BitLogger/docs/api/split-sink-type.md

name, group, category, update-time, description, key-word

name	group	category	update-time	description	key-word
split-sink-type	api	sink	20260613	Public split sink type used for routing records to one of two underlying sinks with a predicate.	sink split type public

Split-sink-type

SplitSink[A, B] is the public routing sink type used for sending each record to one of two underlying sinks based on a predicate. It is the concrete sink type returned by both split_sink(...) and split_by_level(...), and it preserves both wrapped sink types in its type parameters.

Interface

pub struct SplitSink[A, B] {
  left : A
  right : B
  predicate : (Record) -> Bool
}

output

• SplitSink[A, B] - Public synchronous sink type that routes each record to one of two 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, right : B, and predicate : (Record) -> Bool.
• split_sink(...) constructs this type directly from two sink values and a predicate.
• split_by_level(...) also returns this same type after building a level-based predicate wrapper.

How to Use

Here are some specific examples provided.

When Need A Typed Predicate-routing Sink Value

When code should keep the concrete routing sink type visible:

let sink : SplitSink[ConsoleSink, JsonConsoleSink] = split_sink(
  console_sink(),
  json_console_sink(),
  fn(rec) { rec.target == "audit" },
)

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

When Need A Typed Logger With Conditional Delivery

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

let logger : Logger[SplitSink[ConsoleSink, JsonConsoleSink]] = Logger::new(
  split_by_level(console_sink(), json_console_sink(), min_level=Level::Warn),
  target="route",
)

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

Error Case

e.g.:

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

• Routing behavior still depends on the stored predicate and both wrapped sinks, so misrouting or sink-specific limitations remain outside the split type itself.

Notes

1. Use split_sink(...) or split_by_level(...) when you need a value of this type.

2. Use FanoutSink[A, B] when each record should always be delivered to both sides instead of one side conditionally.