Alex 4472fbe8cf Download overhaul - DNS fallback, bypasser enhancements, revamped error handling, better frontend UX (#336) ...

## Changelog

### 🌐 Network Resilience

- **Auto DNS rotation**: New `CUSTOM_DNS=auto` mode (now default) starts
with system DNS and automatically rotates through Cloudflare, Google,
Quad9, and OpenDNS when failures are detected. DNS results are cached to
improve performance.
- **Mirror failover**: Anna's Archive requests automatically fail over
between mirrors (.org, .se, .li) when one is unreachable
- **Round-robin source distribution**: Concurrent downloads are
distributed across different AA partner servers to avoid rate limiting

### 📥 Download Reliability

- **Much more reliable downloads**: Improved parsing of Anna's Archive
pages, smarter source prioritization, and better retry logic with
exponential backoff
- **Download resume support**: Interrupted downloads can now resume from
where they left off (if the server supports Range requests)
- **Cookie sharing**: Cloudflare bypass cookies are extracted and shared
with subsequent requests, often avoiding the need for re-bypass entirely
- **Stall detection**: Downloads with no progress for 5 minutes are
automatically cancelled and retried
- **Staggered concurrent downloads**: Small delays between starting
concurrent downloads to avoid hitting rate limits
- **Source failure tracking**: After multiple failures from the same
source type (e.g., Libgen), that source is temporarily skipped
- **Lazy welib loading**: Welib sources are fetched as a fallback only
when primary sources fail (unless `PRIORITIZE_WELIB` is enabled)

### 🛡️ Cloudflare & Protection Bypass

- **DDOS-Guard support**: Internal bypasser now detects and handles
DDOS-Guard challenges with dedicated bypass strategies
- **Cancellation support**: Bypass operations can now be cancelled
mid-operation when user cancels a download
- **Smart warmup**: Chrome driver is pre-warmed when first client
connects (controlled by `BYPASS_WARMUP_ON_CONNECT` env var) and shuts
down after periods of inactivity

### 🔌 External Bypasser (FlareSolverr)

- **Improved resilience**: Retry with exponential backoff, mirror/DNS
rotation on failure, and proper timeout handling
- **Cancellation support**: External bypasser operations respect
cancellation flags

### 🖥️ Web UI Improvements

- **Simplified download status**: Removed intermediate states
(bypassing, verifying, ingesting) — now just shows Queued → Resolving →
Downloading → Complete
- **Status messages**: Downloads show detailed status like "Trying
Anna's Archive (Server 3)" or "Server busy, trying next...", or live
waitlist countdowns.
- **Improved download sidebar**:
  - Downloads sorted by add time (newest first)
  - X button moved to top-right corner for better UX
  - Wave animation on in-progress items
  - Error messages shown directly on failed items
  - X button on completed/errored items clears them from the list

### ⚙️ Configuration Changes

- **`CUSTOM_DNS=auto`** is now the default (previously empty/system DNS)
- **`DOWNLOAD_PROGRESS_UPDATE_INTERVAL`** default changed from 5s to 1s
for smoother progress
- **`BYPASS_WARMUP_ON_CONNECT`** (default: true) — warm up Chrome when
first client connects

### 🐛 Bug Fixes

- **Download cancellation actually works**: Fixed issue where cancelling
downloads didn't properly stop in-progress operations
- **WELIB prioritization**: Fixed `PRIORITIZE_WELIB` not being respected
- **File exists handling**: Downloads to same filename now get `_1`,
`_2` suffix instead of overwriting
- **Empty search results**: "No books found" now returns empty list
instead of throwing exception
- **Search unavailable error**: Network/mirror failures during search
now return proper 503 error to client

2025-12-14 21:18:05 -05:00

..

E2E_test.py

Download overhaul - DNS fallback, bypasser enhancements, revamped error handling, better frontend UX (#336)

2025-12-14 21:18:05 -05:00