Automated Backup Verification System with Data Integrity Checking and Recovery Time Estimation Go

Okay, here's a detailed breakdown of an Automated Backup Verification System written in Go, with a focus on data integrity checking, recovery time estimation, and real-world considerations. I'll provide the core Go code, explain the logic, and outline what's needed to make it production-ready.

**Project Title:** Automated Backup Verification System with Data Integrity Checking and Recovery Time Estimation

**Project Goal:** To create a robust and automated system that regularly verifies the integrity and recoverability of backups, providing estimated recovery times to ensure business continuity in the event of data loss.

**Core Components:**

1.  **Backup Scanner:**  Discovers backups based on a configurable set of rules (e.g., directory patterns, file naming conventions, backup catalog APIs).
2.  **Data Integrity Checker:** Verifies the integrity of the backup data using checksums, hash comparisons, or other validation techniques.  It supports different integrity check methods based on the backup type.
3.  **Recovery Simulation Engine:** Performs a simulated recovery of a subset of the backup data to a test environment. This assesses the actual recovery process and measures the time required.
4.  **Recovery Time Estimator:** Analyzes the recovery simulation results and backup metadata to estimate the time required to recover the entire backup set.  It considers factors like data size, network bandwidth, storage I/O, and processing overhead.
5.  **Reporting and Alerting:** Generates detailed reports on backup verification results, including integrity check status, recovery simulation times, and estimated recovery times.  It sends alerts (email, Slack, etc.) when issues are detected.
6.  **Configuration Management:** Provides a flexible configuration system to define backup locations, integrity check methods, recovery simulation settings, and reporting parameters.
7.  **Scheduling:**  Includes a scheduler to automate the backup verification process at regular intervals (e.g., daily, weekly).
8.  **Logging:** Detailed logging to track all activities, errors, and performance metrics.

