fix(offline): guard inference paths with HF_HUB_OFFLINE (#503)

* fix(offline): guard inference paths with HF_HUB_OFFLINE (#462)

PR #443 wrapped the model *load* path with `force_offline_if_cached` so
cached models don't phone home at startup. The context manager restores
`HF_HUB_OFFLINE` on exit, which left inference paths (generate,
transcribe, voice-prompt creation) unguarded — and `qwen_tts`,
`mlx_audio`, and `transformers` perform lazy tokenizer/processor/config
lookups during inference. With internet on, those lookups are
near-instant and invisible; with internet off, `requests` hangs on DNS
or connect until the network returns. This is exactly what users in
#462 describe: model shows "Loaded", internet drops, generation
"thinks" forever, internet comes back, generation completes.

Chatterbox and LuxTTS don't exhibit this because their engine libs
resolve everything through already-cached paths at load time.

Fix: wrap each inference-sync body with `force_offline_if_cached(True,
...)`. Since inference only runs after a successful load, weights are
known to be on disk, so `is_cached=True` is unconditional.

Also adds the load-time guard that was missing from
`qwen_custom_voice_backend.py` — CustomVoice previously had no offline
protection at all.

Paths patched:
  - PyTorchTTSBackend.create_voice_prompt (create_voice_clone_prompt)
  - PyTorchTTSBackend.generate (generate_voice_clone)
  - PyTorchSTTBackend.transcribe (Whisper generate + decoder-prompt-ids)
  - MLXTTSBackend.generate (mlx_audio generate, all branches)
  - MLXSTTBackend.transcribe (mlx_audio whisper generate)
  - QwenCustomVoiceBackend._load_model_sync + generate

Does not address the secondary `check_model_inputs() missing 'func'`
error reported in the same issue — that's a `transformers` 5.x
version-skew bug on the install path, separate concern.

Fixes #462.

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>

* fix(offline): mutate cached HF constants + threadsafe refcount

Review feedback on the initial fix surfaced two real issues:

1. ``os.environ`` toggles alone don't flip offline mode.
   ``huggingface_hub.constants.HF_HUB_OFFLINE`` is read once at import
   time into a module-level bool; ``transformers.utils.hub._is_offline_mode``
   mirrors that bool at its own import time. The hot paths
   (``_http._default_backend_factory`` in huggingface_hub,
   ``is_offline_mode`` in transformers) read the cached bools — not the
   env — so mutating only ``os.environ`` was a no-op.

2. Race condition on concurrent inference. Two threads running inside
   ``force_offline_if_cached`` via ``asyncio.to_thread`` could have
   thread A's ``finally`` strip thread B's offline protection mid-run.

Rewrite the helper to:
  - mutate ``huggingface_hub.constants.HF_HUB_OFFLINE`` and
    ``transformers.utils.hub._is_offline_mode`` directly
  - refcount concurrent users under a single ``threading.RLock`` so a
    shared offline window is restored only when the last caller exits
  - still write ``os.environ`` for anything that reads it dynamically

Also addresses the unused-variable ruff flag on the Whisper transcribe
path (``audio, sr`` → ``audio, _sr``).

New unit tests cover the cached-constant mutation, env propagation,
no-op on ``is_cached=False``, nested contexts, and a threaded race
where a slow thread must retain offline mode after a peer exits.

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>

* fix(offline): atomic entry rollback + tidy test assertions

Review follow-up:

- Wrap the `_offline_refcount == 0` setup in a try/except so any failure
  during the cached-constant mutation (including unexpected non-ImportError
  like RuntimeError or AttributeError from a half-initialized module)
  rolls back *all* partial state before re-raising. Without this, a
  mid-setup crash could leave `huggingface_hub.constants.HF_HUB_OFFLINE`
  mutated but the refcount at 0 — a persistent offline flag outliving
  the process.
- Swap ruff-flagged Yoda comparisons in the new test file (SIM300) and
  add a module-level note warning that these tests mutate global state
  and are not safe under cross-process parallelism.

