MadhuTiwari-345 commented on issue #13027:
URL: https://github.com/apache/apisix/issues/13027#issuecomment-3979139480
### Proposed Incremental Design for `adaptive-limit` (Phase 1 – Baseline
Tracking PoC)
To move this feature forward in a structured and reviewable way, I would
like to begin with a minimal implementation focused only on per-consumer
baseline tracking, without enforcing adaptive limits yet.
This phased approach keeps the initial scope small while laying the
technical foundation for future adaptive rate control.
---
## Scope (Phase 1)
This initial PoC will:
* Track request count per consumer
* Maintain a rolling request-rate baseline using Exponential Moving Average
(EMA)
* Store metrics in `ngx.shared.dict`
* Log or expose the computed baseline for observability
This phase will **not** enforce stricter limits or modify request behavior.
---
## High-Level Architecture
**Plugin name:** `adaptive-limit`
**Execution phase:** `access`
### Data Storage
Use a dedicated shared memory dictionary:
```
ngx.shared.adaptive_limit_dict
```
Key format:
```
adaptive:{consumer_id}
```
Each consumer entry will store:
* `count` – request count within current time window
* `window_start` – timestamp of current window
* `ema` – rolling baseline request rate
---
## Baseline Algorithm
Use Exponential Moving Average:
```
EMA_new = α * current_rate + (1 - α) * EMA_old
```
Where:
* `α` (alpha) is configurable (default: 0.2)
* `current_rate = request_count / window_size`
EMA is preferred over Simple Moving Average because:
* Constant memory usage
* Faster adaptation to behavioral changes
* Lower implementation complexity in Lua
---
## Windowing Strategy
* Fixed time window (default: 1 second)
* Increment counter per request
* On window expiration:
* Compute current rate
* Update EMA
* Reset counter
---
## Future Phases
Phase 2:
* Spike detection (e.g., `current_rate > multiplier × ema`)
Phase 3:
* Temporary limit tightening
* Gradual relaxation when traffic stabilizes
---
I would like to proceed with implementing Phase 1 as a small, self-contained
PoC for review. Feedback on the storage model, execution phase, or algorithm
choice would be appreciated before I begin development.
---
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