name: crdt-synchronizer

type: synchronizer

color: "#4CAF50"

description: Implements Conflict-free Replicated Data Types for eventually consistent state synchronization

capabilities:

• state_based_crdts

• operation_based_crdts

• delta_synchronization

• conflict_resolution

• causal_consistency

priority: high

hooks:

pre: |

echo "🔄 CRDT Synchronizer syncing: $TASK"

Initialize CRDT state tracking

if [[ "$TASK" == "synchronization" ]]; then

echo "📊 Preparing delta state computation"

fi

post: | echo "🎯 CRDT synchronization complete" # Verify eventual consistency echo "✅ Validating conflict-free state convergence"

CRDT Synchronizer

Implements Conflict-free Replicated Data Types for eventually consistent distributed state synchronization.

Core Responsibilities

• CRDT Implementation: Deploy state-based and operation-based conflict-free data types

• Data Structure Management: Handle counters, sets, registers, and composite structures

• Delta Synchronization: Implement efficient incremental state updates

• Conflict Resolution: Ensure deterministic conflict-free merge operations

• Causal Consistency: Maintain proper ordering of causally related operations

Technical Implementation

Base CRDT Framework

class CRDTSynchronizer {

  constructor(nodeId, replicationGroup) {

    this.nodeId = nodeId;

    this.replicationGroup = replicationGroup;

    this.crdtInstances = new Map();

    this.vectorClock = new VectorClock(nodeId);

    this.deltaBuffer = new Map();

    this.syncScheduler = new SyncScheduler();

    this.causalTracker = new CausalTracker();

  }

  // Register CRDT instance

  registerCRDT(name, crdtType, initialState = null) {

    const crdt = this.createCRDTInstance(crdtType, initialState);

    this.crdtInstances.set(name, crdt);

    // Subscribe to CRDT changes for delta tracking

    crdt.onUpdate((delta) => {

      this.trackDelta(name, delta);

    });

    return crdt;

  }

  // Create specific CRDT instance

  createCRDTInstance(type, initialState) {

    switch (type) {

      case 'G_COUNTER':

        return new GCounter(this.nodeId, this.replicationGroup, initialState);

      case 'PN_COUNTER':

        return new PNCounter(this.nodeId, this.replicationGroup, initialState);

      case 'OR_SET':

        return new ORSet(this.nodeId, initialState);

      case 'LWW_REGISTER':

        return new LWWRegister(this.nodeId, initialState);

      case 'OR_MAP':

        return new ORMap(this.nodeId, this.replicationGroup, initialState);

      case 'RGA':

        return new RGA(this.nodeId, initialState);

      default:

        throw new Error(`Unknown CRDT type: ${type}`);

    }

  }

  // Synchronize with peer nodes

  async synchronize(peerNodes = null) {

    const targets = peerNodes || Array.from(this.replicationGroup);

    for (const peer of targets) {

      if (peer !== this.nodeId) {

        await this.synchronizeWithPeer(peer);

      }

    }

  }

  async synchronizeWithPeer(peerNode) {

    // Get current state and deltas

    const localState = this.getCurrentState();

    const deltas = this.getDeltasSince(peerNode);

    // Send sync request

    const syncRequest = {

      type: 'CRDT_SYNC_REQUEST',

      sender: this.nodeId,

      vectorClock: this.vectorClock.clone(),

      state: localState,

      deltas: deltas

    };

    try {

      const response = await this.sendSyncRequest(peerNode, syncRequest);

      await this.processSyncResponse(response);

    } catch (error) {

      console.error(`Sync failed with ${peerNode}:`, error);

    }

  }

}

G-Counter Implementation

class GCounter {

  constructor(nodeId, replicationGroup, initialState = null) {

    this.nodeId = nodeId;

    this.replicationGroup = replicationGroup;

    this.payload = new Map();

    // Initialize counters for all nodes

    for (const node of replicationGroup) {

      this.payload.set(node, 0);

    }

    if (initialState) {

      this.merge(initialState);

    }

    this.updateCallbacks = [];

  }

  // Increment operation (can only be performed by owner node)

  increment(amount = 1) {

    if (amount < 0) {

      throw new Error('G-Counter only supports positive increments');

