docs/tools/qemu-storage-daemon.rst | 14 ++++++++++++ storage-daemon/qemu-storage-daemon.c | 34 ++++++++++++++++++++++++++++ 2 files changed, 48 insertions(+)
Daemons often have a --pidfile option where the pid is written to a file
so that scripts can stop the daemon by sending a signal.
The pid file also acts as a lock to prevent multiple instances of the
daemon from launching for a given pid file.
QEMU, qemu-nbd, qemu-ga, virtiofsd, and qemu-pr-helper all support the
--pidfile option. Add it to qemu-storage-daemon too.
Reported-by: Richard W.M. Jones <rjones@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
v2:
* Add documentation about startup order [Rich, Daniel]
docs/tools/qemu-storage-daemon.rst | 14 ++++++++++++
storage-daemon/qemu-storage-daemon.c | 34 ++++++++++++++++++++++++++++
2 files changed, 48 insertions(+)
diff --git a/docs/tools/qemu-storage-daemon.rst b/docs/tools/qemu-storage-daemon.rst
index f63627eaf6..3d9704d835 100644
--- a/docs/tools/qemu-storage-daemon.rst
+++ b/docs/tools/qemu-storage-daemon.rst
@@ -118,6 +118,20 @@ Standard options:
List object properties with ``<type>,help``. See the :manpage:`qemu(1)`
manual page for a description of the object properties.
+.. option:: --pidfile PATH
+
+ is the path to a file where the daemon writes its pid. This allows scripts to
+ stop the daemon by sending a signal::
+
+ $ kill -SIGTERM $(<path/to/qsd.pid)
+
+ A file lock is applied to the file so only one instance of the daemon can run
+ with a given pid file path. The daemon unlinks its pid file when terminating.
+
+ The pid file is written after chardevs, exports, and NBD servers have been
+ created but before accepting connections. The daemon has started successfully
+ when the pid file is written and clients may begin connecting.
+
Examples
--------
Launch the daemon with QMP monitor socket ``qmp.sock`` so clients can execute
diff --git a/storage-daemon/qemu-storage-daemon.c b/storage-daemon/qemu-storage-daemon.c
index 9021a46b3a..86cf6a1f08 100644
--- a/storage-daemon/qemu-storage-daemon.c
+++ b/storage-daemon/qemu-storage-daemon.c
@@ -59,6 +59,7 @@
#include "sysemu/runstate.h"
#include "trace/control.h"
+static const char *pid_file;
static volatile bool exit_requested = false;
void qemu_system_killed(int signal, pid_t pid)
@@ -126,6 +127,7 @@ enum {
OPTION_MONITOR,
OPTION_NBD_SERVER,
OPTION_OBJECT,
+ OPTION_PIDFILE,
};
extern QemuOptsList qemu_chardev_opts;
@@ -164,6 +166,7 @@ static void process_options(int argc, char *argv[])
{"monitor", required_argument, NULL, OPTION_MONITOR},
{"nbd-server", required_argument, NULL, OPTION_NBD_SERVER},
{"object", required_argument, NULL, OPTION_OBJECT},
+ {"pidfile", required_argument, NULL, OPTION_PIDFILE},
{"trace", required_argument, NULL, 'T'},
{"version", no_argument, NULL, 'V'},
{0, 0, 0, 0}
@@ -275,6 +278,9 @@ static void process_options(int argc, char *argv[])
qobject_unref(args);
break;
}
+ case OPTION_PIDFILE:
+ pid_file = optarg;
+ break;
default:
g_assert_not_reached();
}
@@ -285,6 +291,27 @@ static void process_options(int argc, char *argv[])
}
}
+static void pid_file_cleanup(void)
+{
+ unlink(pid_file);
+}
+
+static void pid_file_init(void)
+{
+ Error *err = NULL;
+
+ if (!pid_file) {
+ return;
+ }
+
+ if (!qemu_write_pidfile(pid_file, &err)) {
+ error_reportf_err(err, "cannot create PID file: ");
+ exit(EXIT_FAILURE);
+ }
+
+ atexit(pid_file_cleanup);
+}
+
int main(int argc, char *argv[])
{
#ifdef CONFIG_POSIX
@@ -312,6 +339,13 @@ int main(int argc, char *argv[])
qemu_init_main_loop(&error_fatal);
process_options(argc, argv);
+ /*
+ * Write the pid file after creating chardevs, exports, and NBD servers but
+ * before accepting connections. This ordering is documented. Do not change
+ * it.