**Go Code Structure (Illustrative)**

```go
package main

import (
	"crypto/md5"
	"encoding/hex"
	"fmt"
	"io"
	"log"
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"time"

	"github.com/robfig/cron/v3"
	"gopkg.in/yaml.v3"
)

// Configuration structure
type Config struct {
	BackupLocations []string `yaml:"backup_locations"`
	IntegrityCheck  struct {
		Method string `yaml:"method"` // "md5", "sha256", "none"
	} `yaml:"integrity_check"`
	RecoverySimulation struct {
		Enabled      bool   `yaml:"enabled"`
		SubsetSizeMB int    `yaml:"subset_size_mb"`
		TargetDir    string `yaml:"target_dir"`
	} `yaml:"recovery_simulation"`
	Reporting struct {
		Email struct {
			Enabled  bool   `yaml:"enabled"`
			SMTPHost string `yaml:"smtp_host"`
			SMTPPort int    `yaml:"smtp_port"`
			Username string `yaml:"username"`
			Password string `yaml:"password"`
			Sender   string `yaml:"sender"`
			Recipients []string `yaml:"recipients"`
		} `yaml:"email"`
		Slack struct {
			Enabled bool   `yaml:"enabled"`
			WebhookURL string `yaml:"webhook_url"`
		} `yaml:"slack"`
	} `yaml:"reporting"`
	Scheduler struct {
		CronSchedule string `yaml:"cron_schedule"`
	} `yaml:"scheduler"`
	Logging struct {
		LogFile string `yaml:"log_file"`
		LogLevel string `yaml:"log_level"` // "debug", "info", "warn", "error"
	} `yaml:"logging"`
}

// BackupFile represents a single backup file
type BackupFile struct {
	Path         string
	Size         int64
	LastModified time.Time
	MD5Checksum  string
}

var (
	cfg Config
	logger *log.Logger
)


// LoadConfig loads the configuration from a YAML file
func LoadConfig(filename string) error {
	f, err := os.Open(filename)
	if err != nil {
		return fmt.Errorf("error opening config file: %w", err)
	}
	defer f.Close()

	decoder := yaml.NewDecoder(f)
	err = decoder.Decode(&cfg)
	if err != nil {
		return fmt.Errorf("error decoding config file: %w", err)
	}

	return nil
}

// InitializeLogger initializes the logger
func InitializeLogger(logFile string, logLevel string) (*log.Logger, error) {
	// Open log file
	file, err := os.OpenFile(logFile, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0666)
	if err != nil {
		return nil, fmt.Errorf("failed to open log file: %w", err)
	}

	// Create a multiwriter to write to both file and stdout
	multiWriter := io.MultiWriter(file, os.Stdout)

	// Create a new logger
	logger := log.New(multiWriter, "BackupVerifier: ", log.Ldate|log.Ltime|log.Lshortfile)

	// Set log level
	// You might want to use a dedicated logging library with more advanced level handling
	// For simplicity, we'll just use basic string comparisons
	switch strings.ToLower(logLevel) {
	case "debug":
		// No filtering needed for debug
	case "info":
		// Filter out debug logs
	case "warn":
		// Filter out debug and info logs
	case "error":
		// Filter out debug, info, and warn logs
		// This is a very basic example; a real logging library would have more sophisticated filtering
		// Implement your own log filtering logic here if needed
	default:
		logger.Printf("Invalid log level '%s', defaulting to 'info'", logLevel)
	}

	return logger, nil
}

// ScanBackupLocations scans the specified backup locations for backup files.
func ScanBackupLocations(locations []string) ([]BackupFile, error) {
	var backupFiles []BackupFile

	for _, location := range locations {
		err := filepath.Walk(location, func(path string, info os.FileInfo, err error) error {
			if err != nil {
				return err
			}
			if !info.Mode().IsRegular() {
				return nil // Skip directories and other non-file entities
			}

			backupFile := BackupFile{
				Path:         path,
				Size:         info.Size(),
				LastModified: info.ModTime(),
			}
			backupFiles = append(backupFiles, backupFile)
			return nil
		})

		if err != nil {
			return nil, fmt.Errorf("error walking backup location %s: %w", location, err)
		}
	}

	return backupFiles, nil
}

// CalculateMD5Checksum calculates the MD5 checksum of a file.
func CalculateMD5Checksum(filePath string) (string, error) {
	file, err := os.Open(filePath)
	if err != nil {
		return "", fmt.Errorf("error opening file: %w", err)
	}
	defer file.Close()

	hash := md5.New()
	if _, err := io.Copy(hash, file); err != nil {
		return "", fmt.Errorf("error reading file: %w", err)
	}

	checksum := hex.EncodeToString(hash.Sum(nil))
	return checksum, nil
}

// VerifyDataIntegrity verifies the data integrity of the backup files.
func VerifyDataIntegrity(files []BackupFile, method string) (map[string]bool, error) {
	results := make(map[string]bool)

	for _, file := range files {
		switch method {
		case "md5":
			checksum, err := CalculateMD5Checksum(file.Path)
			if err != nil {
				logger.Printf("Error calculating MD5 checksum for %s: %v", file.Path, err)
				results[file.Path] = false
				continue
			}
			file.MD5Checksum = checksum // Store for future comparison if needed
			// In a real system, you'd likely compare this against a known good checksum
			// stored in a metadata database or alongside the backup file.
			//For this example, we will simply set it to true
			results[file.Path] = true

			logger.Printf("MD5 checksum for %s: %s", file.Path, checksum)

		case "none":
			// No integrity check performed
			results[file.Path] = true
			logger.Printf("No integrity check performed for %s", file.Path)
		default:
			logger.Printf("Unsupported integrity check method: %s", method)
			results[file.Path] = false
		}
	}

	return results, nil
}

// SimulateRecovery simulates the recovery of a subset of the backup data.
func SimulateRecovery(files []BackupFile, subsetSizeMB int, targetDir string) (time.Duration, error) {
	startTime := time.Now()

	// Create the target directory if it doesn't exist
	if _, err := os.Stat(targetDir); os.IsNotExist(err) {
		if err := os.MkdirAll(targetDir, 0755); err != nil {
			return 0, fmt.Errorf("error creating target directory: %w", err)
