Thnnathat opened a new issue, #13584:
URL: https://github.com/apache/apisix/issues/13584
### Current Behavior
### Description
We noticed an inconsistency in how the `limit-conn` plugin handles
consumer-level limits compared to the `limit-req` plugin.
When configuring the `limit-conn` plugin directly on a **Consumer** object:
1. Requests made by the same consumer to **Route A** and **Route B** do not
share the same concurrency counter (cross-route leakage).
2. Requests made across **multiple APISIX instances (replica pods)** do not
share the counter because different instances can end up using slightly
different configuration versions internally, generating different Redis keys
(cross-pod leakage).
3. Under the hood, the Redis/Valkey key is constructed using
`ctx.conf_version` and `ctx.conf_type` (in
`apisix/plugins/limit-conn/init.lua`):
```lua
key = key .. ctx.conf_type .. ctx.conf_version
```
This isolates the counter per-route and across instances (pods).
We recall that for `limit-req`, a similar issue was fixed in PR #13019 by
using `parent.resource_key` to share the counter across routes and instances at
the consumer level.
We would like to ask the community/maintainers:
* Is this behavior intended for `limit-conn`, or is it an
inconsistency/oversight that should be aligned with how `limit-req` works to
support shared counters across routes and multiple gateway instances?
### Expected Behavior
_No response_
### Error Logs
_No response_
### Steps to Reproduce
1. Define a consumer with the `limit-conn` plugin activated (concurrency
limit `conn: 1`, policy `redis` / `redis-cluster`).
2. Deploy APISIX with 2 replica pods.
3. Scenario A (Cross-route): Make concurrent requests to `/route-a` and
`/route-b` using the same consumer credentials.
4. Scenario B (Cross-pod): Make concurrent requests targeting different pods
(Pod A and Pod B) for the same consumer credentials.
5. **Observation:** Both requests succeed simultaneously. Checking Redis
shows separate keys generated because the suffix (`ctx.conf_version` /
`ctx.conf_type`) differs between the routes/pods.
### Environment
- APISIX version: >= 3.16.0 (including 3.17.0)
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