How to fix P1017: Server has closed the connection in Prisma

# For PostgreSQL
psql "postgresql://user:password@host:5432/database"

# For MySQL
mysql -h host -u user -p database

# Test connection from your application server
telnet your-database-host 5432

# Set DEBUG environment variable
DEBUG="*" npx prisma migrate dev

# Or in your application
DEBUG="prisma:*" npm start

# PostgreSQL
tail -f /var/log/postgresql/postgresql-*.log

# MySQL
tail -f /var/log/mysql/error.log

# Before
DATABASE_URL="postgresql://user:password@host:5432/db"

# After - increase pool timeout and connection limit
DATABASE_URL="postgresql://user:password@host:5432/db?connection_limit=10&pool_timeout=20"

import { PrismaClient } from '@prisma/client';

const prisma = new PrismaClient();

async function queryWithRetry<T>(
  operation: () => Promise<T>,
  maxRetries = 3,
  delay = 1000
): Promise<T> {
  for (let attempt = 1; attempt <= maxRetries; attempt++) {
    try {
      return await operation();
    } catch (error: any) {
      if (error.code === 'P1017' && attempt < maxRetries) {
        console.log(`Retry attempt ${attempt} after connection closed`);
        await new Promise(resolve => setTimeout(resolve, delay * attempt));
        continue;
      }
      throw error;
    }
  }
  throw new Error('Max retries exceeded');
}

// Usage
const users = await queryWithRetry(() =>
  prisma.user.findMany()
);

# Check current version
npx prisma --version

# Downgrade to a specific version (e.g., 5.9.1)
npm install [email protected] @prisma/[email protected]

# Test migrations
npx prisma migrate dev