		}
	}

	var totalBytes int64
	for _, file := range files {
		// Copy a subset of the file (up to subsetSizeMB) to the target directory
		bytesToCopy := int64(subsetSizeMB) * 1024 * 1024 // Convert MB to bytes
		if file.Size < bytesToCopy {
			bytesToCopy = file.Size
		}
		err := copyFileSubset(file.Path, filepath.Join(targetDir, filepath.Base(file.Path)), bytesToCopy)

		if err != nil {
			return 0, fmt.Errorf("error copying file: %w", err)
		}
		totalBytes += bytesToCopy

		// Stop copying files if we reach the subset size
		if totalBytes >= int64(subsetSizeMB)*1024*1024 {
			break
		}
	}

	endTime := time.Now()
	duration := endTime.Sub(startTime)

	return duration, nil
}

// copyFileSubset copies a subset of a file from source to destination.
func copyFileSubset(source, destination string, bytesToCopy int64) error {
	sourceFile, err := os.Open(source)
	if err != nil {
		return fmt.Errorf("error opening source file: %w", err)
	}
	defer sourceFile.Close()

	destinationFile, err := os.Create(destination)
	if err != nil {
		return fmt.Errorf("error creating destination file: %w", err)
	}
	defer destinationFile.Close()

	_, err = io.CopyN(destinationFile, sourceFile, bytesToCopy)
	if err != nil {
		return fmt.Errorf("error copying file: %w", err)
	}

	return nil
}

// EstimateRecoveryTime estimates the time required to recover the entire backup set.
func EstimateRecoveryTime(simulationDuration time.Duration, subsetSizeMB int, totalBackupSizeGB float64) time.Duration {
	subsetSizeGB := float64(subsetSizeMB) / 1024
	if subsetSizeGB == 0 {
		return 0 // Avoid division by zero
	}

	// Estimate the recovery time based on the ratio of the subset size to the total backup size.
	estimatedDuration := time.Duration(float64(simulationDuration) * (totalBackupSizeGB / subsetSizeGB))

	return estimatedDuration
}

// SendEmail sends an email notification.
func SendEmail(subject, body string) error {
	// Implement your email sending logic here using the cfg.Reporting.Email configuration.
	// This is a placeholder.  You'll need a library like "net/smtp" or a dedicated email package.

	fmt.Printf("Sending email - Subject: %s, Body: %s\n", subject, body) // Placeholder
	return nil
}

// SendSlackNotification sends a Slack notification.
func SendSlackNotification(message string) error {
	// Implement your Slack notification logic here using the cfg.Reporting.Slack configuration.
	// This is a placeholder. You'll need a library like "github.com/slack-go/slack"

	fmt.Printf("Sending Slack notification: %s\n", message) // Placeholder
	return nil
}

// RunBackupVerification performs the backup verification process.
func RunBackupVerification() error {
	logger.Println("Starting backup verification...")

	// 1. Scan backup locations
	backupFiles, err := ScanBackupLocations(cfg.BackupLocations)
	if err != nil {
		return fmt.Errorf("error scanning backup locations: %w", err)
	}

	totalBackupSizeGB := float64(0)

	for _, file := range backupFiles {
		totalBackupSizeGB += float64(file.Size) / (1024 * 1024 * 1024)
	}

	logger.Printf("Found %d backup files. Total backup size: %.2f GB", len(backupFiles), totalBackupSizeGB)

	// 2. Verify data integrity
	integrityResults, err := VerifyDataIntegrity(backupFiles, cfg.IntegrityCheck.Method)
	if err != nil {
		return fmt.Errorf("error verifying data integrity: %w", err)
	}

	// Check for integrity failures
	integrityFailed := false
	for file, ok := range integrityResults {
		if !ok {
			logger.Printf("Integrity check failed for %s", file)
			integrityFailed = true
		}
	}

	// 3. Simulate recovery
	var recoveryTime time.Duration
	if cfg.RecoverySimulation.Enabled {
		recoveryTime, err = SimulateRecovery(backupFiles, cfg.RecoverySimulation.SubsetSizeMB, cfg.RecoverySimulation.TargetDir)
		if err != nil {
			return fmt.Errorf("error simulating recovery: %w", err)
		}
		logger.Printf("Recovery simulation completed in %s", recoveryTime)
	} else {
		logger.Println("Recovery simulation disabled.")
	}

	// 4. Estimate recovery time
	estimatedRecoveryTime := EstimateRecoveryTime(recoveryTime, cfg.RecoverySimulation.SubsetSizeMB, totalBackupSizeGB)
	logger.Printf("Estimated total recovery time: %s", estimatedRecoveryTime)

	// 5. Reporting and Alerting
	report := fmt.Sprintf("Backup Verification Report:\nTotal Backup Size: %.2f GB\nIntegrity Check: %v\nEstimated Recovery Time: %s\n",
		totalBackupSizeGB, !integrityFailed, estimatedRecoveryTime)

	if integrityFailed {
		report += "Integrity check failed for some files. See logs for details.\n"
	}

	if cfg.Reporting.Email.Enabled {
		err = SendEmail("Backup Verification Report", report)
		if err != nil {
			logger.Printf("Error sending email: %v", err)
		}
	}

	if cfg.Reporting.Slack.Enabled {
		err = SendSlackNotification(report)
		if err != nil {
			logger.Printf("Error sending Slack notification: %v", err)
		}
	}

	logger.Println("Backup verification completed.")
	return nil
}

func main() {
	// Load configuration
	err := LoadConfig("config.yaml")
	if err != nil {
		log.Fatalf("Error loading configuration: %v", err)
	}

	// Initialize logger
	logger, err = InitializeLogger(cfg.Logging.LogFile, cfg.Logging.LogLevel)
	if err != nil {
		log.Fatalf("Error initializing logger: %v", err)
	}

	defer func() {
		if r := recover(); r != nil {
			logger.Printf("Panic occurred: %v", r)
			// Optionally send an alert about the panic
		}
	}()
	//Start the cron scheduler
	c := cron.New()
	_, err = c.AddFunc(cfg.Scheduler.CronSchedule, func() {
		if err := RunBackupVerification(); err != nil {
			logger.Printf("Backup verification failed: %v", err)
			// Optionally send an alert about the failure
		}
	})

	if err != nil {
		logger.Fatalf("Error scheduling backup verification: %v", err)
	}

	c.Start()

	// Keep the main function running
	select {}
}
```

