NewMgr creates a new Mgr.

DefaultImportNumGoroutines is the default number of threads for import.

DefaultMergeRegionKeyCount is the default region key count, 960000.

DefaultMergeRegionSizeBytes is the default region split size, 96MB.

default version checker.

no check.

version checker for PiTR.

Mgr manages connections to a TiDB cluster.