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5615f4929a
fixes https://github.com/zrepl/zrepl/issues/742 Before this PR, when chaining replication from A => B => C, if B had placeholders and the `filesystems` included these placeholders, we'd incorrectly fail the planning phase with error `sender does not have any versions`. The non-placeholder child filesystems of these placeholders would then fail to replicate because of the initial-replication-dependency-tracking that we do, i.e., their parent failed to initially replication, hence they fail to replicate as well (`parent(s) failed during initial replication`). We can do better than that because we have the information whether a sender-side filesystem is a placeholder. This PR makes the planner act on that information. The outcome is that placeholders are replicated as placeholders (albeit the receiver remains in control of how these placeholders are created, i.e., `recv.placeholders`) The mechanism to do it is: 1. Don't plan any replication steps for filesystems that are placeholders on the sender. 2. Ensure that, if a receiving-side filesystem exists, it is indeed a placeholder. Check (2) may seem overly restrictive, but, the goal here is not just to mirror all non-placeholder filesystems, but also to mirror the hierarchy. Testing performed: - [x] confirm with issue reporter that this PR fixes their issue - [x] add a regression test that fails without the changes in this PR |
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