BlakeOrth commented on code in PR #18855: URL: https://github.com/apache/datafusion/pull/18855#discussion_r2593409700
########## datafusion/execution/src/cache/list_files_cache.rs: ########## @@ -0,0 +1,731 @@ +// Licensed to the Apache Software Foundation (ASF) under one +// or more contributor license agreements. See the NOTICE file +// distributed with this work for additional information +// regarding copyright ownership. The ASF licenses this file +// to you under the Apache License, Version 2.0 (the +// "License"); you may not use this file except in compliance +// with the License. You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, +// software distributed under the License is distributed on an +// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY +// KIND, either express or implied. See the License for the +// specific language governing permissions and limitations +// under the License. + +use std::{ + sync::{Arc, Mutex}, + time::Duration, +}; + +use datafusion_common::instant::Instant; +use object_store::{path::Path, ObjectMeta}; + +use crate::cache::{cache_manager::ListFilesCache, lru_queue::LruQueue, CacheAccessor}; + +/// Default implementation of [`ListFilesCache`] +/// +/// Caches file metadata for file listing operations. +/// +/// # Internal details +/// +/// The `memory_limit` parameter controls the maximum size of the cache, which uses a Least +/// Recently Used eviction algorithm. When adding a new entry, if the total number of entries in +/// the cache exceeds `memory_limit`, the least recently used entries are evicted until the total +/// size is lower than the `memory_limit`. +/// +/// # `Extra` Handling +/// +/// Users should use the [`Self::get`] and [`Self::put`] methods. The +/// [`Self::get_with_extra`] and [`Self::put_with_extra`] methods simply call +/// `get` and `put`, respectively. +#[derive(Default)] +pub struct DefaultListFilesCache { + state: Mutex<DefaultListFilesCacheState>, +} + +impl DefaultListFilesCache { + /// Creates a new instance of [`DefaultListFilesCache`]. + /// + /// # Arguments + /// * `memory_limit` - The maximum size of the cache, in bytes. + /// * `ttl` - The TTL (time-to-live) of entries in the cache. + pub fn new(memory_limit: usize, ttl: Option<Duration>) -> Self { + Self { + state: Mutex::new(DefaultListFilesCacheState::new(memory_limit, ttl)), + } + } + + /// Returns the cache's memory limit in bytes. + pub fn cache_limit(&self) -> usize { + self.state.lock().unwrap().memory_limit + } + + /// Updates the cache with a new memory limit in bytes. + pub fn update_cache_limit(&self, limit: usize) { + let mut state = self.state.lock().unwrap(); + state.memory_limit = limit; + state.evict_entries(); + } + + /// Returns the TTL (time-to-live) applied to cache entries. + pub fn cache_ttl(&self) -> Option<Duration> { + self.state.lock().unwrap().ttl + } +} + +struct ListFilesEntry { + metas: Arc<Vec<ObjectMeta>>, + size_bytes: usize, + expires: Option<Instant>, +} + +impl ListFilesEntry { + fn try_new(metas: Arc<Vec<ObjectMeta>>, ttl: Option<Duration>) -> Option<Self> { + let size_bytes = (metas.capacity() * size_of::<ObjectMeta>()) + + metas.iter().map(meta_heap_bytes).reduce(|acc, b| acc + b)?; + + Some(Self { + metas, + size_bytes, + expires: ttl.map(|t| Instant::now() + t), + }) + } +} + +/// Calculates the number of bytes an [`ObjectMeta`] occupies in the heap. +fn meta_heap_bytes(object_meta: &ObjectMeta) -> usize { + let mut size = object_meta.location.as_ref().len(); + + if let Some(e) = &object_meta.e_tag { + size += e.len(); + } + if let Some(v) = &object_meta.version { + size += v.len(); + } + + size +} + +/// The default memory limit for the [`DefaultListFilesCache`] +pub(super) const