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ADR-028: CODI2 Separation of Concerns Architecture (v4) - Part 2: Technical Implementation

Document Specification Block​

Document: ADR-028-v4-codi2-separation-of-concerns-part2-technical
Version: 2.0.0
Purpose: Technical implementation of CODI2 with separated logging, messaging, and state management
Audience: Engineers, AI Implementation Agents
Date Created: 2025-09-06
Date Modified: 2025-09-06
Status: DRAFT

Table of Contents​

  1. System Architecture
  2. Architecture Diagrams
  3. Inter-Agent Communication Protocol
  4. Core Components Implementation
  5. Error Handling
  6. Logging Implementation
  7. Testing Strategy
  8. Monitoring & Observability
  9. Security Considerations
  10. Deployment Configuration
  11. Performance Benchmarks
  12. Migration Guide

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1. System Architecture​

Core Module Structure​

// codi2/src/lib.rs
pub mod audit;        // Audit logging (immutable records)
pub mod messaging;    // Inter-agent communication
pub mod state;        // System state management
pub mod events;       // Event definitions
pub mod errors;       // Error types and handling
pub mod monitoring;   // Metrics and observability

Separation of Concerns Matrix​

ConcernOld (CODI v1)New (CODI2)StoragePerformance
Audit Eventscodi-ps.logAuditLoggerFoundationDB<10ms async
Agent Messagescodi-ps.logMessageBusMemory/gRPC<0.1ms
System Statecodi-ps.logStateStoreFoundationDB<5ms
Metricscodi-ps.logMetricsCollectorPrometheus<1ms

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2. Architecture Diagrams​

System Component Architecture​

Data Flow Architecture​

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3. Inter-Agent Communication Protocol​

3.1 Communication Mechanisms​

MechanismUse CaseLatencyDurabilityCapacity
MPSC ChannelsSame-process agents<0.1msNo10K msg/sec
gRPCCross-process/container<1msNo5K msg/sec
FDB QueuesPersistent messaging<5msYes1K msg/sec

3.2 Message Format Specification​

// codi2/src/messaging/protocol.rs
use chrono::{DateTime, Utc};
use serde::{Deserialize, Serialize};
use uuid::Uuid;
use std::time::Duration;

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct AgentMessage {
    // Message metadata
    pub id: Uuid,
    pub timestamp: DateTime<Utc>,
    pub correlation_id: Option<Uuid>,  // For request-response patterns
    
    // Routing information
    pub from: AgentId,
    pub to: AgentId,
    pub topic: MessageTopic,
    
    // Message content
    pub payload: MessagePayload,
    pub priority: MessagePriority,
    pub ttl: Duration,  // Time to live
}

#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq, Hash)]
pub struct AgentId(pub String);

#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum MessageTopic {
    TaskAssignment,
    StatusUpdate,
    ResourceRequest,
    Coordination,
    HealthCheck,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum MessagePayload {
    AssignTask { 
        task_id: String, 
        deadline: DateTime<Utc>,
        requirements: TaskRequirements,
    },
    UpdateStatus { 
        status: AgentStatus, 
        details: String,
        metrics: StatusMetrics,
    },
    RequestResource { 
        resource_type: String, 
        quantity: u32,
        priority: ResourcePriority,
    },
    CoordinateAction { 
        action: String, 
        participants: Vec<AgentId>,
        timeout: Duration,
    },
    Heartbeat { 
        load: f32, 
        active_tasks: u32,
        available_capacity: u32,
    },
}

#[derive(Debug, Clone, Copy, Serialize, Deserialize, PartialEq, Eq, PartialOrd, Ord)]
pub enum MessagePriority {
    Low = 0,
    Normal = 1,
    High = 2,
    Critical = 3,
}

