PAUSE Command Overview
Purpose
The PAUSE command provides a mechanism to temporarily halt the delivery of events for specific event types without unsubscribing. This capability is essential for implementing maintenance windows, managing backpressure, and controlling event flow in high-load scenarios.
Key Capabilities
Temporary Subscription Suspension
Unlike UNSUB which completely removes a subscription, PAUSE maintains the subscription while temporarily stopping event delivery. This allows clients to resume delivery later without losing their place in the event stream.
Backpressure Management
When a service is experiencing high load or processing bottlenecks, it can use PAUSE to temporarily stop receiving new events until it catches up with its current workload, implementing an effective backpressure mechanism.
Selective Pausing
Clients can pause specific event types while continuing to receive others, allowing for fine-grained control over event processing priorities during peak loads or maintenance periods.
Maintenance Mode
During planned maintenance or deployments, services can pause event reception to prevent event processing during sensitive operations, then resume normal operation afterward.
Technical Implementation
The PAUSE command works by:
Authenticating the client using their client ID
Verifying that the client has an active subscription to the specified event type
Marking the subscription as paused in the client registry
Stopping event delivery for the specified event type while maintaining the client's position
Continuing to queue events for later delivery when the subscription is resumed
This implementation ensures that no events are lost during the pause period, and that clients can resume processing from exactly where they left off.
Integration Points
The PAUSE command integrates with:
Authentication System: Verifies client identity and permissions
Subscription Registry: Updates subscription status to paused
Event Delivery System: Stops delivering events for paused subscriptions
Position Tracking System: Maintains client position during pause period
Use Cases
Implementing maintenance windows for services
Managing backpressure during high-load periods
Prioritizing critical event types by pausing less important ones
Temporarily stopping event processing during sensitive operations
Implementing circuit breaker patterns for downstream service failures
Controlling event flow during deployment or configuration changes