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>

* test(offline): make concurrency test deterministic and bounded

Replace the `sleep(0.15)` ordering hack with an explicit `threading.Event`
the fast thread sets in `finally`. The slow thread waits on that event
(bounded), then observes the flag — so we deterministically verify the
slow thread still sees offline mode after the fast thread has exited.

Also add timeouts to `barrier.wait()` and assert `not thread.is_alive()`
after the joins so the test can't hang on an unexpected failure path.

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>

---------

Co-authored-by: Claude Opus 4.7 (1M context) <[email protected]>
This commit is contained in:
Jamie Pine
2026-04-19 19:27:42 -07:00
committed by GitHub
co-authored by Claude Opus 4.7
parent 5964af5dea
commit 5aa1677a25
5 changed files with 339 additions and 102 deletions
+35 -23
View File
@@ -193,6 +193,8 @@ class MLXTTSBackend:
logger.info("Generating audio for text: %s", text)
model_name = f"qwen-tts-{self._current_model_size}"
def _generate_sync():
"""Run synchronous generation in thread pool."""
# MLX generate() returns a generator yielding GenerationResult objects
@@ -218,36 +220,40 @@ class MLXTTSBackend:
logger.warning("Regenerating without voice prompt.")
ref_audio = None
# Check if model supports voice cloning via generate method
# MLX API may support ref_audio parameter directly
try:
# Try with voice cloning parameters if supported
if ref_audio:
# Check if generate accepts ref_audio parameter
import inspect
# Model is loaded → weights are on disk. Force offline so
# lazy tokenizer/config lookups inside mlx_audio don't hang
# when the user is disconnected (issue #462).
with force_offline_if_cached(True, model_name):
# Check if model supports voice cloning via generate method
# MLX API may support ref_audio parameter directly
try:
# Try with voice cloning parameters if supported
if ref_audio:
# Check if generate accepts ref_audio parameter
import inspect
sig = inspect.signature(self.model.generate)
if "ref_audio" in sig.parameters:
# Generate with voice cloning
for result in self.model.generate(text, ref_audio=ref_audio, ref_text=ref_text, lang_code=lang):
audio_chunks.append(np.array(result.audio))
sample_rate = result.sample_rate
sig = inspect.signature(self.model.generate)
if "ref_audio" in sig.parameters:
# Generate with voice cloning
for result in self.model.generate(text, ref_audio=ref_audio, ref_text=ref_text, lang_code=lang):
audio_chunks.append(np.array(result.audio))
sample_rate = result.sample_rate
else:
# Fallback: generate without voice cloning
for result in self.model.generate(text, lang_code=lang):
audio_chunks.append(np.array(result.audio))
sample_rate = result.sample_rate
else:
# Fallback: generate without voice cloning
# No voice prompt, generate normally
for result in self.model.generate(text, lang_code=lang):
audio_chunks.append(np.array(result.audio))
sample_rate = result.sample_rate
else:
# No voice prompt, generate normally
except Exception as e:
# If voice cloning fails, try without it
logger.warning("Voice cloning failed, generating without voice prompt: %s", e)
for result in self.model.generate(text, lang_code=lang):
audio_chunks.append(np.array(result.audio))
sample_rate = result.sample_rate
except Exception as e:
# If voice cloning fails, try without it
logger.warning("Voice cloning failed, generating without voice prompt: %s", e)
for result in self.model.generate(text, lang_code=lang):
audio_chunks.append(np.array(result.audio))
sample_rate = result.sample_rate
# Concatenate all chunks
if audio_chunks:
@@ -341,6 +347,8 @@ class MLXSTTBackend:
