---
url: https://wvlet.org/uni/control.md
---
# Control Flow

uni provides utilities for handling failures gracefully and managing resources properly.

## Overview

| Component | Description |
|-----------|-------------|
| [Retry](./retry) | Automatic retry with backoff strategies |
| [Circuit Breaker](./circuit-breaker) | Prevent cascade failures |
| [Rate Limiter](./rate-limiter) | Throttle operation throughput (JVM) |
| [Cache](./cache) | TTL and LRU caching |
| [Resource](./resource) | Safe resource acquisition and release |
| [Background Task](./background-task) | Cancellable, progress-pollable background worker |

## Quick Example

```scala
import wvlet.uni.control.{Retry, CircuitBreaker, Control}

// Retry a flaky operation
val result = Retry.withBackOff(maxRetry = 3).run {
  callExternalService()
}

// Protect with circuit breaker
val breaker = CircuitBreaker.withConsecutiveFailures(5)
val guarded = breaker.run {
  riskyOperation()
}

// Safe resource handling
Control.withResource(openConnection()) { conn =>
  useConnection(conn)
} // Automatically closed
```

## When to Use

### Retry

* Network calls that may fail transiently
* Database operations during high load
* API calls with rate limiting

### Circuit Breaker

* External service dependencies
* Preventing cascade failures
* Graceful degradation

### Caching

* Expensive computations
* Frequently accessed data
* Rate-limited API responses

### Resource Management

* File handles
* Database connections
* Network sockets

## Package

```scala
import wvlet.uni.control.*
```