**Configuration (config.yaml - Example)**

```yaml
backup_locations:
  - "/path/to/backup/location1"
  - "/path/to/backup/location2"

integrity_check:
  method: "md5" # "md5", "sha256", "none"

recovery_simulation:
  enabled: true
  subset_size_mb: 100  # Size of the subset to recover (in MB)
  target_dir: "/tmp/recovery_test"

reporting:
  email:
    enabled: false
    smtp_host: "smtp.example.com"
    smtp_port: 587
    username: "your_email@example.com"
    password: "your_password"
    sender: "backup_verifier@example.com"
    recipients:
      - "admin@example.com"
  slack:
    enabled: false
    webhook_url: "https://hooks.slack.com/services/..."

scheduler:
  cron_schedule: "0 0 * * *" # Run daily at midnight

logging:
  log_file: "/var/log/backup_verifier.log"
  log_level: "info" # "debug", "info", "warn", "error"

```

**Logic of Operation:**

1.  **Configuration Loading:**  The program starts by loading configuration data from a YAML file (`config.yaml`).  This configuration defines the backup locations, integrity check methods, recovery simulation parameters, reporting options, scheduling, and logging settings.

2.  **Backup Scanning:** The `ScanBackupLocations` function recursively searches the specified directories for backup files. It gathers information about each file, such as its path, size, and last modified time.

3.  **Data Integrity Checking:** The `VerifyDataIntegrity` function checks the integrity of the backup data.  It supports different methods, such as MD5 checksums.  For each file, it calculates the checksum and compares it to a stored checksum (this part is simplified in the example and would need to be expanded for real-world use).  If the checksums don't match, it indicates data corruption.

4.  **Recovery Simulation:** If enabled in the configuration, the `SimulateRecovery` function simulates the recovery process by copying a subset of the backup files to a temporary recovery directory.  It measures the time required to copy this subset, providing an indication of the recovery speed.

