[ci skip] f1-stream: add stream health checker and HLS proxy (Phases 4-5)
Phase 4 - Stream Health and Fallback: - StreamHealthChecker with partial GET validation of m3u8 content - Bitrate extraction from BANDWIDTH tags - Response time measurement for quality ranking - Fallback ordering: live first, fastest response time first - GET /streams now only returns health-verified streams Phase 5 - HLS Proxy Core: - GET /proxy?url= - m3u8 playlist fetch with full URI rewriting - GET /relay?url= - chunked segment relay (never buffers full segment) - m3u8 rewriter handles master, variant, and segment URIs - Base64url encoding for URL parameters - CORS middleware for browser playback - Range header forwarding for seeking support
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Viktor Barzin
parent
00d9458dec
commit
9bf0523ea9
6 changed files with 926 additions and 20 deletions
229
stacks/f1-stream/files/backend/proxy.py
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229
stacks/f1-stream/files/backend/proxy.py
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"""HLS proxy - fetches upstream m3u8 playlists and relays media segments.
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Two core functions:
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1. Playlist proxy: fetches an upstream m3u8 playlist, rewrites all URIs
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to route through our /proxy and /relay endpoints, returns the rewritten
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playlist to the client.
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2. Segment relay: fetches an upstream media segment (TS, fMP4, init) and
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streams it to the client using chunked transfer encoding, never buffering
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the full segment in memory.
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All responses include CORS headers for browser playback.
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"""
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import logging
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from typing import AsyncGenerator
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import httpx
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from fastapi import HTTPException
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from backend.m3u8_rewriter import decode_url, rewrite_playlist
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logger = logging.getLogger(__name__)
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# Chunk size for relay streaming (64 KB)
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RELAY_CHUNK_SIZE = 65536
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# Timeout for upstream playlist fetches (seconds)
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PLAYLIST_TIMEOUT = 15.0
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# Timeout for upstream segment relay - longer because segments are bigger
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RELAY_TIMEOUT = 30.0
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# User-Agent for upstream requests
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USER_AGENT = (
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"Mozilla/5.0 (Windows NT 10.0; Win64; x64) "
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"AppleWebKit/537.36 (KHTML, like Gecko) "
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"Chrome/120.0.0.0 Safari/537.36"
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)
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async def proxy_playlist(encoded_url: str, proxy_base: str) -> str:
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"""Fetch an upstream m3u8 playlist and rewrite all URIs through our proxy.
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Args:
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encoded_url: Base64url-encoded URL of the upstream m3u8 playlist.
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proxy_base: The base URL of our proxy service for rewriting URIs
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(e.g., "https://f1.viktorbarzin.me").
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Returns:
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The rewritten m3u8 playlist text.
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Raises:
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HTTPException: If the URL can't be decoded, upstream fails, or
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content is not a valid HLS playlist.
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"""
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# Decode the URL
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try:
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url = decode_url(encoded_url)
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except Exception as e:
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logger.error("Failed to decode proxy URL: %s", e)
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raise HTTPException(status_code=400, detail=f"Invalid encoded URL: {e}")
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logger.info("Proxying playlist: %s", url)
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# Fetch the upstream playlist
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try:
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async with httpx.AsyncClient(
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timeout=PLAYLIST_TIMEOUT,
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follow_redirects=True,
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headers={
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"User-Agent": USER_AGENT,
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"Accept": "*/*",
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},
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) as client:
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response = await client.get(url)
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if response.status_code != 200:
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logger.warning(
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"Upstream playlist returned HTTP %d for %s",
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response.status_code,
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url,
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)
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raise HTTPException(
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status_code=502,
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detail=f"Upstream returned HTTP {response.status_code}",
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)
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content = response.text
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except httpx.TimeoutException:
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logger.error("Timeout fetching upstream playlist: %s", url)
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raise HTTPException(status_code=504, detail="Upstream playlist timeout")
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except httpx.HTTPError as e:
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logger.error("HTTP error fetching upstream playlist: %s - %s", url, e)
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raise HTTPException(status_code=502, detail=f"Upstream error: {e}")
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except HTTPException:
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raise
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except Exception as e:
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logger.exception("Unexpected error fetching playlist: %s", url)
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raise HTTPException(status_code=500, detail=f"Internal error: {e}")
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# Validate it looks like an m3u8 playlist
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if "#EXTM3U" not in content:
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logger.warning("Upstream response is not a valid m3u8 playlist: %s", url)
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raise HTTPException(
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status_code=502,
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detail="Upstream response is not a valid HLS playlist",
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)
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# Rewrite all URIs to go through our proxy
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rewritten = rewrite_playlist(content, url, proxy_base)
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logger.debug(
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"Proxied playlist from %s: %d bytes -> %d bytes",
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url,
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len(content),
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len(rewritten),
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)
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return rewritten
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async def relay_stream(
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encoded_url: str,
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range_header: str | None = None,
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) -> tuple[AsyncGenerator[bytes, None], dict[str, str], int]:
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"""Relay an upstream media segment as a chunked byte stream.
