Skip to content

fix(sync): keep a superseded snapshot until every device has read past it #1562

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
A-EDev merged 2 commits into from
Oct 29, 2026
Merged

fix(sync): keep a superseded snapshot until every device has read past it #1562

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
393fc78
fix(sync): keep a superseded snapshot until every device has read pas…
A-EDev Oct 29, 2026
0ebe0e2
chore: merge main
A-EDev Oct 29, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
2 changes: 2 additions & 0 deletions .github/nightly-notes/2026-10-29-fix-sync2-gc-manifest-ack.md
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
## Fixed
- Linked devices: a device no longer gets stuck behind another one that cleaned up a snapshot it hadn't read yet (#1075)
8 changes: 5 additions & 3 deletions app/src/main/java/io/github/aedev/flow/sync2/engine/GarbageCollection.kt
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -77,10 +77,12 @@ class Facts(

private fun acknowledged(link: String?): List<Logged> = manifests.filter { it.manifest.link == link && acked(it.did) >= it.seq }

/** A newer acknowledged snapshot covers [old], and every device read past [old] itself, so its removal leaves no gap. */
private fun superseded(old: Logged): Boolean =
acknowledged(old.manifest.link).any { newer ->
newer != old && old.manifest.vv.all { (did, tip) -> (newer.manifest.vv[did]?.seq ?: -1) >= tip.seq }
}
acked(old.did) >= old.seq &&
acknowledged(old.manifest.link).any { newer ->
newer != old && old.manifest.vv.all { (did, tip) -> (newer.manifest.vv[did]?.seq ?: -1) >= tip.seq }
}

/** How far every link's newest acknowledged snapshot covers [did]'s log. */
private fun covered(did: String): Long =
Expand Down
11 changes: 11 additions & 0 deletions app/src/test/java/io/github/aedev/flow/sync2/GarbageCollectionTest.kt
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -71,6 +71,17 @@ class GarbageCollectionTest {
assertTrue(plan(setOf("a", "b"), setOf("a"), mapOf("b" to mapOf("a" to 4L)), listOf(old, new)).manifests.isEmpty())
}

@Test
fun a_snapshot_stays_until_every_device_read_past_it_even_when_another_covers_it() {
// The Mac's manifest 573 is covered by the phone's acknowledged snapshot, but the phone has read the Mac's log only to 572.
val mac = snapshot("mac", 573, "mac" to 572, "phone" to 40)
val phone = snapshot("phone", 41, "mac" to 572, "phone" to 40)
val acks = mapOf("mac" to mapOf("phone" to 41L))
val devices = setOf("mac", "phone")
assertTrue(plan(devices, setOf("mac"), acks + ("phone" to mapOf("mac" to 572L)), listOf(mac, phone)).manifests.isEmpty())
assertEquals(listOf(mac), plan(devices, setOf("mac"), acks + ("phone" to mapOf("mac" to 573L)), listOf(mac, phone)).manifests)
}

@Test
fun every_link_batches_name_needs_an_acknowledged_snapshot() {
val acks = mapOf("b" to mapOf("a" to 9L))
Expand Down
Loading