perplexity-reliability-patterns skill

---
name: perplexity-reliability-patterns
description: |
  Implement Perplexity reliability patterns including circuit breakers, idempotency, and graceful degradation.
  Use when building fault-tolerant Perplexity integrations, implementing retry strategies,
  or adding resilience to production Perplexity services.
  Trigger with phrases like "perplexity reliability", "perplexity circuit breaker",
  "perplexity idempotent", "perplexity resilience", "perplexity fallback", "perplexity bulkhead".
allowed-tools: Read, Write, Edit
version: 1.0.0
license: MIT
author: Jeremy Longshore <[email protected]>
---

# Perplexity Reliability Patterns

## Overview
Production-grade reliability patterns for Perplexity integrations.

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

## Circuit Breaker

```typescript
import CircuitBreaker from 'opossum';

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

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

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

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

// Usage
async function safePerplexityCall<T>(fn: () => Promise<T>): Promise<T> {
  return perplexityBreaker.fire(fn);
}
```

## Idempotency Keys

```typescript
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

```typescript
import PQueue from 'p-queue';

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

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

// Usage
await prioritizedPerplexityCall('critical', () =>
  perplexityClient.processPayment(order)
);

await prioritizedPerplexityCall('bulk', () =>
  perplexityClient.syncCatalog(products)
);
```

## Timeout Hierarchy

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

async function timedoutPerplexityCall<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(`Perplexity ${operation} timeout`)), timeout)
    ),
  ]);
}
```

## Graceful Degradation

```typescript
interface PerplexityFallback {
  enabled: boolean;
  data: any;
  staleness: 'fresh' | 'stale' | 'very_stale';
}

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

## Dead Letter Queue

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

class PerplexityDeadLetterQueue {
  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 perplexityClient[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

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

async function perplexityHealthCheck(): Promise<{
  status: HealthStatus;
  details: Record<string, any>;
}> {
  const checks = {
    api: await checkApiConnectivity(),
    circuitBreaker: perplexityBreaker.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 Perplexity 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 Perplexity 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
```typescript
const state = perplexityBreaker.stats().state;
console.log('Perplexity circuit:', state);
```

## Resources
- [Circuit Breaker Pattern](https://martinfowler.com/bliki/CircuitBreaker.html)
- [Opossum Documentation](https://nodeshift.dev/opossum/)
- [Perplexity Reliability Guide](https://docs.perplexity.com/reliability)

## Next Steps
For policy enforcement, see `perplexity-policy-guardrails`.