TiDB 服务器的连接数报表看不懂了

有猫万事足 · 2024 年10 月 11 日 13:55

已知bug，见这个帖子。

github.com/pingcap/tidb

server: refine the connection counter logic (#54546)

release-8.1 ← ti-chi-bot:cherry-pick-54546-to-release-8.1

已打开 05:13AM - 15 Jul 24 UTC

ti-chi-bot

+119 -13

This is an automated cherry-pick of #54546 ### What problem does this PR solve?… Issue Number: close #54545, close #54428 Problem Summary: This PR solve two problems: 1. The inc/dec of the connection doesn't organize in pair, so the connection count may decrease below zero. It actually increases in `registerConn`, and decreases in `conn.Close()` (if the `conn.getCtx()` is not nil). If the connection exists before handshake successfully, for example authentication failed, the total connection count will decrease one :facepalm:. 2. `SET SESSION_STATES` (usually used by `tiproxy`) didn't INC/DEC the connection count for the resource group if it's changed. ### What changed and how does it work? This PR reorganized the codes INC/DEC the metric gauge in the following pattern: 1. It's increased in `newConn` with default resource group name, so that it can make sure the connection count will always increase. 2. It's decreased in `closeConn`. If the connection doesn't have a valid context, it'll decrease in the default resource group. Other use case of the `ConnGauge` always comes in pair: increase one and decrease another one. This PR provides a method `SetResourceGroupName` to change the session vars and always INC/DEC the metric counter. It'll be called in `SET SESSION_STATES`, `SET RESOURCE GROUP` and authentication (because the user may carry a resource group info). ### Check List Tests - [ ] Unit test - [x] Integration test - [ ] Manual test (add detailed scripts or steps below) - [ ] No need to test > - [ ] I checked and no code files have been changed. > ### Release note ```release-note Fix the issue that the connection count is not correct if some connection exits before handshake finishes. Fix the issue that with tiproxy and non-default resource group, the connection count of each resource group is not correct. ```

合并到8.1分支的时间是8.5。
升到8.1.1应该能解决这个问题。