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v8.5.5: Add circuit breaker variable (#19678) #21176

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ti-chi-bot merged 3 commits into from
Dec 29, 2025
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v8.5.5: Add circuit breaker variable (#19678) #21176

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Update system-variables.md
hfxsd Jan 23, 2025
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9 changes: 9 additions & 0 deletions system-variables.md
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Expand Up @@ -1245,6 +1245,15 @@ mysql> SELECT job_info FROM mysql.analyze_jobs ORDER BY end_time DESC LIMIT 1;
- 这个变量用于控制是否开启[自动捕获绑定](/sql-plan-management.md#自动捕获绑定-baseline-capturing)功能。该功能依赖 Statement Summary，因此在使用自动绑定之前需打开 Statement Summary 开关。
- 开启该功能后会定期遍历一次 Statement Summary 中的历史 SQL 语句，并为至少出现两次的 SQL 语句自动创建绑定。

### `tidb_cb_pd_metadata_error_rate_threshold_ratio` <span class="version-mark">从 v9.0.0 版本开始引入</span>

- 作用域：GLOBAL
- 是否持久化到集群：是
- 是否受 Hint [SET_VAR](/optimizer-hints.md#set_varvar_namevar_value) 控制：否
- 默认值：`0`
- 取值范围：`[0, 1]`
- 该变量用于控制 TiDB 何时触发熔断器。设置为 `0`（默认值）表示禁用熔断器。设置为 `0.01` 到 `1` 之间的值时，表示启用熔断器，当发送到 PD 的特定请求的错误率达到或超过该阈值时，熔断器会被触发。

### `tidb_cdc_write_source` <span class="version-mark">从 v6.5.0 版本开始引入</span>

- 作用域：SESSION
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