Improvements

• Add more types of write queries to QPS dimensions in the hotspot scheduler #3869
• Support dynamically adjusting the retry limit of the balance region scheduler to improve the performance of the scheduler #3744
• Update TiDB Dashboard to v2021.10.08.1 #4070
• Support that the evict leader scheduler can schedule regions with unhealthy peers #4093
• Speed up the exit process of schedulers #4146

Bug Fixes

• Fix the issue that PD incorrectly delete the peers with data and in pending status because the number of peers exceeds the number of configured peers #4045
• Fix the issue that PD does not fix down peers in time #4077
• Fix the issue that the scatter range scheduler cannot schedule empty regions #4118
• Fix the issue that the key manager cost too much CPU #4071
• Fix the data race issue that might occur when setting configurations of hot region scheduler #4159
• Fix slow leader election caused by stucked region syncer#3936