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fix: handle SoundCloud API 5xx errors with client_id refresh, backoff, and cursor fallback

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SoundCloud began rejecting the fabricated pagination cursor with 500
errors. Fixed cursor user_id padding (zfill 22→20) to match the
documented format, added 5xx retry with exponential backoff in _api_get,
and added a fallback in fetch_likes that drops the fabricated cursor
when it causes persistent 500s.

Made-with: Cursor
This commit is contained in:
cottongin
2026-03-25 08:20:20 -04:00
parent b353f606e5
commit a328684af0
2 changed files with 100 additions and 7 deletions
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30
src/ntr_fetcher/soundcloud.py
View File

@@ -1,3 +1,4 @@
import asyncio
import json
import logging
import re
@@ -17,7 +18,7 @@ HYDRATION_PATTERN = re.compile(r"__sc_hydration\s*=\s*(\[.*?\])\s*;", re.DOTALL)
def _build_cursor(until: datetime, user_id: int) -> str:
ts = until.strftime("%Y-%m-%dT%H:%M:%S.000Z")
padded_user = str(user_id).zfill(22)
padded_user = str(user_id).zfill(20)
return f"{ts},user-track-likes,000-{padded_user}-99999999999999999999"
@@ -55,19 +56,27 @@ class SoundCloudClient:
params = dict(params or {})
params["client_id"] = client_id
for attempt in range(3):
max_attempts = 3
for attempt in range(max_attempts):
resp = await self._http.get(url, params=params)
if resp.status_code == 401:
logger.warning("Got 401 from SoundCloud API, refreshing client_id (attempt %d)", attempt + 1)
if resp.status_code == 401 or resp.status_code >= 500:
logger.warning(
"Got %d from SoundCloud API, refreshing client_id (attempt %d/%d)",
resp.status_code, attempt + 1, max_attempts,
)
self.invalidate_client_id()
if resp.status_code >= 500:
await asyncio.sleep(2 ** attempt)
client_id = await self._extract_client_id()
params["client_id"] = client_id
continue
resp.raise_for_status()
return resp
raise httpx.HTTPStatusError(
"Failed after 3 attempts (401)",
f"Failed after {max_attempts} attempts (last status: {resp.status_code})",
request=resp.request,
response=resp,
)
@@ -86,15 +95,24 @@ class SoundCloudClient:
until: datetime,
limit: int = 50,
) -> list[Track]:
cursor = _build_cursor(until, user_id)
cursor: str | None = _build_cursor(until, user_id)
collected: list[Track] = []
used_fabricated_cursor = True
while True:
params: dict = {"limit": limit}
if cursor:
params["offset"] = cursor
try:
resp = await self._api_get(f"{API_BASE}/users/{user_id}/likes", params=params)
except httpx.HTTPStatusError as exc:
if used_fabricated_cursor and cursor and exc.response.status_code >= 500:
logger.warning("Fabricated cursor rejected (HTTP %d), retrying without cursor", exc.response.status_code)
cursor = None
used_fabricated_cursor = False
continue
raise
data = resp.json()
collection = data.get("collection", [])

75
tests/test_soundcloud.py
View File

@@ -1,6 +1,8 @@
import re
from datetime import datetime, timezone
from unittest.mock import patch
import httpx
import pytest
from ntr_fetcher.soundcloud import SoundCloudClient
@@ -151,3 +153,76 @@ async def test_fetch_likes_retries_on_401(httpx_mock):
until=datetime(2026, 3, 10, 0, 0, 0, tzinfo=timezone.utc),
)
assert len(tracks) == 1
@pytest.mark.asyncio
@patch("ntr_fetcher.soundcloud.asyncio.sleep", return_value=None)
async def test_fetch_likes_retries_on_500(mock_sleep, httpx_mock):
httpx_mock.add_response(url="https://soundcloud.com", text=FAKE_HTML)
httpx_mock.add_response(
url=re.compile(r"https://api-v2\.soundcloud\.com/users/206979918/likes.*"),
status_code=500,
)
httpx_mock.add_response(
url="https://soundcloud.com",
text=FAKE_HTML.replace("test_client_id_abc123", "fresh_client_id_789"),
)
httpx_mock.add_response(
url=re.compile(r"https://api-v2\.soundcloud\.com/users/206979918/likes.*"),
json=FAKE_LIKES_RESPONSE,
)
client = SoundCloudClient()
tracks = await client.fetch_likes(
user_id=206979918,
since=datetime(2026, 3, 1, 0, 0, 0, tzinfo=timezone.utc),
until=datetime(2026, 3, 10, 0, 0, 0, tzinfo=timezone.utc),
)
assert len(tracks) == 1
mock_sleep.assert_called_once_with(1)
@pytest.mark.asyncio
@patch("ntr_fetcher.soundcloud.asyncio.sleep", return_value=None)
async def test_fetch_likes_falls_back_to_no_cursor_on_persistent_500(mock_sleep, httpx_mock):
"""When the fabricated cursor causes persistent 500s, fall back to no cursor."""
httpx_mock.add_response(url="https://soundcloud.com", text=FAKE_HTML)
for _ in range(3):
httpx_mock.add_response(
url=re.compile(r"https://api-v2\.soundcloud\.com/users/206979918/likes.*"),
status_code=500,
)
httpx_mock.add_response(url="https://soundcloud.com", text=FAKE_HTML)
httpx_mock.add_response(
url=re.compile(r"https://api-v2\.soundcloud\.com/users/206979918/likes.*"),
json=FAKE_LIKES_RESPONSE,
)
client = SoundCloudClient()
tracks = await client.fetch_likes(
user_id=206979918,
since=datetime(2026, 3, 1, 0, 0, 0, tzinfo=timezone.utc),
until=datetime(2026, 3, 10, 0, 0, 0, tzinfo=timezone.utc),
)
assert len(tracks) == 1
assert mock_sleep.call_count == 3
@pytest.mark.asyncio
@patch("ntr_fetcher.soundcloud.asyncio.sleep", return_value=None)
async def test_fetch_likes_raises_when_all_requests_fail_500(mock_sleep, httpx_mock):
"""When both fabricated cursor and cursorless fallback fail, the error propagates."""
httpx_mock.add_response(url="https://soundcloud.com", text=FAKE_HTML)
# 3 retries for fabricated cursor + 3 retries for cursorless fallback = 6 API calls
for _ in range(6):
httpx_mock.add_response(
url=re.compile(r"https://api-v2\.soundcloud\.com/users/206979918/likes.*"),
status_code=500,
)
httpx_mock.add_response(url="https://soundcloud.com", text=FAKE_HTML)
client = SoundCloudClient()
with pytest.raises(httpx.HTTPStatusError, match="500"):
await client.fetch_likes(
user_id=206979918,
since=datetime(2026, 3, 1, 0, 0, 0, tzinfo=timezone.utc),
until=datetime(2026, 3, 10, 0, 0, 0, tzinfo=timezone.utc),
)
assert mock_sleep.call_count == 6