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suggested refactoring to err out awaiting

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This commit is contained in:
Joonas Koivunen
2022-10-31 19:51:36 +02:00
committed by Konstantin Knizhnik
parent 8769fef1a5
commit 35890bb293
1 changed files with 11 additions and 5 deletions
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16
pageserver/src/page_image_cache.rs
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@@ -25,7 +25,7 @@ const TEST_PAGE_CACHE_SIZE: usize = 50;
enum PageImageState {
Vacant, // entry is not used
Loaded(Bytes), // page is loaded
Loaded(Option<Bytes>), // page is loaded or has failed
Loading(Option<Arc<Condvar>>), // page in process of loading, Condvar is created on demand when some thread need to wait load completion
}
@@ -210,7 +210,7 @@ pub fn lookup(timeline: &Timeline, rel: RelTag, blkno: BlockNumber, lsn: Lsn) ->
let page = cached_page.clone();
cache.unlink(index);
cache.link_after(0, index);
return Ok(page);
return page.ok_or(anyhow::anyhow!("page loading failed earlier"));
}
PageImageState::Loading(event) => {
// Create event on which to sleep if not yet assigned
@@ -273,7 +273,7 @@ pub fn lookup(timeline: &Timeline, rel: RelTag, blkno: BlockNumber, lsn: Lsn) ->
drop(cache); //release lock
// Load page
let page = timeline.get_rel_page_at_lsn(rel, blkno, lsn, true)?;
let res = timeline.get_rel_page_at_lsn(rel, blkno, lsn, true);
cache = this.lock().unwrap();
if let PageImageState::Loading(event) = &cache.pages[index].state {
@@ -288,7 +288,12 @@ pub fn lookup(timeline: &Timeline, rel: RelTag, blkno: BlockNumber, lsn: Lsn) ->
if cache.is_empty(index) {
// entry was not marked as deleted {
// Page is loaded
cache.pages[index].state = PageImageState::Loaded(page.clone());
// match &res { ... } is same as `res.as_ref().ok().cloned()`
cache.pages[index].state = PageImageState::Loaded(match &res {
Ok(page) => Some(page.clone()),
Err(_) => None,
});
// Link the page to the head of LRU list
cache.link_after(0, index);
} else {
@@ -297,6 +302,7 @@ pub fn lookup(timeline: &Timeline, rel: RelTag, blkno: BlockNumber, lsn: Lsn) ->
cache.pages[index].next = cache.free_list;
cache.free_list = index;
}
return Ok(page);
// only the first one gets the full error from `get_rel_page_at_lsn`
return res;
}
}