5.  **Recovery Time Estimation:** The `EstimateRecoveryTime` function calculates the estimated time to recover the entire backup set based on the recovery simulation results, the size of the simulated subset, and the total size of the backup.  This provides a rough estimate of how long it would take to restore the entire backup.

6.  **Reporting and Alerting:** The program generates a report summarizing the results of the backup verification process, including the integrity check status, recovery simulation time, and estimated recovery time.  It then sends this report via email and/or Slack, depending on the configuration. Alerts are sent if integrity checks fail.

7.  **Scheduling:** The `cron` library is used to schedule the backup verification process to run automatically at regular intervals, as defined in the `cron_schedule` setting.

8. **Logging**: The program logs events, errors, and performance metrics to both the console and a specified log file. The log level can be configured to control the verbosity of the logging.

**Real-World Considerations & Project Details:**

*   **Backup Discovery:**
    *   **Backup Catalogs:**  Integrate with backup software APIs (e.g., Veeam, Commvault, NetBackup, AWS Backup, Azure Backup) to automatically discover backups and their metadata.  This is much more reliable than simply scanning directories.
    *   **Configuration Files:** Parse configuration files of the backup software to determine the backup location and metadata.
    *   **Naming Conventions:**  Support flexible naming conventions for backup files using regular expressions.  The scanner needs to be highly configurable to adapt to various backup strategies.

*   **Data Integrity:**
    *   **Checksum Storage:**  Store checksums (or other integrity information) in a reliable metadata database (e.g., PostgreSQL, MySQL). The checksums should be associated with the backup files.
    *   **Algorithm Selection:** Support a range of cryptographic hash functions (MD5, SHA-256, SHA-512) and other integrity checks (e.g., PAR2 parity files) based on the needs of the backed-up data.  Allow for different algorithms per backup type.
    *   **Bit Rot Detection:** Consider integrating with tools that can detect bit rot (silent data corruption) on storage media.  This is especially important for long-term archival backups.
    *   **Incremental Backups:**  Handle incremental and differential backups correctly. Integrity checks should verify the chain of backups.

*   **Recovery Simulation:**
    *   **Virtualization:**  Use virtualization (e.g., Docker, VMware, Hyper-V) to create isolated test environments for recovery simulation.  This prevents conflicts with production systems.
    *   **Application Verification:**  After recovering the subset of data, perform application-level verification (e.g., database consistency checks, website availability tests) to ensure that the recovered data is functional.
    *   **Resource Monitoring:**  Monitor CPU, memory, disk I/O, and network usage during the recovery simulation to identify bottlenecks.
    *   **Database Recovery Simulation:**  For databases, simulate point-in-time recovery to a test database.
    *   **Automated cleanup**: Delete the test environment and recovered data after simulation is completed.

*   **Recovery Time Estimation:**
    *   **Historical Data:**  Store historical recovery simulation results to improve the accuracy of recovery time estimates.  Use machine learning techniques to predict recovery times based on past performance.
    *   **Parallelism:**  Account for the level of parallelism that can be achieved during the actual recovery process. Some recovery tools can restore multiple files or database tables simultaneously.
    *   **Resource Contention:**  Consider potential resource contention during a real recovery (e.g., network congestion, storage I/O bottlenecks).
    *   **Network Bandwidth:**  Accurately measure or estimate network bandwidth between the backup storage location and the recovery target.

*   **Reporting and Alerting:**
    *   **Centralized Dashboard:**  Create a centralized dashboard to visualize backup verification results, recovery time estimates, and any detected issues.
    *   **Customizable Alerts:**  Allow users to customize alert thresholds and notification channels.
    *   **Detailed Reports:**  Generate detailed reports that can be used for compliance auditing and troubleshooting.
    *   **Integration with Monitoring Systems:**  Integrate with existing monitoring systems (e.g., Prometheus, Grafana, Nagios) to provide a comprehensive view of system health.
    *   **Alert Prioritization:**  Implement a system for prioritizing alerts based on the severity of the issue.

