LittleQ

Queue system with mathematical SLA guarantees using Little's Law. Bounded queue processing with Little's Law autoscaling and DLQ isolation. Queue flow control using Little's Law for predictable SLA compliance. Capacity-aware queue processor with Little's Law scaling.

1. SLA Assurance:  Little's Law to mathematically derive autoscaling thresholds, ensuring we scale before we breach user contracts, not just when CPU is high.
2. Resilience: Implemented Circuit Breaking patterns like exponential backoff with jitter and Dead Letter Queues to prevent cascading failures.
3. Concurrency: Used Go's primitives (channels/semaphores) for bounded parallelism to protect downstream resources.
4. Observability: Instrumented with Prometheus to drive K8s HPA decisions based on custom business metrics."

Little's Law

L = lambda * W

• L: Maximum queue depth
• lambda: Arrival rate (jobs/second)
• W: SLA wait time (seconds)

Quick Start

docker compose up -d redis
go run cmd/worker/main.go -queue=realtime
go run cmd/producer/main.go -queue=realtime -count=50

Real-Time Testing

Terminal 1 - Redis:

docker compose up redis

Terminal 2 - Monitor (live scaling decisions):

go run cmd/monitor/main.go -queue=realtime

Terminal 3 - Worker:

go run cmd/worker/main.go -queue=realtime

Terminal 4 - Producer:

go run cmd/producer/main.go -queue=realtime -count=50
go run cmd/producer/main.go -queue=realtime -count=100 -burst

Architecture

Component	Purpose
config	SLA definitions with Little's Law calculations
queue	Pluggable backends (Redis, Kafka, SQS)
worker	Semaphore-based concurrency control
retry	Exponential backoff with DLQ
autoscale	Queue-depth based scaling logic
metrics	Prometheus instrumentation

Configuration

SLAQueueConfig{
    Name:           "realtime",
    ArrivalRate:    20,
    SLASeconds:     1,
    JobsPerWorker:  5,
    ScaleThreshold: 0.7,
    MaxRetries:     3,
}

CLI Tools

Worker

go run cmd/worker/main.go -queue=realtime -concurrency=8 -redis=localhost:6379

Producer

go run cmd/producer/main.go -queue=realtime -count=100 -interval=50ms -burst

Monitor

go run cmd/monitor/main.go -queue=realtime -interval=2s

Metrics

Metric	Type	Description
sla_jobs_processed_total	Counter	Jobs processed by status
sla_queue_depth	Gauge	Current queue depth
sla_job_duration_seconds	Histogram	Processing duration
sla_breaches_total	Counter	SLA violations

Kubernetes

kubectl apply -f deployments/k8s/hpa.yaml

Queue Backends

Backend	Queue Depth Metric
Redis	LLEN
Kafka	Consumer lag
SQS	ApproximateNumberOfMessagesVisible

Tests

Test Files

Package	File	Coverage
config	internal/config/config_test.go	Little's Law calculations
autoscale	internal/autoscale/scaler_test.go	Scaling decisions
retry	internal/retry/retry_test.go	Backoff logic

Run All Tests

go test ./...

Verbose Output

go test ./... -v

Test Coverage

go test ./... -cover

Run Specific Package

go test ./internal/config -v
go test ./internal/autoscale -v
go test ./internal/retry -v

License

MIT