API · Errors
routeErrors()
Split successful values and recoverable record errors into two reliable branches.
Signature
routeErrors(): {
output: Exstream<T, C>
deadLetters: Exstream<{ error: ExstreamError<T>; input: T }, C>
}Example
const { output, deadLetters } = pipeline.routeErrors()
await Promise.all([output.pipeTo(destination), deadLetters.map(formatDeadLetter).pipeTo(rejects)])Outputs
output receives every successful value and no record errors. deadLetters receives one { error, input } object for every record error, where input is the original error.exstreamInput. Both branches preserve their relevant source order and record contexts.
An Error intentionally wrapped with exstream.data(error) is ordinary data and travels through output.
Pressure
Both outputs are reliable forks. Consume them concurrently: the source advances only when both active branches can accept their next relevant record. Leaving either output without demand can stop the graph.
Call routeErrors() before the source starts because it creates both forks synchronously. Like fork(), it throws if reliable branches can no longer be added.
Errors
Fatal source, sink, lifecycle, and cancellation failures bypass dead-letter routing and abort both branches. A structural CSV or single-document JSON failure may be emitted briefly as a dead letter before its format operator aborts the graph; routing it cannot make a partial document recoverable. Failures inside one downstream destination affect that branch according to normal fork lifecycle; coordinate sibling cancellation at the application boundary when required.
Forms
routeErrors() operates on a live stream and returns live branches. Use the instance method or pass the stream to the standalone function; it is not available on reusable pipeline definitions:
stream.routeErrors()
exstream.routeErrors(stream)