*   **Configuration Management:**
    *   **Centralized Configuration:**  Use a centralized configuration management system (e.g., etcd, Consul, ZooKeeper) to manage the configuration of the backup verification system.
    *   **Version Control:**  Store the configuration files in a version control system (e.g., Git) to track changes and enable rollback.
    *   **API-Driven Configuration:**  Provide an API for managing the configuration programmatically.
    *   **Secrets Management:**  Use a secrets management solution (e.g., HashiCorp Vault) to securely store sensitive information, such as passwords and API keys.

*   **Scalability and Performance:**
    *   **Parallel Processing:**  Use goroutines and channels to perform backup scanning, integrity checks, and recovery simulations in parallel.
    *   **Caching:**  Implement caching to reduce the load on backup storage systems.
    *   **Distributed Architecture:**  Consider a distributed architecture to scale the backup verification system to handle large environments.
    *   **Database Optimization:**  Optimize database queries for storing and retrieving metadata and historical data.

*   **Security:**
    *   **Access Control:**  Implement strict access control to prevent unauthorized access to backup data and configuration.
    *   **Encryption:**  Use encryption to protect backup data both in transit and at rest.
    *   **Auditing:**  Log all actions performed by the backup verification system for auditing purposes.
    *   **Vulnerability Scanning:**  Regularly scan the backup verification system for security vulnerabilities.

*   **Error Handling:**
    *   **Retry Mechanisms:**  Implement retry mechanisms for failed operations, such as integrity checks and recovery simulations.
    *   **Circuit Breaker Pattern:**  Use the circuit breaker pattern to prevent cascading failures.
    *   **Graceful Degradation:**  Design the system to degrade gracefully in the event of a failure.

*   **Deployment:**
    *   **Containerization:**  Use containerization (e.g., Docker) to package the backup verification system and its dependencies.
    *   **Orchestration:**  Use a container orchestration platform (e.g., Kubernetes) to deploy and manage the backup verification system.
    *   **Infrastructure as Code:**  Use infrastructure as code (e.g., Terraform, CloudFormation) to automate the provisioning and configuration of the infrastructure.

*   **Testing:**
    *   **Unit Tests:**  Write unit tests to verify the functionality of individual components.
    *   **Integration Tests:**  Write integration tests to verify the interaction between different components.
    *   **End-to-End Tests:**  Write end-to-end tests to verify the entire backup verification process.
    *   **Chaos Engineering:**  Use chaos engineering techniques to simulate failures and test the resilience of the system.

**Example Workflow:**

1.  **Scheduled Task:** The cron scheduler triggers the `RunBackupVerification` function at the configured interval.
2.  **Backup Discovery:** The system uses the backup catalog API to identify the latest backup set.
3.  **Integrity Check:** The system retrieves checksums from the metadata database and compares them to newly calculated checksums for the backup files.
4.  **Recovery Simulation:**  A virtual machine is provisioned, and a subset of the backup data is restored to the VM.  Application-level checks are performed to verify the restored data.
5.  **Recovery Time Estimation:** The system analyzes the recovery simulation results and estimates the time required to restore the entire backup set.
6.  **Reporting:** A detailed report is generated and sent to the appropriate stakeholders via email and posted to a centralized dashboard.
7.  **Alerting:** If any issues are detected (e.g., integrity check failures, recovery time exceeds threshold), alerts are sent via email and Slack.

**Key Libraries and Technologies:**

*   **Go standard library:** `os`, `io`, `time`, `log`, `path/filepath`, `crypto/md5`, `encoding/hex`
*   **YAML parsing:** `gopkg.in/yaml.v3`
*   **Cron scheduling:** `github.com/robfig/cron/v3`
*   **Email sending:** `net/smtp` (or a dedicated email package)
*   **Slack integration:** `github.com/slack-go/slack`
*   **Metadata Database:** PostgreSQL, MySQL
*   **Virtualization:** Docker, VMware, Hyper-V
*   **Container Orchestration:** Kubernetes
*   **Secrets Management:** HashiCorp Vault

This detailed breakdown provides a comprehensive foundation for building a robust automated backup verification system. Remember to tailor the specific implementation to your environment and backup technologies. Good luck!