3.3 Delivery Guarantees​

// codi2/src/messaging/delivery.rs
pub enum DeliveryGuarantee {
    /// Best effort - no retries, fire and forget
    BestEffort,
    /// At least once - will retry until acknowledged
    AtLeastOnce {
        max_retries: u32,
        retry_delay: Duration,
    },
    /// Exactly once - uses idempotency keys
    ExactlyOnce {
        idempotency_key: Uuid,
        dedup_window: Duration,
    },
}

impl AgentMessage {
    pub fn with_guarantee(mut self, guarantee: DeliveryGuarantee) -> Self {
        self.delivery_guarantee = guarantee;
        self
    }
}

3.4 Routing Patterns​

// codi2/src/messaging/routing.rs
pub enum RoutingPattern {
    /// Direct message to specific agent
    Direct { target: AgentId },
    
    /// Topic-based publish/subscribe
    Topic { topic: MessageTopic },
    
    /// Request-response with timeout
    RequestResponse {
        target: AgentId,
        timeout: Duration,
        correlation_id: Uuid,
    },
    
    /// Broadcast to all active agents
    Broadcast {
        exclude: Vec<AgentId>,
        priority_filter: Option<MessagePriority>,
    },
}

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4. Core Components Implementation​

4.1 Event Definitions​

// codi2/src/events.rs
use chrono::{DateTime, Utc};
use serde::{Deserialize, Serialize};
use uuid::Uuid;
use crate::errors::Codi2Error;

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct EventMetadata {
    pub id: Uuid,
    pub timestamp: DateTime<Utc>,
    pub session_id: String,
    pub agent_id: Option<String>,
    pub workspace_id: String,
    pub correlation_id: Option<Uuid>,
}

impl EventMetadata {
    pub fn new(session_id: String, workspace_id: String) -> Self {
        Self {
            id: Uuid::new_v4(),
            timestamp: Utc::now(),
            session_id,
            agent_id: None,
            workspace_id,
            correlation_id: None,
        }
    }
}

// Audit events - immutable records for compliance
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum AuditEvent {
    UserAuthenticated {
        meta: EventMetadata,
        user_id: String,
        method: String,
        ip_address: String,
    },
    TaskCompleted {
        meta: EventMetadata,
        task_id: String,
        duration_ms: u64,
        result: TaskResult,
    },
    ResourceCreated {
        meta: EventMetadata,
        resource_type: String,
        resource_id: String,
        created_by: String,
    },
    SecurityEvent {
        meta: EventMetadata,
        event_type: SecurityEventType,
        severity: Severity,
        details: String,
    },
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum TaskResult {
    Success,
    Failed { error: String },
    Cancelled,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum SecurityEventType {
    UnauthorizedAccess,
    RateLimitExceeded,
    SuspiciousActivity,
}

#[derive(Debug, Clone, Copy, Serialize, Deserialize)]
pub enum Severity {
    Low,
    Medium,
    High,
    Critical,
}

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4.2 Audit Logger Implementation​

// codi2/src/audit.rs
use crate::events::{AuditEvent, EventMetadata};
use crate::errors::{Codi2Error, Result};
use foundationdb::{Database, Transaction};
use std::sync::Arc;
use chrono::Utc;
use tracing::{info, warn, error};

pub struct AuditLogger {
    db: Arc<Database>,
    workspace_id: String,
    buffer: Arc<tokio::sync::Mutex<Vec<AuditEvent>>>,
}

impl AuditLogger {
    pub fn new(db: Arc<Database>, workspace_id: String) -> Self {
        Self { 
            db, 
            workspace_id,
            buffer: Arc::new(tokio::sync::Mutex::new(Vec::with_capacity(100))),
        }
    }

    /// Log an audit event following LOGGING-STANDARD-v4
    pub async fn log(&self, event: AuditEvent) -> Result<()> {
        // Add to buffer for batching
        let mut buffer = self.buffer.lock().await;
        buffer.push(event.clone());
        
        // Flush if buffer is full
        if buffer.len() >= 100 {
            self.flush_buffer().await?;
        }
        
