fix handling of tenative cursor presence if protection strategy doesn't use it #714
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The new test `ReplicationIncrementalHandlesFromVersionEqTentativeCursorCorrectly` fails with panic: impl error: "#zrepl_CURSORTENTATIVE__G_15cbdccbc1f99b2f_J_sender-job" would be destroyed because it is considered stale but it is part of of sendArgs=zfs.ZFSSendArgsValidated The updated existing test `ReplicationIncrementalCleansUpStaleAbstractionsWithCacheOnSecondReplication`, which, despite what its name suggests, invalidates the cache, fails with panic: impl error: "@3" would be destroyed because it is considered stale but it is part of of sendArgs=zfs.ZFSSendArgsValidated The test that doesn't invalidate the cache doesn't fail. That makes sense because without the cursor in the cache, we can't make the overly cautious decision that causes the panic. with '#' will be ignored, and an empty message aborts the commit.
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Before this PR, we would panic in the
checkphase ofendpoint.Send()'sTryBatchDestroycall in the following cases: the current protection strategy does NOT produce a tentative replication cursor ANDFromVersionis a tentative cursor bookmarkFromVersionis a snapshot, and there exists a tentative cursor bookmark for that snapshotFromVersionis a bookmark != tentative cursor bookmark, but there exists a tentative cursor bookmark for the same snapshot as theFromVersionbookmarkIn those cases, the
checkconcluded that we would deleteFromVersion.It came to that conclusion because the tentative cursor isn't part of
obsoleteAbsif the protection strategy doesn't produce a tentative replication cursor.The scenarios above can happen if the user changes the protection strategy from "with tentative cursor" to one "without tentative replication cursor", while there is a tentative replication cursor on disk.
The workaround was to rename the tentative cursor.
In all cases above,
TryBatchDestroywould have destroyed the tentative cursor.In case 1, that would fail the
Sendstep and potentially break replication if the cursor is the last common bookmark. Thecheckconclusion was correct.In cases 2 and 3, deleting the tentative cursor would have been fine because
FromVersionwas a different entity than the tentative cursor. So, destroying the tentative cursor would be the right call.The solution in this PR is as follows:
FromVersionto theliveAbsset of live abstractionscheckclosure to use the full dataset path (fullpath) to identify the concrete ZFS object instead of thezfs.FilesystemVersionEqualIdentity, which is only identified by matching GUID.FromVersionin any case, so disregard them.fixes #666