200 lines
6.9 KiB
Rust
200 lines
6.9 KiB
Rust
//! Low memory caching stuff
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use std::path::PathBuf;
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use std::str::FromStr;
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use std::sync::atomic::{AtomicU64, Ordering};
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use std::sync::Arc;
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use async_trait::async_trait;
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use futures::StreamExt;
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use log::{warn, LevelFilter};
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use sqlx::{sqlite::SqliteConnectOptions, ConnectOptions, SqlitePool};
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use tokio::{
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fs::remove_file,
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sync::mpsc::{channel, unbounded_channel, Sender, UnboundedSender},
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};
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use tokio_stream::wrappers::ReceiverStream;
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use super::{BoxedImageStream, Cache, CacheError, CacheKey, CacheStream, ImageMetadata};
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pub struct LowMemCache {
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disk_path: PathBuf,
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disk_cur_size: AtomicU64,
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file_size_channel_sender: UnboundedSender<u32>,
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db_update_channel_sender: Sender<DbMessage>,
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}
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enum DbMessage {
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Get(Arc<CacheKey>),
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Put(PathBuf, u32),
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}
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impl LowMemCache {
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/// Constructs a new low memory cache at the provided path and capaci ty.
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/// This internally spawns a task that will wait for filesystem
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/// notifications when a file has been written.
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#[allow(clippy::new_ret_no_self)]
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pub async fn new(disk_max_size: u64, disk_path: PathBuf) -> Arc<Box<dyn Cache>> {
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let (file_size_tx, mut file_size_rx) = unbounded_channel();
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let (db_tx, db_rx) = channel(128);
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let db_pool = {
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let db_url = format!("sqlite:{}/metadata.sqlite", disk_path.to_str().unwrap());
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let mut options = SqliteConnectOptions::from_str(&db_url)
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.unwrap()
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.create_if_missing(true);
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options.log_statements(LevelFilter::Trace);
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let db = SqlitePool::connect_with(options).await.unwrap();
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// Run db init
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sqlx::query_file!("./db_queries/init.sql")
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.execute(&mut db.acquire().await.unwrap())
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.await
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.unwrap();
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db
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};
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let new_self: Arc<Box<dyn Cache>> = Arc::new(Box::new(Self {
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disk_path,
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disk_cur_size: AtomicU64::new(0),
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file_size_channel_sender: file_size_tx,
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db_update_channel_sender: db_tx,
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}));
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// Spawns a new task that continuously listens for events received by
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// the channel, which informs the low memory cache the total size of the
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// item that was put into the cache.
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let new_self_0 = Arc::clone(&new_self);
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let db_pool_0 = db_pool.clone();
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tokio::spawn(async move {
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let db_pool = db_pool_0;
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let max_on_disk_size = disk_max_size / 20 * 19;
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// This will never return None, effectively a loop
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while let Some(new_size) = file_size_rx.recv().await {
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new_self_0.increase_usage(new_size);
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if new_self_0.on_disk_size() >= max_on_disk_size {
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let mut conn = db_pool.acquire().await.unwrap();
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let items = sqlx::query!(
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"select id, size from Images order by accessed asc limit 1000"
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)
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.fetch_all(&mut conn)
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.await
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.unwrap();
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let mut size_freed = 0;
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for item in items {
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size_freed += item.size as u64;
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tokio::spawn(remove_file(item.id));
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}
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new_self_0.decrease_usage(size_freed);
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}
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}
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});
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// Spawn a new task that will listen for updates to the db.
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tokio::spawn(async move {
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let db_pool = db_pool;
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let mut recv_stream = ReceiverStream::new(db_rx).ready_chunks(128);
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while let Some(messages) = recv_stream.next().await {
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let now = chrono::Utc::now();
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let mut transaction = db_pool.begin().await.unwrap();
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for message in messages {
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match message {
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DbMessage::Get(entry) => {
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let key = entry.to_string();
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let query = sqlx::query!(
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"update Images set accessed = ? where id = ?",
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now,
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key
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)
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.execute(&mut transaction)
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.await;
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if let Err(e) = query {
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warn!("Failed to update timestamp in db for {}: {}", key, e);
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}
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}
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DbMessage::Put(entry, size) => {
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let key = entry.as_os_str().to_str();
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let query = sqlx::query!(
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"insert into Images (id, size, accessed) values (?, ?, ?)",
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key,
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size,
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now,
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)
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.execute(&mut transaction)
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.await;
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if let Err(e) = query {
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warn!("Failed to add {:?} to db: {}", key, e);
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}
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}
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}
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}
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transaction.commit().await.unwrap();
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}
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});
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new_self
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}
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}
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#[async_trait]
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impl Cache for LowMemCache {
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async fn get(
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&self,
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key: Arc<CacheKey>,
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) -> Option<Result<(CacheStream, ImageMetadata), CacheError>> {
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let channel = self.db_update_channel_sender.clone();
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let key_0 = Arc::clone(&key);
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tokio::spawn(async move { channel.send(DbMessage::Get(key_0)).await });
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let path = self
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.disk_path
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.clone()
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.join(PathBuf::from(Arc::clone(&key).as_ref()));
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super::fs::read_file(&path)
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.await
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.map(|res| res.map_err(Into::into))
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}
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async fn put(
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&self,
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key: Arc<CacheKey>,
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image: BoxedImageStream,
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metadata: ImageMetadata,
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) -> Result<CacheStream, CacheError> {
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let channel = self.db_update_channel_sender.clone();
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let path = self.disk_path.clone().join(PathBuf::from(key.as_ref()));
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let path_0 = path.clone();
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let db_callback = |size: u32| async move {
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let _ = channel.send(DbMessage::Put(path_0, size)).await;
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};
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super::fs::write_file(
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&path,
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image,
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metadata,
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self.file_size_channel_sender.clone(),
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db_callback,
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)
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.await
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.map_err(Into::into)
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}
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#[inline]
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fn increase_usage(&self, amt: u32) {
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self.disk_cur_size.fetch_add(amt as u64, Ordering::Release);
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}
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#[inline]
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fn on_disk_size(&self) -> u64 {
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(self.disk_cur_size.load(Ordering::Acquire) + 4095) / 4096 * 4096
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}
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fn decrease_usage(&self, amt: u64) {
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self.disk_cur_size.fetch_sub(amt, Ordering::Release);
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}
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}
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