---

name: exa-reliability-patterns description: | Implement Exa reliability patterns including circuit breakers, idempotency, and graceful degradation. Use when building fault-tolerant Exa integrations, implementing retry strategies, or adding resilience to production Exa services. Trigger with phrases like "exa reliability", "exa circuit breaker", "exa idempotent", "exa resilience", "exa fallback", "exa bulkhead". allowed-tools: Read, Write, Edit version: 1.0.0 license: MIT author: Jeremy Longshore jeremy@intentsolutions.io

Exa Reliability Patterns

Overview

Production-grade reliability patterns for Exa integrations.

Prerequisites

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

Circuit Breaker

Copyimport CircuitBreaker from 'opossum';

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

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

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

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

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

Idempotency Keys

Copyimport { 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

Copyimport PQueue from 'p-queue';

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

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

// Usage
await prioritizedExaCall('critical', () =>
  exaClient.processPayment(order)
);

await prioritizedExaCall('bulk', () =>
  exaClient.syncCatalog(products)
);

Timeout Hierarchy

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

async function timedoutExaCall<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(`Exa ${operation} timeout`)), timeout)
    ),
  ]);
}

Graceful Degradation

Copyinterface ExaFallback {
  enabled: boolean;
  data: any;
  staleness: 'fresh' | 'stale' | 'very_stale';
}

async function withExaFallback<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('Exa failed, using fallback:', error.message);
    const data = await fallbackFn();
    return { data, fallback: true };
  }
}

Dead Letter Queue

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

class ExaDeadLetterQueue {
  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 exaClient[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

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

async function exaHealthCheck(): Promise<{
  status: HealthStatus;
  details: Record<string, any>;
}> {
  const checks = {
    api: await checkApiConnectivity(),
    circuitBreaker: exaBreaker.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 Exa 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 Exa calls
• Idempotency preventing duplicates
• Bulkhead isolation implemented
• DLQ for failed operations

Error Handling

Examples

Quick Circuit Check

Copyconst state = exaBreaker.stats().state;
console.log('Exa circuit:', state);

Resources

• Circuit Breaker Pattern
• Opossum Documentation
• Exa Reliability Guide

Next Steps

For policy enforcement, see exa-policy-guardrails.