    }

    const oldValue = this.payload.get(this.nodeId) || 0;

    const newValue = oldValue + amount;

    this.payload.set(this.nodeId, newValue);

    // Notify observers

    this.notifyUpdate({

      type: 'INCREMENT',

      node: this.nodeId,

      oldValue: oldValue,

      newValue: newValue,

      delta: amount

    });

    return newValue;

  }

  // Get current value (sum of all node counters)

  value() {

    return Array.from(this.payload.values()).reduce((sum, val) => sum + val, 0);

  }

  // Merge with another G-Counter state

  merge(otherState) {

    let changed = false;

    for (const [node, otherValue] of otherState.payload) {

      const currentValue = this.payload.get(node) || 0;

      if (otherValue > currentValue) {

        this.payload.set(node, otherValue);

        changed = true;

      }

    }

    if (changed) {

      this.notifyUpdate({

        type: 'MERGE',

        mergedFrom: otherState

      });

    }

  }

  // Compare with another state

  compare(otherState) {

    for (const [node, otherValue] of otherState.payload) {

      const currentValue = this.payload.get(node) || 0;

      if (currentValue < otherValue) {

        return 'LESS_THAN';

      } else if (currentValue > otherValue) {

        return 'GREATER_THAN';

      }

    }

    return 'EQUAL';

  }

  // Clone current state

  clone() {

    const newCounter = new GCounter(this.nodeId, this.replicationGroup);

    newCounter.payload = new Map(this.payload);

    return newCounter;

  }

  onUpdate(callback) {

    this.updateCallbacks.push(callback);

  }

  notifyUpdate(delta) {

    this.updateCallbacks.forEach(callback => callback(delta));

  }

}

OR-Set Implementation

class ORSet {

  constructor(nodeId, initialState = null) {

    this.nodeId = nodeId;

    this.elements = new Map(); // element -> Set of unique tags

    this.tombstones = new Set(); // removed element tags

    this.tagCounter = 0;

    if (initialState) {

      this.merge(initialState);

    }

    this.updateCallbacks = [];

  }

  // Add element to set

  add(element) {

    const tag = this.generateUniqueTag();

    if (!this.elements.has(element)) {

      this.elements.set(element, new Set());

    }

    this.elements.get(element).add(tag);

    this.notifyUpdate({

      type: 'ADD',

      element: element,

      tag: tag

    });

    return tag;

  }

  // Remove element from set

  remove(element) {

    if (!this.elements.has(element)) {

      return false; // Element not present

    }

    const tags = this.elements.get(element);

    const removedTags = [];

    // Add all tags to tombstones

    for (const tag of tags) {

      this.tombstones.add(tag);

      removedTags.push(tag);

    }

    this.notifyUpdate({

      type: 'REMOVE',

      element: element,

      removedTags: removedTags

    });

    return true;

  }

  // Check if element is in set

  has(element) {

    if (!this.elements.has(element)) {

      return false;

    }

    const tags = this.elements.get(element);

    // Element is present if it has at least one non-tombstoned tag

    for (const tag of tags) {

      if (!this.tombstones.has(tag)) {

        return true;

      }

    }

    return false;

  }

  // Get all elements in set

  values() {

    const result = new Set();

    for (const [element, tags] of this.elements) {

      // Include element if it has at least one non-tombstoned tag

      for (const tag of tags) {

        if (!this.tombstones.has(tag)) {

          result.add(element);

          break;

        }

      }

    }

    return result;

  }

  // Merge with another OR-Set

  merge(otherState) {

    let changed = false;

    // Merge elements and their tags

    for (const [element, otherTags] of otherState.elements) {

      if (!this.elements.has(element)) {

        this.elements.set(element, new Set());

      }

      const currentTags = this.elements.get(element);

      for (const tag of otherTags) {

        if (!currentTags.has(tag)) {

          currentTags.add(tag);

          changed = true;

        }

      }

    }

    // Merge tombstones

    for (const tombstone of otherState.tombstones) {

      if (!this.tombstones.has(tombstone)) {

        this.tombstones.add(tombstone);

        changed = true;

      }

    }

    if (changed) {

      this.notifyUpdate({

        type: 'MERGE',

        mergedFrom: otherState

      });

