build: teach run script how to temporarily stop systemd units

When testing locally built daemons on a systemd host there can be quite
a few systemd units that need temporarily stopping, and ideally
restarting after the test is complete. This becomes a massive burden
when modular daemons are running and you want to test libvirtd, as a
huge number of units need stopping.

The run script can facilitate this usage by looking at what units are
running and automatically stopping any that are known to conflict with
the daemon that is about to be run. This is only done when running as
root, since non-root libvirtd does not (currently) use systemd.

Reviewed-by: Martin Kletzander <mkletzan@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

run.in

@@ -44,6 +44,7 @@ import os
 import os.path
 import random
 import sys
+import subprocess
 
 # Function to intelligently prepend a path to an environment variable.
 # See https://stackoverflow.com/a/9631350
@@ -77,5 +78,86 @@ env["LIBVIRT_DIR_OVERRIDE"] = "1"
 # read problems when using glibc.
 env["MALLOC_PERTURB_"] = "%d" % random.randint(1, 255)
 
-# Run the program.
-os.execvpe(prog, args, env)
+modular_daemons = [
+    "virtinterfaced",
+    "virtlxcd",
+    "virtnetworkd",
+    "virtnodedevd",
+    "virtnwfilterd",
+    "virtproxyd",
+    "virtqemud",
+    "virtsecretd",
+    "virtstoraged",
+    "virtvboxd",
+    "virtvzd",
+    "virtxend",
+]
+
+def is_modular_daemon(name):
+    return name in modular_daemons
+
+def is_monolithic_daemon(name):
+    return name == "libvirtd"
+
+def is_systemd_host():
+    if os.getuid() != 0:
+        return False
+    return os.path.exists("/run/systemd/system")
+
+def daemon_units(name):
+    return [name + suffix for suffix in [
+        ".service", ".socket", "-ro.socket", "-admin.socket"]]
+
+def is_unit_active(name):
+    ret = subprocess.call(["systemctl", "is-active", "-q", name])
+    return ret == 0
+
+def change_unit(name, action):
+    ret = subprocess.call(["systemctl", action, "-q", name])
+    return ret == 0
+
+try_stop_units = []
+if is_systemd_host():
+    name = os.path.basename(prog)
+
+    maybe_stopped_units = []
+    if is_modular_daemon(name):
+        # Only need to stop libvirtd or this specific modular unit
+        maybe_stopped_units += daemon_units("libvirtd")
+        maybe_stopped_units += daemon_units(name)
+    elif is_monolithic_daemon(name):
+        # Need to stop libvirtd and/or all modular units
+        maybe_stopped_units += daemon_units("libvirtd")
+        for entry in modular_daemons:
+            maybe_stopped_units += daemon_units(entry)
+
+    for unit in maybe_stopped_units:
+        if is_unit_active(unit):
+            try_stop_units.append(unit)
+
+if len(try_stop_units) == 0:
+    # Run the program directly, replacing ourselves
+    os.execvpe(prog, args, env)
+else:
+    print("Temporarily stopping systemd units...")
+    stopped_units = []
+
+    try:
+        for unit in try_stop_units:
+            print(" > %s" % unit)
+            if not change_unit(unit, "stop"):
+                raise Exception("Unable to stop '%s'" % unit)
+
+            stopped_units.append(unit)
+
+        print("Running %s..." % prog)
+        ret = subprocess.call([prog] + args, env=env)
+    except KeyboardInterrupt as ex:
+        pass
+    finally:
+        print("Re-starting original systemd units...")
+        stopped_units.reverse()
+        for unit in stopped_units:
+            print(" > %s" % unit)
+            if not change_unit(unit, "start"):
+                print(" ! unable to restart %s" % unit, file=sys.stderr)