Pull Request: Backup and Disaster Recovery System

Summary

Implements a comprehensive backup and disaster recovery system for the TeachLink backend with automated database backups, cross-region replication, integrity verification, automated recovery testing, and RTO monitoring.

Related Issue

Closes #113

📋 What Was Implemented

Core Features

• ✅ Automated Weekly Backups: PostgreSQL database backups every Sunday at 2:00 AM UTC
• ✅ AWS KMS Encryption: All backups encrypted at rest using AWS Key Management Service
• ✅ Cross-Region Replication: Automatic replication from us-east-1 (primary) to us-west-2 (secondary)
• ✅ Integrity Verification: MD5 and SHA256 checksum validation for all backups
• ✅ Automated Recovery Testing: Periodic restoration to test database to validate backup usability
• ✅ RTO Monitoring: Recovery Time Objective tracking with 15-minute threshold alerts

Technical Architecture

Files Created (19 files)

Enums (4 files)

• src/backup/enums/backup-status.enum.ts - Backup lifecycle states
• src/backup/enums/backup-type.enum.ts - Backup types (FULL)
• src/backup/enums/recovery-test-status.enum.ts - Recovery test states
• src/backup/enums/region.enum.ts - AWS regions

Entities (2 files)

• src/backup/entities/backup-record.entity.ts - Backup metadata with checksums and encryption details
• src/backup/entities/recovery-test.entity.ts - Recovery test results and performance metrics

DTOs (4 files)

• src/backup/dto/restore-backup.dto.ts - Disaster recovery restore request
• src/backup/dto/backup-response.dto.ts - Backup record response
• src/backup/dto/recovery-test-response.dto.ts - Recovery test results
• src/backup/dto/trigger-recovery-test.dto.ts - Recovery test trigger request

Services (6 files)

• src/backup/backup.service.ts - Orchestrates backups, scheduled jobs
• src/backup/integrity/data-integrity.service.ts - Verifies backup integrity using checksums
• src/backup/processing/backup-queue.processor.ts - BullMQ async job processing
• src/backup/testing/recovery-testing.service.ts - Automated recovery tests
• src/backup/disaster-recovery/disaster-recovery.service.ts - Disaster recovery with RTO tracking
• src/backup/monitoring/backup-monitoring.service.ts - Health checks and Prometheus metrics

Infrastructure (3 files)

• src/backup/backup.controller.ts - REST API endpoints
• src/backup/backup.module.ts - NestJS module configuration
• src/backup/interfaces/backup.interfaces.ts - Job data interfaces

Media Module (2 files) - Required for S3 operations

• src/media/media.module.ts
• src/media/storage/file-storage.service.ts

Testing Guide

Prerequisites

1. PostgreSQL Running

   psql -l  # Verify PostgreSQL is running

2. Redis Running

   redis-cli ping  # Should return PONG

3. Database Created

   createdb teachlink

Step 1: Create Database Tables

psql -U your_username -d teachlink << 'EOF'
CREATE TABLE IF NOT EXISTS backup_records (
  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
  backup_type VARCHAR(50) NOT NULL DEFAULT 'full',
  status VARCHAR(50) NOT NULL DEFAULT 'pending',
  region VARCHAR(50) NOT NULL,
  database_name VARCHAR(255) NOT NULL,
  storage_key VARCHAR(500),
  encrypted_storage_key VARCHAR(500),
  replicated_storage_key VARCHAR(500),
  kms_key_id VARCHAR(500),
  backup_size_bytes BIGINT,
  metadata JSONB,
  error_message TEXT,
  retry_count INTEGER DEFAULT 0,
  checksum_md5 VARCHAR(32),
  checksum_sha256 VARCHAR(64),
  integrity_verified BOOLEAN DEFAULT FALSE,
  verified_at TIMESTAMP,
  completed_at TIMESTAMP,
  expires_at TIMESTAMP,
  created_at TIMESTAMP DEFAULT NOW(),
  updated_at TIMESTAMP DEFAULT NOW()
);

CREATE INDEX IF NOT EXISTS idx_backup_status_created ON backup_records(status, created_at);
CREATE INDEX IF NOT EXISTS idx_backup_region ON backup_records(region);
CREATE INDEX IF NOT EXISTS idx_backup_completed ON backup_records(completed_at);

CREATE TABLE IF NOT EXISTS recovery_tests (
  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
  backup_record_id UUID REFERENCES backup_records(id) ON DELETE CASCADE,
  status VARCHAR(50) NOT NULL DEFAULT 'pending',
  test_database_name VARCHAR(255) NOT NULL,
  validation_results JSONB,
  performance_metrics JSONB,
  error_message TEXT,
  retry_count INTEGER DEFAULT 0,
  test_completed_at TIMESTAMP,
  created_at TIMESTAMP DEFAULT NOW(),
  updated_at TIMESTAMP DEFAULT NOW()
);

CREATE INDEX IF NOT EXISTS idx_recovery_test_backup ON recovery_tests(backup_record_id);
CREATE INDEX IF NOT EXISTS idx_recovery_test_status ON recovery_tests(status);
EOF

Step 2: Configure Environment

Ensure .env has database credentials:

DB_HOST=localhost
DB_PORT=5432
DB_USERNAME=your_postgres_username
DB_PASSWORD=
DB_DATABASE=teachlink
REDIS_HOST=localhost
REDIS_PORT=6379
BACKUP_TEST_DATABASE=teachlink_backup_test
SKIP_AWS_OPERATIONS=true

Step 3: Start Application

npm run start:dev

Expected Output:

[Nest] LOG [NestFactory] Starting Nest application...
[Nest] LOG [InstanceLoader] BackupModule dependencies initialized
[Nest] LOG [RouterExplorer] Mapped {/backup/health, GET} route
[Nest] LOG [RouterExplorer] Mapped {/backup/restore, POST} route
[Nest] LOG [RouterExplorer] Mapped {/backup/test, POST} route
[Nest] LOG [RouterExplorer] Mapped {/backup/test/:testId, GET} route
[Nest] LOG [NestApplication] Nest application successfully started

Step 4: Test Health Endpoint

curl http://localhost:3000/backup/health

Expected Response:

{
  "healthy": false,
  "issues": ["No backups found"]
}

✅ Pass Criteria: Returns 200 status with JSON response

Step 5: Verify Database Tables

psql -U your_username -d teachlink -c "\dt backup_records"
psql -U your_username -d teachlink -c "\dt recovery_tests"

Expected Output:

                List of relations
 Schema |      Name       | Type  |     Owner
--------+-----------------+-------+----------------
 public | backup_records  | table | your_username
 public | recovery_tests  | table | your_username

✅ Pass Criteria: Both tables exist

Step 6: Test Backup Endpoints (Manual Trigger)

Since automated backups run weekly, you can manually insert a test record:

psql -U your_username -d teachlink << 'EOF'
INSERT INTO backup_records (
  backup_type, status, region, database_name,
  storage_key, encrypted_storage_key
) VALUES (
  'full', 'completed', 'us-east-1', 'teachlink',
  'backups/test-backup.sql', 'backups/test-backup.sql.encrypted'
) RETURNING id;
EOF

Copy the returned ID, then test restore endpoint:

curl -X POST http://localhost:3000/backup/restore \
  -H "Content-Type: application/json" \
  -d '{"backupRecordId": "PASTE_ID_HERE"}'

Expected Response:

{
  "message": "Restore initiated"
}

📊 API Endpoints