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feat(pageserver): support btm-gc-compaction for child branches (#8519)
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part of #8002

For child branches, we will pull the image of the modified keys from the
parant into the child branch, which creates a full history for
generating key retention. If there are not enough delta keys, the image
won't be wrote eventually, and we will only keep the deltas inside the
child branch. We could avoid the wasteful work to pull the image from
the parent if we can know the number of deltas in advance, in the future
(currently we always pull image for all modified keys in the child
branch)


---------

Signed-off-by: Alex Chi Z <[email protected]>
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@skyzh @arpad-m
skyzh authored and arpad-m committed Aug 5, 2024
1 parent 0356fc4 commit 311cc71
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293 changes: 292 additions & 1 deletion pageserver/src/tenant.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -7347,6 +7347,7 @@ mod tests {
Lsn(0x60),
&[Lsn(0x20), Lsn(0x40), Lsn(0x50)],
3,
None,
)
.await
.unwrap();
Expand Down Expand Up @@ -7471,7 +7472,7 @@ mod tests {
),
];
let res = tline
.generate_key_retention(key, &history, Lsn(0x60), &[Lsn(0x40), Lsn(0x50)], 3)
.generate_key_retention(key, &history, Lsn(0x60), &[Lsn(0x40), Lsn(0x50)], 3, None)
.await
.unwrap();
let expected_res = KeyHistoryRetention {
Expand Down Expand Up @@ -7517,6 +7518,114 @@ mod tests {
};
assert_eq!(res, expected_res);

// In case of branch compaction, the branch itself does not have the full history, and we need to provide
// the ancestor image in the test case.

let history = vec![
(
key,
Lsn(0x20),
Value::WalRecord(NeonWalRecord::wal_append(";0x20")),
),
(
key,
Lsn(0x30),
Value::WalRecord(NeonWalRecord::wal_append(";0x30")),
),
(
key,
Lsn(0x40),
Value::WalRecord(NeonWalRecord::wal_append(";0x40")),
),
(
key,
Lsn(0x70),
Value::WalRecord(NeonWalRecord::wal_append(";0x70")),
),
];
let res = tline
.generate_key_retention(
key,
&history,
Lsn(0x60),
&[],
3,
Some((key, Lsn(0x10), Bytes::copy_from_slice(b"0x10"))),
)
.await
.unwrap();
let expected_res = KeyHistoryRetention {
below_horizon: vec![(
Lsn(0x60),
KeyLogAtLsn(vec![(
Lsn(0x60),
Value::Image(Bytes::copy_from_slice(b"0x10;0x20;0x30;0x40")), // use the ancestor image to reconstruct the page
)]),
)],
above_horizon: KeyLogAtLsn(vec![(
Lsn(0x70),
Value::WalRecord(NeonWalRecord::wal_append(";0x70")),
)]),
};
assert_eq!(res, expected_res);

let history = vec![
(
key,
Lsn(0x20),
Value::WalRecord(NeonWalRecord::wal_append(";0x20")),
),
(
key,
Lsn(0x40),
Value::WalRecord(NeonWalRecord::wal_append(";0x40")),
),
(
key,
Lsn(0x60),
Value::WalRecord(NeonWalRecord::wal_append(";0x60")),
),
(
key,
Lsn(0x70),
Value::WalRecord(NeonWalRecord::wal_append(";0x70")),
),
];
let res = tline
.generate_key_retention(
key,
&history,
Lsn(0x60),
&[Lsn(0x30)],
3,
Some((key, Lsn(0x10), Bytes::copy_from_slice(b"0x10"))),
)
.await
.unwrap();
let expected_res = KeyHistoryRetention {
below_horizon: vec![
(
Lsn(0x30),
KeyLogAtLsn(vec![(
Lsn(0x20),
Value::WalRecord(NeonWalRecord::wal_append(";0x20")),
)]),
),
(
Lsn(0x60),
KeyLogAtLsn(vec![(
Lsn(0x60),
Value::Image(Bytes::copy_from_slice(b"0x10;0x20;0x40;0x60")),
)]),
),
],
above_horizon: KeyLogAtLsn(vec![(
Lsn(0x70),
Value::WalRecord(NeonWalRecord::wal_append(";0x70")),
)]),
};
assert_eq!(res, expected_res);

Ok(())
}

Expand Down Expand Up @@ -7715,4 +7824,186 @@ mod tests {

Ok(())
}

#[tokio::test]
async fn test_simple_bottom_most_compaction_on_branch() -> anyhow::Result<()> {
let harness = TenantHarness::create("test_simple_bottom_most_compaction_on_branch").await?;
let (tenant, ctx) = harness.load().await;

fn get_key(id: u32) -> Key {
let mut key = Key::from_hex("000000000033333333444444445500000000").unwrap();
key.field6 = id;
key
}

let img_layer = (0..10)
.map(|id| (get_key(id), Bytes::from(format!("value {id}@0x10"))))
.collect_vec();

