add tracking issue

text/0115-circuit-breaker.md

@@ -1,7 +1,7 @@
 # Title
 
 - RFC PR: https://github.com/tikv/rfcs/pull/115
-- Tracking Issue: https://github.com/tikv/repo/issues/0000
+- Tracking Issue: https://github.com/tikv/pd/issues/8678
 
 ## Summary
 
@@ -37,18 +37,17 @@ In order to limit number of system variables, we will use a single system variab
 * Defines how long to track errors before evaluating error_rate_threshold.
 * Default: 10
 * Unit: seconds
-
+---
 * `min_qps_to_open`
 * Defines the average qps over the `error_rate_window` that must be met before evaluating the error rate threshold.
 * Default: 10
 * Unit: integer
-
+---
 * `cooldown_interval`
 * Defines how long to wait after circuit breaker is open before go to half-open state to send a probe request. This interval always equally jittered in the `[value/2, value]` interval.
 * Default: 60
 * Unit: seconds
-
-
+---
 * `half_open_success_count`
 * Defines how many subsequent requests to test after cooldown period before fully close the circuit. All request in excess of this count will be errored till the circuit is fully closed pending results of the firsts `half_open_success_count` requests. 
 * Default: 10