Add Retry with Exponential Backoff

This skill adds automatic retry logic with exponential backoff to a Cubit method.

What This Skill Does

Adds the retry parameter to a mix() call so that failed methods automatically retry with configurable:

• Number of retry attempts
• Initial delay before first retry
• Delay multiplier (exponential backoff)
• Maximum delay cap

Instructions

Step 1: Identify the Method to Add Retry

Ask the user which Cubit method should have retry logic, or identify methods that:

• Make network/API calls
• May fail due to transient errors
• Would benefit from automatic retry

Step 2: Add Basic Retry

Add retry: retry to the mix() call:

import 'package:bloc_superpowers/bloc_superpowers.dart';

class UserCubit extends Cubit<User> {
  UserCubit() : super(User());

  void loadData() => mix(
    key: this,
    retry: retry,  // Add this line
    () async {
      final user = await api.loadUser();
      if (user == null) throw UserException('Failed to load user');
      emit(user);
    },
  );
}

Step 3: Customize Retry Parameters (Optional)

The default retry configuration:

• maxRetries: 3 — Three retry attempts after initial failure (4 total attempts)
• initialDelay: 350ms — Delay before first retry
• multiplier: 2 — Each delay doubles (350ms → 700ms → 1400ms)
• maxDelay: 5 seconds — Maximum delay between retries

Customize as needed:

void loadData() => mix(
  key: this,
  retry: retry(
    maxRetries: 5,           // 5 retries (6 total attempts)
    initialDelay: 1.sec,     // Start with 1 second delay
    multiplier: 2.0,         // Double each time: 1s → 2s → 4s → 8s → 10s
    maxDelay: 10.sec,        // Cap at 10 seconds
  ),
  () async {
    final user = await api.loadUser();
    emit(user);
  },
);

Configuration Options

Limited Retries (Default)

retry                           // 3 retries with defaults
retry(maxRetries: 5)            // 5 retries
retry(maxRetries: 10)           // 10 retries

Unlimited Retries

Use for critical operations that must eventually succeed:

retry.unlimited                 // Retry forever with default timing
retry(maxRetries: -1)           // Same as above

// Unlimited with custom timing
retry(initialDelay: 500.millis).unlimited
retry(initialDelay: 1.sec, maxDelay: 30.sec).unlimited

Custom Timing

// Faster initial retry
retry(initialDelay: 100.millis)

// Slower backoff
retry(multiplier: 1.5)

// Higher cap
retry(maxDelay: 30.sec)

// Full customization
retry(
  maxRetries: 5,
  initialDelay: 500.millis,
  multiplier: 1.5,
  maxDelay: 15.sec,
)

Timing Behavior

The retry delay starts after the method execution completes (not from when it started).

Example with default settings and a method that takes 1 second to fail:

• Attempt 1: Starts at 0s, fails at 1s
• Attempt 2: Starts at 1.35s (1s + 350ms delay), fails at 2.35s
• Attempt 3: Starts at 3.05s (2.35s + 700ms delay), fails at 4.05s
• Attempt 4: Starts at 5.45s (4.05s + 1400ms delay), fails at 6.45s
• Final error thrown at 6.45s

Error Handling

• Only the final error is thrown after all retries are exhausted
• Previous errors are discarded
• The error will trigger context.isFailed() and show in UserExceptionDialog

Common Patterns

Retry with Internet Check

Combine retry with internet connectivity check:

void loadData() => mix(
  key: this,
  checkInternet: checkInternet,
  retry: retry,
  () async {
    final data = await api.getData();
    emit(data);
  },
);

Retry Until Internet Returns

For critical startup data, retry forever until internet is available:

void loadInitialData() => mix(
  key: this,
  checkInternet: checkInternet(maxRetryDelay: 1.sec),
  retry: retry.unlimited,
  () async {
    final data = await api.getInitialData();
    emit(data);
  },
);

Accessing Retry Context

Use mix.ctx to access retry information inside the method:

void loadData() => mix.ctx(
  key: this,
  retry: retry,
  (ctx) async {
    final retryCtx = ctx.retry!;
    final attempt = retryCtx.attempt;  // Zero-based (0, 1, 2, ...)
    final maxRetries = retryCtx.config.maxRetries;

    print('Attempt ${attempt + 1} of ${maxRetries + 1}');

    final data = await api.getData();
    emit(data);
  },
);

When to Use Retry

Good candidates for retry:

• API calls that may fail due to network issues
• Database operations that may timeout
• File operations that may be temporarily locked
• Any operation with transient failures

Not recommended for retry:

• Validation errors (user input problems won't fix themselves)
• Authentication failures (wrong credentials won't become right)
• Business logic errors (invalid state won't change)

User Preferences

Ask the user:

1. How many retries? Default is 3, but critical operations may need more
2. Unlimited retries? For must-succeed operations like initial app data
3. Custom timing? Faster retries for quick operations, slower for expensive ones