caching the existence of blobs to avoid duplicate checking
caching the existence of blobs to avoid duplicate checking

wknet123/harbor,wy65701436/harbor,reasonerjt/harbor,wemeya/harbor,wy65701436/harbor,steven-zou/harbor,wknet123/harbor,steven-zou/harbor,reasonerjt/harbor,wemeya/harbor,reasonerjt/harbor,wemeya/harbor,steven-zou/harbor,wy65701436/harbor,wemeya/harbor,reasonerjt/harbor,steven-zou/harbor,wy65701436/harbor,wemeya/harbor,wy65701436/harbor,wknet123/harbor,wemeya/harbor,reasonerjt/harbor,wknet123/harbor,steven-zou/harbor,wknet123/harbor,reasonerjt/harbor,steven-zou/harbor,wy65701436/harbor,wknet123/harbor