DEFAULT_LIST_FILES_CACHE_MEMORY_LIMIT: usize = 1024 * 1024; // 1MiB + +/// Handles the inner state of the [`DefaultListFilesCache`] struct. +pub struct DefaultListFilesCacheState { + lru_queue: LruQueue<Path, ListFilesEntry>, + memory_limit: usize, + memory_used: usize, + ttl: Option<Duration>, +} + +impl Default for DefaultListFilesCacheState { + fn default() -> Self { + Self { + lru_queue: LruQueue::new(), + memory_limit: DEFAULT_LIST_FILES_CACHE_MEMORY_LIMIT, + memory_used: 0, + ttl: None, + } + } +} + +impl DefaultListFilesCacheState { + fn new(memory_limit: usize, ttl: Option<Duration>) -> Self { + Self { + lru_queue: LruQueue::new(), + memory_limit, + memory_used: 0, + ttl, + } + } + + /// Returns the respective entry from the cache, if it exists and the entry has not expired. + /// If the entry exists it becomes the most recently used. If the entry has expired it is + /// removed from the cache + fn get(&mut self, key: &Path) -> Option<Arc<Vec<ObjectMeta>>> { + let entry = self.lru_queue.get(key)?; + + match entry.expires { + Some(exp) if Instant::now() > exp => { + self.remove(key); + None + } + _ => Some(Arc::clone(&entry.metas)), + } + } + + /// Checks if the respective entry is currently cached. If the entry has expired it is removed + /// from the cache. + /// The LRU queue is not updated. + fn contains_key(&mut self, k: &Path) -> bool { + let Some(entry) = self.lru_queue.peek(k) else { + return false; + }; + + match entry.expires { + Some(exp) if Instant::now() > exp => { + self.remove(k); + false + } + _ => true, + } + } + + /// Adds a new key-value pair to cache, meaning LRU entries might be evicted if required. + /// If the key is already in the cache, the previous entry is returned. + /// If the size of the entry is greater than the `memory_limit`, the value is not inserted. + fn put( + &mut self, + key: &Path, + value: Arc<Vec<ObjectMeta>>, + ) -> Option<Arc<Vec<ObjectMeta>>> { + let entry = ListFilesEntry::try_new(value, self.ttl)?; + let entry_size = entry.size_bytes; + + // no point in trying to add this value to the cache if it cannot fit entirely + if entry_size > self.memory_limit { + return None; + } + + // if the key is already in the cache, the old value is removed + let old_value = self.lru_queue.put(key.clone(), entry); + self.memory_used += entry_size; + + if let Some(entry) = &old_value { + self.memory_used -= entry.size_bytes; + } + + self.evict_entries(); + + old_value.map(|v| v.metas) + } + + /// Evicts entries from the LRU cache until `memory_used` is lower than `memory_limit`. + fn evict_entries(&mut self) { + while self.memory_used > self.memory_limit { + if let Some(removed) = self.lru_queue.pop() { + self.memory_used -= removed.1.size_bytes; + } else { + // cache is empty while memory_used > memory_limit, cannot happen + debug_assert!( + false, + "cache is empty while memory_used > memory_limit, cannot happen" + ); + return; + } + } + } + + /// Removes an entry from the cache and returns it, if it exists. + fn remove(&mut self, k: &Path) -> Option<Arc<Vec<ObjectMeta>>> { + if let Some(entry) = self.lru_queue.remove(k) { + self.memory_used -= entry.size_bytes; + Some(entry.metas) + } else { + None + } + } + + /// Returns the number of entries currently cached. + fn len(&self) -> usize { + self.lru_queue.len() + } + + /// Removes all entries from the cache. + fn clear(&mut self) { + self.lru_queue.clear(); + self.memory_used = 0; + } +} + +impl ListFilesCache for DefaultListFilesCache { + fn cache_limit(&self) -> usize { + let state = self.state.lock().unwrap(); + state.memory_limit + } + + fn cache_ttl(&self) -> Option<Duration> { + let state = self.state.lock().unwrap(); + state.ttl + } + + fn