pd-server v4.0.0-beta

• Support optimizing hotspot scheduling according to the load information of storage nodes
  • #1870 #1982 #1998 #1843 #1750
• Add the Placement Rules feature that supports controlling the number of replicas of any data range, the storage location, the storage host type and roles by combining different scheduling rules
  • #2051 #1999 #2042 #1917 #1904
  • #1897 #1894 #1865 #1855 #1834
• Support using plugins (experimental) #1799
• Add the feature that the schedulers support the customized configuration and key ranges (experimental)
  • #1735 #1783 #1791
• Support automatically adjusting the scheduling speed according the cluster load information (experimental, disabled by default)
  • #1875 #1887 #1902