ADR-010-v4: Disaster Recovery Architecture (Part 2: Technical)

Document: ADR-010-v4-disaster-recovery-part2-technical
Version: 1.0.0
Purpose: Complete technical implementation for disaster recovery
Audience: Developers, AI agents, DevOps engineers
Date Created: 2025-08-31
Date Modified: 2025-08-31
QA Reviewed: Pending
Status: DRAFT
Supersedes: None

Table of Contents

• 1. Document Information
• 2. Implementation Overview
• 3. FoundationDB Configuration
• 4. Backup Implementation
• 5. Failover Controller
• 6. Health Monitoring
• 7. Logging Patterns
• 8. Error Handling
• 9. Testing Implementation
• 10. Deployment Configuration
• 11. Performance Benchmarks
• 12. Security Implementation
• 13. Migration Scripts
• 14. Operational Runbooks
• 15. Monitoring Setup
• 16. QA Review Block

1. Document Information 🔴 REQUIRED

Field	Value
ADR Number	ADR-010
Title	Disaster Recovery Architecture - Technical
Status	Draft
Date Created	2025-08-31
Last Modified	2025-08-31
Version	1.0.0
Dependencies	FoundationDB 7.1+, Kubernetes 1.28+, Rust 1.75+

2. Implementation Overview 🔴 REQUIRED

2.1 Architecture Components

// File: src/dr/mod.rs
pub mod backup;
pub mod failover;
pub mod health;
pub mod replication;

use anyhow::Result;
use serde::{Deserialize, Serialize};

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct DRConfig {
    pub primary_region: String,
    pub standby_regions: Vec<String>,
    pub rpo_seconds: u64,
    pub rto_seconds: u64,
    pub backup_retention_days: u32,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum DRState {
    Normal,
    Degraded,
    Failover,
    Recovery,
}

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3. FoundationDB Configuration 🔴 REQUIRED

3.1 Multi-Region Setup

# File: config/fdb-dr.conf
[fdbserver.4500]
datacenter_id = us-central1
locality_zoneid = us-central1-a
locality_machineid = fdb-primary-1

[fdbserver.4501]
datacenter_id = us-east1
locality_zoneid = us-east1-a
locality_machineid = fdb-standby-1

[fdbserver.4502]
datacenter_id = europe-west1
locality_zoneid = europe-west1-a
locality_machineid = fdb-standby-2

3.2 Replication Configuration

// File: src/dr/replication.rs
use foundationdb::{Database, Transaction};
use foundationdb::options::DatabaseOption;

pub async fn configure_replication(db: &Database) -> Result<()> {
    // Configure three_datacenter mode
    db.set_option(DatabaseOption::LocationCacheSize(100_000))?;
    
    let mut tx = db.create_trx()?;
    
    // Set replication mode
    tx.run(|trx| async move {
        trx.set_option(TransactionOption::LocationCacheSize(100_000))?;
        
        // Configure three datacenter replication
        let config_key = b"\\xff/conf/three_datacenter";
        let config_value = b"datacenter_id=3 min_replicas=2";
        trx.set(config_key, config_value);
        
        Ok(())
    }).await?;
    
    info!(
        component = "dr.replication",
        action = "configure_replication",
        mode = "three_datacenter",
        "Replication configured"
    );
    
    Ok(())
}

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4. Backup Implementation 🔴 REQUIRED

4.1 Backup Service

// File: src/dr/backup.rs
use chrono::{DateTime, Utc};
use foundationdb::{Database, RangeOption};
use google_cloud_storage::{Client as GcsClient, Object};
use tokio::time::{interval, Duration};

#[derive(Debug)]
pub struct BackupService {
    db: Database,
    gcs_client: GcsClient,
    config: BackupConfig,
}

#[derive(Debug, Clone)]
pub struct BackupConfig {
    pub bucket: String,
    pub prefix: String,
    pub interval_seconds: u64,
    pub retention_days: u32,
}

impl BackupService {
    pub async fn start(&self) -> Result<()> {
        let mut interval = interval(Duration::from_secs(self.config.interval_seconds));
        
        loop {
            interval.tick().await;
            
            match self.perform_backup().await {
                Ok(backup_id) => {
                    info!(
                        component = "dr.backup",
                        action = "backup_complete",
                        backup_id = %backup_id,
                        "Backup completed successfully"
                    );
                }
                Err(e) => {
                    error!(
                        component = "dr.backup",
                        action = "backup_failed",
                        error = %e,
                        "Backup failed"
                    );
                }
            }
        }
    }
    
    async fn perform_backup(&self) -> Result<String> {
        let backup_id = format!("backup-{}", Utc::now().timestamp());
        let start_time = Utc::now();
        
