rmote 0.3.1

Control any remote host. No agent. No install. Just a bare interpreter.

rmote

Control any remote host. No agent. No install. Just a bare interpreter.

---

Installation

pip install rmote

Python 3.11+ is required on the local side. The remote needs only a standard Python 3 interpreter.

Quick Start

Connect to a local subprocess and call remote methods:

import asyncio
import sys
from rmote.protocol import Protocol
from rmote.tools.fs import FileSystem


async def main():
    process = await asyncio.create_subprocess_exec(
        sys.executable, "-qui",
        stdin=asyncio.subprocess.PIPE,
        stdout=asyncio.subprocess.PIPE,
    )
    async with await Protocol.from_subprocess(process) as proto:
        content = await proto(FileSystem.read_str, "/etc/hostname")
        print(content)


if __name__ == "__main__":
    asyncio.run(main())

For SSH, replace from_subprocess with from_ssh:

import asyncio
from rmote.protocol import Protocol
from rmote.tools import FileSystem


async def main():
    async with await Protocol.from_ssh("user@server") as proto:
        content = await proto(FileSystem.read_str, "/etc/hostname")
        print(content)


if __name__ == "__main__":
    asyncio.run(main())

How It Works

Three steps happen on every connection:

1. Bootstrap — protocol.py is lzma-compressed, base64-encoded (~few KB), and written to the remote's stdin. The remote executes it and writes PROTOCOL READY.
2. Tool sync — On first use, the tool class source is sent to the remote as a SYNC packet. The remote exec()s it into a fresh module. Subsequent calls over the same connection skip this step.
3. RPC — Each await proto(Tool.method, *args) gets a unique packet_id. The remote runs the method (sync or async) and returns the result. Multiple in-flight calls execute concurrently on both sides.

Local                          Remote (injected process)
──────                         ──────────────────────────
await from_subprocess()  ───►  exec(decompress(b64decode(payload)))
                         ◄───  PROTOCOL READY

await proto(Tool.method) ───►  SYNC tool source
                         ◄───  ACK

await proto(Tool.method) ───►  REQUEST {method, args, id=1}
                         ◄───  RESPONSE {result, id=1}

Writing Custom Tools

A Tool is a Python class whose methods execute on the remote side. Define it locally; the source is transferred automatically on first use.

import dataclasses
from rmote.protocol import Tool


@dataclasses.dataclass
class DiskInfo:
    path: str
    free: int


class SystemTool(Tool):
    @staticmethod
    def hostname() -> str:
        import socket
        return socket.gethostname()

    @staticmethod
    def disk_free(path: str = "/") -> "DiskInfo":
        import shutil
        _, _, free = shutil.disk_usage(path)
        return DiskInfo(path=path, free=free)

    @staticmethod
    async def read(path: str) -> str:
        with open(path) as f:
            return f.read()

import asyncio
import sys
from rmote.protocol import Protocol


async def main():
    process = await asyncio.create_subprocess_exec(
        sys.executable, "-qui",
        stdin=asyncio.subprocess.PIPE,
        stdout=asyncio.subprocess.PIPE,
    )
    async with await Protocol.from_subprocess(process) as proto:
        host = await proto(SystemTool.hostname)
        info = await proto(SystemTool.disk_free, "/")
        print(f"{host}: {info.free // 2**30} GB free on /")


if __name__ == "__main__":
    asyncio.run(main())

Rules:

• Inherit from Tool
• No __init__ — the metaclass raises TypeError if defined
• Static or class methods only — no instance state across calls
• Stdlib imports only — put import statements inside the method body so they run on the remote
• Any picklable value can be returned, including dataclasses
• Use process() for subprocesses — never subprocess.run or os.system directly (see below)

Running Subprocesses

The remote Python process communicates with the local side over its own stdin / stdout as a binary packet stream. Any child process that inherits the default file descriptors will share those pipes — anything the child writes to stdout will corrupt the packet framing and break the connection permanently.

Use process from rmote.protocol instead. It always redirects stdin, stdout, and stderr away from the protocol pipes:

from rmote.protocol import Tool, process


class DeployTool(Tool):
    @staticmethod
    def apt_update() -> int:
        """Update package lists; return exit code."""
        result = process("apt-get", "update")
        return result.returncode

    @staticmethod
    def git_log(repo: str) -> str:
        """Return the last commit message."""
        result = process("git", "-C", repo, "log", "-1", "--oneline",
                         capture_output=True, text=True, check=True)
        return result.stdout.strip()

process is available in every tool namespace without an import for inline tools. For file-level tools add from rmote.protocol import process at the top of the file.

