รูปแบบแรงดันย้อนกลับและการควบคุมภาระงาน

When work arrives faster than a system can process it, queues grow and latency explodes. Backpressure is the practice of signalling producers to slow down so the system stays stable instead of melting down.

An async gen_server:cast never blocks the caller, so its mailbox can grow without limit under load — the system runs out of memory before it ever rejects work.

Using gen_server:call instead of cast makes the caller wait until the server is ready, naturally throttling producers to the server speed.

Maintain an explicit counter of in-flight work and reject or block new requests once a limit is reached, rather than letting the mailbox grow.

Under extreme load, the best move can be to shed low-priority work fast — returning an error immediately — to protect the system for high-priority requests.

A token-bucket limiter grants a fixed number of permits per interval; requests beyond that wait or fail. This caps throughput predictably.

The mailbox length of a bottleneck process is a live pressure gauge. Monitor it and trigger shedding before it grows dangerous.

A pool of worker processes (e.g. via poolboy) bounds concurrency: requests queue for a free worker, giving natural backpressure with controlled parallelism.

When a downstream dependency is failing, a circuit breaker opens to stop sending requests for a cooldown period, preventing pileups and giving the dependency time to recover.

Always give gen_server:call a finite timeout. An unbounded wait lets a stuck server block callers indefinitely; a timeout converts a hang into a fast, recoverable error.

Combine patterns: synchronous calls for natural throttling, bounded queues to cap memory, rate limiting for fairness, and load shedding plus circuit breakers as last-resort protection.

You learned to keep systems stable under overload:

• Backpressure signals producers to slow down
• Synchronous call throttles naturally; bounded queues cap memory
• Rate limiting enforces fairness; load shedding protects priority work
• Worker pools bound concurrency; circuit breakers stop downstream pileups
• Monitor mailbox length as a live pressure gauge