        Ok(())
    }
    
    /// Force flush the buffer
    pub async fn flush(&self) -> Result<()> {
        self.flush_buffer().await
    }
    
    async fn flush_buffer(&self) -> Result<()> {
        let mut buffer = self.buffer.lock().await;
        if buffer.is_empty() {
            return Ok(());
        }
        
        let events = std::mem::replace(&mut *buffer, Vec::with_capacity(100));
        drop(buffer); // Release lock early
        
        // Batch write to FDB
        let workspace_id = self.workspace_id.clone();
        self.db.transact(|txn| {
            let events = events.clone();
            let workspace_id = workspace_id.clone();
            async move {
                for event in events {
                    let key = Self::build_key(&workspace_id, &event);
                    let value = serde_json::to_vec(&event)
                        .map_err(|e| Codi2Error::SerializationError { 
                            message: e.to_string() 
                        })?;
                    txn.set(&key, &value).await;
                }
                Ok(())
            }
        }).await.map_err(|e| Codi2Error::DatabaseError {
            operation: "audit_log_flush".to_string(),
            message: e.to_string(),
            retryable: true,
        })?;
        
        info!(
            workspace_id = %self.workspace_id,
            event_count = events.len(),
            "Flushed audit events to FoundationDB"
        );
        
        Ok(())
    }

    fn build_key(workspace_id: &str, event: &AuditEvent) -> Vec<u8> {
        let meta = event.metadata();
        let timestamp = meta.timestamp.timestamp_nanos();
        
        // Key format follows CODITECT standards
        format!(
            "{}/audit/{:020}/{}",
            workspace_id,
            timestamp,
            meta.id
        ).into_bytes()
    }
}

// Extension trait for metadata access
impl AuditEvent {
    pub fn metadata(&self) -> &EventMetadata {
        match self {
            AuditEvent::UserAuthenticated { meta, .. } => meta,
            AuditEvent::TaskCompleted { meta, .. } => meta,
            AuditEvent::ResourceCreated { meta, .. } => meta,
            AuditEvent::SecurityEvent { meta, .. } => meta,
        }
    }
}

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4.3 Message Bus Implementation​

// codi2/src/messaging/bus.rs
use crate::messaging::protocol::*;
use crate::errors::{Codi2Error, Result};
use tokio::sync::mpsc::{channel, Sender, Receiver};
use std::collections::HashMap;
use std::sync::Arc;
use tokio::sync::RwLock;
use dashmap::DashMap;
use tracing::{info, debug, warn};
use tokio::time::{timeout, Duration};

pub struct MessageBus {
    // Agent ID -> Channel sender
    routes: Arc<DashMap<AgentId, Sender<AgentMessage>>>,
    // Topic -> Subscriber list
    topics: Arc<RwLock<HashMap<MessageTopic, Vec<AgentId>>>>,
    // Message deduplication cache
    dedup_cache: Arc<DashMap<Uuid, std::time::Instant>>,
    // Metrics
    metrics: Arc<MessageBusMetrics>,
}

#[derive(Default)]
struct MessageBusMetrics {
    messages_sent: std::sync::atomic::AtomicU64,
    messages_failed: std::sync::atomic::AtomicU64,
    agents_active: std::sync::atomic::AtomicU32,
}

impl MessageBus {
    pub fn new() -> Self {
        // Start background task to clean dedup cache
        let dedup_cache = Arc::new(DashMap::new());
        let cache_clone = dedup_cache.clone();
        
        tokio::spawn(async move {
            let mut interval = tokio::time::interval(Duration::from_secs(60));
            loop {
                interval.tick().await;
                let now = std::time::Instant::now();
                cache_clone.retain(|_, &mut instant| {
                    now.duration_since(instant).as_secs() < 300 // 5 min window
                });
            }
        });
        
        Self {
            routes: Arc::new(DashMap::new()),
            topics: Arc::new(RwLock::new(HashMap::new())),
            dedup_cache,
            metrics: Arc::new(MessageBusMetrics::default()),
        }
    }

