

• Runtime behavior still depends on both wrapped sinks, so any sink-specific limitations remain unchanged behind the fanout wrapper.

Notes

1. Use fanout_sink(...) when you need a value of this type.

2. Use SplitSink[A, B] when records should go to one side conditionally instead of always going to both sides.