hermes-agent/tools/environments/ssh.py
kshitijk4poor d64446e315 feat(file-sync): sync remote changes back to host on teardown
Salvage of PR #8018 by @alt-glitch onto current main.

On sandbox teardown, FileSyncManager now downloads the remote .hermes/
directory, diffs against SHA-256 hashes of what was originally pushed,
and applies only changed files back to the host.

Core (tools/environments/file_sync.py):
- sync_back(): orchestrates download -> unpack -> diff -> apply with:
  - Retry with exponential backoff (3 attempts, 2s/4s/8s)
  - SIGINT trap + defer (prevents partial writes on Ctrl-C)
  - fcntl.flock serialization (concurrent gateway sandboxes)
  - Last-write-wins conflict resolution with warning
  - New remote files pulled back via _infer_host_path prefix matching

Backends:
- SSH: _ssh_bulk_download — tar cf - piped over SSH
- Modal: _modal_bulk_download — exec tar cf - -> proc.stdout.read
- Daytona: _daytona_bulk_download — exec tar cf -> SDK download_file
- All three call sync_back() at the top of cleanup()

Fixes applied during salvage (vs original PR #8018):

| # | Issue | Fix |
|---|-------|-----|
| C1 | import fcntl unconditional — crashes Windows | try/except with fallback; _sync_back_locked skips locking when fcntl=None |
| W1 | assert for runtime guard (stripped by -O) | Replaced with proper if/raise RuntimeError |
| W2 | O(n*m) from _get_files_fn() called per file | Cache mapping once at start of _sync_back_impl, pass to resolve/infer |
| W3 | Dead BulkDownloadFn imports in 3 backends | Removed unused imports |
| W4 | Modal hardcodes root/.hermes, no explanation | Added docstring comment explaining Modal always runs as root |
| S1 | SHA-256 computed for new files where pushed_hash=None | Skip hashing when pushed_hash is None (comparison always False) |
| S2 | Daytona /tmp/.hermes_sync.tar never cleaned up | Added rm -f after download (best-effort) |

Tests: 49 passing (17 new: _infer_host_path edge cases, SIGINT
main/worker thread, Windows fcntl=None fallback, Daytona tar cleanup).

