| Message ID | 20210302092926.163080-1-stefanha@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | [v2] qemu-storage-daemon: add --pidfile option | expand |
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
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.
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
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); }
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(+)