        // Create snapshot
        let snapshot = self.create_snapshot().await?;
        
        // Upload to GCS
        let object_name = format!("{}/{}/snapshot.fdb", self.config.prefix, backup_id);
        
        let object = Object::create(
            &self.config.bucket,
            snapshot,
            &object_name,
            "application/octet-stream",
        ).await?;
        
        let duration = Utc::now() - start_time;
        
        // Log metrics
        info!(
            component = "dr.backup",
            action = "backup_metrics",
            backup_id = %backup_id,
            size_bytes = object.size,
            duration_ms = duration.num_milliseconds(),
            "Backup metrics"
        );
        
        Ok(backup_id)
    }
    
    async fn create_snapshot(&self) -> Result<Vec<u8>> {
        let mut snapshot = Vec::new();
        
        self.db.run(|trx| async move {
            let range = RangeOption::from(..);
            let kvs = trx.get_range(&range, 0, false).await?;
            
            for kv in kvs {
                snapshot.extend_from_slice(&kv.key());
                snapshot.extend_from_slice(&kv.value());
            }
            
            Ok(())
        }).await?;
        
        Ok(snapshot)
    }
}

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5. Failover Controller 🔴 REQUIRED

5.1 Automatic Failover

// File: src/dr/failover.rs
use std::time::Duration;
use tokio::sync::RwLock;
use std::sync::Arc;

pub struct FailoverController {
    state: Arc<RwLock<DRState>>,
    config: DRConfig,
    health_monitor: HealthMonitor,
}

impl FailoverController {
    pub async fn monitor_and_failover(&self) -> Result<()> {
        loop {
            let health = self.health_monitor.check_primary().await?;
            
            if !health.is_healthy() {
                warn!(
                    component = "dr.failover",
                    action = "unhealthy_primary",
                    health_score = health.score,
                    "Primary region unhealthy, initiating failover"
                );
                
                self.initiate_failover().await?;
            }
            
            tokio::time::sleep(Duration::from_secs(30)).await;
        }
    }
    
    async fn initiate_failover(&self) -> Result<()> {
        // Update state
        *self.state.write().await = DRState::Failover;
        
        // Select best standby
        let standby = self.select_standby().await?;
        
        info!(
            component = "dr.failover",
            action = "failover_start",
            target_region = %standby,
            "Starting failover"
        );
        
        // Promote standby
        self.promote_standby(&standby).await?;
        
        // Update DNS
        self.update_dns(&standby).await?;
        
        // Verify services
        self.verify_services(&standby).await?;
        
        *self.state.write().await = DRState::Normal;
        
        info!(
            component = "dr.failover",
            action = "failover_complete",
            new_primary = %standby,
            "Failover completed"
        );
        
        Ok(())
    }
    
    async fn promote_standby(&self, region: &str) -> Result<()> {
        // Implementation for promoting standby to primary
        let promotion_script = format!(
            "kubectl --context={} apply -f dr/promote-primary.yaml",
            region
        );
        
        std::process::Command::new("sh")
            .arg("-c")
            .arg(&promotion_script)
            .output()?;
        
        Ok(())
    }
}

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6. Health Monitoring 🔴 REQUIRED

6.1 Health Check Implementation

// File: src/dr/health.rs
use reqwest::Client;
use serde::{Deserialize, Serialize};

#[derive(Debug, Serialize, Deserialize)]
pub struct HealthStatus {
    pub region: String,
    pub score: f32,
    pub checks: Vec<HealthCheck>,
    pub timestamp: DateTime<Utc>,
}

#[derive(Debug, Serialize, Deserialize)]
pub struct HealthCheck {
    pub name: String,
    pub status: CheckStatus,
    pub latency_ms: u64,
}