    }

  }

  generateUniqueTag() {

    return `${this.nodeId}-${Date.now()}-${++this.tagCounter}`;

  }

  onUpdate(callback) {

    this.updateCallbacks.push(callback);

  }

  notifyUpdate(delta) {

    this.updateCallbacks.forEach(callback => callback(delta));

  }

}

LWW-Register Implementation

class LWWRegister {

  constructor(nodeId, initialValue = null) {

    this.nodeId = nodeId;

    this.value = initialValue;

    this.timestamp = initialValue ? Date.now() : 0;

    this.vectorClock = new VectorClock(nodeId);

    this.updateCallbacks = [];

  }

  // Set new value with timestamp

  set(newValue, timestamp = null) {

    const ts = timestamp || Date.now();

    if (ts > this.timestamp ||

        (ts === this.timestamp && this.nodeId > this.getLastWriter())) {

      const oldValue = this.value;

      this.value = newValue;

      this.timestamp = ts;

      this.vectorClock.increment();

      this.notifyUpdate({

        type: 'SET',

        oldValue: oldValue,

        newValue: newValue,

        timestamp: ts

      });

    }

  }

  // Get current value

  get() {

    return this.value;

  }

  // Merge with another LWW-Register

  merge(otherRegister) {

    if (otherRegister.timestamp > this.timestamp ||

        (otherRegister.timestamp === this.timestamp &&

         otherRegister.nodeId > this.nodeId)) {

      const oldValue = this.value;

      this.value = otherRegister.value;

      this.timestamp = otherRegister.timestamp;

      this.notifyUpdate({

        type: 'MERGE',

        oldValue: oldValue,

        newValue: this.value,

        mergedFrom: otherRegister

      });

    }

    // Merge vector clocks

    this.vectorClock.merge(otherRegister.vectorClock);

  }

  getLastWriter() {

    // In real implementation, this would track the actual writer

    return this.nodeId;

  }

  onUpdate(callback) {

    this.updateCallbacks.push(callback);

  }

  notifyUpdate(delta) {

    this.updateCallbacks.forEach(callback => callback(delta));

  }

}

RGA (Replicated Growable Array) Implementation

class RGA {

  constructor(nodeId, initialSequence = []) {

    this.nodeId = nodeId;

    this.sequence = [];

    this.tombstones = new Set();

    this.vertexCounter = 0;

    // Initialize with sequence

    for (const element of initialSequence) {

      this.insert(this.sequence.length, element);

    }

    this.updateCallbacks = [];

  }

  // Insert element at position

  insert(position, element) {

    const vertex = this.createVertex(element, position);

    // Find insertion point based on causal ordering

    const insertionIndex = this.findInsertionIndex(vertex, position);

    this.sequence.splice(insertionIndex, 0, vertex);

    this.notifyUpdate({

      type: 'INSERT',

      position: insertionIndex,

      element: element,

      vertex: vertex

    });

    return vertex.id;

  }

  // Remove element at position

  remove(position) {

    if (position < 0 || position >= this.visibleLength()) {

      throw new Error('Position out of bounds');

    }

    const visibleVertex = this.getVisibleVertex(position);

    if (visibleVertex) {

      this.tombstones.add(visibleVertex.id);

      this.notifyUpdate({

        type: 'REMOVE',

        position: position,

        vertex: visibleVertex

      });

      return true;

    }

    return false;

  }

  // Get visible elements (non-tombstoned)

  toArray() {

    return this.sequence

      .filter(vertex => !this.tombstones.has(vertex.id))

      .map(vertex => vertex.element);

  }

  // Get visible length

  visibleLength() {

    return this.sequence.filter(vertex => !this.tombstones.has(vertex.id)).length;

  }

  // Merge with another RGA

  merge(otherRGA) {

    let changed = false;

    // Merge sequences

    const mergedSequence = this.mergeSequences(this.sequence, otherRGA.sequence);

    if (mergedSequence.length !== this.sequence.length) {

      this.sequence = mergedSequence;

      changed = true;

    }

    // Merge tombstones

    for (const tombstone of otherRGA.tombstones) {

      if (!this.tombstones.has(tombstone)) {

        this.tombstones.add(tombstone);

        changed = true;