+ */
+ pid_file_init();
+
while (!exit_requested) {
main_loop_wait(false);
}
--
2.29.2
On Tue, Mar 02, 2021 at 09:29:26AM +0000, Stefan Hajnoczi wrote: > Daemons often have a --pidfile option where the pid is written to a file > so that scripts can stop the daemon by sending a signal. > > The pid file also acts as a lock to prevent multiple instances of the > daemon from launching for a given pid file. > > QEMU, qemu-nbd, qemu-ga, virtiofsd, and qemu-pr-helper all support the > --pidfile option. Add it to qemu-storage-daemon too. > > Reported-by: Richard W.M. Jones <rjones@redhat.com> > Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> > --- > v2: > * Add documentation about startup order [Rich, Daniel] > > docs/tools/qemu-storage-daemon.rst | 14 ++++++++++++ > storage-daemon/qemu-storage-daemon.c | 34 ++++++++++++++++++++++++++++ > 2 files changed, 48 insertions(+) > > diff --git a/docs/tools/qemu-storage-daemon.rst b/docs/tools/qemu-storage-daemon.rst > index f63627eaf6..3d9704d835 100644 > --- a/docs/tools/qemu-storage-daemon.rst > +++ b/docs/tools/qemu-storage-daemon.rst > @@ -118,6 +118,20 @@ Standard options: > List object properties with ``<type>,help``. See the :manpage:`qemu(1)` > manual page for a description of the object properties. > > +.. option:: --pidfile PATH > + > + is the path to a file where the daemon writes its pid. This allows scripts to > + stop the daemon by sending a signal:: > + > + $ kill -SIGTERM $(<path/to/qsd.pid) > + > + A file lock is applied to the file so only one instance of the daemon can run > + with a given pid file path. The daemon unlinks its pid file when terminating. > + > + The pid file is written after chardevs, exports, and NBD servers have been > + created but before accepting connections. The daemon has started successfully > + when the pid file is written and clients may begin connecting. > + > Examples > -------- > Launch the daemon with QMP monitor socket ``qmp.sock`` so clients can execute > diff --git a/storage-daemon/qemu-storage-daemon.c b/storage-daemon/qemu-storage-daemon.c > index 9021a46b3a..86cf6a1f08 100644 > --- a/storage-daemon/qemu-storage-daemon.c > +++ b/storage-daemon/qemu-storage-daemon.c > @@ -59,6 +59,7 @@ > #include "sysemu/runstate.h" > #include "trace/control.h" > > +static const char *pid_file; > static volatile bool exit_requested = false; > > void qemu_system_killed(int signal, pid_t pid) > @@ -126,6 +127,7 @@ enum { > OPTION_MONITOR, > OPTION_NBD_SERVER, > OPTION_OBJECT, > + OPTION_PIDFILE, > }; > > extern QemuOptsList qemu_chardev_opts; > @@ -164,6 +166,7 @@ static void process_options(int argc, char *argv[]) > {"monitor", required_argument, NULL, OPTION_MONITOR}, > {"nbd-server", required_argument, NULL, OPTION_NBD_SERVER}, > {"object", required_argument, NULL, OPTION_OBJECT}, > + {"pidfile", required_argument, NULL, OPTION_PIDFILE}, > {"trace", required_argument, NULL, 'T'}, > {"version", no_argument, NULL, 'V'}, > {0, 0, 0, 0} > @@ -275,6 +278,9 @@ static void process_options(int argc, char *argv[]) > qobject_unref(args); > break; > } > + case OPTION_PIDFILE: > + pid_file = optarg; > + break; > default: > g_assert_not_reached(); > } > @@ -285,6 +291,27 @@ static void process_options(int argc, char *argv[]) > } > } > > +static void pid_file_cleanup(void) > +{ > + unlink(pid_file); > +} > + > +static void pid_file_init(void) > +{ > + Error *err = NULL; > + > + if (!pid_file) { > + return; > + } > + > + if (!qemu_write_pidfile(pid_file, &err)) { > + error_reportf_err(err, "cannot create PID file: "); > + exit(EXIT_FAILURE); > + } > + > + atexit(pid_file_cleanup); > +} > + > int main(int argc, char *argv[]) > { > #ifdef CONFIG_POSIX > @@ -312,6 +339,13 @@ int main(int argc, char *argv[]) > qemu_init_main_loop(&error_fatal); > process_options(argc, argv); > > + /* > + * Write the pid file after creating chardevs, exports, and NBD servers but > + * before accepting connections. This ordering is documented. Do not change > + * it. > + */ > + pid_file_init(); > + > while (!exit_requested) { > main_loop_wait(false); > } > -- Looks good: Reviewed-by: Richard W.M. Jones <rjones@redhat.com> Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com virt-df lists disk usage of guests without needing to install any software inside the virtual machine. Supports Linux and Windows. http://people.redhat.com/~rjones/virt-df/
Am 02.03.2021 um 10:29 hat Stefan Hajnoczi geschrieben: > Daemons often have a --pidfile option where the pid is written to a file > so that scripts can stop the daemon by sending a signal. > > The pid file also acts as a lock to prevent multiple instances of the > daemon from launching for a given pid file. > > QEMU, qemu-nbd, qemu-ga, virtiofsd, and qemu-pr-helper all support the > --pidfile option. Add it to qemu-storage-daemon too. > > Reported-by: Richard W.M. Jones <rjones@redhat.com> > Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> I think we should also mention --pidfile in the --help output. Kevin
On Tue, Mar 02, 2021 at 09:29:26AM +0000, Stefan Hajnoczi wrote: > Daemons often have a --pidfile option where the pid is written to a file > so that scripts can stop the daemon by sending a signal. > > The pid file also acts as a lock to prevent multiple instances of the > daemon from launching for a given pid file. > > QEMU, qemu-nbd, qemu-ga, virtiofsd, and qemu-pr-helper all support the > --pidfile option. Add it to qemu-storage-daemon too. > > Reported-by: Richard W.M. Jones <rjones@redhat.com> > Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> > --- > v2: > * Add documentation about startup order [Rich, Daniel] > > docs/tools/qemu-storage-daemon.rst | 14 ++++++++++++ > storage-daemon/qemu-storage-daemon.c | 34 ++++++++++++++++++++++++++++ > 2 files changed, 48 insertions(+) Reviewed-by: Daniel P. Berrangé <berrange@redhat.com> Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
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