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Merged
merged 3 commits into from
Jul 28, 2025
Merged

Skip any erroring entry in FilesystemStore::list #3799

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982aaf5
Replace race-y `metadata` call with `DirEntry::metadata`
tnull May 24, 2025
9d32931
Implement `loop` retrying `list` to reach a consistent view
tnull Jul 28, 2025
6681a69
Don't `io::Error::map_err` to `ErrorKind::Other`
tnull Jul 28, 2025
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78 changes: 54 additions & 24 deletions lightning-persister/src/fs_store.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -33,6 +33,10 @@ fn path_to_windows_str<T: AsRef<OsStr>>(path: &T) -> Vec<u16> {
// The number of read/write/remove/list operations after which we clean up our `locks` HashMap.
const GC_LOCK_INTERVAL: usize = 25;

// The number of times we retry listing keys in `FilesystemStore::list` before we give up reaching
// a consistent view and error out.
const LIST_DIR_CONSISTENCY_RETRIES: usize = 10;

/// A [`KVStoreSync`] implementation that writes to and reads from the file system.
pub struct FilesystemStore {
data_dir: PathBuf,
Expand Down Expand Up @@ -306,23 +310,45 @@ impl KVStoreSync for FilesystemStore {
check_namespace_key_validity(primary_namespace, secondary_namespace, None, "list")?;

let prefixed_dest = self.get_dest_dir_path(primary_namespace, secondary_namespace)?;
let mut keys = Vec::new();

if !Path::new(&prefixed_dest).exists() {
return Ok(Vec::new());
}

for entry in fs::read_dir(&prefixed_dest)? {
let entry = entry?;
let p = entry.path();
let mut keys;
let mut retries = LIST_DIR_CONSISTENCY_RETRIES;

if !dir_entry_is_key(&p)? {
continue;
}
'retry_list: loop {
keys = Vec::new();
'skip_entry: for entry in fs::read_dir(&prefixed_dest)? {
let entry = entry?;
let p = entry.path();

let key = get_key_from_dir_entry(&p, &prefixed_dest)?;

keys.push(key);
let res = dir_entry_is_key(&entry);
match res {
Ok(true) => {
let key = get_key_from_dir_entry_path(&p, &prefixed_dest)?;
keys.push(key);
},
Ok(false) => {
// We didn't error, but the entry is not a valid key (e.g., a directory,
// or a temp file).
continue 'skip_entry;
},
Err(e) => {
if e.kind() == lightning::io::ErrorKind::NotFound && retries > 0 {
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I don't think this is right because the dir_entry_is_key metadata() call gets its error mapped to an ErrorKind::Other.

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Ah, good catch, I had forgotten we started to do that at some point. Now added a commit reverting this, as remapping to ErrorKind::Other is nonsense, IMO, if we already have stronger typed io::Error.

// We had found the entry in `read_dir` above, so some race happend.
// Retry the `read_dir` to get a consistent view.
retries -= 1;
continue 'retry_list;
} else {
// For all errors or if we exhausted retries, bubble up.
return Err(e.into());
}
},
}
}
break 'retry_list;
}

self.garbage_collect_locks();
Expand All @@ -331,7 +357,8 @@ impl KVStoreSync for FilesystemStore {
}
}

fn dir_entry_is_key(p: &Path) -> Result<bool, lightning::io::Error> {
fn dir_entry_is_key(dir_entry: &fs::DirEntry) -> Result<bool, lightning::io::Error> {
let p = dir_entry.path();
if let Some(ext) = p.extension() {
#[cfg(target_os = "windows")]
{
Expand All @@ -346,7 +373,7 @@ fn dir_entry_is_key(p: &Path) -> Result<bool, lightning::io::Error> {
}
}

let metadata = p.metadata().map_err(|e| {
let metadata = dir_entry.metadata().map_err(|e| {
let msg = format!(
"Failed to list keys at path {}: {}",
PrintableString(p.to_str().unwrap_or_default()),
Expand Down Expand Up @@ -377,7 +404,7 @@ fn dir_entry_is_key(p: &Path) -> Result<bool, lightning::io::Error> {
Ok(true)
}

fn get_key_from_dir_entry(p: &Path, base_path: &Path) -> Result<String, lightning::io::Error> {
fn get_key_from_dir_entry_path(p: &Path, base_path: &Path) -> Result<String, lightning::io::Error> {
match p.strip_prefix(&base_path) {
Ok(stripped_path) => {
if let Some(relative_path) = stripped_path.to_str() {
Expand Down Expand Up @@ -435,24 +462,27 @@ impl MigratableKVStore for FilesystemStore {
let mut keys = Vec::new();

'primary_loop: for primary_entry in fs::read_dir(prefixed_dest)? {
let primary_path = primary_entry?.path();
let primary_entry = primary_entry?;
let primary_path = primary_entry.path();

if dir_entry_is_key(&primary_path)? {
if dir_entry_is_key(&primary_entry)? {
let primary_namespace = String::new();
let secondary_namespace = String::new();
let key = get_key_from_dir_entry(&primary_path, prefixed_dest)?;
let key = get_key_from_dir_entry_path(&primary_path, prefixed_dest)?;
keys.push((primary_namespace, secondary_namespace, key));
continue 'primary_loop;
}

// The primary_entry is actually also a directory.
'secondary_loop: for secondary_entry in fs::read_dir(&primary_path)? {
let secondary_path = secondary_entry?.path();
let secondary_entry = secondary_entry?;
let secondary_path = secondary_entry.path();

if dir_entry_is_key(&secondary_path)? {
let primary_namespace = get_key_from_dir_entry(&primary_path, prefixed_dest)?;
if dir_entry_is_key(&secondary_entry)? {
let primary_namespace =
get_key_from_dir_entry_path(&primary_path, prefixed_dest)?;
let secondary_namespace = String::new();
let key = get_key_from_dir_entry(&secondary_path, &primary_path)?;
let key = get_key_from_dir_entry_path(&secondary_path, &primary_path)?;
keys.push((primary_namespace, secondary_namespace, key));
continue 'secondary_loop;
}
Expand All @@ -462,12 +492,12 @@ impl MigratableKVStore for FilesystemStore {
let tertiary_entry = tertiary_entry?;
let tertiary_path = tertiary_entry.path();

if dir_entry_is_key(&tertiary_path)? {
if dir_entry_is_key(&tertiary_entry)? {
let primary_namespace =
get_key_from_dir_entry(&primary_path, prefixed_dest)?;
get_key_from_dir_entry_path(&primary_path, prefixed_dest)?;
let secondary_namespace =
get_key_from_dir_entry(&secondary_path, &primary_path)?;
let key = get_key_from_dir_entry(&tertiary_path, &secondary_path)?;
get_key_from_dir_entry_path(&secondary_path, &primary_path)?;
let key = get_key_from_dir_entry_path(&tertiary_path, &secondary_path)?;
keys.push((primary_namespace, secondary_namespace, key));
} else {
debug_assert!(
Expand Down
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