Default	Why
stdin=DEVNULL	Child cannot consume protocol data
stdout=DEVNULL (unless capture_output=True)	Child cannot corrupt the packet stream
stderr=DEVNULL (unless capture_output=True)	Remote stderr is the same channel

import subprocess
from rmote.protocol import process

if __name__ == "__main__":
    # BAD — child inherits the protocol pipes
    subprocess.run(["apt-get", "update"])

    # GOOD
    process("apt-get", "update")

Concurrent Calls

Multiple RPC calls execute concurrently over the same connection via asyncio.gather:

import asyncio
import sys
from rmote.protocol import Protocol
from rmote.tools import FileSystem


async def main():
    process = await asyncio.create_subprocess_exec(
        sys.executable, "-qui",
        stdin=asyncio.subprocess.PIPE,
        stdout=asyncio.subprocess.PIPE,
    )
    async with await Protocol.from_subprocess(process) as proto:
        hosts, uptime = await asyncio.gather(
            proto(FileSystem.read_str, "/etc/hosts"),
            proto(FileSystem.read_str, "/etc/hostname"),
        )
        print(hosts[:50])
        print(uptime.strip())


if __name__ == "__main__":
    asyncio.run(main())

Both calls are dispatched immediately — the channel does not wait for the first response before sending the second. Each response is matched back to its caller by packet_id.

Multi-Host Fan-Out

Fan out to several SSH hosts in parallel with asyncio.gather:

import asyncio
from rmote.protocol import Protocol
from rmote.tools import FileSystem

HOSTS = ["web1", "web2", "web3"]


async def read_hostname(host: str) -> str:
    async with await Protocol.from_ssh(host) as proto:
        return await proto(FileSystem.read_str, "/etc/hostname")


async def main() -> None:
    names = await asyncio.gather(*[read_hostname(h) for h in HOSTS])
    for host, name in zip(HOSTS, names):
        print(f"{host}: {name.strip()}")


if __name__ == "__main__":
    asyncio.run(main())

Pass return_exceptions=True so a failure on one host does not cancel the others:

import asyncio
from rmote.protocol import Protocol
from rmote.tools import FileSystem

HOSTS = ["web1", "web2", "broken-host"]


async def read_hostname(host: str) -> str:
    async with await Protocol.from_ssh(host) as proto:
        return await proto(FileSystem.read_str, "/etc/hostname")


async def main() -> None:
    results = await asyncio.gather(
        *[read_hostname(h) for h in HOSTS],
        return_exceptions=True,
    )
    for host, result in zip(HOSTS, results):
        if isinstance(result, BaseException):
            print(f"{host}: ERROR — {result}")
        else:
            print(f"{host}: {result.strip()}")


if __name__ == "__main__":
    asyncio.run(main())

To keep connections open across multiple rounds, use AsyncExitStack:

import asyncio
from contextlib import AsyncExitStack
from rmote.protocol import Protocol
from rmote.tools import FileSystem

HOSTS = ["web1", "web2", "web3"]


async def main() -> None:
    async with AsyncExitStack() as stack:
        protos = await asyncio.gather(*[
            stack.enter_async_context(await Protocol.from_ssh(h))
            for h in HOSTS
        ])

        # Round 1 — read hostnames (FileSystem synced once per connection)
        names = await asyncio.gather(*[
            p(FileSystem.read_str, "/etc/hostname") for p in protos
        ])
        print("hostnames:", [n.strip() for n in names])

        # Round 2 — list log files (no re-sync needed)
        logs = await asyncio.gather(*[
            p(FileSystem.glob, "/var/log", "*.log") for p in protos
        ])
        for host, filelist in zip(HOSTS, logs):
            print(f"{host}: {len(filelist)} log files")


if __name__ == "__main__":
    asyncio.run(main())

Templating

rmote includes a minimal template engine — no Jinja2 needed on the remote side.

Variable interpolation

Wrap any Python expression in ${…}:

from rmote.protocol import Template

assert Template("Hello, ${name}!").render(name="Alice") == "Hello, Alice!"
assert Template("${', '.join(sorted(d.keys()))}").render(d={"b": 2, "a": 1}) == "a, b"

Control flow

Lines starting with % are Python control flow. endfor / endif / end close blocks:

from rmote.protocol import Template

tmpl = Template("""\
% for item in items:
- ${item}
% endfor""")
assert tmpl.render(items=["alpha", "beta", "gamma"]) == "- alpha\n- beta\n- gamma"

tmpl = Template("""\
% if n > 0:
positive
% elif n == 0:
zero
% else:
negative
% endif""")
assert tmpl.render(n=1) == "positive"
assert tmpl.render(n=0) == "zero"
assert tmpl.render(n=-1) == "negative"

Lines starting with ## are stripped; %% emits a literal %; \${ escapes interpolation:

from rmote.protocol import Template

assert Template("## ignored\nresult: ${v}").render(v=42) == "result: 42"
assert Template("%% done ${n}/10").render(n=7) == "% done 7/10"
assert Template(r"\${not_a_var}").render() == "${not_a_var}"

Pickling

Template instances are picklable — compile locally, pass as an argument to a remote tool call, and render on the remote with host-specific variables:

import pickle
from rmote.protocol import Template

tmpl = Template("server_name ${hostname}; listen ${port};")
restored = pickle.loads(pickle.dumps(tmpl))
assert restored.render(hostname="example.com", port=443) == "server_name example.com; listen 443;"

render_template

render_template compiles and renders in one step:

from rmote.protocol import render_template

result = render_template(
    "Hi ${name}, you have ${count} message${'s' if count != 1 else ''}.",
    name="Bob",
    count=3,
)
assert result == "Hi Bob, you have 3 messages."

