* [PATCH v2] qemu-storage-daemon: add --pidfile option
@ 2021-03-02 9:29 Stefan Hajnoczi
2021-03-02 10:32 ` Daniel P. Berrangé
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: Stefan Hajnoczi @ 2021-03-02 9:29 UTC (permalink / raw)
To: qemu-devel
Cc: Kevin Wolf, Daniel Berrange, qemu-block, afrosi,
Richard W . M . Jones, Stefan Hajnoczi
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
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH v2] qemu-storage-daemon: add --pidfile option
2021-03-02 9:29 [PATCH v2] qemu-storage-daemon: add --pidfile option Stefan Hajnoczi
@ 2021-03-02 10:32 ` Daniel P. Berrangé
2021-03-02 11:49 ` Richard W.M. Jones
2021-03-02 13:57 ` Kevin Wolf
2 siblings, 0 replies; 4+ messages in thread
From: Daniel P. Berrangé @ 2021-03-02 10:32 UTC (permalink / raw)
To: Stefan Hajnoczi
Cc: Kevin Wolf, afrosi, qemu-devel, qemu-block, Richard W . M . Jones
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 :|
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v2] qemu-storage-daemon: add --pidfile option
2021-03-02 9:29 [PATCH v2] qemu-storage-daemon: add --pidfile option Stefan Hajnoczi
2021-03-02 10:32 ` Daniel P. Berrangé
@ 2021-03-02 11:49 ` Richard W.M. Jones
2021-03-02 13:57 ` Kevin Wolf
2 siblings, 0 replies; 4+ messages in thread
From: Richard W.M. Jones @ 2021-03-02 11:49 UTC (permalink / raw)
To: Stefan Hajnoczi
Cc: Kevin Wolf, afrosi, Daniel Berrange, qemu-devel, qemu-block
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/
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v2] qemu-storage-daemon: add --pidfile option
2021-03-02 9:29 [PATCH v2] qemu-storage-daemon: add --pidfile option Stefan Hajnoczi
2021-03-02 10:32 ` Daniel P. Berrangé
2021-03-02 11:49 ` Richard W.M. Jones
@ 2021-03-02 13:57 ` Kevin Wolf
2 siblings, 0 replies; 4+ messages in thread
From: Kevin Wolf @ 2021-03-02 13:57 UTC (permalink / raw)
To: Stefan Hajnoczi
Cc: afrosi, Daniel Berrange, qemu-devel, qemu-block, Richard W . M . Jones
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
^ permalink raw reply [flat|nested] 4+ messages in thread
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2021-03-02 9:29 [PATCH v2] qemu-storage-daemon: add --pidfile option Stefan Hajnoczi
2021-03-02 10:32 ` Daniel P. Berrangé
2021-03-02 11:49 ` Richard W.M. Jones
2021-03-02 13:57 ` Kevin Wolf
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