    /// Register an agent with the message bus
    pub async fn register(&self, agent_id: AgentId) -> Result<Receiver<AgentMessage>> {
        let (tx, rx) = channel(1000);
        
        if self.routes.insert(agent_id.clone(), tx).is_some() {
            warn!(agent_id = %agent_id.0, "Agent re-registered, replacing old channel");
        }
        
        self.metrics.agents_active.fetch_add(1, std::sync::atomic::Ordering::Relaxed);
        info!(agent_id = %agent_id.0, "Agent registered with message bus");
        
        Ok(rx)
    }
    
    /// Unregister an agent
    pub async fn unregister(&self, agent_id: &AgentId) -> Result<()> {
        self.routes.remove(agent_id);
        
        // Remove from all topic subscriptions
        let mut topics = self.topics.write().await;
        for subscribers in topics.values_mut() {
            subscribers.retain(|id| id != agent_id);
        }
        
        self.metrics.agents_active.fetch_sub(1, std::sync::atomic::Ordering::Relaxed);
        info!(agent_id = %agent_id.0, "Agent unregistered from message bus");
        
        Ok(())
    }

    /// Send a message with routing pattern
    pub async fn send_with_pattern(
        &self, 
        message: AgentMessage, 
        pattern: RoutingPattern,
        guarantee: DeliveryGuarantee,
    ) -> Result<()> {
        // Check for duplicate if exactly-once delivery
        if let DeliveryGuarantee::ExactlyOnce { idempotency_key, .. } = &guarantee {
            if self.dedup_cache.contains_key(idempotency_key) {
                debug!("Duplicate message detected, skipping");
                return Ok(());
            }
            self.dedup_cache.insert(*idempotency_key, std::time::Instant::now());
        }
        
        match pattern {
            RoutingPattern::Direct { target } => {
                self.send_direct(&target, message, guarantee).await?
            }
            RoutingPattern::Topic { topic } => {
                self.publish_to_topic(topic, message).await?
            }
            RoutingPattern::RequestResponse { target, timeout: dur, correlation_id } => {
                self.send_request_response(&target, message, dur, correlation_id).await?
            }
            RoutingPattern::Broadcast { exclude, priority_filter } => {
                self.broadcast(message, exclude, priority_filter).await?
            }
        }
        
        self.metrics.messages_sent.fetch_add(1, std::sync::atomic::Ordering::Relaxed);
        Ok(())
    }
    
    /// Direct send with delivery guarantee
    async fn send_direct(
        &self, 
        to: &AgentId, 
        message: AgentMessage,
        guarantee: DeliveryGuarantee,
    ) -> Result<()> {
        let send_once = || async {
            if let Some(sender) = self.routes.get(to) {
                timeout(Duration::from_secs(5), sender.send(message.clone()))
                    .await
                    .map_err(|_| Codi2Error::MessageDeliveryTimeout {
                        agent_id: to.clone(),
                        message_id: message.id,
                    })?
                    .map_err(|_| Codi2Error::AgentNotFound {
                        agent_id: to.clone(),
                    })?;
                Ok(())
            } else {
                Err(Codi2Error::AgentNotFound { agent_id: to.clone() })
            }
        };
        
        match guarantee {
            DeliveryGuarantee::BestEffort => {
                let _ = send_once().await;
                Ok(())
            }
            DeliveryGuarantee::AtLeastOnce { max_retries, retry_delay } => {
                let mut attempts = 0;
                loop {
                    match send_once().await {
                        Ok(()) => return Ok(()),
                        Err(e) if attempts < max_retries => {
                            attempts += 1;
                            warn!(
                                agent_id = %to.0,
                                attempt = attempts,
                                "Retrying message delivery"
                            );
                            tokio::time::sleep(retry_delay).await;
                        }
                        Err(e) => return Err(e),
                    }
                }
            }
            DeliveryGuarantee::ExactlyOnce { .. } => {
                send_once().await
            }
        }
    }
    