"""
await self.load_model_async(model_size)
progress_model_name = f"whisper-{self.model_size}"
def _transcribe_sync():
"""Run synchronous transcription in thread pool."""
# MLX Whisper transcription using generate method
@@ -349,7 +357,11 @@ class MLXSTTBackend:
if language:
decode_options["language"] = language
result = self.model.generate(str(audio_path), **decode_options)
# Model is loaded → weights are on disk. Force offline so
# lazy tokenizer/config lookups don't hang when the user is
# disconnected (issue #462).
with force_offline_if_cached(True, progress_model_name):
result = self.model.generate(str(audio_path), **decode_options)
# Extract text from result
if isinstance(result, str):
+56 -39
View File
@@ -172,13 +172,19 @@ class PyTorchTTSBackend:
# This shouldn't happen in practice, but handle it
return {"prompt": cached_prompt}, True
model_name = f"qwen-tts-{self._current_model_size}"
def _create_prompt_sync():
"""Run synchronous voice prompt creation in thread pool."""
return self.model.create_voice_clone_prompt(
ref_audio=str(audio_path),
ref_text=reference_text,
x_vector_only_mode=False,
)
# Model is loaded → weights are on disk. Force offline so
# lazy tokenizer/config lookups inside qwen_tts don't hang
# when the user is disconnected (issue #462).
with force_offline_if_cached(True, model_name):
return self.model.create_voice_clone_prompt(
ref_audio=str(audio_path),
ref_text=reference_text,
x_vector_only_mode=False,
)
# Run blocking operation in thread pool
voice_prompt_items = await asyncio.to_thread(_create_prompt_sync)
@@ -221,19 +227,24 @@ class PyTorchTTSBackend:
# Load model
await self.load_model_async(None)
model_name = f"qwen-tts-{self._current_model_size}"
def _generate_sync():
"""Run synchronous generation in thread pool."""
# Set seed if provided
if seed is not None:
manual_seed(seed, self.device)
# Generate audio - this is the blocking operation
wavs, sample_rate = self.model.generate_voice_clone(
text=text,
voice_clone_prompt=voice_prompt,
language=LANGUAGE_CODE_TO_NAME.get(language, "auto"),
instruct=instruct,
)
# Model is loaded → weights are on disk. Force offline so
# lazy tokenizer/config lookups inside qwen_tts don't hang
# when the user is disconnected (issue #462).
with force_offline_if_cached(True, model_name):
wavs, sample_rate = self.model.generate_voice_clone(
text=text,
voice_clone_prompt=voice_prompt,
language=LANGUAGE_CODE_TO_NAME.get(language, "auto"),
instruct=instruct,
)
return wavs[0], sample_rate
# Run blocking inference in thread pool to avoid blocking event loop
@@ -331,40 +342,46 @@ class PyTorchSTTBackend:
"""
await self.load_model_async(model_size)
progress_model_name = f"whisper-{self.model_size}"
def _transcribe_sync():
"""Run synchronous transcription in thread pool."""
# Load audio
audio, sr = load_audio(audio_path, sample_rate=16000)
audio, _sr = load_audio(audio_path, sample_rate=16000)
# Process audio
inputs = self.processor(
audio,
sampling_rate=16000,
return_tensors="pt",
)
inputs = inputs.to(self.device)
# Generate transcription
# If language is provided, force it; otherwise let Whisper auto-detect
generate_kwargs = {}
if language:
forced_decoder_ids = self.processor.get_decoder_prompt_ids(
language=language,
task="transcribe",
# Model is loaded → weights are on disk. Force offline so
# `get_decoder_prompt_ids` and any lazy tokenizer lookups
# don't hang when the user is disconnected (issue #462).
with force_offline_if_cached(True, progress_model_name):
# Process audio
inputs = self.processor(
audio,
sampling_rate=16000,
return_tensors="pt",
)
generate_kwargs["forced_decoder_ids"] = forced_decoder_ids
inputs = inputs.to(self.device)
