---

name: effect-queues-background description: Queue and PubSub patterns, background fibers, and graceful shutdown. Use for decoupling producers/consumers. allowed-tools: Read, Grep, Glob, Edit, Write

Queues, PubSub & Background

When to use

• Decoupling producers/consumers with backpressure
• Broadcasting events to multiple subscribers
• Running background loops with graceful shutdown

Queue (bounded)

Copyimport { Queue } from "effect"
const q = yield* Queue.bounded<string>(32)
yield* Queue.offer(q, "job")
const job = yield* Queue.take(q)

PubSub (broadcast)

Copyimport { PubSub } from "effect"
const ps = yield* PubSub.bounded<string>(32)
yield* PubSub.publish(ps, "evt")

Background Fiber

Copyconst fiber = yield* Effect.fork(loop)
yield* Fiber.interrupt(fiber)

Guidance

• Prefer bounded queues to apply natural backpressure
• Use multiple workers by forking consumers
• Ensure background fibers are interrupted during shutdown

Pitfalls

• Unbounded queues lead to memory growth
• Silent background failures → add logging/metrics

Cross-links

• Concurrency for pools and interruption
• Time/Logging for observability of background tasks

Local Source Reference

CRITICAL: Search local Effect source before implementing

The full Effect source code is available at docs/effect-source/. Always search the actual implementation before writing Effect code.

Key Source Files

• Queue: docs/effect-source/effect/src/Queue.ts
• PubSub: docs/effect-source/effect/src/PubSub.ts
• Fiber: docs/effect-source/effect/src/Fiber.ts

Example Searches

Copy# Find Queue patterns
grep -F "bounded" docs/effect-source/effect/src/Queue.ts
grep -F "offer" docs/effect-source/effect/src/Queue.ts
grep -F "take" docs/effect-source/effect/src/Queue.ts

# Study PubSub operations
grep -F "publish" docs/effect-source/effect/src/PubSub.ts
grep -F "subscribe" docs/effect-source/effect/src/PubSub.ts

# Find background fiber patterns
grep -F "fork" docs/effect-source/effect/src/Fiber.ts
grep -F "interrupt" docs/effect-source/effect/src/Fiber.ts

# Look at Queue test examples
grep -F "Queue." docs/effect-source/effect/test/Queue.test.ts

Workflow

1. Identify the Queue or PubSub API you need
2. Search docs/effect-source/effect/src/Queue.ts or PubSub.ts for the implementation
3. Study the types and backpressure patterns
4. Look at test files for usage examples
5. Write your code based on real implementations

Real source code > documentation > assumptions

References

• Agent Skills overview: https://www.anthropic.com/news/skills
• Skills guide: https://docs.claude.com/en/docs/claude-code/skills