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pageserver: remove legacy read path (#8601)
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## Problem

We have been maintaining two read paths (legacy and vectored) for a
while now. The legacy read-path was only used for cross validation in some tests.

## Summary of changes
* Tweak all tests that were using the legacy read path to use the
vectored read path instead
* Remove the read path dispatching based on the pageserver configs
* Remove the legacy read path code

We will be able to remove the single blob io code in
`pageserver/src/tenant/blob_io.rs` when #7386 is complete.

Closes #8005
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@VladLazar @jcsp
VladLazar authored and jcsp committed Aug 12, 2024
1 parent b2bc579 commit 608c3ce
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Showing 8 changed files with 121 additions and 850 deletions.
53 changes: 41 additions & 12 deletions pageserver/src/tenant.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -4122,7 +4122,7 @@ pub(crate) mod harness {

#[cfg(test)]
mod tests {
use std::collections::BTreeMap;
use std::collections::{BTreeMap, BTreeSet};

use super::*;
use crate::keyspace::KeySpaceAccum;
Expand Down Expand Up @@ -4797,7 +4797,7 @@ mod tests {
lsn: Lsn,
repeat: usize,
key_count: usize,
) -> anyhow::Result<()> {
) -> anyhow::Result<HashMap<Key, BTreeSet<Lsn>>> {
let compact = true;
bulk_insert_maybe_compact_gc(tenant, timeline, ctx, lsn, repeat, key_count, compact).await
}
Expand All @@ -4810,7 +4810,9 @@ mod tests {
repeat: usize,
key_count: usize,
compact: bool,
) -> anyhow::Result<()> {
) -> anyhow::Result<HashMap<Key, BTreeSet<Lsn>>> {
let mut inserted: HashMap<Key, BTreeSet<Lsn>> = Default::default();

let mut test_key = Key::from_hex("010000000033333333444444445500000000").unwrap();
let mut blknum = 0;

Expand All @@ -4831,6 +4833,7 @@ mod tests {
ctx,
)
.await?;
inserted.entry(test_key).or_default().insert(lsn);
writer.finish_write(lsn);
drop(writer);

Expand All @@ -4855,7 +4858,7 @@ mod tests {
assert_eq!(res.layers_removed, 0, "this never removes anything");
}

Ok(())
Ok(inserted)
}

//
Expand Down Expand Up @@ -4902,7 +4905,7 @@ mod tests {
.await?;

let lsn = Lsn(0x10);
bulk_insert_compact_gc(&tenant, &tline, &ctx, lsn, 50, 10000).await?;
let inserted = bulk_insert_compact_gc(&tenant, &tline, &ctx, lsn, 50, 10000).await?;

let guard = tline.layers.read().await;
guard.layer_map().dump(true, &ctx).await?;
Expand Down Expand Up @@ -4963,9 +4966,39 @@ mod tests {
&ctx,
)
.await;
tline
.validate_get_vectored_impl(&vectored_res, read, reads_lsn, &ctx)
.await;

let mut expected_lsns: HashMap<Key, Lsn> = Default::default();
let mut expect_missing = false;
let mut key = read.start().unwrap();
while key != read.end().unwrap() {
if let Some(lsns) = inserted.get(&key) {
let expected_lsn = lsns.iter().rfind(|lsn| **lsn <= reads_lsn);
match expected_lsn {
Some(lsn) => {
expected_lsns.insert(key, *lsn);
}
None => {
expect_missing = true;
break;
}
}
} else {
expect_missing = true;
break;
}

key = key.next();
}

if expect_missing {
assert!(matches!(vectored_res, Err(GetVectoredError::MissingKey(_))));
} else {
for (key, image) in vectored_res? {
let expected_lsn = expected_lsns.get(&key).expect("determined above");
let expected_image = test_img(&format!("{} at {}", key.field6, expected_lsn));
assert_eq!(image?, expected_image);
}
}
}

Ok(())
Expand Down Expand Up @@ -5015,10 +5048,6 @@ mod tests {
)
.await;

child_timeline
.validate_get_vectored_impl(&vectored_res, aux_keyspace, read_lsn, &ctx)
.await;

let images = vectored_res?;
assert!(images.is_empty());
Ok(())
Expand Down
15 changes: 0 additions & 15 deletions pageserver/src/tenant/storage_layer.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -435,21 +435,6 @@ impl ReadableLayer {
}
}

/// Return value from [`Layer::get_value_reconstruct_data`]
#[derive(Clone, Copy, Debug)]
pub enum ValueReconstructResult {
/// Got all the data needed to reconstruct the requested page
Complete,
/// This layer didn't contain all the required data, the caller should look up
/// the predecessor layer at the returned LSN and collect more data from there.
Continue,

/// This layer didn't contain data needed to reconstruct the page version at
/// the returned LSN. This is usually considered an error, but might be OK
/// in some circumstances.
Missing,
}