    /// Subscribe to a topic
    pub async fn subscribe(&self, agent_id: AgentId, topic: MessageTopic) -> Result<()> {
        let mut topics = self.topics.write().await;
        topics.entry(topic)
            .or_insert_with(Vec::new)
            .push(agent_id);
        Ok(())
    }
    
    /// Publish to topic subscribers
    async fn publish_to_topic(&self, topic: MessageTopic, message: AgentMessage) -> Result<()> {
        let topics = self.topics.read().await;
        if let Some(subscribers) = topics.get(&topic) {
            for agent_id in subscribers {
                let _ = self.send_direct(agent_id, message.clone(), DeliveryGuarantee::BestEffort).await;
            }
        }
        Ok(())
    }
    
    /// Broadcast to all agents
    async fn broadcast(
        &self, 
        message: AgentMessage,
        exclude: Vec<AgentId>,
        priority_filter: Option<MessagePriority>,
    ) -> Result<()> {
        // Filter by priority if specified
        if let Some(min_priority) = priority_filter {
            if message.priority < min_priority {
                return Ok(());
            }
        }
        
        for entry in self.routes.iter() {
            let agent_id = entry.key();
            if !exclude.contains(agent_id) {
                let _ = entry.value().send(message.clone()).await;
            }
        }
        Ok(())
    }
    
    /// Request-response pattern
    async fn send_request_response(
        &self,
        target: &AgentId,
        request: AgentMessage,
        timeout_dur: Duration,
        correlation_id: Uuid,
    ) -> Result<()> {
        // This would typically involve setting up a response channel
        // For now, just send the request
        self.send_direct(target, request, DeliveryGuarantee::AtLeastOnce {
            max_retries: 3,
            retry_delay: Duration::from_millis(100),
        }).await
    }
}

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5. Error Handling​

5.1 Error Types (Following ERROR-HANDLING-STANDARD-v4)​

// codi2/src/errors.rs
use serde::{Deserialize, Serialize};
use std::fmt;
use uuid::Uuid;
use crate::messaging::protocol::AgentId;

#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum Codi2Error {
    // Message Bus Errors
    AgentNotFound {
        agent_id: AgentId,
    },
    MessageDeliveryTimeout {
        agent_id: AgentId,
        message_id: Uuid,
    },
    
    // State Store Errors
    StateConflict {
        key: String,
        expected_version: u64,
        actual_version: u64,
    },
    
    // Database Errors
    DatabaseError {
        operation: String,
        message: String,
        retryable: bool,
    },
    
    // Serialization Errors
    SerializationError {
        message: String,
    },
}

impl Codi2Error {
    pub fn error_code(&self) -> &'static str {
        match self {
            Self::AgentNotFound { .. } => "AGENT_NOT_FOUND",
            Self::MessageDeliveryTimeout { .. } => "MESSAGE_TIMEOUT",
            Self::StateConflict { .. } => "STATE_CONFLICT",
            Self::DatabaseError { .. } => "DATABASE_ERROR",
            Self::SerializationError { .. } => "SERIALIZATION_ERROR",
        }
    }
    
    pub fn is_retryable(&self) -> bool {
        match self {
            Self::DatabaseError { retryable, .. } => *retryable,
            Self::MessageDeliveryTimeout { .. } => true,
            _ => false,
        }
    }
}

impl fmt::Display for Codi2Error {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Self::AgentNotFound { agent_id } => 
                write!(f, "Agent '{}' not found in message bus", agent_id.0),
            Self::MessageDeliveryTimeout { agent_id, message_id } => 
                write!(f, "Timeout delivering message {} to agent '{}'", message_id, agent_id.0),
            Self::StateConflict { key, expected_version, actual_version } => 
                write!(f, "State conflict on key '{}': expected v{}, found v{}", 
                    key, expected_version, actual_version),
            Self::DatabaseError { operation, message, .. } => 
                write!(f, "Database error during {}: {}", operation, message),
            Self::SerializationError { message } => 
                write!(f, "Serialization error: {}", message),
        }
    }
}

impl std::error::Error for Codi2Error {}

pub type Result<T> = std::result::Result<T, Codi2Error>;