update_cache_limit(&self, limit: usize) { + let mut state = self.state.lock().unwrap(); + state.memory_limit = limit; + state.evict_entries(); + } +} + +impl CacheAccessor<Path, Arc<Vec<ObjectMeta>>> for DefaultListFilesCache { + type Extra = ObjectMeta; + + fn get(&self, k: &Path) -> Option<Arc<Vec<ObjectMeta>>> { + let mut state = self.state.lock().unwrap(); + state.get(k) + } + + fn get_with_extra(&self, k: &Path, _e: &Self::Extra) -> Option<Arc<Vec<ObjectMeta>>> { + self.get(k) + } + + fn put( + &self, + key: &Path, + value: Arc<Vec<ObjectMeta>>, + ) -> Option<Arc<Vec<ObjectMeta>>> { + let mut state = self.state.lock().unwrap(); + state.put(key, value) + } + + fn put_with_extra( + &self, + key: &Path, + value: Arc<Vec<ObjectMeta>>, + _e: &Self::Extra, + ) -> Option<Arc<Vec<ObjectMeta>>> { + self.put(key, value) + } + + fn remove(&self, k: &Path) -> Option<Arc<Vec<ObjectMeta>>> { + let mut state = self.state.lock().unwrap(); + state.remove(k) + } + + fn contains_key(&self, k: &Path) -> bool { + let mut state = self.state.lock().unwrap(); + state.contains_key(k) + } + + fn len(&self) -> usize { + let state = self.state.lock().unwrap(); + state.len() + } + + fn clear(&self) { + let mut state = self.state.lock().unwrap(); + state.clear(); + } + + fn name(&self) -> String { + String::from("DefaultListFilesCache") + } +} + +#[cfg(test)] +mod tests { + use super::*; + use chrono::DateTime; + use std::thread; + + /// Helper function to create a test ObjectMeta with a specific path and location string size + fn create_test_object_meta(path: &str, location_size: usize) -> ObjectMeta { + // Create a location string of the desired size by padding with zeros + let location_str = if location_size > path.len() { + format!("{}{}", path, "0".repeat(location_size - path.len())) + } else { + path.to_string() + }; + + ObjectMeta { + location: Path::from(location_str), + last_modified: DateTime::parse_from_rfc3339("2022-09-27T22:36:00+02:00") + .unwrap() + .into(), + size: 1024, + e_tag: None, + version: None, + } + } + + /// Helper function to create a vector of ObjectMeta with at least meta_size bytes + fn create_test_list_files_entry( + path: &str, + count: usize, + meta_size: usize, + ) -> (Path, Arc<Vec<ObjectMeta>>, usize) { + let metas: Vec<ObjectMeta> = (0..count) + .map(|i| create_test_object_meta(&format!("file{i}"), meta_size)) + .collect(); + let metas = Arc::new(metas); + + // Calculate actual size using the same logic as ListFilesEntry::try_new + let size = (metas.capacity() * size_of::<ObjectMeta>()) + + metas.iter().map(meta_heap_bytes).sum::<usize>(); + + (Path::from(path), metas, size) + } + + #[test] + fn test_basic_operations() { + let cache = DefaultListFilesCache::default(); + let path = Path::from("test_path"); + + // Initially cache is empty + assert!(cache.get(&path).is_none()); + assert!(!cache.contains_key(&path)); + assert_eq!(cache.len(), 0); + + // Put an entry + let meta = create_test_object_meta("file1", 50); + let value = Arc::new(vec![meta.clone()]); + cache.put(&path, Arc::clone(&value)); + + // Entry should be retrievable + assert!(cache.contains_key(&path)); + assert_eq!(cache.len(), 1); + let retrieved = cache.get(&path).unwrap(); + assert_eq!(retrieved.len(), 1); + assert_eq!(retrieved[0].location, meta.location); + + // Remove the entry + let removed = cache.remove(&path).unwrap(); + assert_eq!(removed.len(), 1); + assert!(!cache.contains_key(&path)); + assert_eq!(cache.len(), 0); + + // Put multiple entries + let (path1, value1, _) = create_test_list_files_entry("path1", 2, 50); + let (path2, value2, _) = create_test_list_files_entry("path2", 3, 50); + cache.put(&path1, value1); + cache.put(&path2, value2); + assert_eq!