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Creating Services and Libraries

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Available Generators

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Fastify API Services

yarn new:fastify

• App configuration (src/app/app.ts)
• Entry point (src/main.ts)
• Docker setup
• ESLint settings
• Testing infrastructure

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Route Organization

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Post-Generation Steps

1. Add the new service to docker-compose.yml with appropriate networking and environment configuration
2. Update CI/CD pipeline configurations
3. Configure environment variables

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Node.js Applications

yarn new:node

• Background workers
• Message queue consumers
• Scheduled jobs
• CLI tools

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Bootstrap Pattern

import { logger } from '@cowprotocol/shared';

async function main() {
  logger.info('Starting service...');

  // Application logic here

  process.on('SIGTERM', async () => {
    logger.info('Shutting down gracefully...');
    // Cleanup logic
    process.exit(0);
  });
}

main().catch((error) => {
  logger.error({ err: error }, 'Fatal error');
  process.exit(1);
});

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Shared Libraries

yarn new:lib

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Post-Generation Setup

1. TypeScript path alias - Register in tsconfig.base.json:

{
  "paths": {
    "@cowprotocol/my-library": ["libs/my-library/src/index.ts"]
  }
}

2. Public API - Define exports in src/index.ts:

export { MyService } from './lib/my-service';
export { MyRepository } from './lib/my-repository';
export type { MyInterface } from './lib/types';

3. Module boundaries - Follow these rules:
   • Apps can import from libs
   • Libs should only import from other libs
   • Never create circular dependencies

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Existing Libraries

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Architecture Enforcement

• Apps can import from libs
• Libs should only import from other libs
• Circular dependencies are prevented

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Pre-Commit Checklist

# Run tests
yarn test

# Run linter
yarn lint

# Build the project
yarn build