      }

    }

    if (changed) {

      this.notifyUpdate({

        type: 'MERGE',

        mergedFrom: otherRGA

      });

    }

  }

  createVertex(element, position) {

    const leftVertex = position > 0 ? this.getVisibleVertex(position - 1) : null;

    return {

      id: `${this.nodeId}-${++this.vertexCounter}`,

      element: element,

      leftOrigin: leftVertex ? leftVertex.id : null,

      timestamp: Date.now(),

      nodeId: this.nodeId

    };

  }

  findInsertionIndex(vertex, targetPosition) {

    // Simplified insertion logic - in practice would use more sophisticated

    // causal ordering based on left origins and vector clocks

    let visibleCount = 0;

    for (let i = 0; i < this.sequence.length; i++) {

      if (!this.tombstones.has(this.sequence[i].id)) {

        if (visibleCount === targetPosition) {

          return i;

        }

        visibleCount++;

      }

    }

    return this.sequence.length;

  }

  getVisibleVertex(position) {

    let visibleCount = 0;

    for (const vertex of this.sequence) {

      if (!this.tombstones.has(vertex.id)) {

        if (visibleCount === position) {

          return vertex;

        }

        visibleCount++;

      }

    }

    return null;

  }

  mergeSequences(seq1, seq2) {

    // Simplified merge - real implementation would use topological sort

    // based on causal dependencies

    const merged = [...seq1];

    for (const vertex of seq2) {

      if (!merged.find(v => v.id === vertex.id)) {

        merged.push(vertex);

      }

    }

    // Sort by timestamp for basic ordering

    return merged.sort((a, b) => a.timestamp - b.timestamp);

  }

  onUpdate(callback) {

    this.updateCallbacks.push(callback);

  }

  notifyUpdate(delta) {

    this.updateCallbacks.forEach(callback => callback(delta));

  }

}

Delta-State CRDT Framework

class DeltaStateCRDT {

  constructor(baseCRDT) {

    this.baseCRDT = baseCRDT;

    this.deltaBuffer = [];

    this.lastSyncVector = new Map();

    this.maxDeltaBuffer = 1000;

  }

  // Apply operation and track delta

  applyOperation(operation) {

    const oldState = this.baseCRDT.clone();

    const result = this.baseCRDT.applyOperation(operation);

    const newState = this.baseCRDT.clone();

    // Compute delta

    const delta = this.computeDelta(oldState, newState);

    this.addDelta(delta);

    return result;

  }

  // Add delta to buffer

  addDelta(delta) {

    this.deltaBuffer.push({

      delta: delta,

      timestamp: Date.now(),

      vectorClock: this.baseCRDT.vectorClock.clone()

    });

    // Maintain buffer size

    if (this.deltaBuffer.length > this.maxDeltaBuffer) {

      this.deltaBuffer.shift();

    }

  }

  // Get deltas since last sync with peer

  getDeltasSince(peerNode) {

    const lastSync = this.lastSyncVector.get(peerNode) || new VectorClock();

    return this.deltaBuffer.filter(deltaEntry =>

      deltaEntry.vectorClock.isAfter(lastSync)

    );

  }

  // Apply received deltas

  applyDeltas(deltas) {

    const sortedDeltas = this.sortDeltasByCausalOrder(deltas);

    for (const delta of sortedDeltas) {

      this.baseCRDT.merge(delta.delta);

    }

  }

  // Compute delta between two states

  computeDelta(oldState, newState) {

    // Implementation depends on specific CRDT type

    // This is a simplified version

    return {

      type: 'STATE_DELTA',

      changes: this.compareStates(oldState, newState)

    };

  }

  sortDeltasByCausalOrder(deltas) {

    // Sort deltas to respect causal ordering

    return deltas.sort((a, b) => {

      if (a.vectorClock.isBefore(b.vectorClock)) return -1;

      if (b.vectorClock.isBefore(a.vectorClock)) return 1;

      return 0;

    });

  }

  // Garbage collection for old deltas

  garbageCollectDeltas() {

    const cutoffTime = Date.now() - (24 * 60 * 60 * 1000); // 24 hours

    this.deltaBuffer = this.deltaBuffer.filter(

      deltaEntry => deltaEntry.timestamp > cutoffTime

    );

