Pullonly

Pullonly is a term used to describe a mode or architecture in which data, configurations, or updates are retrieved by consumers from a source rather than being pushed to them by the producer. In a pull-only setup, the responsibility for obtaining the latest state lies with the client or replica, which periodically or event-drivenly polls the source for changes and applies them locally.

Common contexts for pull-only patterns include data replication, software update mechanisms, and message processing. In data replication, a pull-based replica fetches logs or data from a primary. In software delivery, clients poll a repository or update server to acquire new builds. In messaging systems, consumers pull messages from queues or topics rather than having the broker push deliveries. In GitOps and configuration management, pull-based agents reconcile desired state by pulling from a central store such as a Git repository.

Advantages of pull-only systems include reduced load on producers, easier horizontal scaling, and improved suitability for disconnected or intermittently connected environments. They can simplify access control and auditing because data is served in a controlled, centralized manner. Limitations include higher update latency, the need for effective polling and backoff strategies, potential inefficiencies from repeated data transfers, and reliance on client-side correctness and security.

Implementation considerations involve secure authentication and encryption, idempotent operations, and robust failure handling. Rate limiting, backoff, and error handling are important to prevent thundering herd effects. In practice, pull-only patterns are common across distributed systems and streaming platforms (such as Kafka consumers) and are frequently contrasted with push-based approaches where producers actively disseminate updates.