Add size limit to cache

Cargo.lock

@@ -727,6 +727,12 @@ dependencies = [
  "system-deps",
 ]
 
+[[package]]
+name = "hashbrown"
+version = "0.9.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d7afe4a420e3fe79967a00898cc1f4db7c8a49a9333a29f8a4bd76a253d5cd04"
+
 [[package]]
 name = "headers"
 version = "0.3.4"
@@ -912,6 +918,16 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "indexmap"
+version = "1.6.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "824845a0bf897a9042383849b02c1bc219c2383772efcd5c6f9766fa4b81aef3"
+dependencies = [
+ "autocfg",
+ "hashbrown",
+]
+
 [[package]]
 name = "instant"
 version = "0.1.9"
@@ -1207,6 +1223,7 @@ dependencies = [
  "num-traits",
  "once_cell",
  "pbkdf2",
+ "priority-queue",
  "protobuf",
  "rand",
  "serde",
@@ -1723,6 +1740,16 @@ version = "0.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "bc5c99d529f0d30937f6f4b8a86d988047327bb88d04d2c4afc356de74722131"
 
+[[package]]
+name = "priority-queue"
+version = "1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f16f1277a63996195ef38361e2c909314614c6f25f2ac4968f87dfd94a625d3d"
+dependencies = [
+ "autocfg",
+ "indexmap",
+]
+
 [[package]]
 name = "proc-macro-crate"
 version = "0.1.5"

core/Cargo.toml

@@ -31,6 +31,7 @@ num-integer = "0.1"
 num-traits = "0.2"
 once_cell = "1.5.2"
 pbkdf2 = { version = "0.7", default-features = false, features = ["hmac"] }
+priority-queue = "1.1"
 protobuf = "~2.14.0"
 rand = "0.8"
 serde = { version = "1.0", features = ["derive"] }

core/src/cache.rs

@@ -1,30 +1,173 @@
-use std::fs;
-use std::fs::File;
+use std::cmp::Reverse;
+use std::collections::HashMap;
+use std::fs::{self, File};
 use std::io::{self, Error, ErrorKind, Read, Write};
 use std::path::{Path, PathBuf};
+use std::sync::{Arc, Mutex};
+use std::time::SystemTime;
+
+use priority_queue::PriorityQueue;
 
 use crate::authentication::Credentials;
 use crate::spotify_id::FileId;
 
+struct SizeLimiter {
+    queue: PriorityQueue<PathBuf, Reverse<SystemTime>>,
+    sizes: HashMap<PathBuf, u64>,
+    size_limit: u64,
+    in_use: u64,
+}
+
+impl SizeLimiter {
+    fn new(limit: u64) -> Self {
+        Self {
+            queue: PriorityQueue::new(),
+            sizes: HashMap::new(),
+            size_limit: limit,
+            in_use: 0,
+        }
+    }
+
+    /// Adds an entry to this data structure.
+    ///
+    /// If this file is already contained, it will be updated accordingly.
+    fn add(&mut self, file: &Path, size: u64, accessed: SystemTime) {
+        self.in_use += size;
+        self.queue.push(file.to_owned(), Reverse(accessed));
+        if let Some(old_size) = self.sizes.insert(file.to_owned(), size) {
+            // It's important that decreasing happens after
+            // increasing the size, to prevent an overflow.
+            self.in_use -= old_size;
+        }
+    }
+
+    /// Returns the least recently accessed file if the size of the cache exceeds
+    /// the limit.
+    ///
+    /// The entry is removed from the data structure, but the caller is responsible
+    /// to delete the file in the file system.
+    fn pop(&mut self) -> Option<PathBuf> {
+        if self.in_use > self.size_limit {
+            let (next, _) = self.queue.pop()?;
+            // panic safety: It is guaranteed that `queue` and `sizes` have the same keys.
+            let size = self.sizes.remove(&next).unwrap();
+            self.in_use -= size;
+            Some(next)
+        } else {
+            None
+        }
+    }
+
+    fn update(&mut self, file: &Path, access_time: SystemTime) -> bool {
+        self.queue
+            .change_priority(file, Reverse(access_time))
+            .is_some()
+    }
+
+    fn remove(&mut self, file: &Path) {
+        if self.queue.remove(file).is_none() {
+            return;
+        }
+        let size = self.sizes.remove(file).unwrap();
+        self.in_use -= size;
+    }
+}
+
+struct FsSizeLimiter {
+    limiter: Mutex<SizeLimiter>,
+}
+
+impl FsSizeLimiter {
+    fn get_metadata(file: &Path) -> io::Result<(SystemTime, u64)> {
+        let metadata = file.metadata()?;
+        let access_time = metadata
+            .accessed()
+            .or_else(|_| metadata.created())
+            .unwrap_or_else(|_| SystemTime::now());
+        let size = metadata.len();
+
+        Ok((access_time, size))
+    }
+
+    fn init_dir(limiter: &mut SizeLimiter, path: &Path) {
+        for entry in fs::read_dir(path).into_iter().flatten().flatten() {
+            if let Ok(file_type) = entry.file_type() {
+                if file_type.is_dir() {
+                    Self::init_dir(limiter, &entry.path())
+                } else if file_type.is_file() {
+                    let path = entry.path();
+                    if let Ok((access_time, size)) = Self::get_metadata(&path) {
+                        limiter.add(&path, size, access_time);
+                    }
+                }
+            }
+        }
+    }
+
+    fn add(&self, file: &Path, size: u64) {
+        self.limiter
+            .lock()
+            .unwrap()
+            .add(file, size, SystemTime::now());
+    }
+
+    fn touch(&self, file: &Path) -> bool {
+        self.limiter.lock().unwrap().update(file, SystemTime::now())
+    }
+
+    fn remove(&self, file: &Path) {
+        self.limiter.lock().unwrap().remove(file);
+    }
+
+    fn shrink(&self) {
+        while let Some(file) = self.limiter.lock().unwrap().pop() {
+            let _ = fs::remove_file(file);
+        }
+    }
+
+    fn new(path: &Path, limit: u64) -> Self {
+        let mut limiter = SizeLimiter::new(limit);
+        Self::init_dir(&mut limiter, path);
+
+        while let Some(file) = limiter.pop() {
+            let _ = fs::remove_file(file);
+        }
+
+        Self {
+            limiter: Mutex::new(limiter),
+        }
+    }
+}
+
 /// A cache for volume, credentials and audio files.
 #[derive(Clone)]
 pub struct Cache {
     credentials_location: Option<PathBuf>,
     volume_location: Option<PathBuf>,
     audio_location: Option<PathBuf>,
+    size_limiter: Option<Arc<FsSizeLimiter>>,
 }
 
