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https://issues.apache.org/jira/browse/HDDS-17733?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Siyao Meng updated HDDS-17733:
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Affects Version/s: 2.3.0
> Snapshot diff page token is not checked against the current report
> ------------------------------------------------------------------
>
> Key: HDDS-17733
> URL: https://issues.apache.org/jira/browse/HDDS-17733
> Project: Apache Ozone
> Issue Type: Bug
> Affects Versions: 2.3.0
> Reporter: Siyao Meng
> Priority: Minor
> Attachments: MC-8-reject-page-token-not-in-current-report.patch
>
>
> h3. Mechanism
> A snapshot diff page token is the suffix of the key of the next report row.
> Each page request looks up the job of the snapshot pair again, and
> {{SnapshotDiffManager.createPageResponse}} scans from {{<jobId>-<token>}},
> the row the token names, without checking that this row belongs to the
> current report.
> A report is stored in one of two key formats: dependency ordered rows are
> {{<jobId>-0<20 digits>}}, unordered rows are {{<jobId>-<1..4><20 digits>}}.
> When the job of a snapshot pair has been regenerated as an unordered report
> between two page requests of a dependency ordered report, the token of the
> earlier run sorts before every row of the new run, and the resumed read
> continues from the first row of the new run.
> h3. Trigger
> Requires {{ozone.om.snapshot.diff.optimized.enabled}} = true (default false)
> and an FSO bucket, where dependency ordered reports are produced (added by
> HDDS-15391, not in any release).
> # A client reads page 1 of a dependency ordered report and keeps the token.
> # The job expires through {{SnapshotDiffCleanupService}}
> ({{ozone.om.snapshot.diff.job.report.persistent.time}}, 7 days by default,
> counted from job creation).
> # An unordered report is requested for the same snapshot pair and completes.
> # The client requests the next page with its token.
> h3. Impact
> The resumed read returns the whole new report, so the rows of the pages
> already read appear twice; for a 5 entry report read with page size 2 the
> client assembles 7 rows. No error is returned.
> h3. Reproduction
> This issue has no standalone reproduction; the regression test in the patch
> is the reproduction.
> {{TestSnapshotDiffManager#testCreatePageResponseRejectsTokenOfRegeneratedReport}}
> applies a token of a dependency ordered run to an unordered report of the
> same snapshot pair and expects it to be rejected. On
> d3b75c75bf9ad475551202477c3a21a3f4b968b7 it fails with "Expected
> java.io.IOException to be thrown, but nothing was thrown", because the scan
> restarts at the first row.
> h3. Patch
> [^MC-8-reject-page-token-not-in-current-report.patch], against
> d3b75c75bf9ad475551202477c3a21a3f4b968b7. It also applies to master at
> bbc8505e00d.
> {{createPageResponse}} now looks up the row the token names before scanning
> and, for a report with entries, rejects a token that names no row of the
> current report with "Token ... does not belong to the current report of this
> snapshot diff. The report may have been regenerated, retry from the first
> page without a token." A token of the current report pages exactly as before;
> the cost is one point lookup per page request that carries a token. The token
> format is unchanged.
> The new test also checks that a token of the current report still returns the
> rows from the one it names. Without the change it fails as above; with it
> {{TestSnapshotDiffManager}} (85 tests) and the mini cluster suite
> {{TestOmSnapshotFsoWithoutNativeLib}} pass and checkstyle is clean.
> Found by TLA+ model checking and code review of the OM optimized snapshot
> diff paths under HDDS-15926, on commit
> d3b75c75bf9ad475551202477c3a21a3f4b968b7. Checked against HDDS issues and
> apache/ozone pull requests for duplicates before filing. The attached patch
> is a proposal for review. Generated with Specula (Claude Opus 5.5).
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