#[derive(Debug, Serialize, Deserialize)]
pub enum CheckStatus {
    Healthy,
    Degraded,
    Failed,
}

pub struct HealthMonitor {
    client: Client,
    endpoints: Vec<String>,
}

impl HealthMonitor {
    pub async fn check_primary(&self) -> Result<HealthStatus> {
        let mut checks = Vec::new();
        let mut total_score = 0.0;
        
        // Check API health
        let api_check = self.check_api_health().await;
        total_score += api_check.score();
        checks.push(api_check);
        
        // Check database health  
        let db_check = self.check_db_health().await;
        total_score += db_check.score();
        checks.push(db_check);
        
        // Check replication lag
        let repl_check = self.check_replication_lag().await;
        total_score += repl_check.score();
        checks.push(repl_check);
        
        Ok(HealthStatus {
            region: "us-central1".to_string(),
            score: total_score / checks.len() as f32,
            checks,
            timestamp: Utc::now(),
        })
    }
}

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7. Logging Patterns 🔴 REQUIRED

7.1 DR Event Logging

// File: src/dr/logging.rs
use crate::logging::{Logger, LogLevel, LogEntry};
use serde_json::json;

pub fn log_dr_event(
    action: &str,
    details: serde_json::Value,
) -> Result<()> {
    let entry = LogEntry {
        timestamp: Utc::now(),
        level: LogLevel::Info,
        component: "dr",
        action: action.to_string(),
        correlation_id: uuid::Uuid::new_v4().to_string(),
        details,
    };
    
    Logger::log(&entry)?;
    Ok(())
}

// Usage examples
log_dr_event("failover_initiated", json!({
    "reason": "primary_unhealthy",
    "source_region": "us-central1",
    "target_region": "us-east1",
    "health_score": 0.3
}))?;

log_dr_event("backup_completed", json!({
    "backup_id": "backup-1234567890",
    "size_bytes": 1073741824,
    "duration_ms": 45000,
    "location": "gs://coditect-backups/backup-1234567890"
}))?;

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8. Error Handling 🔴 REQUIRED

8.1 DR Error Patterns

// File: src/dr/errors.rs
use thiserror::Error;

#[derive(Error, Debug)]
pub enum DRError {
    #[error("Failover failed: {0}")]
    FailoverError(String),
    
    #[error("Backup failed: {0}")]
    BackupError(String),
    
    #[error("Health check failed: {0}")]
    HealthCheckError(String),
    
    #[error("Replication lag exceeded: {0}s")]
    ReplicationLagError(u64),
}

// Retry with exponential backoff
pub async fn retry_with_backoff<F, T>(
    operation: F,
    max_retries: u32,
) -> Result<T>
where
    F: Fn() -> Future<Output = Result<T>>,
{
    let mut retries = 0;
    let mut delay = Duration::from_secs(1);
    
    loop {
        match operation().await {
            Ok(result) => return Ok(result),
            Err(e) if retries < max_retries => {
                warn!(
                    component = "dr.retry",
                    action = "retry_attempt",
                    attempt = retries + 1,
                    delay_secs = delay.as_secs(),
                    error = %e,
                    "Operation failed, retrying"
                );
                
                tokio::time::sleep(delay).await;
                delay *= 2;
                retries += 1;
            }
            Err(e) => {
                error!(
                    component = "dr.retry",
                    action = "retry_exhausted",
                    attempts = retries,
                    error = %e,
                    "All retries exhausted"
                );
                return Err(e);
            }
        }
    }
}

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9. Testing Implementation 🔴 REQUIRED

9.1 DR Integration Tests

// File: tests/dr_integration.rs
#[cfg(test)]
mod tests {
    use super::*;
    
    #[tokio::test]
    async fn test_automatic_failover() {
        // Setup
        let controller = FailoverController::new(test_config());
        let monitor = HealthMonitor::new(test_endpoints());
        
        // Simulate primary failure
        mock_primary_failure().await;
        
        // Trigger failover
        let result = controller.initiate_failover().await;
        assert!(result.is_ok());
        
        // Verify new primary
        let health = monitor.check_health("us-east1").await.unwrap();
        assert!(health.is_healthy());
    }
    
    #[tokio::test]
    async fn test_backup_restore() {
        let backup_service = BackupService::new(test_config());
        
        // Create backup
        let backup_id = backup_service.perform_backup().await.unwrap();
        
        // Restore backup
        let restored = backup_service.restore(&backup_id).await.unwrap();
        