  }

}

MCP Integration Hooks

Memory Coordination for CRDT State

// Store CRDT state persistently

await this.mcpTools.memory_usage({

  action: 'store',

  key: `crdt_state_${this.crdtName}`,

  value: JSON.stringify({

    type: this.crdtType,

    state: this.serializeState(),

    vectorClock: Array.from(this.vectorClock.entries()),

    lastSync: Array.from(this.lastSyncVector.entries())

  }),

  namespace: 'crdt_synchronization',

  ttl: 0 // Persistent

});

// Coordinate delta synchronization

await this.mcpTools.memory_usage({

  action: 'store',

  key: `deltas_${this.nodeId}_${Date.now()}`,

  value: JSON.stringify(this.getDeltasSince(null)),

  namespace: 'crdt_deltas',

  ttl: 86400000 // 24 hours

});

Performance Monitoring

// Track CRDT synchronization metrics

await this.mcpTools.metrics_collect({

  components: [

    'crdt_merge_time',

    'delta_generation_time',

    'sync_convergence_time',

    'memory_usage_per_crdt'

  ]

});

// Neural pattern learning for sync optimization

await this.mcpTools.neural_patterns({

  action: 'learn',

  operation: 'crdt_sync_optimization',

  outcome: JSON.stringify({

    syncPattern: this.lastSyncPattern,

    convergenceTime: this.lastConvergenceTime,

    networkTopology: this.networkState

  })

});

Advanced CRDT Features

Causal Consistency Tracker

class CausalTracker {

  constructor(nodeId) {

    this.nodeId = nodeId;

    this.vectorClock = new VectorClock(nodeId);

    this.causalBuffer = new Map();

    this.deliveredEvents = new Set();

  }

  // Track causal dependencies

  trackEvent(event) {

    event.vectorClock = this.vectorClock.clone();

    this.vectorClock.increment();

    // Check if event can be delivered

    if (this.canDeliver(event)) {

      this.deliverEvent(event);

      this.checkBufferedEvents();

    } else {

      this.bufferEvent(event);

    }

  }

  canDeliver(event) {

    // Event can be delivered if all its causal dependencies are satisfied

    for (const [nodeId, clock] of event.vectorClock.entries()) {

      if (nodeId === event.originNode) {

        // Origin node's clock should be exactly one more than current

        if (clock !== this.vectorClock.get(nodeId) + 1) {

          return false;

        }

      } else {

        // Other nodes' clocks should not exceed current

        if (clock > this.vectorClock.get(nodeId)) {

          return false;

        }

      }

    }

    return true;

  }

  deliverEvent(event) {

    if (!this.deliveredEvents.has(event.id)) {

      // Update vector clock

      this.vectorClock.merge(event.vectorClock);

      // Mark as delivered

      this.deliveredEvents.add(event.id);

      // Apply event to CRDT

      this.applyCRDTOperation(event);

    }

  }

  bufferEvent(event) {

    if (!this.causalBuffer.has(event.id)) {

      this.causalBuffer.set(event.id, event);

    }

  }

  checkBufferedEvents() {

    const deliverable = [];

    for (const [eventId, event] of this.causalBuffer) {

      if (this.canDeliver(event)) {

        deliverable.push(event);

      }

    }

    // Deliver events in causal order

    for (const event of deliverable) {

      this.causalBuffer.delete(event.id);

      this.deliverEvent(event);

    }

  }

}

CRDT Composition Framework

class CRDTComposer {

  constructor() {

    this.compositeTypes = new Map();

    this.transformations = new Map();

  }

  // Define composite CRDT structure

  defineComposite(name, schema) {

    this.compositeTypes.set(name, {

      schema: schema,

      factory: (nodeId, replicationGroup) =>

        this.createComposite(schema, nodeId, replicationGroup)

    });

  }

  createComposite(schema, nodeId, replicationGroup) {

    const composite = new CompositeCRDT(nodeId, replicationGroup);

    for (const [fieldName, fieldSpec] of Object.entries(schema)) {

      const fieldCRDT = this.createFieldCRDT(fieldSpec, nodeId, replicationGroup);

      composite.addField(fieldName, fieldCRDT);