with torch.no_grad():
predicted_ids = self.model.generate(
inputs["input_features"],
**generate_kwargs,
)
# Generate transcription
# If language is provided, force it; otherwise let Whisper auto-detect
generate_kwargs = {}
if language:
forced_decoder_ids = self.processor.get_decoder_prompt_ids(
language=language,
task="transcribe",
)
generate_kwargs["forced_decoder_ids"] = forced_decoder_ids
# Decode
transcription = self.processor.batch_decode(
predicted_ids,
skip_special_tokens=True,
)[0]
with torch.no_grad():
predicted_ids = self.model.generate(
inputs["input_features"],
**generate_kwargs,
)
# Decode
transcription = self.processor.batch_decode(
predicted_ids,
skip_special_tokens=True,
)[0]
return transcription.strip()
+20 -13
View File
@@ -28,6 +28,7 @@ from .base import (
combine_voice_prompts as _combine_voice_prompts,
model_load_progress,
)
from ..utils.hf_offline_patch import force_offline_if_cached
logger = logging.getLogger(__name__)
@@ -104,18 +105,19 @@ class QwenCustomVoiceBackend:
model_path = self._get_model_path(model_size)
logger.info("Loading Qwen CustomVoice %s on %s...", model_size, self.device)
if self.device == "cpu":
self.model = Qwen3TTSModel.from_pretrained(
model_path,
torch_dtype=torch.float32,
low_cpu_mem_usage=False,
)
else:
self.model = Qwen3TTSModel.from_pretrained(
model_path,
device_map=self.device,
torch_dtype=torch.bfloat16,
)
with force_offline_if_cached(is_cached, model_name):
if self.device == "cpu":
self.model = Qwen3TTSModel.from_pretrained(
model_path,
torch_dtype=torch.float32,
low_cpu_mem_usage=False,
)
else:
self.model = Qwen3TTSModel.from_pretrained(
model_path,
device_map=self.device,
torch_dtype=torch.bfloat16,
)
self._current_model_size = model_size
self.model_size = model_size
@@ -184,6 +186,7 @@ class QwenCustomVoiceBackend:
await self.load_model_async(None)
speaker = voice_prompt.get("preset_voice_id") or QWEN_CV_DEFAULT_SPEAKER
model_name = f"qwen-custom-voice-{self._current_model_size}"
def _generate_sync():
if seed is not None:
@@ -203,7 +206,11 @@ class QwenCustomVoiceBackend:
if instruct:
kwargs["instruct"] = instruct
wavs, sample_rate = self.model.generate_custom_voice(**kwargs)
# Model is loaded → weights are on disk. Force offline so
# lazy tokenizer/config lookups inside qwen_tts don't hang
# when the user is disconnected (issue #462).
with force_offline_if_cached(True, model_name):
wavs, sample_rate = self.model.generate_custom_voice(**kwargs)
return wavs[0], sample_rate
audio, sample_rate = await asyncio.to_thread(_generate_sync)
+118
View File
@@ -0,0 +1,118 @@
"""
Unit tests for the ``force_offline_if_cached`` helper.
Verifies that the helper mutates the cached module constants in
``huggingface_hub.constants`` and ``transformers.utils.hub`` — not just
``os.environ`` — and that concurrent users are refcount-coordinated so
one thread's exit can't strip another thread's offline protection.
NOTE: These tests mutate process-global state in ``huggingface_hub.constants``
and ``transformers.utils.hub``. They are not safe under cross-process
parallelism (e.g. ``pytest-xdist`` with ``--dist=loadfile``/``loadscope``);
run this file serially.
"""
import os
import sys
import threading
from pathlib import Path
import pytest
sys.path.insert(0, str(Path(__file__).parent.parent))
from utils.hf_offline_patch import force_offline_if_cached # noqa: E402
def _hf_const():
import huggingface_hub.constants as hf_const
return hf_const
def _tf_hub():
import transformers.utils.hub as tf_hub
return tf_hub
def test_mutates_cached_huggingface_hub_constant():
original = _hf_const().HF_HUB_OFFLINE
with force_offline_if_cached(True, "t"):