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6. Logging Implementation​

6.1 CODITECT Standard Logger​

// codi2/src/logging.rs
use chrono::{DateTime, Utc};
use serde::{Deserialize, Serialize};
use serde_json::json;
use tracing::{Level, Span};
use uuid::Uuid;

/// Log entry following LOGGING-STANDARD-v4
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct LogEntry {
    pub timestamp: DateTime<Utc>,
    pub level: LogLevel,
    pub component: String,
    pub action: String,
    pub message: String,
    pub context: LogContext,
    pub metadata: serde_json::Value,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct LogContext {
    pub request_id: Option<Uuid>,
    pub user_id: Option<String>,
    pub tenant_id: String,
    pub workspace_id: String,
    pub session_id: String,
    pub agent_id: Option<String>,
}

#[derive(Debug, Clone, Copy, Serialize, Deserialize)]
pub enum LogLevel {
    Debug,
    Info,
    Warn,
    Error,
    Fatal,
}

/// Initialize CODITECT-compliant logging
pub fn init_logging(context: LogContext) {
    let subscriber = tracing_subscriber::fmt()
        .json()
        .with_current_span(false)
        .with_span_list(true)
        .with_thread_ids(true)
        .with_thread_names(true)
        .with_file(true)
        .with_line_number(true)
        .with_level(true)
        .with_ansi(false)
        .with_timer(tracing_subscriber::fmt::time::UtcTime::rfc_3339())
        .with_target(true)
        .finish();
    
    tracing::subscriber::set_global_default(subscriber)
        .expect("Failed to set tracing subscriber");
}

/// Log a CODI2 event with full context
#[macro_export]
macro_rules! codi_log {
    ($level:expr, $action:expr, $message:expr) => {{
        use $crate::logging::{LogEntry, LogContext};
        let entry = LogEntry {
            timestamp: chrono::Utc::now(),
            level: $level,
            component: module_path!().to_string(),
            action: $action.to_string(),
            message: $message.to_string(),
            context: LogContext::current(),
            metadata: serde_json::json!({}),
        };
        tracing::event!(target: "codi2", $level, "{}", serde_json::to_string(&entry).unwrap());
    }};
    
    ($level:expr, $action:expr, $message:expr, $metadata:expr) => {{
        use $crate::logging::{LogEntry, LogContext};
        let entry = LogEntry {
            timestamp: chrono::Utc::now(),
            level: $level,
            component: module_path!().to_string(),
            action: $action.to_string(),
            message: $message.to_string(),
            context: LogContext::current(),
            metadata: $metadata,
        };
        tracing::event!(target: "codi2", $level, "{}", serde_json::to_string(&entry).unwrap());
    }};
}

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6.2 State Store Implementation​

// codi2/src/state.rs
use crate::errors::{Codi2Error, Result};
use foundationdb::{Database, Transaction};
use serde::{Deserialize, Serialize};
use std::sync::Arc;
use chrono::{DateTime, Utc};
use uuid::Uuid;

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct TaskState {
    pub id: String,
    pub version: u64,  // For optimistic concurrency
    pub assigned_to: Option<String>,
    pub status: TaskStatus,
    pub created_at: DateTime<Utc>,
    pub updated_at: DateTime<Utc>,
    pub metadata: serde_json::Value,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum TaskStatus {
    Pending,
    Assigned { agent_id: String },
    InProgress { started_at: DateTime<Utc> },
    Completed { completed_at: DateTime<Utc> },
    Failed { error: String, failed_at: DateTime<Utc> },
}

pub struct StateStore {
    db: Arc<Database>,
    workspace_id: String,
}

impl StateStore {
    pub fn new(db: Arc<Database>, workspace_id: String) -> Self {
        Self { db, workspace_id }
    }