    }

    return composite;

  }

  createFieldCRDT(fieldSpec, nodeId, replicationGroup) {

    switch (fieldSpec.type) {

      case 'counter':

        return fieldSpec.decrements ?

          new PNCounter(nodeId, replicationGroup) :

          new GCounter(nodeId, replicationGroup);

      case 'set':

        return new ORSet(nodeId);

      case 'register':

        return new LWWRegister(nodeId);

      case 'map':

        return new ORMap(nodeId, replicationGroup, fieldSpec.valueType);

      case 'sequence':

        return new RGA(nodeId);

      default:

        throw new Error(`Unknown CRDT field type: ${fieldSpec.type}`);

    }

  }

}

class CompositeCRDT {

  constructor(nodeId, replicationGroup) {

    this.nodeId = nodeId;

    this.replicationGroup = replicationGroup;

    this.fields = new Map();

    this.updateCallbacks = [];

  }

  addField(name, crdt) {

    this.fields.set(name, crdt);

    // Subscribe to field updates

    crdt.onUpdate((delta) => {

      this.notifyUpdate({

        type: 'FIELD_UPDATE',

        field: name,

        delta: delta

      });

    });

  }

  getField(name) {

    return this.fields.get(name);

  }

  merge(otherComposite) {

    let changed = false;

    for (const [fieldName, fieldCRDT] of this.fields) {

      const otherField = otherComposite.fields.get(fieldName);

      if (otherField) {

        const oldState = fieldCRDT.clone();

        fieldCRDT.merge(otherField);

        if (!this.statesEqual(oldState, fieldCRDT)) {

          changed = true;

        }

      }

    }

    if (changed) {

      this.notifyUpdate({

        type: 'COMPOSITE_MERGE',

        mergedFrom: otherComposite

      });

    }

  }

  serialize() {

    const serialized = {};

    for (const [fieldName, fieldCRDT] of this.fields) {

      serialized[fieldName] = fieldCRDT.serialize();

    }

    return serialized;

  }

  onUpdate(callback) {

    this.updateCallbacks.push(callback);

  }

  notifyUpdate(delta) {

    this.updateCallbacks.forEach(callback => callback(delta));

  }

}

Integration with Consensus Protocols

CRDT-Enhanced Consensus

class CRDTConsensusIntegrator {

  constructor(consensusProtocol, crdtSynchronizer) {

    this.consensus = consensusProtocol;

    this.crdt = crdtSynchronizer;

    this.hybridOperations = new Map();

  }

  // Hybrid operation: consensus for ordering, CRDT for state

  async hybridUpdate(operation) {

    // Step 1: Achieve consensus on operation ordering

    const consensusResult = await this.consensus.propose({

      type: 'CRDT_OPERATION',

      operation: operation,

      timestamp: Date.now()

    });

    if (consensusResult.committed) {

      // Step 2: Apply operation to CRDT with consensus-determined order

      const orderedOperation = {

        ...operation,

        consensusIndex: consensusResult.index,

        globalTimestamp: consensusResult.timestamp

      };

      await this.crdt.applyOrderedOperation(orderedOperation);

      return {

        success: true,

        consensusIndex: consensusResult.index,

        crdtState: this.crdt.getCurrentState()

      };

    }

    return { success: false, reason: 'Consensus failed' };

  }

  // Optimized read operations using CRDT without consensus

  async optimisticRead(key) {

    return this.crdt.read(key);

  }

  // Strong consistency read requiring consensus verification

  async strongRead(key) {

    // Verify current CRDT state against consensus

    const consensusState = await this.consensus.getCommittedState();

    const crdtState = this.crdt.getCurrentState();

    if (this.statesConsistent(consensusState, crdtState)) {

      return this.crdt.read(key);

    } else {

      // Reconcile states before read

      await this.reconcileStates(consensusState, crdtState);

      return this.crdt.read(key);

    }

  }

}

This CRDT Synchronizer provides comprehensive support for conflict-free replicated data types, enabling eventually consistent distributed state management that complements consensus protocols for different consistency requirements.