(cache.len(), 2); + + // Clear all entries + cache.clear(); + assert_eq!(cache.len(), 0); + assert!(!cache.contains_key(&path1)); + assert!(!cache.contains_key(&path2)); + } + + #[test] + fn test_lru_eviction_basic() { + let (path1, value1, size) = create_test_list_files_entry("path1", 1, 100); + let (path2, value2, _) = create_test_list_files_entry("path2", 1, 100); + let (path3, value3, _) = create_test_list_files_entry("path3", 1, 100); + + // Set cache limit to exactly fit all three entries + let cache = DefaultListFilesCache::new(size * 3, None); + + // All three entries should fit + cache.put(&path1, value1); + cache.put(&path2, value2); + cache.put(&path3, value3); + assert_eq!(cache.len(), 3); + assert!(cache.contains_key(&path1)); + assert!(cache.contains_key(&path2)); + assert!(cache.contains_key(&path3)); + + // Adding a new entry should evict path1 (LRU) + let (path4, value4, _) = create_test_list_files_entry("path4", 1, 100); + cache.put(&path4, value4); + + assert_eq!(cache.len(), 3); + assert!(!cache.contains_key(&path1)); // Evicted + assert!(cache.contains_key(&path2)); + assert!(cache.contains_key(&path3)); + assert!(cache.contains_key(&path4)); + } + + #[test] + fn test_lru_ordering_after_access() { + let (path1, value1, size) = create_test_list_files_entry("path1", 1, 100); + let (path2, value2, _) = create_test_list_files_entry("path2", 1, 100); + let (path3, value3, _) = create_test_list_files_entry("path3", 1, 100); + + // Set cache limit to fit exactly three entries + let cache = DefaultListFilesCache::new(size * 3, None); + + cache.put(&path1, value1); + cache.put(&path2, value2); + cache.put(&path3, value3); + assert_eq!(cache.len(), 3); + + // Access path1 to move it to front (MRU) + // Order is now: path2 (LRU), path3, path1 (MRU) + cache.get(&path1); + + // Adding a new entry should evict path2 (the LRU) + let (path4, value4, _) = create_test_list_files_entry("path4", 1, 100); + cache.put(&path4, value4); + + assert_eq!(cache.len(), 3); + assert!(cache.contains_key(&path1)); // Still present (recently accessed) + assert!(!cache.contains_key(&path2)); // Evicted (was LRU) + assert!(cache.contains_key(&path3)); + assert!(cache.contains_key(&path4)); + } + + #[test] + fn test_reject_too_large() { + let (path1, value1, size) = create_test_list_files_entry("path1", 1, 100); + let (path2, value2, _) = create_test_list_files_entry("path2", 1, 100); + + // Set cache limit to fit both entries + let cache = DefaultListFilesCache::new(size * 2, None); + + cache.put(&path1, value1); + cache.put(&path2, value2); + assert_eq!(cache.len(), 2); + + // Try to add an entry that's too large to fit in the cache + let (path_large, value_large, _) = create_test_list_files_entry("large", 1, 1000); + cache.put(&path_large, value_large); + + // Large entry should not be added + assert!(!cache.contains_key(&path_large)); + assert_eq!(cache.len(), 2); + assert!(cache.contains_key(&path1)); + assert!(cache.contains_key(&path2)); + } + + #[test] + fn test_multiple_evictions() { + let (path1, value1, size) = create_test_list_files_entry("path1", 1, 100); + let (path2, value2, _) = create_test_list_files_entry("path2", 1, 100); + let (path3, value3, _) = create_test_list_files_entry("path3", 1, 100); + + // Set cache limit for exactly 3 entries + let cache = DefaultListFilesCache::new(size * 3, None); + + cache.put(&path1, value1); + cache.put(&path2, value2); + cache.put(&path3, value3); + assert_eq!(cache.len(), 3); + + // Add a large entry that requires evicting 2 entries + let (path_large, value_large, _) = create_test_list_files_entry("large", 1, 200); + cache.put(&path_large, value_large); + + // path1 and path2 should be evicted (both LRU), path3 and path_large remain + assert_eq!