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feat: add explicit --offline mode for air-gapped clusters (#1525)

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## Motivation

Closes #1510

There is currently no reliable way to run exo on an air-gapped or offline cluster where models are pre-staged on local disks. The two existing mechanisms — `--no-downloads` and `HF_HUB_OFFLINE=1` — each cover only a subset of the problem:

1. **`--no-downloads` blocks model loading**: When passed, `DownloadCoordinator` is not created. No `NodeDownloadProgress` events are ever emitted, so `_model_needs_download()` in `plan.py` perpetually returns `DownloadModel`, short-circuiting `_load_model()` and preventing the model from ever being loaded.

2. **`HF_HUB_OFFLINE=1` doesn't cover exo's aiohttp code**: exo's download pipeline primarily uses raw `aiohttp` for HTTP operations (file list fetching, file downloads, HEAD verification), not the `huggingface_hub` library. These calls will attempt connections and time out on air-gapped networks.

3. **`skip_internet` is not propagated to `download_file_with_retry()`**: Even when `internet_connection = False`, the `_download_file()` function still makes HTTP HEAD calls via `file_meta()` to verify local files and unconditionally attempts downloads for missing files.

## Changes

### `src/exo/main.py`
- Add `--offline` flag to `Args` with env var detection (`EXO_OFFLINE=1`, `HF_HUB_OFFLINE=1`)
- Pass `offline` to `DownloadCoordinator` at creation and re-creation (election loop)

### `src/exo/download/coordinator.py`
- Add `offline: bool = False` field
- In offline mode: set `internet_connection = False` immediately in `__post_init__`, skip `_test_internet_connection()` ping (avoids 3s timeout), skip `_check_internet_connection` periodic loop
- In `_start_download()`: if model is not fully available locally, emit `DownloadFailed` with clear message instead of starting a download task

### `src/exo/download/download_utils.py`
- Add `skip_internet: bool` parameter to `download_file_with_retry()` and `_download_file()`
- When `skip_internet=True` in `_download_file()`: return local file immediately without HTTP HEAD verification; raise `FileNotFoundError` for missing files
- Propagate `skip_internet` from `download_shard()` to `download_file_with_retry()`

### `src/exo/download/tests/test_offline_mode.py` (new)
- 8 tests covering `_download_file`, `download_file_with_retry`, and `fetch_file_list_with_cache` in offline mode

## Why It Works

Unlike `--no-downloads` which disables `DownloadCoordinator` entirely, `--offline` keeps the coordinator running in a restricted mode. The existing `_emit_existing_download_progress()` disk scanner still runs every 60 seconds, emitting `DownloadCompleted` events for pre-staged models. These events flow through the event-sourcing pipeline and populate `state.downloads`, which unblocks `_model_needs_download()` in `plan.py` — no changes to the planning logic required.

```
--offline flag
  → DownloadCoordinator (offline mode)
    → Skip 1.1.1.1 ping, internet_connection = False
    → _emit_existing_download_progress scans disk
      → Emits DownloadCompleted for pre-staged models
        → _model_needs_download sees DownloadCompleted
          → _load_model proceeds normally
```

## Test Plan

### Automated Testing
- `ruff check` — passes
- 8 new tests in `test_offline_mode.py` — all pass
- 11 existing download tests in `test_download_verification.py` — all pass (no regressions)

### Manual Testing
1. Pre-stage a model on disk (e.g., `~/.exo/models/mlx-community--Qwen3-0.6B-4bit/`)
2. Start exo with `--offline` (or `EXO_OFFLINE=1`)
3. Place an instance via API or dashboard
4. Verify: model loads into memory and inference works without any network calls

