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perf: eliminate double disk read in thumbnail generation (read-once buffer)

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This commit is contained in:
Dionisio
2026-02-26 00:32:02 +01:00
parent 71727faab4
commit fb4eaf2cf9
1 changed files with 41 additions and 24 deletions
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src/infrastructure/services/thumbnail_service.rs
+41 -24
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@@ -192,7 +192,11 @@ impl ThumbnailService {
}
// 2. Generate thumbnail (CPU-bound, runs in spawn_blocking)
tracing::info!("🎨 Generating thumbnail: {} {:?}", file_id_owned, size);
tracing::info!(
"🎨 Generating thumbnail: {} {:?}",
file_id_owned,
size
);
match self.generate_thumbnail(&original_owned, size).await {
Ok(bytes) => {
// Save to disk (best-effort — don't fail the request)
@@ -241,16 +245,18 @@ impl ThumbnailService {
let max_dim = size.max_dimension();
// Acquire semaphore permit — bounds peak RAM from concurrent decodes
let _permit = self
.decode_semaphore
.acquire()
.await
let _permit = self.decode_semaphore.acquire().await
.map_err(|_| ThumbnailError::TaskError("Decode semaphore closed".into()))?;
// Run image processing in blocking thread pool
let result = tokio::task::spawn_blocking(move || -> Result<Vec<u8>, ThumbnailError> {
// Safety check: read dimensions from headers only (no full decode)
let (w, h) = image::ImageReader::open(&path)
// Single read: load file once into memory, then work from the buffer
let data = std::fs::read(&path)
.map_err(|e| ThumbnailError::ImageError(e.to_string()))?;
// Safety check: read dimensions from in-memory buffer (no 2nd I/O)
let (w, h) = image::ImageReader::new(std::io::Cursor::new(&data))
.with_guessed_format()
.map_err(|e| ThumbnailError::ImageError(e.to_string()))?
.into_dimensions()
.map_err(|e| ThumbnailError::ImageError(e.to_string()))?;
@@ -261,8 +267,9 @@ impl ThumbnailService {
)));
}
// Load image (full decode — now safe within semaphore + resolution guard)
let img = image::open(&path).map_err(|e| ThumbnailError::ImageError(e.to_string()))?;
// Full decode from the same in-memory buffer (no 2nd disk read)
let img = image::load_from_memory(&data)
.map_err(|e| ThumbnailError::ImageError(e.to_string()))?;
// Calculate new dimensions preserving aspect ratio
let (orig_width, orig_height) = (img.width(), img.height());
@@ -277,9 +284,9 @@ impl ThumbnailService {
// Adaptive filter: faster filters for smaller sizes where
// quality difference vs Lanczos3 is imperceptible
let filter = match size {
ThumbnailSize::Icon => FilterType::Triangle, // 150px — max speed
ThumbnailSize::Icon => FilterType::Triangle, // 150px — max speed
ThumbnailSize::Preview => FilterType::CatmullRom, // 400px — good balance
ThumbnailSize::Large => FilterType::CatmullRom, // 800px — sufficient quality
ThumbnailSize::Large => FilterType::CatmullRom, // 800px — sufficient quality
};
let thumbnail = img.resize(new_width, new_height, filter);
@@ -311,10 +318,7 @@ impl ThumbnailService {
let _permit = match self.decode_semaphore.acquire().await {
Ok(p) => p,
Err(_) => {
tracing::warn!(
"Decode semaphore closed, skipping thumbnails for {}",
file_id
);
tracing::warn!("Decode semaphore closed, skipping thumbnails for {}", file_id);
return;
}
};
@@ -323,8 +327,13 @@ impl ThumbnailService {
// Single spawn_blocking: 1 read + 1 decode + 3 resize + 3 encode
let results = tokio::task::spawn_blocking(move || {
// Safety check: read dimensions from headers only (no full decode)
let (w, h) = image::ImageReader::open(&path)
// Single read: load file once into memory
let data = std::fs::read(&path)
.map_err(|e| ThumbnailError::ImageError(e.to_string()))?;
// Safety check: read dimensions from in-memory buffer (no 2nd I/O)
let (w, h) = image::ImageReader::new(std::io::Cursor::new(&data))
.with_guessed_format()
.map_err(|e| ThumbnailError::ImageError(e.to_string()))?
.into_dimensions()
.map_err(|e| ThumbnailError::ImageError(e.to_string()))?;
@@ -335,8 +344,9 @@ impl ThumbnailService {
)));
}
let img =
image::open(&path).map_err(|e| ThumbnailError::ImageError(e.to_string()))?;
// Full decode from the same in-memory buffer (no 2nd disk read)
let img = image::load_from_memory(&data)
.map_err(|e| ThumbnailError::ImageError(e.to_string()))?;
let (orig_w, orig_h) = (img.width(), img.height());
@@ -354,15 +364,18 @@ impl ThumbnailService {
};
let filter = match size {
ThumbnailSize::Icon => FilterType::Triangle,
ThumbnailSize::Icon => FilterType::Triangle,
ThumbnailSize::Preview => FilterType::CatmullRom,
ThumbnailSize::Large => FilterType::CatmullRom,
ThumbnailSize::Large => FilterType::CatmullRom,
};
let thumb = img.resize(new_w, new_h, filter);
let mut buf = Vec::new();
thumb
.write_to(&mut std::io::Cursor::new(&mut buf), ImageFormat::WebP)
.write_to(
&mut std::io::Cursor::new(&mut buf),
ImageFormat::WebP,
)
.map_err(|e| ThumbnailError::ImageError(e.to_string()))?;
Ok((size, Bytes::from(buf)))
@@ -375,11 +388,15 @@ impl ThumbnailService {
let thumbnails = match results {
Ok(Ok(t)) => t,
Ok(Err(e)) => {
tracing::warn!("Thumbnail generation failed for {}: {}", file_id, e);
tracing::warn!(
"Thumbnail generation failed for {}: {}", file_id, e
);
return;
}
Err(e) => {
tracing::warn!("Thumbnail task panicked for {}: {}", file_id, e);
tracing::warn!(
"Thumbnail task panicked for {}: {}", file_id, e
);
return;
}
};