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Ensures a singleton AuditTrail node exists in a Neo4j database, creating it if necessary, and returns its unique identifier.

Purpose

This function implements an idempotent operation to guarantee the existence of exactly one AuditTrail node in a Neo4j graph database. It first checks if an AuditTrail node already exists by querying for it. If found, it returns the existing node's UID. If not found, it creates a new AuditTrail node with a generated UUID and creation timestamp, then returns the new UID. This is typically used in audit logging systems where a central audit trail node serves as an anchor point for tracking changes, events, or operations in the database.

Source Code

def ensure_audit_trail_exists(driver: Driver) -> str:
    """
    Ensure that audit trail node exists in the database.
    
    Args:
        driver: Neo4j driver instance
        
    Returns:
        UID of the audit trail node
    """
    try:
        with driver.session() as session:
            # Check if audit trail exists
            result = session.run(
                """
                MATCH (t:AuditTrail)
                RETURN t.UID as uid
                LIMIT 1
                """
            )
            record = result.single()
            
            if record:
                return record["uid"]
            
            # Create audit trail
            audit_trail_uid = str(uuid.uuid4())
            
            session.run(
                """
                CREATE (t:AuditTrail {
                    UID: $uid,
                    createdDate: datetime()
                })
                """,
                {"uid": audit_trail_uid}
            )
            
            return audit_trail_uid
    except Exception as e:
        logger.error(f"Error ensuring audit trail exists: {e}")
        return None

Parameters

Parameter Details

driver: A Neo4j Driver instance that provides connection to the Neo4j database. This should be an active, authenticated driver object created using neo4j.GraphDatabase.driver(). The driver manages connection pooling and session creation for database operations.

Return Value

Type: str

Returns a string containing the UID (Unique Identifier) of the AuditTrail node, either from an existing node or newly created. The UID is a UUID v4 string format (e.g., '550e8400-e29b-41d4-a716-446655440000'). Returns None if an exception occurs during database operations, with the error logged via the logger.

Dependencies

• neo4j
• uuid
• logging

Required Imports

from neo4j import Driver
import uuid
import logging

Usage Example

from neo4j import GraphDatabase
import logging
import uuid

# Setup logger
logger = logging.getLogger(__name__)
logging.basicConfig(level=logging.INFO)

# Create Neo4j driver
uri = "bolt://localhost:7687"
username = "neo4j"
password = "password"
driver = GraphDatabase.driver(uri, auth=(username, password))

try:
    # Ensure audit trail exists
    audit_trail_uid = ensure_audit_trail_exists(driver)
    
    if audit_trail_uid:
        print(f"Audit trail UID: {audit_trail_uid}")
        # Use the UID for subsequent audit operations
    else:
        print("Failed to ensure audit trail exists")
finally:
    driver.close()

Best Practices

• Always close the Neo4j driver connection when done using it to prevent resource leaks
• Ensure the logger is properly configured before calling this function to capture error messages
• Check if the returned value is None before using it, as this indicates a failure condition
• This function is idempotent and safe to call multiple times - it will not create duplicate AuditTrail nodes
• Consider wrapping calls to this function in try-except blocks for additional error handling at the application level
• The function uses LIMIT 1 in the query, assuming only one AuditTrail node should exist; if multiple exist, only the first found will be returned
• The createdDate property uses Neo4j's datetime() function which stores timezone-aware timestamps

Tags

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