(cache.len(), 2); + assert!(!cache.contains_key(&path1)); // Evicted + assert!(!cache.contains_key(&path2)); // Evicted + assert!(cache.contains_key(&path3)); + assert!(cache.contains_key(&path_large)); + } + + #[test] + fn test_cache_limit_resize() { + let (path1, value1, size) = create_test_list_files_entry("path1", 1, 100); + let (path2, value2, _) = create_test_list_files_entry("path2", 1, 100); + let (path3, value3, _) = create_test_list_files_entry("path3", 1, 100); + + let cache = DefaultListFilesCache::new(size * 3, None); + + // Add three entries + cache.put(&path1, value1); + cache.put(&path2, value2); + cache.put(&path3, value3); + assert_eq!(cache.len(), 3); + + // Resize cache to only fit one entry + cache.update_cache_limit(size); + + // Should keep only the most recent entry (path3, the MRU) + assert_eq!(cache.len(), 1); + assert!(cache.contains_key(&path3)); + // Earlier entries (LRU) should be evicted + assert!(!cache.contains_key(&path1)); + assert!(!cache.contains_key(&path2)); + } + + #[test] + fn test_entry_update_with_size_change() { + let (path1, value1, size) = create_test_list_files_entry("path1", 1, 100); + let (path2, value2, _) = create_test_list_files_entry("path2", 1, 100); + let (path3, value3_v1, _) = create_test_list_files_entry("path3", 1, 100); + + let cache = DefaultListFilesCache::new(size * 3, None); + + // Add three entries + cache.put(&path1, value1); + cache.put(&path2, value2); + cache.put(&path3, value3_v1); + assert_eq!(cache.len(), 3); + + // Update path3 with same size - should not cause eviction + let (_, value3_v2, _) = create_test_list_files_entry("path3", 1, 100); + cache.put(&path3, value3_v2); + + assert_eq!(cache.len(), 3); + assert!(cache.contains_key(&path1)); + assert!(cache.contains_key(&path2)); + assert!(cache.contains_key(&path3)); + + // Update path3 with larger size that requires evicting path1 (LRU) + let (_, value3_v3, _) = create_test_list_files_entry("path3", 1, 200); + cache.put(&path3, value3_v3); + + assert_eq!(cache.len(), 2); + assert!(!cache.contains_key(&path1)); // Evicted (was LRU) + assert!(cache.contains_key(&path2)); + assert!(cache.contains_key(&path3)); + } + + #[test] + fn test_cache_with_ttl() { + let ttl = Duration::from_millis(100); + let cache = DefaultListFilesCache::new(10000, Some(ttl)); + + let (path1, value1, _) = create_test_list_files_entry("path1", 2, 50); + let (path2, value2, _) = create_test_list_files_entry("path2", 2, 50); + + cache.put(&path1, value1); + cache.put(&path2, value2); + + // Entries should be accessible immediately + assert!(cache.get(&path1).is_some()); + assert!(cache.get(&path2).is_some()); + assert!(cache.contains_key(&path1)); + assert!(cache.contains_key(&path2)); + assert_eq!(cache.len(), 2); + + // Wait for TTL to expire + thread::sleep(Duration::from_millis(150)); + + // Entries should now return None and be removed when observed through get or contains_key + assert!(cache.get(&path1).is_none()); + assert_eq!(cache.len(), 1); // path1 was removed by get() + assert!(!cache.contains_key(&path2)); + assert_eq!(cache.len(), 0); // path2 was removed by contains_key() + } + + #[test] + fn test_cache_with_ttl_and_lru() { Review Comment: Yeah, I agree this is almost certainly due to timing. I can't think of a surefire way to test TTL based items outside of timing unfortunately. We could relax the test criteria a bit here and simply omit this test since we exercise LRU and TTL separately in other tests. LRU+TTL is a bit of a more complex interaction, but in theory if they work in isolation they should work as expected together. What do you think? -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
