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fix(pageserver): gc-compaction verification false failure (#11564)

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## Problem

https://github.com/neondatabase/neon/pull/11515 introduced a bug that
some key history cannot be verified.

If a key only exists above the horizon, the verification will fail for
its first occurrence because the history does not exist at that point.

As gc-compaction skips a key range whenever an error occurs, it might be
doing some wasted work in staging/prod now. But I'm not planning a
hotfix this week as the bug doesn't affect correctness/performance.

## Summary of changes

Allow keys with only above horizon history in the verification.

Signed-off-by: Alex Chi Z <chi@neon.tech>
This commit is contained in:
Alex Chi Z.
2025-04-15 09:58:32 -04:00
committed by GitHub
parent 19bea5fd0c
commit a4ea7d6194
1 changed files with 20 additions and 11 deletions
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31
pageserver/src/tenant/timeline/compaction.rs
View File

@@ -819,7 +819,15 @@ impl KeyHistoryRetention {
base_img: &Option<(Lsn, &Bytes)>,
history: &[(Lsn, &NeonWalRecord)],
tline: &Arc<Timeline>,
skip_empty: bool,
) -> anyhow::Result<()> {
if base_img.is_none() && history.is_empty() {
if skip_empty {
return Ok(());
}
anyhow::bail!("verification failed: key {} has no history at {}", key, lsn);
};
let mut records = history
.iter()
.map(|(lsn, val)| (*lsn, (*val).clone()))
@@ -860,17 +868,12 @@ impl KeyHistoryRetention {
if *retain_lsn >= min_lsn {
// Only verify after the key appears in the full history for the first time.
if base_img.is_none() && history.is_empty() {
anyhow::bail!(
"verificatoin failed: key {} has no history at {}",
key,
retain_lsn
);
};
// We don't modify history: in theory, we could replace the history with a single
// image as in `generate_key_retention` to make redos at later LSNs faster. But we
// want to verify everything as if they are read from the real layer map.
collect_and_verify(key, *retain_lsn, &base_img, &history, tline).await?;
collect_and_verify(key, *retain_lsn, &base_img, &history, tline, false)
.await
.context("below horizon retain_lsn")?;
}
}
@@ -878,13 +881,17 @@ impl KeyHistoryRetention {
match val {
Value::Image(img) => {
// Above the GC horizon, we verify every time we see an image.
collect_and_verify(key, *lsn, &base_img, &history, tline).await?;
collect_and_verify(key, *lsn, &base_img, &history, tline, true)
.await
.context("above horizon full image")?;
base_img = Some((*lsn, img));
history.clear();
}
Value::WalRecord(rec) if val.will_init() => {
// Above the GC horizon, we verify every time we see an init record.
collect_and_verify(key, *lsn, &base_img, &history, tline).await?;
collect_and_verify(key, *lsn, &base_img, &history, tline, true)
.await
.context("above horizon init record")?;
base_img = None;
history.clear();
history.push((*lsn, rec));
@@ -895,7 +902,9 @@ impl KeyHistoryRetention {
}
}
// Ensure the latest record is readable.
collect_and_verify(key, max_lsn, &base_img, &history, tline).await?;
collect_and_verify(key, max_lsn, &base_img, &history, tline, false)
.await
.context("latest record")?;
Ok(())
}
}