Based on #8018 by @alt-glitch.
2026-04-16 19:39:21 -07:00

275 lines
11 KiB
Python

"""SSH remote execution environment with ControlMaster connection persistence."""
import logging
import os
import shlex
import shutil
import subprocess
import tempfile
from pathlib import Path
from tools.environments.base import BaseEnvironment, _popen_bash
from tools.environments.file_sync import (
FileSyncManager,
iter_sync_files,
quoted_mkdir_command,
quoted_rm_command,
unique_parent_dirs,
)
logger = logging.getLogger(__name__)
def _ensure_ssh_available() -> None:
"""Fail fast with a clear error when the SSH client is unavailable."""
if not shutil.which("ssh"):
raise RuntimeError(
"SSH is not installed or not in PATH. Install OpenSSH client: apt install openssh-client"
)
class SSHEnvironment(BaseEnvironment):
"""Run commands on a remote machine over SSH.
Spawn-per-call: every execute() spawns a fresh ``ssh ... bash -c`` process.
Session snapshot preserves env vars across calls.
CWD persists via in-band stdout markers.
Uses SSH ControlMaster for connection reuse.
"""
def __init__(self, host: str, user: str, cwd: str = "~",
timeout: int = 60, port: int = 22, key_path: str = ""):
super().__init__(cwd=cwd, timeout=timeout)
self.host = host
self.user = user
self.port = port
self.key_path = key_path
self.control_dir = Path(tempfile.gettempdir()) / "hermes-ssh"
self.control_dir.mkdir(parents=True, exist_ok=True)
self.control_socket = self.control_dir / f"{user}@{host}:{port}.sock"
_ensure_ssh_available()
self._establish_connection()
self._remote_home = self._detect_remote_home()
self._ensure_remote_dirs()
self._sync_manager = FileSyncManager(
get_files_fn=lambda: iter_sync_files(f"{self._remote_home}/.hermes"),
upload_fn=self._scp_upload,
delete_fn=self._ssh_delete,
bulk_upload_fn=self._ssh_bulk_upload,
bulk_download_fn=self._ssh_bulk_download,
)
self._sync_manager.sync(force=True)
self.init_session()
def _build_ssh_command(self, extra_args: list | None = None) -> list:
cmd = ["ssh"]
cmd.extend(["-o", f"ControlPath={self.control_socket}"])
cmd.extend(["-o", "ControlMaster=auto"])
cmd.extend(["-o", "ControlPersist=300"])
cmd.extend(["-o", "BatchMode=yes"])
cmd.extend(["-o", "StrictHostKeyChecking=accept-new"])
cmd.extend(["-o", "ConnectTimeout=10"])
if self.port != 22:
cmd.extend(["-p", str(self.port)])
if self.key_path:
cmd.extend(["-i", self.key_path])
if extra_args:
cmd.extend(extra_args)
cmd.append(f"{self.user}@{self.host}")
return cmd
def _establish_connection(self):
cmd = self._build_ssh_command()
cmd.append("echo 'SSH connection established'")
try:
result = subprocess.run(cmd, capture_output=True, text=True, timeout=15)
if result.returncode != 0:
error_msg = result.stderr.strip() or result.stdout.strip()
raise RuntimeError(f"SSH connection failed: {error_msg}")
except subprocess.TimeoutExpired:
raise RuntimeError(f"SSH connection to {self.user}@{self.host} timed out")
def _detect_remote_home(self) -> str:
"""Detect the remote user's home directory."""
try:
cmd = self._build_ssh_command()
cmd.append("echo $HOME")
result = subprocess.run(cmd, capture_output=True, text=True, timeout=10)
home = result.stdout.strip()
if home and result.returncode == 0:
logger.debug("SSH: remote home = %s", home)
return home
except Exception:
pass
if self.user == "root":
return "/root"
return f"/home/{self.user}"
# ------------------------------------------------------------------
# File sync (via FileSyncManager)
# ------------------------------------------------------------------
def _ensure_remote_dirs(self) -> None:
"""Create base ~/.hermes directory tree on remote in one SSH call."""
base = f"{self._remote_home}/.hermes"
dirs = [base, f"{base}/skills", f"{base}/credentials", f"{base}/cache"]
cmd = self._build_ssh_command()
cmd.append(quoted_mkdir_command(dirs))
subprocess.run(cmd, capture_output=True, text=True, timeout=10)
# _get_sync_files provided via iter_sync_files in FileSyncManager init
def _scp_upload(self, host_path: str, remote_path: str) -> None:
"""Upload a single file via scp over ControlMaster."""
parent = str(Path(remote_path).parent)
mkdir_cmd = self._build_ssh_command()
mkdir_cmd.append(f"mkdir -p {shlex.quote(parent)}")
subprocess.run(mkdir_cmd, capture_output=True, text=True, timeout=10)
scp_cmd = ["scp", "-o", f"ControlPath={self.control_socket}"]
if self.port != 22:
scp_cmd.extend(["-P", str(self.port)])
if self.key_path:
scp_cmd.extend(["-i", self.key_path])
scp_cmd.extend([host_path, f"{self.user}@{self.host}:{remote_path}"])
result = subprocess.run(scp_cmd, capture_output=True, text=True, timeout=30)
