Add initial version of sdnotify-wrapper

.github/workflows/on-push.yml

@@ -0,0 +1,48 @@
+name: on-push
+
+on: [push]
+
+jobs:
+  static_checks:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v3
+    - name: Set up Python
+      uses: actions/setup-python@v3
+      with:
+        python-version: 3.11
+    - name: Install dependencies
+      run: |
+        pip install .[test]
+    - name: Lint with Pylint
+      run: pylint --score=n *.py
+    - name: Check format with Black
+      run: black --check .
+    - name: Check import statement order with isort
+      run: isort --check .
+    - name: Check spelling
+      run: git ls-files -z | xargs -0 -- codespell
+  release:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v3
+    - name: Set up Python
+      uses: actions/setup-python@v3
+      with:
+        python-version: 3.11
+    - name: Install dependencies
+      run: |
+        # python3-build is broken on 22.04:
+        # https://bugs.launchpad.net/ubuntu/+source/python-build/+bug/1992108
+        # install everything from pip instead
+        pip install build twine
+    - name: Build dist packages
+      run: |
+        export SOURCE_DATE_EPOCH=$(git log -1 --pretty=%ct)
+        python3 -m build
+    - name: Upload to PyPi
+      env:
+        TWINE_USERNAME: __token__
+        TWINE_PASSWORD: ${{ secrets.PYPI_API_TOKEN }}
+      if: ${{ github.ref_type == 'tag' && startsWith(github.ref_name, 'v') && env.TWINE_PASSWORD != '' }}
+      run: twine upload --non-interactive dist/*

.gitignore

@@ -0,0 +1,2 @@
+/venv/
+/dist/

LICENSE.txt

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2024-present Simon Holesch <simon@holesch.de>
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

@@ -0,0 +1 @@
+# sdnotify-wrapper-py

get_version

@@ -0,0 +1,39 @@
+#!/bin/sh -e
+# called by meson to get project version
+
+main() {
+    if [ "$1" = "--save" ]; then
+        get_git_version > "${MESON_DIST_ROOT:?}/VERSION"
+    elif [ -e VERSION ]; then
+        cat VERSION
+    else
+        get_git_version
+    fi
+}
+
+get_git_version() {
+    version="$(git_describe)"
+    version="${version#v}" # remove "v" prefix
+
+    case "$version" in
+    *-*)
+        # not an exact match: make version PEP 440 compliant
+        # e.g. 1.2.3-5-gd63c80c is turned into 1.2.3.dev5+gd63c80c
+        latest_release="${version%%-*}"
+        suffix="${version#*-}"
+        dev_num="${suffix%%-*}"
+        commit="${suffix#*-}"
+        echo "$latest_release.dev$dev_num+$commit"
+        ;;
+    *)
+        echo "$version"
+    esac
+}
+
+git_describe() {
+    if ! git -C "${MESON_SOURCE_ROOT:-$PWD}" describe --match "v*" --tags 2>/dev/null; then
+        echo "v0.1.0-0-g$(git rev-parse --short HEAD)"
+    fi
+}
+
+main "$@"

meson.build

@@ -0,0 +1,10 @@
+project(
+  'sdnotify-wrapper-py',
+  version: run_command('./get_version', check: true).stdout().strip()
+)
+
+meson.add_dist_script('./get_version', '--save')
+
+py = import('python').find_installation()
+
+py.install_sources('sdnotify_wrapper.py')

pyproject.toml

@@ -0,0 +1,60 @@
+[project]
+# For more information on how to specify metadata, see
+# https://packaging.python.org/en/latest/specifications/pyproject-toml/
+name = "sdnotify-wrapper-py"
+description = "Notify readiness to systemd by writing to stdout in a service"
+readme = "README.md"
+requires-python = ">=3.7"
+license = {file = "LICENSE.txt"}
+authors = [
+    {name = "Simon Holesch", email = "simon@holesch.de"},
+]
+keywords = ["systemd", "readiness", "sd_notify"]
+classifiers = [
+    "Development Status :: 5 - Production/Stable",
+    "Environment :: Console",
+    "Intended Audience :: Developers",
+    "License :: OSI Approved :: MIT License",
+    "Operating System :: POSIX :: Linux",
+    "Programming Language :: Python",
+    "Programming Language :: Python :: 3.7",
+    "Programming Language :: Python :: 3.8",
+    "Programming Language :: Python :: 3.9",
+    "Programming Language :: Python :: 3.10",
+    "Programming Language :: Python :: 3.11",
+    "Programming Language :: Python :: 3.12",
+    "Programming Language :: Python :: 3.13",
+    "Topic :: System :: Boot :: Init",
+    "Topic :: System :: Systems Administration",
+]
+dependencies = []
+dynamic = ["version"]
+
+[project.urls]
+Issues = "https://github.com/holesch/sdnotify-wrapper-py/issues"
+Source = "https://github.com/holesch/sdnotify-wrapper-py"
+
+[project.scripts]
+sdnotify-wrapper = "sdnotify_wrapper:main"
+
+[project.optional-dependencies]
+test = [
+    "black",
+    "codespell",
+    "isort",
+    "pylint",
+]
+
+[build-system]
+build-backend = "mesonpy"
+requires = ["meson-python"]
+
+[tool.pylint."MESSAGES CONTROL"]
+disable = [
+    "missing-class-docstring",
+    "missing-function-docstring",
+    "missing-module-docstring",
+]
+
+[tool.isort]
+profile = "black"

