resile

Resile: Ergonomic Execution Resilience for Go

Resile is a production-grade execution resilience and retry library for Go, inspired by Python's stamina. It provides a type-safe, ergonomic, and highly observable way to handle transient failures in distributed systems.

Table of Contents

• Installation
• Why Resile?
• Articles & Tutorials
• Examples
• Common Use Cases
  • Simple Retries
  • Value-Yielding Retries (Generics)
  • Request Hedging (Speculative Retries)
  • Stateful Retries & Endpoint Rotation
  • Handling Rate Limits (Retry-After)
  • Aborting Retries (Pushback Signal)
  • Fallback Strategies
  • Layered Defense with Circuit Breaker
  • Macro-Level Protection (Adaptive Retries)
  • Structured Logging & Telemetry
  • Panic Recovery ("Let It Crash")
  • Fast Unit Testing
  • Reusable Clients & Dependency Injection
  • Marking Errors as Fatal
  • Custom Error Filtering
• Configuration Reference
• Architecture & Design
• License

Installation

go get github.com/cinar/resile

Why Resile?

In distributed systems, transient failures are a mathematical certainty. Resile simplifies the "Correct Way" to retry:

• AWS Full Jitter: Uses the industry-standard algorithm to prevent "thundering herd" synchronization.
• Adaptive Retries: Built-in token bucket rate limiting to prevent "retry storms" across a cluster.
• Generic-First: No interface{} or reflection. Full compile-time type safety.
• Context-Aware: Strictly respects context.Context cancellation and deadlines.
• Zero-Dependency Core: The core library only depends on the Go standard library.
• Opinionated Defaults: Sensible production-ready defaults (5 attempts, exponential backoff).

Articles & Tutorials

Want to learn more about the philosophy behind Resile and advanced resilience patterns in Go? Check out these deep dives:

• Stop Writing Manual Retry Loops in Go: Why Your Current Logic is Probably Dangerous
• Python's Stamina for Go: Bringing Ergonomic Resilience to Gophers
• Beating Tail Latency: A Guide to Request Hedging in Go Microservices
• Preventing Microservice Meltdowns: Adaptive Retries and Circuit Breakers in Go
• Self-Healing State Machines: Resilient State Transitions in Go

Examples

The examples/ directory contains standalone programs showing how to use Resile in various scenarios:

• Basic Retry: Simple Do and DoErr calls.
• Request Hedging: Reducing tail latency with speculative retries.
• HTTP with Rate Limits: Respecting Retry-After headers and using slog.
• Fallback Strategies: Returning stale data when all attempts fail.
• Stateful Rotation: Rotating API endpoints using RetryState.
• Circuit Breaker: Layering defensive strategies.
• Adaptive Retries: Preventing retry storms with a token bucket.
• Pushback Signal: Aborting retries immediately using CancelAllRetries.
• Panic Recovery: Implementing Erlang's "Let It Crash" philosophy.
• State Machine: Building resilient state machines inspired by Erlang's gen_statem.

Common Use Cases

1. Simple Retries

Retry a simple operation that only returns an error.

err := resile.DoErr(ctx, func(ctx context.Context) error {
    return db.PingContext(ctx)
})

2. Value-Yielding Retries (Generics)

Fetch data with full type safety. The return type is inferred from your closure.

// val is automatically inferred as *User
user, err := resile.Do(ctx, func(ctx context.Context) (*User, error) {
    return apiClient.GetUser(ctx, userID)
}, resile.WithMaxAttempts(3))

3. Request Hedging (Speculative Retries)

Speculative retries reduce tail latency by starting a second request if the first one doesn't finish within a configured HedgingDelay. The first successful result is used, and the other is cancelled.

// For value-yielding operations
data, err := resile.DoHedged(ctx, action, 
    resile.WithMaxAttempts(3),
    resile.WithHedgingDelay(100 * time.Millisecond),
)

// For error-only operations
err := resile.DoErrHedged(ctx, action,
    resile.WithMaxAttempts(2),
    resile.WithHedgingDelay(50 * time.Millisecond),
)

4. Stateful Retries & Endpoint Rotation

Use DoState (or DoErrState) to access the RetryState, allowing you to rotate endpoints or fallback logic based on the failure history.

endpoints := []string{"api-v1.example.com", "api-v2.example.com"}

data, err := resile.DoState(ctx, func(ctx context.Context, state resile.RetryState) (string, error) {
    // Rotate endpoint based on attempt number
    url := endpoints[state.Attempt % uint(len(endpoints))]
    return client.Get(ctx, url)
})

5. Handling Rate Limits (Retry-After)

Resile automatically detects if an error implements RetryAfterError. It can override the jittered backoff with a server-dictated duration and can also signal immediate termination (pushback).

type RateLimitError struct {
    WaitUntil time.Time
}

func (e *RateLimitError) Error() string { return "too many requests" }
func (e *RateLimitError) RetryAfter() time.Duration {
    return time.Until(e.WaitUntil)
}
func (e *RateLimitError) CancelAllRetries() bool {
    // Return true to abort the entire retry loop immediately.
    return false 
}

// Resile will sleep exactly until WaitUntil when this error is encountered.