assert _hf_const().HF_HUB_OFFLINE is True
assert original == _hf_const().HF_HUB_OFFLINE
def test_mutates_cached_transformers_constant():
original = _tf_hub()._is_offline_mode
with force_offline_if_cached(True, "t"):
assert _tf_hub()._is_offline_mode is True
assert original == _tf_hub()._is_offline_mode
def test_sets_env_variable():
original = os.environ.get("HF_HUB_OFFLINE")
with force_offline_if_cached(True, "t"):
assert "1" == os.environ.get("HF_HUB_OFFLINE")
assert original == os.environ.get("HF_HUB_OFFLINE")
def test_noop_when_not_cached():
before = _hf_const().HF_HUB_OFFLINE
with force_offline_if_cached(False, "t"):
assert before == _hf_const().HF_HUB_OFFLINE
def test_nested_contexts_respect_refcount():
original = _hf_const().HF_HUB_OFFLINE
with force_offline_if_cached(True, "outer"):
assert _hf_const().HF_HUB_OFFLINE is True
with force_offline_if_cached(True, "inner"):
assert _hf_const().HF_HUB_OFFLINE is True
# inner exit must not restore while outer is still active
assert _hf_const().HF_HUB_OFFLINE is True
assert original == _hf_const().HF_HUB_OFFLINE
def test_concurrent_threads_share_offline_window():
"""A slow thread must keep seeing offline mode even if a peer exits first."""
original = _hf_const().HF_HUB_OFFLINE
observations: list[bool] = []
errors: list[Exception] = []
barrier = threading.Barrier(2)
fast_exited = threading.Event()
def slow():
try:
with force_offline_if_cached(True, "slow"):
barrier.wait(timeout=5)
assert fast_exited.wait(timeout=5), "fast thread did not exit"
observations.append(_hf_const().HF_HUB_OFFLINE)
except Exception as exc: # noqa: BLE001
errors.append(exc)
def fast():
try:
with force_offline_if_cached(True, "fast"):
barrier.wait(timeout=5)
except Exception as exc: # noqa: BLE001
errors.append(exc)
finally:
fast_exited.set()
t_slow = threading.Thread(target=slow)
t_fast = threading.Thread(target=fast)
t_slow.start()
t_fast.start()
t_slow.join(timeout=5)
t_fast.join(timeout=5)
assert not t_slow.is_alive(), "slow thread did not finish"
assert not t_fast.is_alive(), "fast thread did not finish"
assert not errors, errors
assert observations == [True], "slow thread lost offline protection"
assert original == _hf_const().HF_HUB_OFFLINE
if __name__ == "__main__":
pytest.main([__file__, "-v"])
+110 -27
View File
@@ -6,6 +6,7 @@ are already downloaded. Must be imported BEFORE mlx_audio.
import logging
import os
import threading
from contextlib import contextmanager
from pathlib import Path
from typing import Optional, Union
@@ -13,13 +14,33 @@ from typing import Optional, Union
logger = logging.getLogger(__name__)
# huggingface_hub reads ``HF_HUB_OFFLINE`` once at import time into
# ``huggingface_hub.constants.HF_HUB_OFFLINE``; transformers mirrors that into
# ``transformers.utils.hub._is_offline_mode`` at *its* import time. Toggling
# ``os.environ`` after either module is imported does not flip those cached
# bools, and the hot paths (``_http._default_backend_factory``,
# ``transformers.utils.hub.is_offline_mode``) read the bools — not the env.
# We mutate the cached constants directly, guarded by a refcount so
# concurrent inference threads share a single offline window safely.
_offline_lock = threading.RLock()
_offline_refcount = 0
_saved_env: Optional[str] = None
_saved_hf_const: Optional[bool] = None
_saved_transformers_const: Optional[bool] = None
@contextmanager
def force_offline_if_cached(is_cached: bool, model_label: str = ""):
"""Context manager that sets ``HF_HUB_OFFLINE=1`` while loading a cached model.
"""Force offline mode for the duration of a cached-model operation.
Flips ``HF_HUB_OFFLINE`` in the process env **and** in the cached bools
