effect-io-ai

Package: effect
Module: References

References.CurrentLogSpans

Context reference for managing log spans that track the duration and hierarchy of operations. Each span represents a labeled time period for performance analysis and debugging.

When to use

Use to carry the active log span stack that should be included with log entries in the current context.

Example (Tracking log spans)

import { Console, Effect, References } from "effect"

const logSpanExample = Effect.gen(function*() {
  // Get current spans (empty by default)
  const current = yield* References.CurrentLogSpans
  console.log(current.length) // 0

  // Add a log span manually
  const databaseConnectionStartedAt = 0
  yield* Effect.provideService(
    Effect.gen(function*() {
      // Simulate some work
      yield* Effect.sleep("100 millis")
      yield* Console.log("Database operation in progress")

      const spans = yield* References.CurrentLogSpans
      console.log("Active spans:", spans.map(([label]) => label)) // ["database-connection"]
    }),
    References.CurrentLogSpans,
    [["database-connection", databaseConnectionStartedAt]]
  )

  // Add another span
  const dataProcessingStartedAt = 100
  yield* Effect.provideService(
    Effect.gen(function*() {
      const spans = yield* References.CurrentLogSpans
      console.log("Active spans:", spans.map(([label]) => label)) // ["database-connection", "data-processing"]

      yield* Console.log("Multiple operations in progress")
    }),
    References.CurrentLogSpans,
    [
      ["database-connection", databaseConnectionStartedAt],
      ["data-processing", dataProcessingStartedAt]
    ]
  )

  // Clear spans when operations complete
  yield* Effect.provideService(
    Effect.gen(function*() {
      const spans = yield* References.CurrentLogSpans
      console.log("Active spans:", spans.length) // 0
    }),
    References.CurrentLogSpans,
    []
  )
})

Signature

declare const CurrentLogSpans: Context.Reference<ReadonlyArray<[label: string, timestamp: number]>>

Source

Since v4.0.0