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Never buffers the full segment in memory. Streams chunks as they
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arrive from the upstream server.
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Args:
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encoded_url: Base64url-encoded URL of the upstream segment.
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range_header: Optional HTTP Range header from the client to
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forward to upstream.
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Returns:
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A tuple of (async_generator, headers_dict, status_code) where:
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- async_generator yields bytes chunks
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- headers_dict contains content-type and other relevant headers
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- status_code is the HTTP status (200 or 206)
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Raises:
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HTTPException: If the URL can't be decoded or upstream fails.
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"""
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# Decode the URL
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try:
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url = decode_url(encoded_url)
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except Exception as e:
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logger.error("Failed to decode relay URL: %s", e)
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raise HTTPException(status_code=400, detail=f"Invalid encoded URL: {e}")
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logger.debug("Relaying segment: %s", url)
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# Build upstream request headers
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headers = {
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"User-Agent": USER_AGENT,
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"Accept": "*/*",
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}
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if range_header:
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headers["Range"] = range_header
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# Create the client and stream - caller is responsible for cleanup
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# via the async generator protocol
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client = httpx.AsyncClient(
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timeout=RELAY_TIMEOUT,
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follow_redirects=True,
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)
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try:
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response = await client.send(
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client.build_request("GET", url, headers=headers),
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stream=True,
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)
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if response.status_code not in (200, 206):
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await response.aclose()
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await client.aclose()
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logger.warning(
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"Upstream segment returned HTTP %d for %s",
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response.status_code,
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url,
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)
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raise HTTPException(
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status_code=502,
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detail=f"Upstream returned HTTP {response.status_code}",
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)
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# Collect relevant response headers to forward
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response_headers: dict[str, str] = {}
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content_type = response.headers.get("content-type", "video/mp2t")
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response_headers["Content-Type"] = content_type
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if "content-length" in response.headers:
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response_headers["Content-Length"] = response.headers["content-length"]
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if "content-range" in response.headers:
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response_headers["Content-Range"] = response.headers["content-range"]
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status_code = response.status_code
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async def _stream_chunks() -> AsyncGenerator[bytes, None]:
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"""Yield chunks from the upstream response, then clean up."""
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try:
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async for chunk in response.aiter_bytes(chunk_size=RELAY_CHUNK_SIZE):
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yield chunk
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except Exception as e:
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logger.error("Error streaming segment from %s: %s", url, e)
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finally:
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await response.aclose()
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await client.aclose()
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return _stream_chunks(), response_headers, status_code
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except HTTPException:
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raise
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except httpx.TimeoutException:
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await client.aclose()
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logger.error("Timeout relaying segment: %s", url)
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raise HTTPException(status_code=504, detail="Upstream segment timeout")
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except httpx.HTTPError as e:
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await client.aclose()
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logger.error("HTTP error relaying segment: %s - %s", url, e)
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raise HTTPException(status_code=502, detail=f"Upstream error: {e}")
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except Exception as e:
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await client.aclose()
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logger.exception("Unexpected error relaying segment: %s", url)
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raise HTTPException(status_code=500, detail=f"Internal error: {e}")
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