Fix UI unresponsiveness during downloads (Issue #54) #71
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This commit addresses the UI freezing issue that occurs when multiple downloads are running simultaneously. Changes: - Add UI update throttling (500ms) to prevent excessive re-renders - Add file manager refresh throttling (2s) for expensive operations - Implement log batching in YoutubeDownloadQueueService (flushes every 5s instead of writing to DB on every log line) - Replace fire-and-forget async event handlers in YtdlpService with proper Channel-based log processing - Fix un-awaited InvokeAsync calls in Blazor components - Add 20 unit tests for YoutubeDownloadQueueService including thread safety tests for concurrent log appends The key improvements reduce database writes during YouTube downloads from 100+/download to ~5-10/download, and limit UI renders to 2/second max instead of unbounded updates.
Summary of ChangesHello @thromel, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed! This pull request significantly improves the application's UI responsiveness and backend performance, particularly when handling multiple concurrent YouTube downloads. It addresses several identified root causes of unresponsiveness, including excessive UI re-renders and frequent database writes, by introducing intelligent throttling mechanisms and a more efficient asynchronous log processing pipeline. The changes aim to provide a smoother user experience and reduce the load on the database during intensive operations. Highlights
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Code Review
This is an excellent pull request that addresses critical UI performance issues through well-thought-out changes like UI throttling, log batching, and safer async handling. The introduction of comprehensive unit tests is also a great addition. My review focuses on a couple of subtle but important concurrency issues in the new log batching mechanism to ensure its robustness and prevent data loss.
SaveHere/SaveHere.Tests/Services/YoutubeDownloadQueueServiceTests.cs
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CI NoteThe failing test The error is: This is a known issue with All 20 new tests added in this PR pass successfully, and all other existing tests pass (127/128 passed, 1 pre-existing failure). |
- Add SemaphoreSlim to prevent race conditions when multiple threads trigger FlushLogsAsync simultaneously for the same itemId - Re-queue logs on DbUpdateConcurrencyException instead of silently discarding them, preventing potential data loss - Strengthen test assertion to verify batching behavior by checking that subsequent logs within the flush interval are not immediately persisted - Properly dispose of SemaphoreSlim in CleanupLogsForItem
The test was failing in CI because it accessed _factory.Services which triggers WebApplicationFactory to start the server, causing a FileNotFoundException for MvcTestingAppManifest.json. The test doesn't actually need the factory - it only tests the local TestHttpMessageHandler. Removed the unnecessary factory dependency to fix the CI failure.
The test was using 'invalid<>name.txt' which contains characters that are invalid on Windows but valid on Linux, causing the test to fail in CI. Changed to use 'invalid/name.txt' which contains a path separator that is invalid in filenames on all platforms.
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Summary
This PR fixes the UI freezing/unresponsiveness issue reported in #54 where components become unresponsive while downloading, particularly with multiple YouTube downloads.
Root Causes Identified
StateHasChangedcalls on every progress update)InvokeAsynccalls causing update queue buildupChanges Made
UI Components (
DownloadFromDirectLink.razor,DownloadVideoAudio.razor):StateHasChangedcallsInvokeAsynccallsInvokeAsyncpatternsYoutubeDownloadQueueService:
ConcurrentQueue- logs are queued in memory and flushed to database every 5 seconds instead of on every log lineFlushLogsAsync()method for explicit flushing on download completionYtdlpService:
async voidevent handlers with properChannel<T>-based log processingPerformance Improvements
Tests Added
YoutubeDownloadQueueServiceTest Plan
Fixes #54