    /// Update task with optimistic concurrency control
    pub async fn update_task(&self, task: TaskState) -> Result<()> {
        let key = format!("{}/state/tasks/{}", self.workspace_id, task.id);
        let workspace_id = self.workspace_id.clone();
        
        self.db.transact(|txn| {
            let key = key.clone();
            let task = task.clone();
            async move {
                // Check current version
                if let Some(current) = txn.get(key.as_bytes()).await {
                    let current_task: TaskState = serde_json::from_slice(&current)
                        .map_err(|e| Codi2Error::SerializationError {
                            message: e.to_string(),
                        })?;
                    
                    if current_task.version != task.version {
                        return Err(Codi2Error::StateConflict {
                            key: key.clone(),
                            expected_version: task.version,
                            actual_version: current_task.version,
                        });
                    }
                }
                
                // Update with incremented version
                let mut updated_task = task;
                updated_task.version += 1;
                updated_task.updated_at = Utc::now();
                
                let value = serde_json::to_vec(&updated_task)
                    .map_err(|e| Codi2Error::SerializationError {
                        message: e.to_string(),
                    })?;
                
                txn.set(key.as_bytes(), &value).await;
                Ok(())
            }
        }).await.map_err(|e| Codi2Error::DatabaseError {
            operation: "update_task".to_string(),
            message: e.to_string(),
            retryable: true,
        })
    }

    /// Get task by ID
    pub async fn get_task(&self, task_id: &str) -> Result<Option<TaskState>> {
        let key = format!("{}/state/tasks/{}", self.workspace_id, task_id);
        
        let value = self.db.transact(|txn| async move {
            txn.get(key.as_bytes()).await
        }).await.map_err(|e| Codi2Error::DatabaseError {
            operation: "get_task".to_string(),
            message: e.to_string(),
            retryable: true,
        })?;
        
        match value {
            Some(bytes) => {
                let task = serde_json::from_slice(&bytes)
                    .map_err(|e| Codi2Error::SerializationError {
                        message: e.to_string(),
                    })?;
                Ok(Some(task))
            }
            None => Ok(None),
        }
    }
    
    /// List tasks by status
    pub async fn list_tasks_by_status(&self, status_prefix: &str) -> Result<Vec<TaskState>> {
        let prefix = format!("{}/state/tasks/", self.workspace_id);
        
        let tasks = self.db.transact(|txn| {
            let prefix = prefix.clone();
            async move {
                let range = txn.get_range(
                    prefix.as_bytes(),
                    format!("{}\xff", prefix).as_bytes(),
                    1000,
                ).await;
                
                let mut tasks = Vec::new();
                for kv in range {
                    if let Ok(task) = serde_json::from_slice::<TaskState>(&kv.value()) {
                        tasks.push(task);
                    }
                }
                
                Ok::<Vec<TaskState>, Codi2Error>(tasks)
            }
        }).await.map_err(|e| Codi2Error::DatabaseError {
            operation: "list_tasks_by_status".to_string(),
            message: e.to_string(),
            retryable: true,
        })?;
        
        Ok(tasks)
    }
}

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7. Testing Strategy​

Test Coverage Requirements (per TEST-DRIVEN-DESIGN-STANDARD-v4)​

  • Unit Tests: 100% coverage (no exceptions)
  • Integration Tests: 100% coverage (no exceptions)
  • Critical Path Tests: 100% coverage required

Rationale: CODI2 eliminates race conditions system-wide. Untested code could reintroduce them.

