python-dynamodb-lock

import boto3 from python_dynamodb_lock import DynamoDBLockClient import os import time # Configure AWS credentials and region (e.g., via environment variables or ~/.aws/credentials) # For local testing, you might use 'local' endpoint_url dynamodb_resource = boto3.resource( 'dynamodb', region_name=os.environ.get('AWS_REGION', 'us-east-1'), endpoint_url=os.environ.get('DYNAMODB_ENDPOINT_URL', None) ) table_name = os.environ.get('DYNAMODB_LOCK_TABLE_NAME', 'MyDistributedLockTable') # It's recommended to create the table beforehand with a 'lock_key' primary key and TTL enabled # For demonstration, we'll try to create it if it doesn't exist try: table = dynamodb_resource.Table(table_name) table.load() except dynamodb_resource.meta.client.exceptions.ResourceNotFoundException: print(f"Creating DynamoDB table: {table_name}") dynamodb_resource.create_table( TableName=table_name, KeySchema=[{'AttributeName': 'lock_key', 'KeyType': 'HASH'}], AttributeDefinitions=[{'AttributeName': 'lock_key', 'AttributeType': 'S'}], BillingMode='PAY_PER_REQUEST' ) # Wait for the table to be active dynamodb_resource.meta.client.get_waiter('table_exists').wait(TableName=table_name) print(f"Table {table_name} created.") # Instantiate the lock client # The 'owner_name' helps identify who holds the lock (e.g., hostname + process ID) lock_client = DynamoDBLockClient( dynamodb_resource, table_name=table_name, owner_name=f"{os.uname()[1]}-{os.getpid()}" ) lock_key = "my-critical-resource" try: print(f"Attempting to acquire lock for {lock_key}...") # Use the 'lock' method as a context manager for a specific lock with lock_client.lock(lock_key): print(f"Successfully acquired lock for {lock_key}. Performing critical section...") # Simulate work time.sleep(5) print(f"Finished critical section for {lock_key}.") print(f"Lock for {lock_key} automatically released.") except Exception as e: print(f"Failed to acquire or process with lock for {lock_key}: {e}") finally: # It's important to close the client to stop background heartbeat threads print("Closing lock client...") lock_client.close() print("Lock client closed.")