sdnotify_wrapper.py

@@ -0,0 +1,127 @@
+#!/usr/bin/env python3
+
+import getopt
+import os
+import struct
+import sys
+import typing
+
+
+def usage():
+    print(
+        "usage: sdnotify-wrapper [ -d fd ] [ -f ] [ -t timeout ] [ -k ] prog...",
+        file=sys.stderr,
+    )
+
+
+def main():
+    args = Arguments.parse()
+
+    if "NOTIFY_SOCKET" not in os.environ:
+        os.execvp(args.argv[0], args.argv)
+
+    main_pid = os.getpid()
+    read_pipe, write_pipe = os.pipe()
+
+    pid = os.fork() if args.fork_once else double_fork()
+    if is_forked_child(pid):
+        os.close(write_pipe)
+        return run_child(read_pipe, args.timeout, main_pid)
+
+    os.close(read_pipe)
+    os.dup2(write_pipe, args.fd)
+    os.close(write_pipe)
+
+    if not args.keep:
+        del os.environ["NOTIFY_SOCKET"]
+
+    return os.execvp(args.argv[0], args.argv)
+
+
+class Arguments(typing.NamedTuple):
+    argv: typing.List[str]
+    fd: int = 1  # default is stdout
+    fork_once: bool = False
+    timeout: typing.Optional[int] = None
+    keep: bool = False
+
+    @classmethod
+    def parse(cls):
+        try:
+            opts, args = getopt.getopt(sys.argv[1:], "d:ft:k")
+        except getopt.GetoptError as err:
+            print(err, file=sys.stderr)
+            usage()
+            sys.exit(2)
+
+        init_args = {}
+        for opt, arg in opts:
+            if opt == "-d":
+                init_args["fd"] = arg
+            elif opt == "-f":
+                init_args["fork_once"] = True
+            elif opt == "-t":
+                init_args["timeout"] = arg
+            elif opt == "-k":
+                init_args["keep"] = True
+            else:
+                assert False, "unhandled option"
+
+        if not args:
+            usage()
+            sys.exit(2)
+
+        return cls(argv=args, **init_args)
+
+
+# pylint: disable=R1732
+# - consider-using-with: can't use a context manager when using fork()
+def double_fork():
+    read_pipe, write_pipe = os.pipe()
+    read_pipe = open(read_pipe, "rb")
+    write_pipe = open(write_pipe, "wb")
+
+    pid = os.fork()
+    if is_forked_child(pid):
+        read_pipe.close()
+        pid = os.fork()
+        if is_forked_child(pid):
+            # grandchild
+            write_pipe.close()
+            return 0
+
+        msg = struct.pack("!Q", pid)
+        write_pipe.write(msg)
+        write_pipe.flush()
+        os._exit(0)
+
+    write_pipe.close()
+    msg = read_pipe.read(8)
+    read_pipe.close()
+    os.waitpid(pid, 0)  # wait for child #1 to exit
+    grandchild = struct.unpack("!Q", msg)[0]
+    return grandchild
+
+
+def is_forked_child(pid):
+    return pid == 0
+
+
+# pylint: disable=W0613
+# - unused-argument: timeout is not implemented, yet
+def run_child(read_pipe, timeout, main_pid):
+    data = b""
+    while b"\n" not in data:
+        data = os.read(read_pipe, 4096)
+        if not data:
+            return 1
+    return notify_systemd(main_pid)
+
+
+def notify_systemd(main_pid):
+    argv = ["systemd-notify", "--ready", f"--pid={main_pid}"]
+    os.execvp(argv[0], argv)
+
+
+if __name__ == "__main__":
+    sys.exit(main())