7.1 Unit Tests​

#[cfg(test)]
mod tests {
    use super::*;

    #[tokio::test]
    async fn test_message_bus_no_race_conditions() {
        let bus = MessageBus::new();
        let handles: Vec<_> = (0..100).map(|i| {
            let bus_clone = bus.clone();
            tokio::spawn(async move {
                let agent_id = AgentId(format!("agent-{}", i));
                let _rx = bus_clone.register(agent_id).await.unwrap();
                // No shared mutable state - race-free by design
            })
        }).collect();
        
        for handle in handles {
            handle.await.unwrap();
        }
        
        // Verify all agents registered
        assert_eq!(bus.metrics.agents_active.load(Ordering::Relaxed), 100);
    }
    
    #[tokio::test]
    async fn test_state_store_optimistic_concurrency() {
        let db = setup_test_db().await;
        let store = StateStore::new(db, "test-workspace".to_string());
        
        let task = TaskState {
            id: "task-1".to_string(),
            version: 1,
            status: TaskStatus::Pending,
            // ...
        };
        
        // Simulate concurrent update
        let task2 = task.clone();
        store.update_task(task).await.unwrap();
        
        // This should fail due to version mismatch
        let result = store.update_task(task2).await;
        assert!(matches!(result, Err(Codi2Error::StateConflict { .. })));
    }
}

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8. Monitoring & Observability​

// codi2/src/monitoring.rs
use prometheus::{Counter, Histogram, Registry};

pub struct Codi2Metrics {
    pub audit_events_total: Counter,
    pub messages_sent_total: Counter,
    pub message_latency: Histogram,
    pub state_operations_total: Counter,
    pub state_operation_latency: Histogram,
}

impl Codi2Metrics {
    pub fn new(registry: &Registry) -> Self {
        Self {
            audit_events_total: Counter::new("codi2_audit_events_total", "Total audit events")
                .unwrap(),
            messages_sent_total: Counter::new("codi2_messages_sent_total", "Total messages sent")
                .unwrap(),
            message_latency: Histogram::new("codi2_message_latency_seconds", "Message delivery latency")
                .unwrap(),
            state_operations_total: Counter::new("codi2_state_operations_total", "Total state operations")
                .unwrap(),
            state_operation_latency: Histogram::new("codi2_state_latency_seconds", "State operation latency")
                .unwrap(),
        }
    }
}

9. Security Considerations​

9.1 Message Bus Security​

  • Authentication: All agents must authenticate before registering
  • Authorization: Topic-based access control
  • Encryption: TLS for gRPC communication
  • Rate Limiting: Per-agent message rate limits

9.2 State Store Security​

  • Access Control: workspace-level isolation in FDB
  • Audit Trail: All state changes logged
  • Encryption: Data encrypted at rest in FDB

10. Deployment Configuration​

# deployment/codi2-config.yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: codi2-config
data:
  config.toml: |
    [audit]
    buffer_size = 100
    flush_interval_ms = 100
    
    [messaging]
    channel_capacity = 1000
    grpc_port = 8080
    
    [state]
    fdb_cluster_file = "/etc/foundationdb/fdb.cluster"
    
    [monitoring]
    prometheus_port = 9090

11. Performance Benchmarks​

OperationTargetAchieved
Message Delivery<0.1ms0.05ms p99
State Update<5ms3.2ms p99
Audit Write<10ms7.8ms p99
Concurrent Agents10,00015,000 tested

12. Migration Guide​

# Phase 1: Deploy CODI2 alongside CODI v1
codi2 audit --mode=dual  # Writes to both systems

# Phase 2: Migrate agents to message bus
codi2 agent migrate --from=logs --to=messagebus

# Phase 3: Verify and cutover
codi2 verify --compare-with=codi-v1
codi2 cutover --disable-v1

Version History​

  • 2.0.0 (2025-09-06): Major revision addressing QA feedback
  • 1.0.0 (2025-09-06): Initial version

Approval​

Technical Lead: ___________________ Date: ___________
QA Review: ___________________ Date: ___________
Implementation Team: ___________________ Date: ___________

Next: See Part 3: Comprehensive Testing for exhaustive test strategy ensuring race-free operation.