let delta1 = vec![
(
get_key(1),
Lsn(0x20),
Value::WalRecord(NeonWalRecord::wal_append("@0x20")),
),
(
get_key(2),
Lsn(0x30),
Value::WalRecord(NeonWalRecord::wal_append("@0x30")),
),
(
get_key(3),
Lsn(0x28),
Value::WalRecord(NeonWalRecord::wal_append("@0x28")),
),
(
get_key(3),
Lsn(0x30),
Value::WalRecord(NeonWalRecord::wal_append("@0x30")),
),
(
get_key(3),
Lsn(0x40),
Value::WalRecord(NeonWalRecord::wal_append("@0x40")),
),
];
let delta2 = vec![
(
get_key(5),
Lsn(0x20),
Value::WalRecord(NeonWalRecord::wal_append("@0x20")),
),
(
get_key(6),
Lsn(0x20),
Value::WalRecord(NeonWalRecord::wal_append("@0x20")),
),
];
let delta3 = vec![
(
get_key(8),
Lsn(0x48),
Value::WalRecord(NeonWalRecord::wal_append("@0x48")),
),
(
get_key(9),
Lsn(0x48),
Value::WalRecord(NeonWalRecord::wal_append("@0x48")),
),
];

let parent_tline = tenant
.create_test_timeline_with_layers(
TIMELINE_ID,
Lsn(0x10),
DEFAULT_PG_VERSION,
&ctx,
vec![], // delta layers
vec![(Lsn(0x18), img_layer)], // image layers
Lsn(0x18),
)
.await?;

parent_tline.add_extra_test_dense_keyspace(KeySpace::single(get_key(0)..get_key(10)));

let branch_tline = tenant
.branch_timeline_test_with_layers(
&parent_tline,
NEW_TIMELINE_ID,
Some(Lsn(0x18)),
&ctx,
vec![
DeltaLayerTestDesc::new_with_inferred_key_range(Lsn(0x20)..Lsn(0x48), delta1),
DeltaLayerTestDesc::new_with_inferred_key_range(Lsn(0x20)..Lsn(0x48), delta2),
DeltaLayerTestDesc::new_with_inferred_key_range(Lsn(0x48)..Lsn(0x50), delta3),
], // delta layers
vec![], // image layers
Lsn(0x50),
)
.await?;

branch_tline.add_extra_test_dense_keyspace(KeySpace::single(get_key(0)..get_key(10)));

{
// Update GC info
let mut guard = parent_tline.gc_info.write().unwrap();
*guard = GcInfo {
retain_lsns: vec![(Lsn(0x18), branch_tline.timeline_id)],
cutoffs: GcCutoffs {
time: Lsn(0x10),
space: Lsn(0x10),
},
leases: Default::default(),
within_ancestor_pitr: false,
};
}

{
// Update GC info
let mut guard = branch_tline.gc_info.write().unwrap();
*guard = GcInfo {
retain_lsns: vec![(Lsn(0x40), branch_tline.timeline_id)],
cutoffs: GcCutoffs {
time: Lsn(0x50),
space: Lsn(0x50),
},
leases: Default::default(),
within_ancestor_pitr: false,
};
}

let expected_result_at_gc_horizon = [
Bytes::from_static(b"value 0@0x10"),
Bytes::from_static(b"value 1@0x10@0x20"),
Bytes::from_static(b"value 2@0x10@0x30"),
Bytes::from_static(b"value 3@0x10@0x28@0x30@0x40"),
Bytes::from_static(b"value 4@0x10"),
Bytes::from_static(b"value 5@0x10@0x20"),
Bytes::from_static(b"value 6@0x10@0x20"),
Bytes::from_static(b"value 7@0x10"),
Bytes::from_static(b"value 8@0x10@0x48"),
Bytes::from_static(b"value 9@0x10@0x48"),
];

let expected_result_at_lsn_40 = [
Bytes::from_static(b"value 0@0x10"),
Bytes::from_static(b"value 1@0x10@0x20"),
Bytes::from_static(b"value 2@0x10@0x30"),
Bytes::from_static(b"value 3@0x10@0x28@0x30@0x40"),
Bytes::from_static(b"value 4@0x10"),
Bytes::from_static(b"value 5@0x10@0x20"),
Bytes::from_static(b"value 6@0x10@0x20"),
Bytes::from_static(b"value 7@0x10"),
Bytes::from_static(b"value 8@0x10"),
Bytes::from_static(b"value 9@0x10"),
];

let verify_result = || async {
for idx in 0..10 {
assert_eq!(
branch_tline
.get(get_key(idx as u32), Lsn(0x50), &ctx)
.await
.unwrap(),
&expected_result_at_gc_horizon[idx]
);
assert_eq!(
branch_tline
.get(get_key(idx as u32), Lsn(0x40), &ctx)
.await
.unwrap(),
&expected_result_at_lsn_40[idx]
);
}
};

verify_result().await;

let cancel = CancellationToken::new();
branch_tline.compact_with_gc(&cancel, &ctx).await.unwrap();

verify_result().await;

Ok(())
}
}
7 changes: 6 additions & 1 deletion pageserver/src/tenant/timeline.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -529,7 +529,6 @@ impl GetVectoredError {
}
}

#[derive(Debug)]
pub struct MissingKeyError {
key: Key,
shard: ShardNumber,
Expand All @@ -540,6 +539,12 @@ pub struct MissingKeyError {
backtrace: Option<std::backtrace::Backtrace>,
}

impl std::fmt::Debug for MissingKeyError {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
write!(f, "{}", self)
}
}

impl std::fmt::Display for MissingKeyError {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
write!(
Expand Down
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