if result.returncode != 0:
raise RuntimeError(f"scp failed: {result.stderr.strip()}")
def _ssh_bulk_upload(self, files: list[tuple[str, str]]) -> None:
"""Upload many files in a single tar-over-SSH stream.
Pipes ``tar c`` on the local side through an SSH connection to
``tar x`` on the remote, transferring all files in one TCP stream
instead of spawning a subprocess per file. Directory creation is
batched into a single ``mkdir -p`` call beforehand.
Typical improvement: ~580 files goes from O(N) scp round-trips
to a single streaming transfer.
"""
if not files:
return
parents = unique_parent_dirs(files)
if parents:
cmd = self._build_ssh_command()
cmd.append(quoted_mkdir_command(parents))
result = subprocess.run(cmd, capture_output=True, text=True, timeout=30)
if result.returncode != 0:
raise RuntimeError(f"remote mkdir failed: {result.stderr.strip()}")
# Symlink staging avoids fragile GNU tar --transform rules.
with tempfile.TemporaryDirectory(prefix="hermes-ssh-bulk-") as staging:
for host_path, remote_path in files:
staged = os.path.join(staging, remote_path.lstrip("/"))
os.makedirs(os.path.dirname(staged), exist_ok=True)
os.symlink(os.path.abspath(host_path), staged)
tar_cmd = ["tar", "-chf", "-", "-C", staging, "."]
ssh_cmd = self._build_ssh_command()
ssh_cmd.append("tar xf - -C /")
tar_proc = subprocess.Popen(
tar_cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE
)
try:
ssh_proc = subprocess.Popen(
ssh_cmd, stdin=tar_proc.stdout, stdout=subprocess.PIPE,
stderr=subprocess.PIPE,
)
except Exception:
tar_proc.kill()
tar_proc.wait()
raise
# Allow tar_proc to receive SIGPIPE if ssh_proc exits early
tar_proc.stdout.close()
try:
_, ssh_stderr = ssh_proc.communicate(timeout=120)
# Use communicate() instead of wait() to drain stderr and
# avoid deadlock if tar produces more than PIPE_BUF of errors.
tar_stderr_raw = b""
if tar_proc.poll() is None:
_, tar_stderr_raw = tar_proc.communicate(timeout=10)
else:
tar_stderr_raw = tar_proc.stderr.read() if tar_proc.stderr else b""
except subprocess.TimeoutExpired:
tar_proc.kill()
ssh_proc.kill()
tar_proc.wait()
ssh_proc.wait()
raise RuntimeError("SSH bulk upload timed out")
if tar_proc.returncode != 0:
raise RuntimeError(
f"tar create failed (rc={tar_proc.returncode}): "
f"{tar_stderr_raw.decode(errors='replace').strip()}"
)
if ssh_proc.returncode != 0:
raise RuntimeError(
f"tar extract over SSH failed (rc={ssh_proc.returncode}): "
f"{ssh_stderr.decode(errors='replace').strip()}"
)
logger.debug("SSH: bulk-uploaded %d file(s) via tar pipe", len(files))
def _ssh_bulk_download(self, dest: Path) -> None:
"""Download remote .hermes/ as a tar archive."""
# Tar from / with the full path so archive entries preserve absolute
# paths (e.g. home/user/.hermes/skills/f.py), matching _pushed_hashes keys.
rel_base = f"{self._remote_home}/.hermes".lstrip("/")
ssh_cmd = self._build_ssh_command()
ssh_cmd.append(f"tar cf - -C / {shlex.quote(rel_base)}")
with open(dest, "wb") as f:
result = subprocess.run(ssh_cmd, stdout=f, stderr=subprocess.PIPE, timeout=120)
if result.returncode != 0:
raise RuntimeError(f"SSH bulk download failed: {result.stderr.decode(errors='replace').strip()}")
def _ssh_delete(self, remote_paths: list[str]) -> None:
"""Batch-delete remote files in one SSH call."""
cmd = self._build_ssh_command()
cmd.append(quoted_rm_command(remote_paths))
result = subprocess.run(cmd, capture_output=True, text=True, timeout=10)
if result.returncode != 0:
raise RuntimeError(f"remote rm failed: {result.stderr.strip()}")
def _before_execute(self) -> None:
"""Sync files to remote via FileSyncManager (rate-limited internally)."""
self._sync_manager.sync()
# ------------------------------------------------------------------
# Execution
# ------------------------------------------------------------------
def _run_bash(self, cmd_string: str, *, login: bool = False,
timeout: int = 120,
stdin_data: str | None = None) -> subprocess.Popen:
"""Spawn an SSH process that runs bash on the remote host."""
cmd = self._build_ssh_command()
if login:
cmd.extend(["bash", "-l", "-c", shlex.quote(cmd_string)])
else:
cmd.extend(["bash", "-c", shlex.quote(cmd_string)])
return _popen_bash(cmd, stdin_data)
def cleanup(self):
if self._sync_manager:
logger.info("SSH: syncing files from sandbox...")
self._sync_manager.sync_back()
if self.control_socket.exists():
try:
cmd = ["ssh", "-o", f"ControlPath={self.control_socket}",
"-O", "exit", f"{self.user}@{self.host}"]
subprocess.run(cmd, capture_output=True, timeout=5)
except (OSError, subprocess.SubprocessError):
pass
try:
self.control_socket.unlink()
except OSError:
pass