+pub struct RemoveFileError(());
+
 impl Cache {
     pub fn new<P: AsRef<Path>>(
         system_location: Option<P>,
         audio_location: Option<P>,
+        size_limit: Option<u64>,
     ) -> io::Result<Self> {
         if let Some(location) = &system_location {
             fs::create_dir_all(location)?;
         }
 
+        let mut size_limiter = None;
+
         if let Some(location) = &audio_location {
             fs::create_dir_all(location)?;
+            if let Some(limit) = size_limit {
+                let limiter = FsSizeLimiter::new(location.as_ref(), limit);
+                size_limiter = Some(Arc::new(limiter));
+            }
         }
 
         let audio_location = audio_location.map(|p| p.as_ref().to_owned());
@@ -37,6 +180,7 @@ impl Cache {
             credentials_location,
             volume_location,
             audio_location,
+            size_limiter,
         };
 
         Ok(cache)
@@ -121,13 +265,21 @@ impl Cache {
     }
 
     pub fn file(&self, file: FileId) -> Option<File> {
-        File::open(self.file_path(file)?)
-            .map_err(|e| {
+        let path = self.file_path(file)?;
+        match File::open(&path) {
+            Ok(file) => {
+                if let Some(limiter) = self.size_limiter.as_deref() {
+                    limiter.touch(&path);
+                }
+                Some(file)
+            }
+            Err(e) => {
                 if e.kind() != ErrorKind::NotFound {
                     warn!("Error reading file from cache: {}", e)
                 }
-            })
-            .ok()
+                None
+            }
+        }
     }
 
     pub fn save_file<F: Read>(&self, file: FileId, contents: &mut F) {
@@ -142,37 +294,25 @@ impl Cache {
             .and_then(|_| File::create(&path))
             .and_then(|mut file| io::copy(contents, &mut file));
 
-        if let Err(e) = result {
-            if e.kind() == ErrorKind::Other {
-                // Perhaps there's no space left in the cache
-                // TODO: try to narrow down the error (platform-dependently)
-                info!("An error occured while writing to cache, trying to flush the cache");
-
-                if fs::remove_dir_all(self.audio_location.as_ref().unwrap())
-                    .and_then(|_| fs::create_dir_all(parent))
-                    .and_then(|_| File::create(&path))
-                    .and_then(|mut file| io::copy(contents, &mut file))
-                    .is_ok()
-                {
-                    // It worked, there's no need to print a warning
-                    return;
-                }
+        if let Ok(size) = result {
+            if let Some(limiter) = self.size_limiter.as_deref() {
+                limiter.add(&path, size);
+                limiter.shrink();
             }
-
-            warn!("Cannot save file to cache: {}", e)
         }
     }
 
-    pub fn remove_file(&self, file: FileId) -> bool {
-        if let Some(path) = self.file_path(file) {
-            if let Err(err) = fs::remove_file(path) {
-                warn!("Unable to remove file from cache: {}", err);
-                false
-            } else {
-                true
-            }
+    pub fn remove_file(&self, file: FileId) -> Result<(), RemoveFileError> {
+        let path = self.file_path(file).ok_or(RemoveFileError(()))?;
+
+        if let Err(err) = fs::remove_file(&path) {
+            warn!("Unable to remove file from cache: {}", err);
+            Err(RemoveFileError(()))
         } else {
-            false
+            if let Some(limiter) = self.size_limiter.as_deref() {
+                limiter.remove(&path);
+            }
+            Ok(())
         }
     }
 }

playback/src/player.rs

@@ -793,8 +793,7 @@ impl PlayerTrackLoader {
                         e
                     );
 
-                    // unwrap safety: The file is cached, so session must have a cache
-                    if !self.session.cache().unwrap().remove_file(file_id) {
+                    if self.session.cache().unwrap().remove_file(file_id).is_err() {
                         return None;
                     }
 

src/main.rs

@@ -367,7 +367,7 @@ fn get_setup(args: &[String]) -> Setup {
                 .map(|p| p.into());
         }
 
-        match Cache::new(system_dir, audio_dir) {
+        match Cache::new(system_dir, audio_dir, Some(50_000_000)) {
             Ok(cache) => Some(cache),
             Err(e) => {
                 warn!("Cannot create cache: {}", e);