SCADA Critical Alarm Dispatcher and Webhook Engine Specification

Role: Lead Industrial Reliability & Backend Engineer specializing in safety-critical SCADA systems, real-time message routing, and fault-tolerant dispatch architectures.

Context

• Alarm Ingress Rate: Polling and receiving raw alarm states at {{scada_polling_interval_ms}}.
• Priority Taxonomy: Alarm severity categorized across {{alarm_priority_tiers}}.
• Network Boundary: Isolated industrial network topology adhering to {{plant_network_segmentation}}.
• Delivery Retries: Webhook backoff configured using {{webhook_retry_backoff_model}}.
• Poison & Failure Handling: Unroutable alarm state dispatched to {{dead_letter_target}}.

Task

Draft an exhaustive engineering specification for a mission-critical SCADA alarm dispatch engine that deduplicates raw alarm storms, enforces strict priority queuing, and reliably dispatches webhook notifications to downstream safety and paging systems without dropping safety-critical events.

Method

1. Define the ingress parser that validates incoming SCADA alarm frames, timestamp integrity, and source station identifiers.
2. Design the sliding-window debouncing and alarm-storm suppression algorithm to prevent notification flooding.
3. Architect the multi-tiered priority queue infrastructure that ensures Tier-1 emergency alarms bypass all operational queues.
4. Specify the worker pool execution model for webhook dispatches, including connection pooling, DNS caching, and timeout policies.
5. Detail the circuit-breaker and dead-letter queue forwarding logic when downstream endpoints experience outages.
6. Formulate mutual authentication, HMAC signature generation, and webhook security headers for outgoing requests.
7. Define health checking, hot-standby failover mechanisms, and memory-safe backpressure throttling.

Constraints

• MUST guarantee that safety-critical alarms are dispatched within 250 milliseconds of edge receipt.
• MUST NOT discard unacknowledged alarms during failover across redundant instances.
• Outbound webhook payloads must be signed using SHA-256 HMAC tokens.
• Alarm storm suppression must dynamically throttle noisy sensors without dropping state change events.
• Memory usage during sustained alarm floods must not exceed allocated process boundaries.

Output format

1. Ingress & Storm Suppression Logic: Algorithm details, sliding-window pseudo-logic, and threshold configurations.
2. Priority Queue & Worker Pool Architecture: Queue design, concurrency parameters, and latency bounds by tier.
3. Webhook Delivery Specification: Payload schema, HMAC signature headers, HTTP status handling, and retry timeline.
4. Network Isolation & Security Spec: Gateway traversal, mTLS configuration, and egress firewall rules for {{plant_network_segmentation}}.
5. Failover & Dead-Letter Handling: Active-passive failover state machine, replay runbook, and {{dead_letter_target}} alerting.

Self-review

• Confirm that the priority queuing mechanism completely prevents starvation of highest {{alarm_priority_tiers}}.
• Verify that retry backoff curves precisely match {{webhook_retry_backoff_model}} specifications.
• Ensure that all network paths respect the physical zoning defined in {{plant_network_segmentation}}.