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https://issues.apache.org/jira/browse/IGNITE-29189?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Nikolay Izhikov resolved IGNITE-29189.
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Resolution: Won't Fix
> Read cpMapSnapshot.bin written by builds with the generated
> EarliestCheckpointMapSnapshot serializer
> ----------------------------------------------------------------------------------------------------
>
> Key: IGNITE-29189
> URL: https://issues.apache.org/jira/browse/IGNITE-29189
> Project: Ignite
> Issue Type: Improvement
> Reporter: Nikolay Izhikov
> Priority: Major
> Time Spent: 10m
> Remaining Estimate: 0h
>
> h3. Context
> IGNITE-29185 made {{EarliestCheckpointMapSnapshot}} write and read
> {{cpMapSnapshot.bin}} in the layout used by 2.17 / 2.18 (UUIDs written with
> {{writeObject}}).
> Builds that contain IGNITE-27775 but not IGNITE-29185 (no release, but
> intermediate master builds) wrote the file with the generated
> {{EarliestCheckpointMapSnapshotSerializer}}, where UUID map keys and
> {{checkpointIds}} elements are written with {{U.writeUuid}} (null flag + two
> longs). Such a file can't be read by the current code, so a node upgraded
> from one of these builds logs "Failed to unmarshal earliest checkpoint map
> snapshot" and rebuilds the earliest checkpoint map.
> h3. Proposal
> Support both layouts on read: {{readExternal}} reads the payload bytes once,
> tries the legacy layout first and, if that fails, re-reads the same bytes
> with a copy of the generated code. The legacy parse of a generated-layout
> payload fails deterministically ({{StreamCorruptedException}}: the first byte
> of a {{U.writeUuid}} UUID is 0x00/0x01, never a valid type code), so the
> fallback is safe. Writing stays in the legacy layout.
> Covered by {{EarliestCheckpointMapSnapshotSerializationTest}} (round trip,
> legacy layout with 2.17 and 2.18 headers, generated layout, empty snapshot)
> and {{CheckpointMapSnapshotCompatibilityTest}}.
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