Rewrite build_debian_packages

Rewrite this in python so that it can be run in parallel.

docker/build_debian_packages.sh

-#!/bin/bash
-
-# Build the Debian packages using Docker images.
-#
-# This script builds the Docker images and then executes them sequentially, each
-# one building a Debian package for the targeted operating system. It is
-# designed to be a "single command" to produce all the images.
-#
-# By default, builds for all known distributions, but a list of distributions
-# can be passed on the commandline for debugging.
-
-set -ex
-
-cd `dirname $0`
-
-if [ $# -lt 1 ]; then
-    DISTS=(
-        debian:stretch
-        debian:buster
-        debian:sid
-        ubuntu:xenial
-        ubuntu:bionic
-        ubuntu:cosmic
-    )
-else
-    DISTS=("$@")
-fi
-
-# Make the dir where the debs will live.
-#
-# Note that we deliberately put this outside the source tree, otherwise we tend
-# to get source packages which are full of debs. (We could hack around that
-# with more magic in the build_debian.sh script, but that doesn't solve the
-# problem for natively-run dpkg-buildpakage).
-
-mkdir -p ../../debs
-
-# Build each OS image;
-for i in "${DISTS[@]}"; do
-    TAG=$(echo ${i} | cut -d ":" -f 2)
-    docker build --tag dh-venv-builder:${TAG} --build-arg distro=${i} -f Dockerfile-dhvirtualenv .
-    docker run -it --rm --volume=$(pwd)/../\:/synapse/source:ro --volume=$(pwd)/../../debs:/debs \
-           -e TARGET_USERID=$(id -u) \
-           -e TARGET_GROUPID=$(id -g) \
-           dh-venv-builder:${TAG}
-done

scripts-dev/build_debian_packages

+#!/usr/bin/env python3
+
+# Build the Debian packages using Docker images.
+#
+# This script builds the Docker images and then executes them sequentially, each
+# one building a Debian package for the targeted operating system. It is
+# designed to be a "single command" to produce all the images.
+#
+# By default, builds for all known distributions, but a list of distributions
+# can be passed on the commandline for debugging.
+
+import argparse
+from concurrent.futures import ThreadPoolExecutor
+import os
+import signal
+import subprocess
+import sys
+import threading
+
+DISTS = (
+    "debian:stretch",
+    "debian:buster",
+    "debian:sid",
+    "ubuntu:xenial",
+    "ubuntu:bionic",
+    "ubuntu:cosmic",
+)
+
+DESC = '''\
+Builds .debs for synapse, using a Docker image for the build environment.
+
+By default, builds for all known distributions, but a list of distributions
+can be passed on the commandline for debugging.
+'''
+
+
+class Builder(object):
+    def __init__(self, redirect_stdout=False):
+        self.redirect_stdout = redirect_stdout
+        self.active_containers = set()
+        self._lock = threading.Lock()
+        self._failed = False
+
+    def run_build(self, dist):
+        """Build deb for a single distribution"""
+
+        if self._failed:
+            print("not building %s due to earlier failure" % (dist, ))
+            raise Exception("failed")
+
+        try:
+            self._inner_build(dist)
+        except Exception as e:
+            print("build of %s failed: %s" % (dist, e), file=sys.stderr)
+            self._failed = True
+            raise
+
+    def _inner_build(self, dist):
+        projdir = os.path.dirname(os.path.dirname(os.path.realpath(__file__)))
+        os.chdir(projdir)
+
+        tag = dist.split(":", 1)[1]
+
+        # Make the dir where the debs will live.
+        #
+        # Note that we deliberately put this outside the source tree, otherwise
+        # we tend to get source packages which are full of debs. (We could hack
+        # around that with more magic in the build_debian.sh script, but that
+        # doesn't solve the problem for natively-run dpkg-buildpakage).
+        debsdir = os.path.join(projdir, '../debs')
+        os.makedirs(debsdir, exist_ok=True)
+
+        if self.redirect_stdout:
+            logfile = os.path.join(debsdir, "%s.buildlog" % (tag, ))
+            print("building %s: directing output to %s" % (dist, logfile))
+            stdout = open(logfile, "w")
+        else:
+            stdout = None
+
+        # first build a docker image for the build environment
+        subprocess.check_call([
+            "docker", "build",
+            "--tag", "dh-venv-builder:" + tag,
+            "--build-arg", "distro=" + dist,
+            "-f", "docker/Dockerfile-dhvirtualenv",
+            "docker",
+        ], stdout=stdout, stderr=subprocess.STDOUT)
+
+        container_name = "synapse_build_" + tag
+        with self._lock:
+            self.active_containers.add(container_name)
+
+        # then run the build itself
+        subprocess.check_call([
+            "docker", "run",
+            "--rm",
+            "--name", container_name,
+            "--volume=" + projdir + ":/synapse/source:ro",
+            "--volume=" + debsdir + ":/debs",
+            "-e", "TARGET_USERID=%i" % (os.getuid(), ),
+            "-e", "TARGET_GROUPID=%i" % (os.getgid(), ),
+            "dh-venv-builder:" + tag,
+        ], stdout=stdout, stderr=subprocess.STDOUT)
+
+        with self._lock:
+            self.active_containers.remove(container_name)
+
+        if stdout is not None:
+            stdout.close()
+            print("Completed build of %s" % (dist, ))
+
+    def kill_containers(self):
+        with self._lock:
+            active = list(self.active_containers)
+
+        for c in active:
+            print("killing container %s" % (c,))
+            subprocess.run([
+                "docker", "kill", c,
+            ], stdout=subprocess.DEVNULL)
+            with self._lock:
+                self.active_containers.remove(c)
+
+
+def run_builds(dists, jobs=1):
+    builder = Builder(redirect_stdout=(jobs > 1))
+
+    def sig(signum, _frame):
+        print("Caught SIGINT")
+        builder.kill_containers()
+    signal.signal(signal.SIGINT, sig)
+
+    with ThreadPoolExecutor(max_workers=jobs) as e:
+        res = e.map(builder.run_build, dists)
+
+    # make sure we consume the iterable so that exceptions are raised.
+    for r in res:
+        pass
+
+
+if __name__ == '__main__':
+    parser = argparse.ArgumentParser(
+        description=DESC,
+    )
+    parser.add_argument(
+        '-j', '--jobs', type=int, default=1,
+        help='specify the number of builds to run in parallel',
+    )
+    parser.add_argument(
+        'dist', nargs='*', default=DISTS,
+        help='a list of distributions to build for. Default: %(default)s',
+    )
+    args = parser.parse_args()
+    run_builds(dists=args.dist, jobs=args.jobs)