effect-io-ai

Package: effect
Module: Layer

Layer.span

Constructs a new Layer which creates a span and registers it as the current parent span.

Details

This allows you to create a traced scope for layer construction, making all operations within the layer constructor part of the same trace span. The span is automatically ended when the layer’s scope is closed. If onEnd is provided, it receives the span and the layer scope’s exit value when the span ends.

Example (Tracing layer construction with a span)

import { Console, Context, Effect, Layer } from "effect"
import type { Tracer } from "effect"

class Database extends Context.Service<Database, {
  readonly query: (sql: string) => Effect.Effect<string>
}>()("Database") {}

// Create a traced layer - all operations performed during construction of
// the `Database` service are part of the "database-init" span
const databaseLayer = Layer.effect(Database, Effect.gen(function*() {
  // These operations are traced under "database-init" span
  yield* Effect.log("Connecting to database")
  yield* Effect.sleep("100 millis")
  yield* Effect.log("Database connected")

  const parentSpan = yield* Effect.currentParentSpan
  yield* Console.log((parentSpan as Tracer.Span).name) // "database-init"

  return {
    query: Effect.fn("Database.query")((sql: string) => Effect.succeed(`Result: ${sql}`))
  }
})).pipe(Layer.provide(Layer.span("database-init")))

// Can also use the `onEnd` callback to execute logic when the span ends
const tracedLayer = Layer.span("service-initialization", {
  attributes: { version: "1.0.0" },
  onEnd: (span, exit) =>
    Effect.sync(() => {
      console.log(`Span ${span.name} ended with:`, exit._tag)
    })
})

Signature

declare const span: (name: string, options?: SpanOptions) => Layer<Tracer.ParentSpan>

Source

Since v2.0.0