When during sync it can happen that the block of dir is already present in A but the block of subdir is not. Then during merge A first starts merging dir which creates an empty directory in A's branch whose version vector is {A: 0, B: 1} (which is the initial version vector dir was originally created with by B) and then proceeds to merge subdir. But because the block of subdir is missing, this fails and the merge ends. This leaves dir in B's branch (vv = {A: 0, B: 2}) as happens-after the one in A's branch (vv = {A: 0, B: 1}). Then when the trash job starts, it identifies the blocks of A's dir as unreachable and removes then both from the block store and the index. Then later when another merge job starts, it tries to open dir in both branches, but the one in A's branch fails on LocatorNotFound because it was previously garbage collected which fails the whole merge job. This situation is then never resolved and so A never gets synced.
Consider two replicas, A and B, where A is initially empty and B has the following content:
When during sync it can happen that the block of
diris already present in A but the block ofsubdiris not. Then during merge A first starts mergingdirwhich creates an empty directory in A's branch whose version vector is{A: 0, B: 1}(which is the initial version vectordirwas originally created with by B) and then proceeds to mergesubdir. But because the block ofsubdiris missing, this fails and the merge ends. This leavesdirin B's branch (vv ={A: 0, B: 2}) as happens-after the one in A's branch (vv ={A: 0, B: 1}). Then when thetrashjob starts, it identifies the blocks of A'sdiras unreachable and removes then both from the block store and the index. Then later when anothermergejob starts, it tries to opendirin both branches, but the one in A's branch fails onLocatorNotFoundbecause it was previously garbage collected which fails the wholemergejob. This situation is then never resolved and so A never gets synced.