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integrate: Timeline::get_value_reconstruct_data

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This commit is contained in:
Joonas Koivunen
2023-08-15 20:00:11 +03:00
parent 2e686ed6ea
commit b4a0f8baf7
1 changed files with 27 additions and 95 deletions
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122
pageserver/src/tenant/timeline.rs
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@@ -1989,20 +1989,9 @@ trait TraversalLayerExt {
fn traversal_id(&self) -> TraversalId;
}
impl TraversalLayerExt for Arc<dyn PersistentLayer> {
impl TraversalLayerExt for Arc<LayerE> {
fn traversal_id(&self) -> TraversalId {
let timeline_id = self.layer_desc().timeline_id;
match self.local_path() {
Some(local_path) => {
debug_assert!(local_path.to_str().unwrap().contains(&format!("{}", timeline_id)),
"need timeline ID to uniquely identify the layer when traversal crosses ancestor boundary",
);
format!("{}", local_path.display())
}
None => {
format!("remote {}/{self}", timeline_id)
}
}
self.local_path().display().to_string()
}
}
@@ -2226,41 +2215,32 @@ impl Timeline {
if let Some(SearchResult { lsn_floor, layer }) = layers.search(key, cont_lsn) {
let layer = guard.get_from_desc(&layer);
// If it's a remote layer, download it and retry.
if let Some(remote_layer) =
super::storage_layer::downcast_remote_layer(&layer)
// Get all the data needed to reconstruct the page version from this layer.
// But if we have an older cached page image, no need to go past that.
let lsn_floor = max(cached_lsn + 1, lsn_floor);
result = match layer
.get_value_reconstruct_data(
key,
lsn_floor..cont_lsn,
reconstruct_state,
ctx,
)
.await
{
// TODO: push a breadcrumb to 'traversal_path' to record the fact that
// we downloaded / would need to download this layer.
remote_layer // download happens outside the scope of `layers` guard object
} else {
// Get all the data needed to reconstruct the page version from this layer.
// But if we have an older cached page image, no need to go past that.
let lsn_floor = max(cached_lsn + 1, lsn_floor);
result = match layer
.get_value_reconstruct_data(
key,
lsn_floor..cont_lsn,
reconstruct_state,
ctx,
)
.await
{
Ok(result) => result,
Err(e) => return Err(PageReconstructError::from(e)),
};
cont_lsn = lsn_floor;
*read_count += 1;
traversal_path.push((
result,
cont_lsn,
Box::new({
let layer = Arc::clone(&layer);
move || layer.traversal_id()
}),
));
continue 'outer;
}
Ok(result) => result,
Err(e) => return Err(PageReconstructError::from(e)),
};
cont_lsn = lsn_floor;
*read_count += 1;
traversal_path.push((
result,
cont_lsn,
Box::new({
let layer = Arc::clone(&layer);
move || layer.traversal_id()
}),
));
continue 'outer;
} else if timeline.ancestor_timeline.is_some() {
// Nothing on this timeline. Traverse to parent
result = ValueReconstructResult::Continue;
@@ -2272,54 +2252,6 @@ impl Timeline {
continue 'outer;
}
};
// Download the remote_layer and replace it in the layer map.
// For that, we need to release the mutex. Otherwise, we'd deadlock.
//
// The control flow is so weird here because `drop(layers)` inside
// the if stmt above is not enough for current rustc: it requires
// that the layers lock guard is not in scope across the download
// await point.
let remote_layer_as_persistent: Arc<dyn PersistentLayer> =
Arc::clone(&remote_layer) as Arc<dyn PersistentLayer>;
let id = remote_layer_as_persistent.traversal_id();
info!(
"need remote layer {} for task kind {:?}",
id,
ctx.task_kind()
);
// The next layer doesn't exist locally. Need to download it.
// (The control flow is a bit complicated here because we must drop the 'layers'
// lock before awaiting on the Future.)
match (
ctx.download_behavior(),
self.conf.ondemand_download_behavior_treat_error_as_warn,
) {
(DownloadBehavior::Download, _) => {
info!(
"on-demand downloading remote layer {id} for task kind {:?}",
ctx.task_kind()
);
timeline.download_remote_layer(remote_layer).await?;
continue 'layer_map_search;
}
(DownloadBehavior::Warn, _) | (DownloadBehavior::Error, true) => {
warn!(
"unexpectedly on-demand downloading remote layer {} for task kind {:?}",
id,
ctx.task_kind()
);
UNEXPECTED_ONDEMAND_DOWNLOADS.inc();
timeline.download_remote_layer(remote_layer).await?;
continue 'layer_map_search;
}
(DownloadBehavior::Error, false) => {
return Err(PageReconstructError::NeedsDownload(
TenantTimelineId::new(self.tenant_id, self.timeline_id),
remote_layer.filename(),
))
}
}
}
}
}