Module sink 

Wire codec and sink trait sub-modules. Consumers implementing a custom Sink or reading/writing envelopes on the wire previously had to depend on obs-core directly; obs-kit re-exports these so obs-kit = "0.2" is the only runtime dep needed. Spec § 5.1. Sinks consume ScrubbedEnvelope and ship it to a destination (stdout, NDJSON file, OTLP, ClickHouse, etc.).

Phase-3 surface (impl-plan tasks 3.7 / 3.12 + 3.1 worker pool):

• Sink trait + flush / shutdown lifecycle.
• NoopSink, InMemorySink (test harness).
• StdoutSink with all four FormatterStyles.
• NdjsonFileSink over RollingFileWriter.
• MakeWriter family: StdoutWriter, StderrWriter, LevelSplitWriter, TeeWriter, RollingFileWriter, NonBlockingWriter.

Modules

fanout

FanOutSink — deliver one envelope to N child sinks.

Structs

ErasedWriter

Erased Box<dyn Write + Send> so LevelSplitWriter::Writer can be a single concrete type (the trait associated type is fixed, can’t be match-ed at the type level).

FanOutSink

Multiplex a single tier’s output across N sinks.

InMemoryHandle

Stable handle to an InMemorySink. Clone-safe; share across threads.

InMemorySink

Test sink: collects envelopes into a bounded ring buffer.

LevelSplitWriter

Composes two writers — INFO+ goes through low, WARN+ through high. The conventional shape for cargo binaries.

NdjsonFileSink

File sink that writes envelopes as JSON lines to the underlying MakeWriter. Buffers a Mutex<ErasedWriter> per batch to avoid re-opening files for every event.

NonBlockingHandle

Per-batch handle. Buffers bytes, flushes to the bg sender on flush() / Drop.

NonBlockingWriter

Wraps a MakeWriter with a background thread + bounded mpsc::SyncSender channel. Overflow drops the line and increments the dropped counter. Spec 20 § 3.5.

NoopSink

A sink that drops every envelope.

RollingFileHandle

Handle returned per-batch by RollingFileWriter. Each write_all rotates if the policy demands it.

RollingFileWriter

Rolling file writer with size + time policies. Spec 20 § 3.4.

RollingFileWriterBuilder

Builder for RollingFileWriter.

StderrWriter

Writes to stderr.

StdoutSink

Stdout / writer-backed sink.

StdoutWriter

Writes to stdout.

TeeWriter

Tee writer — writes to both branches.

WorkerGuard

Returned alongside NonBlockingWriter; flushes + joins the bg thread on drop.

Enums

FormatterStyle

Output style for StdoutSink. See spec 20 § 3.6.

RollingPolicy

Rolling policy. Spec 20 § 3.4.

Traits

MakeWriter

A factory that yields one io::Write per batch. Cheap to call. Spec 20 § 3.3.

Sink

A delivery destination. Called from per-tier worker tasks, never on the emit thread.

Type Aliases

SinkFut

Pinned future returned by Sink::flush / Sink::shutdown. Spec 11 § 4.