### Environment
- macOS (Apple Silicon), multi-node cluster with Thunderbolt interconnect
- Models pre-staged via rsync / NFS mount
This commit is contained in:
vskiwi
2026-02-18 19:18:09 +03:00
committed by GitHub
parent f54c80b121
commit 2ebe6216b4
4 changed files with 279 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/exo/download/coordinator.py
+24 -3
View File
@@ -47,6 +47,7 @@ class DownloadCoordinator:
download_command_receiver: Receiver[ForwarderDownloadCommand]
local_event_sender: Sender[ForwarderEvent]
event_index_counter: Iterator[int]
offline: bool = False
# Local state
download_status: dict[ModelId, DownloadProgress] = field(default_factory=dict)
@@ -62,6 +63,8 @@ class DownloadCoordinator:
def __post_init__(self) -> None:
self.event_sender, self.event_receiver = channel[Event]()
if self.offline:
self.shard_downloader.set_internet_connection(False)
self.shard_downloader.on_progress(self._download_progress_callback)
def _model_dir(self, model_id: ModelId) -> str:
@@ -107,13 +110,17 @@ class DownloadCoordinator:
self._last_progress_time[model_id] = current_time()
async def run(self) -> None:
logger.info("Starting DownloadCoordinator")
self._test_internet_connection()
logger.info(
f"Starting DownloadCoordinator{' (offline mode)' if self.offline else ''}"
)
if not self.offline:
self._test_internet_connection()
async with self._tg as tg:
tg.start_soon(self._command_processor)
tg.start_soon(self._forward_events)
tg.start_soon(self._emit_existing_download_progress)
tg.start_soon(self._check_internet_connection)
if not self.offline:
tg.start_soon(self._check_internet_connection)
def _test_internet_connection(self) -> None:
try:
@@ -202,6 +209,20 @@ class DownloadCoordinator:
)
return
if self.offline:
logger.warning(
f"Offline mode: model {model_id} is not fully available locally, cannot download"
)
failed = DownloadFailed(
shard_metadata=shard,
node_id=self.node_id,
error_message=f"Model files not found locally in offline mode: {model_id}",
model_directory=self._model_dir(model_id),
)
self.download_status[model_id] = failed
await self.event_sender.send(NodeDownloadProgress(download_progress=failed))
return
# Start actual download
self._start_download_task(shard, initial_progress)
src/exo/download/download_utils.py
+12 -1
View File
@@ -448,12 +448,13 @@ async def download_file_with_retry(
target_dir: Path,
on_progress: Callable[[int, int, bool], None] = lambda _, __, ___: None,
on_connection_lost: Callable[[], None] = lambda: None,
skip_internet: bool = False,
) -> Path:
n_attempts = 3
for attempt in range(n_attempts):
try:
return await _download_file(
model_id, revision, path, target_dir, on_progress
model_id, revision, path, target_dir, on_progress, skip_internet
)
except HuggingFaceAuthenticationError:
raise
@@ -487,10 +488,14 @@ async def _download_file(
path: str,
target_dir: Path,
on_progress: Callable[[int, int, bool], None] = lambda _, __, ___: None,
skip_internet: bool = False,
) -> Path:
target_path = target_dir / path
if await aios.path.exists(target_path):
if skip_internet:
return target_path
local_size = (await aios.stat(target_path)).st_size
# Try to verify against remote, but allow offline operation
@@ -510,6 +515,11 @@ async def _download_file(
)
return target_path
if skip_internet:
raise FileNotFoundError(
f"File {path} not found locally and cannot download in offline mode"
)
await aios.makedirs((target_dir / path).parent, exist_ok=True)
length, etag = await file_meta(model_id, revision, path)
remote_hash = etag[:-5] if etag.endswith("-gzip") else etag
@@ -814,6 +824,7 @@ async def download_shard(
file, curr_bytes, total_bytes, is_renamed
),
on_connection_lost=on_connection_lost,
skip_internet=skip_internet,
)
if not skip_download:
src/exo/download/tests/test_offline_mode.py
+230
View File
@@ -0,0 +1,230 @@
"""Tests for offline/air-gapped mode."""
from collections.abc import AsyncIterator
from pathlib import Path
from unittest.mock import AsyncMock, patch
import aiofiles
import aiofiles.os as aios