inside ``huggingface_hub.constants`` / ``transformers.utils.hub`` so HTTP
adapters and offline-mode checks actually see the change. Uses a refcount
so multiple concurrent inference threads share a single offline window
and the last one to exit restores state.
If *is_cached* is ``False`` the block runs normally (network allowed).
If the offline load raises an error containing "offline" we automatically
retry with network access so a partially-cached model still works.
Args:
is_cached: Whether the model weights are already on disk.
@@ -29,34 +50,96 @@ def force_offline_if_cached(is_cached: bool, model_label: str = ""):
yield
return
original_value = os.environ.get("HF_HUB_OFFLINE")
os.environ["HF_HUB_OFFLINE"] = "1"
logger.info(
"[offline-guard] %s is cached — forcing HF_HUB_OFFLINE=1",
model_label or "model",
)
global _offline_refcount, _saved_env, _saved_hf_const, _saved_transformers_const
with _offline_lock:
if _offline_refcount == 0:
# Snapshot prior state, apply new state, roll back on *any*
# failure. Catching only ImportError here would let a partially
# broken install (RuntimeError, AttributeError from a half-init
# module, etc.) leave the cached HF constants mutated without
# bumping the refcount — a persistent offline leak that outlives
# the process and is miserable to debug.
prev_env = os.environ.get("HF_HUB_OFFLINE")
prev_hf: Optional[bool] = None
prev_tf: Optional[bool] = None
try:
try:
import huggingface_hub.constants as hf_const
prev_hf = hf_const.HF_HUB_OFFLINE
hf_const.HF_HUB_OFFLINE = True
except ImportError:
prev_hf = None
try:
import transformers.utils.hub as tf_hub
prev_tf = tf_hub._is_offline_mode
tf_hub._is_offline_mode = True
except ImportError:
prev_tf = None
os.environ["HF_HUB_OFFLINE"] = "1"
except BaseException:
# Roll back whatever we already changed, then re-raise so
# the caller sees the real failure.
if prev_hf is not None:
try:
import huggingface_hub.constants as hf_const
hf_const.HF_HUB_OFFLINE = prev_hf
except ImportError:
pass
if prev_tf is not None:
try:
import transformers.utils.hub as tf_hub
tf_hub._is_offline_mode = prev_tf
except ImportError:
pass
if prev_env is not None:
os.environ["HF_HUB_OFFLINE"] = prev_env
else:
os.environ.pop("HF_HUB_OFFLINE", None)
raise
_saved_env = prev_env
_saved_hf_const = prev_hf
_saved_transformers_const = prev_tf
logger.info(
"[offline-guard] %s is cached — forcing offline mode",
model_label or "model",
)
_offline_refcount += 1
try:
yield
except Exception as exc:
if "offline" in str(exc).lower():
logger.warning(
"[offline-guard] Offline load failed for %s, retrying with network: %s",
model_label or "model",
exc,
)
# Restore original env and retry — caller must wrap the load
# inside force_offline_if_cached so retrying here isn't possible.
# Instead, propagate a flag via the exception so the caller can
# decide. For simplicity we just let it fall through to the
# finally block and re-raise.
raise
raise
finally:
if original_value is not None:
os.environ["HF_HUB_OFFLINE"] = original_value
else:
os.environ.pop("HF_HUB_OFFLINE", None)
with _offline_lock:
_offline_refcount -= 1
if _offline_refcount == 0:
if _saved_env is not None:
os.environ["HF_HUB_OFFLINE"] = _saved_env
else:
os.environ.pop("HF_HUB_OFFLINE", None)
if _saved_hf_const is not None:
try:
import huggingface_hub.constants as hf_const
hf_const.HF_HUB_OFFLINE = _saved_hf_const
except ImportError:
pass
if _saved_transformers_const is not None:
try:
import transformers.utils.hub as tf_hub
tf_hub._is_offline_mode = _saved_transformers_const
except ImportError:
pass
_saved_env = None
_saved_hf_const = None
_saved_transformers_const = None
def patch_huggingface_hub_offline():