replit-reliability-patternsClaude Skill

Replit Reliability Patterns

Overview

Production-grade reliability patterns for Replit integrations.

Prerequisites

• Understanding of circuit breaker pattern
• opossum or similar library installed
• Queue infrastructure for DLQ
• Caching layer for fallbacks

Circuit Breaker

import CircuitBreaker from 'opossum';

const replitBreaker = new CircuitBreaker(
  async (operation: () => Promise<any>) => operation(),
  {
    timeout: 30000,
    errorThresholdPercentage: 50,
    resetTimeout: 30000,
    volumeThreshold: 10,
  }
);

// Events
replitBreaker.on('open', () => {
  console.warn('Replit circuit OPEN - requests failing fast');
  alertOps('Replit circuit breaker opened');
});

replitBreaker.on('halfOpen', () => {
  console.info('Replit circuit HALF-OPEN - testing recovery');
});

replitBreaker.on('close', () => {
  console.info('Replit circuit CLOSED - normal operation');
});

// Usage
async function safeReplitCall<T>(fn: () => Promise<T>): Promise<T> {
  return replitBreaker.fire(fn);
}

Idempotency Keys

import { v4 as uuidv4 } from 'uuid';
import crypto from 'crypto';

// Generate deterministic idempotency key from input
function generateIdempotencyKey(
  operation: string,
  params: Record<string, any>
): string {
  const data = JSON.stringify({ operation, params });
  return crypto.createHash('sha256').update(data).digest('hex');
}

// Or use random key with storage
class IdempotencyManager {
  private store: Map<string, { key: string; expiresAt: Date }> = new Map();

  getOrCreate(operationId: string): string {
    const existing = this.store.get(operationId);
    if (existing && existing.expiresAt > new Date()) {
      return existing.key;
    }

    const key = uuidv4();
    this.store.set(operationId, {
      key,
      expiresAt: new Date(Date.now() + 24 * 60 * 60 * 1000),
    });
    return key;
  }
}

Bulkhead Pattern

import PQueue from 'p-queue';

// Separate queues for different operations
const replitQueues = {
  critical: new PQueue({ concurrency: 10 }),
  normal: new PQueue({ concurrency: 5 }),
  bulk: new PQueue({ concurrency: 2 }),
};

async function prioritizedReplitCall<T>(
  priority: 'critical' | 'normal' | 'bulk',
  fn: () => Promise<T>
): Promise<T> {
  return replitQueues[priority].add(fn);
}

// Usage
await prioritizedReplitCall('critical', () =>
  replitClient.processPayment(order)
);

await prioritizedReplitCall('bulk', () =>
  replitClient.syncCatalog(products)
);

Timeout Hierarchy

const TIMEOUT_CONFIG = {
  connect: 5000,      // Initial connection
  request: 30000,     // Standard requests
  upload: 120000,     // File uploads
  longPoll: 300000,   // Webhook long-polling
};

async function timedoutReplitCall<T>(
  operation: 'connect' | 'request' | 'upload' | 'longPoll',
  fn: () => Promise<T>
): Promise<T> {
  const timeout = TIMEOUT_CONFIG[operation];

  return Promise.race([
    fn(),
    new Promise<never>((_, reject) =>
      setTimeout(() => reject(new Error(`Replit ${operation} timeout`)), timeout)
    ),
  ]);
}

Graceful Degradation

interface ReplitFallback {
  enabled: boolean;
  data: any;
  staleness: 'fresh' | 'stale' | 'very_stale';
}

async function withReplitFallback<T>(
  fn: () => Promise<T>,
  fallbackFn: () => Promise<T>
): Promise<{ data: T; fallback: boolean }> {
  try {
    const data = await fn();
    // Update cache for future fallback
    await updateFallbackCache(data);
    return { data, fallback: false };
  } catch (error) {
    console.warn('Replit failed, using fallback:', error.message);
    const data = await fallbackFn();
    return { data, fallback: true };
  }
}

Dead Letter Queue

interface DeadLetterEntry {
  id: string;
  operation: string;
  payload: any;
  error: string;
  attempts: number;
  lastAttempt: Date;
}

class ReplitDeadLetterQueue {
  private queue: DeadLetterEntry[] = [];

  add(entry: Omit<DeadLetterEntry, 'id' | 'lastAttempt'>): void {
    this.queue.push({
      ...entry,
      id: uuidv4(),
      lastAttempt: new Date(),
    });
  }

  async processOne(): Promise<boolean> {
    const entry = this.queue.shift();
    if (!entry) return false;

    try {
      await replitClient[entry.operation](entry.payload);
      console.log(`DLQ: Successfully reprocessed ${entry.id}`);
      return true;
    } catch (error) {
      entry.attempts++;
      entry.lastAttempt = new Date();

      if (entry.attempts < 5) {
        this.queue.push(entry);
      } else {
        console.error(`DLQ: Giving up on ${entry.id} after 5 attempts`);
        await alertOnPermanentFailure(entry);
      }
      return false;
    }
  }
}

Health Check with Degraded State

type HealthStatus = 'healthy' | 'degraded' | 'unhealthy';

async function replitHealthCheck(): Promise<{
  status: HealthStatus;
  details: Record<string, any>;
}> {
  const checks = {
    api: await checkApiConnectivity(),
    circuitBreaker: replitBreaker.stats(),
    dlqSize: deadLetterQueue.size(),
  };

  const status: HealthStatus =
    !checks.api.connected ? 'unhealthy' :
    checks.circuitBreaker.state === 'open' ? 'degraded' :
    checks.dlqSize > 100 ? 'degraded' :
    'healthy';

  return { status, details: checks };
}

Instructions

Step 1: Implement Circuit Breaker

Wrap Replit calls with circuit breaker.

Step 2: Add Idempotency Keys

Generate deterministic keys for operations.

Step 3: Configure Bulkheads

Separate queues for different priorities.

Step 4: Set Up Dead Letter Queue

Handle permanent failures gracefully.

Output

• Circuit breaker protecting Replit calls
• Idempotency preventing duplicates
• Bulkhead isolation implemented
• DLQ for failed operations

Error Handling

Issue	Cause	Solution
Circuit stays open	Threshold too low	Adjust error percentage
Duplicate operations	Missing idempotency	Add idempotency key
Queue full	Rate too high	Increase concurrency
DLQ growing	Persistent failures	Investigate root cause

Examples

Quick Circuit Check

const state = replitBreaker.stats().state;
console.log('Replit circuit:', state);

Resources

• Circuit Breaker Pattern
• Opossum Documentation
• Replit Reliability Guide

Next Steps

For policy enforcement, see replit-policy-guardrails.