Distributed Consensus Schema Weakness

Version Compatibility Matrix:

CREATE TABLE version_compatibility (
    id SERIAL PRIMARY KEY,
    version_from VARCHAR(50),
    version_to VARCHAR(50),
    compatibility_level VARCHAR(20) CHECK (compatibility_level IN ('FULL', 'PARTIAL', 'NONE')),
    breaking_changes TEXT[],
    migration_required BOOLEAN,
    UNIQUE(version_from, version_to)
);

CREATE TABLE protocol_changes (
    id SERIAL PRIMARY KEY,
    version VARCHAR(50),
    change_type VARCHAR(50) CHECK (change_type IN ('CONSENSUS', 'SCHEMA', 'API', 'FEATURE')),
    description TEXT,
    is_breaking BOOLEAN,
    activation_block BIGINT,
    required_adoption_percent INTEGER
);

-- Check if safe to upgrade
CREATE OR REPLACE FUNCTION is_safe_to_upgrade(
    p_current_version VARCHAR,
    p_target_version VARCHAR,
    p_current_network_percent DECIMAL
) RETURNS BOOLEAN AS $
DECLARE
    v_compatibility version_compatibility;
    v_required_adoption INTEGER;
BEGIN
    SELECT * INTO v_compatibility
    FROM version_compatibility
    WHERE version_from = p_current_version
    AND version_to = p_target_version;
    
    IF v_compatibility.compatibility_level = 'NONE' THEN
        -- Check if enough network has upgraded
        SELECT required_adoption_percent INTO v_required_adoption
        FROM protocol_changes
        WHERE version = p_target_version
        AND is_breaking = true;
        
        RETURN p_current_network_percent >= COALESCE(v_required_adoption, 95);
    END IF;
    
    RETURN true;
END;
$ LANGUAGE plpgsql;

Consensus Monitoring:

CREATE TABLE consensus_state_tracking (
    id BIGSERIAL PRIMARY KEY,
    timestamp TIMESTAMP WITH TIME ZONE DEFAULT NOW(),
    block_height BIGINT,
    block_hash VARCHAR(64),
    node_id VARCHAR(255),
    node_version VARCHAR(50)
);

-- Detect consensus splits
CREATE OR REPLACE FUNCTION detect_consensus_split(p_block_height BIGINT)
RETURNS TABLE(
    block_hash VARCHAR,
    node_count INTEGER,
    versions TEXT[]
) AS $
BEGIN
    RETURN QUERY
    WITH latest_blocks AS (
        SELECT DISTINCT ON (node_id)
            block_hash,
            node_id,
            node_version
        FROM consensus_state_tracking
        WHERE block_height = p_block_height
        ORDER BY node_id, timestamp DESC
    )
    SELECT 
        lb.block_hash,
        COUNT(*)::INTEGER as node_count,
        array_agg(DISTINCT lb.node_version ORDER BY lb.node_version) as versions
    FROM latest_blocks lb
    GROUP BY lb.block_hash
    HAVING COUNT(DISTINCT lb.block_hash) > 1;  -- Multiple hashes = split!
END;
$ LANGUAGE plpgsql;

Forced Update Mechanisms:

CREATE TABLE mandatory_updates (
    id SERIAL PRIMARY KEY,
    min_version_required VARCHAR(50),
    enforcement_date DATE,
    enforcement_type VARCHAR(50) CHECK (enforcement_type IN ('SOFT_FORK', 'HARD_FORK', 'EMERGENCY')),
    description TEXT,
    rollback_version VARCHAR(50)
);

-- Automated update enforcement
CREATE OR REPLACE FUNCTION enforce_version_requirements()
RETURNS void AS $
DECLARE
    v_update mandatory_updates;
    v_non_compliant_nodes INTEGER;
BEGIN
    FOR v_update IN 
        SELECT * FROM mandatory_updates
        WHERE enforcement_date <= CURRENT_DATE
        AND enforcement_type = 'EMERGENCY'
    LOOP
        -- Count non-compliant nodes
        SELECT COUNT(*) INTO v_non_compliant_nodes
        FROM node_version_tracking
        WHERE is_active = true
        AND version < v_update.min_version_required;
        
        IF v_non_compliant_nodes > 0 THEN
            -- Force disconnect non-compliant nodes
            UPDATE node_connections
            SET force_disconnect = true,
                disconnect_reason = 'Version ' || version || ' below required ' || v_update.min_version_required
            WHERE node_id IN (
                SELECT node_id FROM node_version_tracking
                WHERE version < v_update.min_version_required
            );
        END IF;
    END LOOP;
END;
$ LANGUAGE plpgsql;

Schema Evolution Tracking:

CREATE TABLE distributed_schema_versions (
    id SERIAL PRIMARY KEY,
    schema_version VARCHAR(50),
    schema_hash VARCHAR(64),
    migration_script TEXT,
    compatible_with_versions VARCHAR(50)[],
    deployment_status VARCHAR(50),
    nodes_updated INTEGER,
    total_nodes INTEGER
);

-- Gradual rollout tracking
CREATE TABLE schema_rollout_progress (
    id SERIAL PRIMARY KEY,
    schema_version VARCHAR(50),
    node_group VARCHAR(50),
    rollout_percent INTEGER,
    started_at TIMESTAMP WITH TIME ZONE,
    completed_at TIMESTAMP WITH TIME ZONE,
    rollback_triggered BOOLEAN DEFAULT false
);

Additional Best Practices:

• Implement feature flags for gradual rollout
• Use canary deployments for consensus changes
• Maintain version parity monitoring dashboards
• Create automated rollback mechanisms
• Regular "split-brain" simulation exercises