Error Handling

Exceptions raised on the remote side are re-raised locally with the original type:

import asyncio
import sys
from rmote.protocol import Protocol
from rmote.tools import FileSystem


async def main():
    process = await asyncio.create_subprocess_exec(
        sys.executable, "-qui",
        stdin=asyncio.subprocess.PIPE,
        stdout=asyncio.subprocess.PIPE,
    )
    async with await Protocol.from_subprocess(process) as proto:
        try:
            await proto(FileSystem.read_str, "/nonexistent/path/file.txt")
        except FileNotFoundError as e:
            print(f"caught: {e}")


if __name__ == "__main__":
    asyncio.run(main())

SSH Options

All common SSH options are available as keyword arguments to from_ssh:

from rmote.protocol import Protocol


async def main():
    proto = await Protocol.from_ssh(
        "myserver",
        user="deploy",
        port=2222,
        identity="~/.ssh/id_ed25519",
        python="python3.11",
        ssh_options=["-o", "StrictHostKeyChecking=no"],
    )


if __name__ == "__main__":
    import asyncio
    asyncio.run(main())

Built-in Tools

All built-in tools use only the Python stdlib on the remote side.

Tool	What it manages	Platform
FileSystem	Read, write, glob, idempotent line-in-file	any
Exec	Run commands and shell expressions	any
Logger	Remote log level and log record forwarding	any
Template	Mako-like template rendering on the remote	any
Quit	Cleanly exit the remote process	any
Service	systemd units — start, stop, enable, disable	Linux
User	Create and manage users and groups	Linux
Apt	Install and remove packages	Debian / Ubuntu
AptRepository	DEB822 sources and GPG keys	Debian / Ubuntu
Pacman	Install and remove packages	Arch Linux
PacmanRepository	Repository sections and GPG keys	Arch Linux

Comparison

Tool	Remote requires	Native async	Execution model
Fabric	SSH + shell	—	Shell commands only
Ansible	Python 2.6+ + modules	—	Module push (JSON results)
Mitogen	Python only	—	Compressed bootstrap, lower-level channel API
RPyC zero-deploy	Python + Plumbum locally	partial	Transparent object proxies
rmote	Python stdlib only	yes	Compressed bootstrap, asyncio RPC, typed returns

rmote is closest in spirit to Mitogen — same stdin-injection technique — but is built for asyncio from the ground up. Concurrent multi-host calls are first-class, tools are plain Python classes, and return values are typed dataclasses rather than JSON blobs.

Project Status

Beta — version 0.2.0. Semver: patch = bug fix, minor = new tool or protocol feature, major = breaking wire or API change.

Tests

The test suite covers three layers:

Protocol (7 test files) — tool serialization, sync and async RPC round-trips, concurrent in-flight requests matched by packet_id, remote exception propagation with original type preservation, raw packet encoding/decoding, LZMA compression threshold, and a dedicated test that verifies spawning a subprocess inside a tool never corrupts the protocol pipes.

Tools (11 test files, all run against live processes):

• FileSystem, Exec, Logger, Service, User, Template — tested against a local subprocess.
• Apt and AptRepository — tested inside a python:3-slim Docker container: install, remove, idempotency checks, TTL-aware update.
• Pacman and PacmanRepository — tested inside a locally-built archlinux:python Docker image.
• Cross-tool integration: concurrent reads, mixed built-in and custom tools in a single session, error propagation through asyncio.gather.

14 reusable Tool fixtures in tests/tools_cases/ cover the serialization corner cases: async methods, class-level constants, dataclass and nested-dataclass returns, enums defined inside and outside the class, module-level imports, tool inheritance, and same-name tools in different modules (name collision safety).

README and docs examples — pytest treats README.md and all files under docs/ as test sources. Every named code block is executed by markdown-pytest, so every snippet in this file is verified on each commit.

Docker transport

The test suite already runs Python interpreters inside Docker containers using from_subprocess (docker run --rm -i <image> python3 -qui is just another subprocess). A dedicated Protocol.from_docker convenience method is a natural next step.

Type Safety

The entire rmote/ package passes strict mypy with no errors. All public APIs are fully annotated. Tested on Python 3.11, 3.12, 3.13, and 3.14.

Stable

Core protocol, SSH transport, subprocess transport, all 11 built-in tools, templating engine, concurrent multi-host fan-out, Docker-based test infrastructure.

Not yet supported

Windows remote hosts, raw socket / TLS transports, Protocol.from_docker public API, streaming or generator responses.