import pytest
from exo.download.download_utils import (
_download_file, # pyright: ignore[reportPrivateUsage]
download_file_with_retry,
fetch_file_list_with_cache,
)
from exo.shared.types.common import ModelId
from exo.shared.types.worker.downloads import FileListEntry
@pytest.fixture
def model_id() -> ModelId:
return ModelId("test-org/test-model")
@pytest.fixture
async def temp_models_dir(tmp_path: Path) -> AsyncIterator[Path]:
models_dir = tmp_path / "models"
await aios.makedirs(models_dir, exist_ok=True)
with patch("exo.download.download_utils.EXO_MODELS_DIR", models_dir):
yield models_dir
class TestDownloadFileOffline:
"""Tests for _download_file with skip_internet=True."""
async def test_returns_local_file_without_http_verification(
self, model_id: ModelId, tmp_path: Path
) -> None:
"""When skip_internet=True and file exists locally, return it immediately
without making any HTTP calls (no file_meta verification)."""
target_dir = tmp_path / "downloads"
await aios.makedirs(target_dir, exist_ok=True)
local_file = target_dir / "model.safetensors"
async with aiofiles.open(local_file, "wb") as f:
await f.write(b"model weights data")
with patch(
"exo.download.download_utils.file_meta",
new_callable=AsyncMock,
) as mock_file_meta:
result = await _download_file(
model_id,
"main",
"model.safetensors",
target_dir,
skip_internet=True,
)
assert result == local_file
mock_file_meta.assert_not_called()
async def test_raises_file_not_found_for_missing_file(
self, model_id: ModelId, tmp_path: Path
) -> None:
"""When skip_internet=True and file does NOT exist locally,
raise FileNotFoundError instead of attempting download."""
target_dir = tmp_path / "downloads"
await aios.makedirs(target_dir, exist_ok=True)
with pytest.raises(FileNotFoundError, match="offline mode"):
await _download_file(
model_id,
"main",
"missing_model.safetensors",
target_dir,
skip_internet=True,
)
async def test_returns_local_file_in_subdirectory(
self, model_id: ModelId, tmp_path: Path
) -> None:
"""When skip_internet=True and file exists in a subdirectory,
return it without HTTP calls."""
target_dir = tmp_path / "downloads"
subdir = target_dir / "transformer"
await aios.makedirs(subdir, exist_ok=True)
local_file = subdir / "diffusion_pytorch_model.safetensors"
async with aiofiles.open(local_file, "wb") as f:
await f.write(b"weights")
with patch(
"exo.download.download_utils.file_meta",
new_callable=AsyncMock,
) as mock_file_meta:
result = await _download_file(
model_id,
"main",
"transformer/diffusion_pytorch_model.safetensors",
target_dir,
skip_internet=True,
)
assert result == local_file
mock_file_meta.assert_not_called()
class TestDownloadFileWithRetryOffline:
"""Tests for download_file_with_retry with skip_internet=True."""
async def test_propagates_skip_internet_to_download_file(
self, model_id: ModelId, tmp_path: Path
) -> None:
"""Verify skip_internet is passed through to _download_file."""
target_dir = tmp_path / "downloads"
await aios.makedirs(target_dir, exist_ok=True)
local_file = target_dir / "config.json"
async with aiofiles.open(local_file, "wb") as f:
await f.write(b'{"model_type": "qwen2"}')
with patch(
"exo.download.download_utils.file_meta",
new_callable=AsyncMock,
) as mock_file_meta:
result = await download_file_with_retry(
model_id,
"main",
"config.json",
target_dir,
skip_internet=True,
)
assert result == local_file
mock_file_meta.assert_not_called()
async def test_file_not_found_does_not_retry(
self, model_id: ModelId, tmp_path: Path
) -> None:
"""FileNotFoundError from offline mode should not trigger retries."""
target_dir = tmp_path / "downloads"
await aios.makedirs(target_dir, exist_ok=True)
with pytest.raises(FileNotFoundError):
await download_file_with_retry(
model_id,
"main",
"nonexistent.safetensors",
target_dir,
skip_internet=True,
)
class TestFetchFileListOffline:
"""Tests for fetch_file_list_with_cache with skip_internet=True."""
async def test_uses_cached_file_list(
self, model_id: ModelId, temp_models_dir: Path
) -> None:
"""When skip_internet=True and cache file exists, use it without network."""
from pydantic import TypeAdapter
cache_dir = temp_models_dir / "caches" / model_id.normalize()
await aios.makedirs(cache_dir, exist_ok=True)
cached_list = [
FileListEntry(type="file", path="model.safetensors", size=1000),
FileListEntry(type="file", path="config.json", size=200),
]
cache_file = cache_dir / f"{model_id.normalize()}--main--file_list.json"
async with aiofiles.open(cache_file, "w") as f:
await f.write(
TypeAdapter(list[FileListEntry]).dump_json(cached_list).decode()
)
with patch(
"exo.download.download_utils.fetch_file_list_with_retry",
new_callable=AsyncMock,
) as mock_fetch:
result = await fetch_file_list_with_cache(
model_id, "main", skip_internet=True
)
assert result == cached_list
mock_fetch.assert_not_called()
async def test_falls_back_to_local_directory_scan(
self, model_id: ModelId, temp_models_dir: Path
) -> None:
"""When skip_internet=True and no cache but local files exist,
build file list from local directory."""
import json
model_dir = temp_models_dir / model_id.normalize()
await aios.makedirs(model_dir, exist_ok=True)
async with aiofiles.open(model_dir / "config.json", "w") as f:
await f.write('{"model_type": "qwen2"}')
index_data = {
"metadata": {},
"weight_map": {"model.layers.0.weight": "model.safetensors"},
}
async with aiofiles.open(model_dir / "model.safetensors.index.json", "w") as f:
await f.write(json.dumps(index_data))
async with aiofiles.open(model_dir / "model.safetensors", "wb") as f:
await f.write(b"x" * 500)
with patch(
"exo.download.download_utils.fetch_file_list_with_retry",
new_callable=AsyncMock,
) as mock_fetch:
result = await fetch_file_list_with_cache(
model_id, "main", skip_internet=True
)
mock_fetch.assert_not_called()
paths = {entry.path for entry in result}
assert "config.json" in paths
assert "model.safetensors" in paths
async def test_raises_when_no_cache_and_no_local_files(
self, model_id: ModelId, temp_models_dir: Path
) -> None:
"""When skip_internet=True and neither cache nor local files exist,
raise FileNotFoundError."""
with pytest.raises(FileNotFoundError, match="No internet"):
await fetch_file_list_with_cache(model_id, "main", skip_internet=True)
src/exo/main.py
+13
View File
@@ -39,6 +39,7 @@ class Node:
node_id: NodeId
event_index_counter: Iterator[int]
offline: bool
_tg: TaskGroup = field(init=False, default_factory=anyio.create_task_group)
@classmethod
@@ -68,6 +69,7 @@ class Node:
download_command_receiver=router.receiver(topics.DOWNLOAD_COMMANDS),
local_event_sender=router.sender(topics.LOCAL_EVENTS),
event_index_counter=event_index_counter,
offline=args.offline,
)
else:
download_coordinator = None
@@ -132,6 +134,7 @@ class Node:
api,
node_id,
event_index_counter,
args.offline,
)
async def run(self):
@@ -222,6 +225,7 @@ class Node:
),
local_event_sender=self.router.sender(topics.LOCAL_EVENTS),
event_index_counter=self.event_index_counter,
offline=self.offline,
)
self._tg.start_soon(self.download_coordinator.run)
if self.worker:
@@ -260,6 +264,9 @@ def main():
logger.info("Starting EXO")
logger.info(f"EXO_LIBP2P_NAMESPACE: {os.getenv('EXO_LIBP2P_NAMESPACE')}")
if args.offline:
logger.info("Running in OFFLINE mode — no internet checks, local models only")
# Set FAST_SYNCH override env var for runner subprocesses
if args.fast_synch is True:
os.environ["EXO_FAST_SYNCH"] = "on"
@@ -282,6 +289,7 @@ class Args(CamelCaseModel):
tb_only: bool = False
no_worker: bool = False
no_downloads: bool = False
offline: bool = False
fast_synch: bool | None = None # None = auto, True = force on, False = force off
@classmethod
@@ -329,6 +337,11 @@ class Args(CamelCaseModel):
action="store_true",
help="Disable the download coordinator (node won't download models)",
)
parser.add_argument(
"--offline",
action="store_true",
help="Run in offline/air-gapped mode: skip internet checks, use only pre-staged local models",
)
fast_synch_group = parser.add_mutually_exclusive_group()
fast_synch_group.add_argument(
"--fast-synch",