/// Layers contain a hint indicating whether they are likely to be used for reads. This is a hint rather
/// than an authoritative value, so that we do not have to update it synchronously when changing the visibility
/// of layers (for example when creating a branch that makes some previously covered layers visible). It should
Expand Down
91 changes: 1 addition & 90 deletions pageserver/src/tenant/storage_layer/delta_layer.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -36,7 +36,7 @@ use crate::tenant::block_io::{BlockBuf, BlockCursor, BlockLease, BlockReader, Fi
use crate::tenant::disk_btree::{
DiskBtreeBuilder, DiskBtreeIterator, DiskBtreeReader, VisitDirection,
};
use crate::tenant::storage_layer::{Layer, ValueReconstructResult, ValueReconstructState};
use crate::tenant::storage_layer::Layer;
use crate::tenant::timeline::GetVectoredError;
use crate::tenant::vectored_blob_io::{
BlobFlag, MaxVectoredReadBytes, StreamingVectoredReadPlanner, VectoredBlobReader, VectoredRead,
Expand Down Expand Up @@ -826,95 +826,6 @@ impl DeltaLayerInner {
})
}

pub(super) async fn get_value_reconstruct_data(
&self,
key: Key,
lsn_range: Range<Lsn>,
reconstruct_state: &mut ValueReconstructState,
ctx: &RequestContext,
) -> anyhow::Result<ValueReconstructResult> {
let mut need_image = true;
// Scan the page versions backwards, starting from `lsn`.
let block_reader = FileBlockReader::new(&self.file, self.file_id);
let tree_reader = DiskBtreeReader::<_, DELTA_KEY_SIZE>::new(
self.index_start_blk,
self.index_root_blk,
&block_reader,
);
let search_key = DeltaKey::from_key_lsn(&key, Lsn(lsn_range.end.0 - 1));

let mut offsets: Vec<(Lsn, u64)> = Vec::new();

tree_reader
.visit(
&search_key.0,
VisitDirection::Backwards,
|key, value| {
let blob_ref = BlobRef(value);
if key[..KEY_SIZE] != search_key.0[..KEY_SIZE] {
return false;
}
let entry_lsn = DeltaKey::extract_lsn_from_buf(key);
if entry_lsn < lsn_range.start {
return false;
}
offsets.push((entry_lsn, blob_ref.pos()));

!blob_ref.will_init()
},
&RequestContextBuilder::extend(ctx)
.page_content_kind(PageContentKind::DeltaLayerBtreeNode)
.build(),
)
.await?;

let ctx = &RequestContextBuilder::extend(ctx)
.page_content_kind(PageContentKind::DeltaLayerValue)
.build();

// Ok, 'offsets' now contains the offsets of all the entries we need to read
let cursor = block_reader.block_cursor();
let mut buf = Vec::new();
for (entry_lsn, pos) in offsets {
cursor
.read_blob_into_buf(pos, &mut buf, ctx)
.await
.with_context(|| {
format!("Failed to read blob from virtual file {}", self.file.path)
})?;
let val = Value::des(&buf).with_context(|| {
format!(
"Failed to deserialize file blob from virtual file {}",
self.file.path
)
})?;
match val {
Value::Image(img) => {
reconstruct_state.img = Some((entry_lsn, img));
need_image = false;
break;
}
Value::WalRecord(rec) => {
let will_init = rec.will_init();
reconstruct_state.records.push((entry_lsn, rec));
if will_init {
// This WAL record initializes the page, so no need to go further back
need_image = false;
break;
}
}
}
}

// If an older page image is needed to reconstruct the page, let the
// caller know.
if need_image {
Ok(ValueReconstructResult::Continue)
} else {
Ok(ValueReconstructResult::Complete)
}
}

// Look up the keys in the provided keyspace and update
// the reconstruct state with whatever is found.
//
Expand Down
44 changes: 1 addition & 43 deletions pageserver/src/tenant/storage_layer/image_layer.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -32,9 +32,7 @@ use crate::tenant::block_io::{BlockBuf, BlockReader, FileBlockReader};
use crate::tenant::disk_btree::{
DiskBtreeBuilder, DiskBtreeIterator, DiskBtreeReader, VisitDirection,
};
use crate::tenant::storage_layer::{
LayerAccessStats, ValueReconstructResult, ValueReconstructState,
};
use crate::tenant::storage_layer::LayerAccessStats;
use crate::tenant::timeline::GetVectoredError;
use crate::tenant::vectored_blob_io::{
BlobFlag, MaxVectoredReadBytes, StreamingVectoredReadPlanner, VectoredBlobReader, VectoredRead,
Expand Down Expand Up @@ -429,46 +427,6 @@ impl ImageLayerInner {
})
}

pub(super) async fn get_value_reconstruct_data(
&self,
key: Key,
reconstruct_state: &mut ValueReconstructState,
ctx: &RequestContext,
) -> anyhow::Result<ValueReconstructResult> {
let block_reader = FileBlockReader::new(&self.file, self.file_id);
let tree_reader =
DiskBtreeReader::new(self.index_start_blk, self.index_root_blk, &block_reader);

let mut keybuf: [u8; KEY_SIZE] = [0u8; KEY_SIZE];
key.write_to_byte_slice(&mut keybuf);
if let Some(offset) = tree_reader
.get(
&keybuf,
&RequestContextBuilder::extend(ctx)
.page_content_kind(PageContentKind::ImageLayerBtreeNode)
.build(),
)
.await?
{
let blob = block_reader
.block_cursor()
.read_blob(
offset,
&RequestContextBuilder::extend(ctx)
.page_content_kind(PageContentKind::ImageLayerValue)
.build(),
)
.await
.with_context(|| format!("failed to read value from offset {}", offset))?;
let value = Bytes::from(blob);

reconstruct_state.img = Some((self.lsn, value));
Ok(ValueReconstructResult::Complete)
} else {
Ok(ValueReconstructResult::Missing)
}
}

// Look up the keys in the provided keyspace and update
// the reconstruct state with whatever is found.
pub(super) async fn get_values_reconstruct_data(
Expand Down
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