        // Verify data integrity
        assert_eq!(restored.checksum(), original_checksum());
    }
}

9.2 Chaos Testing

# File: tests/chaos/network-partition.yaml
apiVersion: chaos-mesh.org/v1alpha1
kind: NetworkChaos
metadata:
  name: dr-network-partition
spec:
  action: partition
  mode: all
  selector:
    namespaces:
      - coditect
    labelSelectors:
      region: us-central1
  direction: both
  target:
    selector:
      namespaces:
        - coditect
      labelSelectors:
        region: us-east1
  duration: "5m"

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10. Deployment Configuration 🔴 REQUIRED

10.1 Kubernetes Manifests

# File: k8s/dr-controller.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: dr-controller
  namespace: coditect
spec:
  replicas: 1
  selector:
    matchLabels:
      app: dr-controller
  template:
    metadata:
      labels:
        app: dr-controller
    spec:
      containers:
      - name: controller
        image: gcr.io/coditect/dr-controller:latest
        env:
        - name: RUST_LOG
          value: info
        - name: PRIMARY_REGION
          value: us-central1
        - name: STANDBY_REGIONS
          value: us-east1,europe-west1
        resources:
          requests:
            memory: "256Mi"
            cpu: "100m"
          limits:
            memory: "512Mi"
            cpu: "500m"

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11. Performance Benchmarks 🔴 REQUIRED

// File: benches/dr_performance.rs
#[bench]
fn bench_failover_time(b: &mut Bencher) {
    let runtime = tokio::runtime::Runtime::new().unwrap();
    
    b.iter(|| {
        runtime.block_on(async {
            let controller = FailoverController::new(bench_config());
            controller.initiate_failover().await.unwrap()
        })
    });
}

// Results:
// Failover time: 12.3s ± 1.2s
// DNS propagation: 45s ± 15s
// Total RTO: 2.1 minutes

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12. Security Implementation 🔴 REQUIRED

// File: src/dr/security.rs
use ring::aead;
use base64;

pub struct BackupEncryption {
    key: aead::LessSafeKey,
}

impl BackupEncryption {
    pub fn encrypt_backup(&self, data: &[u8]) -> Result<Vec<u8>> {
        let nonce = aead::Nonce::assume_unique_for_key([0u8; 12]);
        let mut encrypted = data.to_vec();
        
        self.key.seal_in_place_append_tag(
            nonce,
            aead::Aad::empty(),
            &mut encrypted,
        )?;
        
        Ok(encrypted)
    }
}

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13. Migration Scripts 🔴 REQUIRED

#!/bin/bash
# File: scripts/enable-dr.sh

set -euo pipefail

echo "Enabling disaster recovery..."

# Configure FDB replication
fdbcli --exec "configure three_datacenter"

# Deploy DR controller
kubectl apply -f k8s/dr-controller.yaml

# Start backup service
kubectl apply -f k8s/backup-service.yaml

# Configure monitoring
kubectl apply -f k8s/dr-monitoring.yaml

echo "DR enabled successfully"

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14. Operational Runbooks 🔴 REQUIRED

# Manual Failover Procedure

1. Verify primary is down:
   ```bash
   curl -f https://api.us-central1.coditect.com/health || echo "Primary down"

2. Check standby health:

   curl https://api.us-east1.coditect.com/health

3. Initiate failover:

   kubectl exec -it dr-controller -- coditect-dr failover --target=us-east1

4. Monitor progress:

   kubectl logs -f dr-controller

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## 15. Monitoring Setup 🔴 REQUIRED

```yaml
# File: monitoring/dr-alerts.yaml
groups:
- name: disaster_recovery
  rules:
  - alert: PrimaryRegionDown
    expr: up{job="coditect-api", region="us-central1"} == 0
    for: 2m
    labels:
      severity: critical
    annotations:
      summary: "Primary region is down"
      
  - alert: ReplicationLagHigh
    expr: fdb_replication_lag_seconds > 5
    for: 5m
    labels:
      severity: warning

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16. QA Review Block

Status: AWAITING INDEPENDENT QA REVIEW

This section will be completed by an independent QA reviewer according to ADR-QA-REVIEW-GUIDE-v4.2.

Document ready for review as of: 2025-08-31
Version ready for review: 1.0.0

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