6. Aborting Retries (Pushback Signal)

If a downstream service returns a terminal error (like "Quota Exceeded") that shouldn't be retried, implement CancelAllRetries() bool to abort the entire retry loop immediately.

type QuotaExceededError struct{}
func (e *QuotaExceededError) Error() string { return "quota exhausted" }
func (e *QuotaExceededError) CancelAllRetries() bool { return true }

// Resile will stop immediately if this error is encountered,
// even if more attempts are remaining.
_, err := resile.Do(ctx, action, resile.WithMaxAttempts(10))

7. Fallback Strategies

Provide a fallback function to handle cases where all retries are exhausted or the circuit breaker is open. This is useful for returning stale data or default values.

data, err := resile.Do(ctx, fetchData,
    resile.WithMaxAttempts(3),
    resile.WithFallback(func(ctx context.Context, err error) (string, error) {
        // Return stale data from cache if the primary fetch fails
        return cache.Get(ctx, key), nil 
    }),
)

8. Layered Defense with Circuit Breaker

Combine retries (for transient blips) with a circuit breaker (for systemic outages).

import "github.com/cinar/resile/circuit"

cb := circuit.New(circuit.Config{
    FailureThreshold: 5,
    ResetTimeout:     30 * time.Second,
})

// Returns circuit.ErrCircuitOpen immediately if the downstream is failing consistently.
err := resile.DoErr(ctx, action, resile.WithCircuitBreaker(cb))

9. Macro-Level Protection (Adaptive Retries)

Prevent "retry storms" by using a token bucket that is shared across your entire cluster of clients. If the downstream service is degraded, the bucket will quickly deplete, causing clients to fail fast locally instead of hammering the service.

// Share this bucket across multiple executions/goroutines
bucket := resile.DefaultAdaptiveBucket()

err := resile.DoErr(ctx, action, resile.WithAdaptiveBucket(bucket))

10. Structured Logging & Telemetry

Integrate with slog or OpenTelemetry without bloating your core dependencies.

import "github.com/cinar/resile/telemetry/resileslog"

logger := slog.Default()
resile.Do(ctx, action, 
    resile.WithName("get-inventory"), // Name your operation for metrics/logs
    resile.WithInstrumenter(resileslog.New(logger)),
)

11. Panic Recovery ("Let It Crash")

Convert unexpected Go panics into retryable errors, allowing your application to reset to a known good state without a hard crash.

// val will succeed even if the first attempt panics
val, err := resile.Do(ctx, riskyAction, 
    resile.WithPanicRecovery(),
)

12. Fast Unit Testing

Never let retry timers slow down your CI. Use WithTestingBypass to make all retries execute instantly.

func TestMyService(t *testing.T) {
    ctx := resile.WithTestingBypass(context.Background())
    
    // This will retry 10 times instantly without sleeping.
    err := service.Handle(ctx)
}

13. Reusable Clients & Dependency Injection

Use resile.New() to create a Retryer interface for cleaner code architecture and easier testing.

// Create a reusable resilience strategy
retryer := resile.New(
    resile.WithMaxAttempts(3),
    resile.WithBaseDelay(200 * time.Millisecond),
)

// Use the interface to execute actions
err := retryer.DoErr(ctx, func(ctx context.Context) error {
    return service.Call(ctx)
})

14. Marking Errors as Fatal

Sometimes you know an error is terminal and shouldn't be retried (e.g., "Invalid API Key"). Use resile.FatalError() to abort the retry loop immediately.

err := resile.DoErr(ctx, func(ctx context.Context) error {
    err := client.Do()
    if errors.Is(err, ErrAuthFailed) {
        return resile.FatalError(err) // Stops retries immediately
    }
    return err
})

15. Resilient State Machines

Build self-healing state machines where every transition is protected by resilience policies, inspired by Erlang's gen_statem.

// Create a state machine: initialState, initialData, transitionFunc, opts
sm := resile.NewStateMachine(Disconnected, data, transition, resile.WithMaxAttempts(3))

// Transitions are protected by retries, circuit breakers, etc.
err := sm.Handle(ctx, Connect)

16. Custom Error Filtering

Control which errors trigger a retry using WithRetryIf (for exact matches) or WithRetryIfFunc (for custom logic like checking status codes).

err := resile.DoErr(ctx, action,
    // Only retry if the error is ErrConnReset
    resile.WithRetryIf(ErrConnReset),
    
    // OR use a custom function for complex logic
    resile.WithRetryIfFunc(func(err error) bool {
        return errors.Is(err, ErrTransient) || isTimeout(err)
    }),
)

Configuration Reference

Architecture & Design

Resile is built for high-performance, concurrent applications:

• Memory Safety: Uses time.NewTimer with proper cleanup to prevent memory leaks in long-running loops.
• Context Integrity: Every internal sleep is a select between the timer and ctx.Done().
• Zero Allocations: Core execution loop is designed to be allocation-efficient.
• Errors are Values: Leverage standard errors.Is and errors.As for all policy decisions.

Acknowledgements

• AWS Architecture Blog: For the definitive Exponential Backoff and Jitter algorithm (Full Jitter).
• Stamina & Tenacity: For pioneering ergonomic retry APIs in the Python ecosystem that inspired the design of Resile.

License

Resile is released under the MIT License.

Copyright (c) 2026 Onur Cinar.
The source code is provided under MIT License.

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of this software and associated documentation files (the "Software"), to deal
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The above copyright notice and this permission notice shall be included in all
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