[systemd-devel] [PATCH 1/3] service: add watchdog timestamp
Michael Olbrich
m.olbrich at pengutronix.de
Fri Nov 4 07:43:26 PDT 2011
On Fri, Nov 04, 2011 at 03:38:40PM +0100, Michael Olbrich wrote:
> This patch adds WatchdogTimestamp[Monotonic] to the systemd service
> D-Bus API. The timestamp is updated to the current time when the
> service calls 'sd_nofity("WATCHDOG=1\n")'.
> Using a timestamp instead of an 'alive' flag has two advantages:
> 1. No timeout is needed to define when a service is no longer alive.
> This simplifies both configuration (no timeout value) and
> implementation (no timeout event).
> 2. It is more robust. A 'dead' service might not be detected should
> systemd 'forget' to reset an 'alive' flag. It is much less likely
> to get a valid new timestamp if a service died.
> ---
Hmmm, somehow git didn't let me annotate the patches, so I'll do it like
this.
Documentation updated as requested. I've also added WatchdogTimestamp to
bus_service_invalidating_properties. Is this correct or is there another
way to handle property updates?
Michael
> man/sd_notify.xml | 12 ++++++++++++
> src/dbus-service.c | 5 +++++
> src/sd-daemon.h | 5 +++++
> src/service.c | 20 ++++++++++++++++++++
> src/service.h | 2 ++
> 5 files changed, 44 insertions(+), 0 deletions(-)
>
> diff --git a/man/sd_notify.xml b/man/sd_notify.xml
> index dd0ba93..4a81d7a 100644
> --- a/man/sd_notify.xml
> +++ b/man/sd_notify.xml
> @@ -151,6 +151,18 @@
> itself. Example:
> "MAINPID=4711"</para></listitem>
> </varlistentry>
> +
> + <varlistentry>
> + <term>WATCHDOG=1</term>
> +
> + <listitem><para>Tells systemd to
> + update the watchdog timestamp.
> + Services using this feature should do
> + this in regular intervals. A watchdog
> + framework can use the timestamps to
> + detect failed
> + services.</para></listitem>
> + </varlistentry>
> </variablelist>
>
> <para>It is recommended to prefix variable names that
> diff --git a/src/dbus-service.c b/src/dbus-service.c
> index 3486623..2f53484 100644
> --- a/src/dbus-service.c
> +++ b/src/dbus-service.c
> @@ -43,6 +43,8 @@
> " <property name=\"NotifyAccess\" type=\"s\" access=\"read\"/>\n" \
> " <property name=\"RestartUSec\" type=\"t\" access=\"read\"/>\n" \
> " <property name=\"TimeoutUSec\" type=\"t\" access=\"read\"/>\n" \
> + " <property name=\"WatchdogTimestamp\" type=\"t\" access=\"read\"/>\n" \
> + " <property name=\"WatchdogTimestampMonotonic\" type=\"t\" access=\"read\"/>\n" \
> BUS_EXEC_COMMAND_INTERFACE("ExecStartPre") \
> BUS_EXEC_COMMAND_INTERFACE("ExecStart") \
> BUS_EXEC_COMMAND_INTERFACE("ExecStartPost") \
> @@ -87,6 +89,7 @@ const char bus_service_invalidating_properties[] =
> "ExecStop\0"
> "ExecStopPost\0"
> "ExecMain\0"
> + "WatchdogTimestamp\0"
> "MainPID\0"
> "ControlPID\0"
> "StatusText\0";
> @@ -104,6 +107,8 @@ DBusHandlerResult bus_service_message_handler(Unit *u, DBusConnection *connectio
> { "org.freedesktop.systemd1.Service", "NotifyAccess", bus_service_append_notify_access, "s", &u->service.notify_access },
> { "org.freedesktop.systemd1.Service", "RestartUSec", bus_property_append_usec, "t", &u->service.restart_usec },
> { "org.freedesktop.systemd1.Service", "TimeoutUSec", bus_property_append_usec, "t", &u->service.timeout_usec },
> + { "org.freedesktop.systemd1.Service", "WatchdogTimestamp", bus_property_append_usec, "t", &u->service.watchdog_timestamp.realtime },
> + { "org.freedesktop.systemd1.Service", "WatchdogTimestampMonotonic",bus_property_append_usec,"t", &u->service.watchdog_timestamp.monotonic },
> BUS_EXEC_COMMAND_PROPERTY("org.freedesktop.systemd1.Service", u->service.exec_command[SERVICE_EXEC_START_PRE], "ExecStartPre"),
> BUS_EXEC_COMMAND_PROPERTY("org.freedesktop.systemd1.Service", u->service.exec_command[SERVICE_EXEC_START], "ExecStart"),
> BUS_EXEC_COMMAND_PROPERTY("org.freedesktop.systemd1.Service", u->service.exec_command[SERVICE_EXEC_START_POST], "ExecStartPost"),
> diff --git a/src/sd-daemon.h b/src/sd-daemon.h
> index 46dc7fd..17536f7 100644
> --- a/src/sd-daemon.h
> +++ b/src/sd-daemon.h
> @@ -217,6 +217,11 @@ int sd_is_mq(int fd, const char *path);
> MAINPID=... The main pid of a daemon, in case systemd did not
> fork off the process itself. Example: "MAINPID=4711"
>
> + WATCHDOG=1 Tells systemd to update the watchdog timestamp.
> + Services using this feature should do this in
> + regular intervals. A watchdog framework can use the
> + timestamps to detect failed services.
> +
> Daemons can choose to send additional variables. However, it is
> recommended to prefix variable names not listed above with X_.
>
> diff --git a/src/service.c b/src/service.c
> index eb475d9..2bd47da 100644
> --- a/src/service.c
> +++ b/src/service.c
> @@ -194,6 +194,19 @@ static void service_connection_unref(Service *s) {
> s->accept_socket = NULL;
> }
>
> +static void service_stop_watchdog(Service *s) {
> + assert(s);
> +
> + s->watchdog_timestamp.realtime = 0;
> + s->watchdog_timestamp.monotonic = 0;
> +}
> +
> +static void service_reset_watchdog(Service *s) {
> + assert(s);
> +
> + dual_timestamp_get(&s->watchdog_timestamp);
> +}
> +
> static void service_done(Unit *u) {
> Service *s = SERVICE(u);
>
> @@ -1523,6 +1536,9 @@ static void service_set_state(Service *s, ServiceState state) {
> service_connection_unref(s);
> }
>
> + if (state == SERVICE_STOP)
> + service_stop_watchdog(s);
> +
> /* For the inactive states unit_notify() will trim the cgroup,
> * but for exit we have to do that ourselves... */
> if (state == SERVICE_EXITED && s->meta.manager->n_reloading <= 0)
> @@ -2994,6 +3010,10 @@ static void service_notify_message(Unit *u, pid_t pid, char **tags) {
> }
>
> }
> + if (strv_find(tags, "WATCHDOG=1")) {
> + log_debug("%s: got WATCHDOG=1", u->meta.id);
> + service_reset_watchdog(s);
> + }
>
> /* Notify clients about changed status or main pid */
> unit_add_to_dbus_queue(u);
> diff --git a/src/service.h b/src/service.h
> index e28f74b..3801e84 100644
> --- a/src/service.h
> +++ b/src/service.h
> @@ -98,6 +98,8 @@ struct Service {
> usec_t restart_usec;
> usec_t timeout_usec;
>
> + dual_timestamp watchdog_timestamp;
> +
> ExecCommand* exec_command[_SERVICE_EXEC_COMMAND_MAX];
> ExecContext exec_context;
>
> --
> 1.7.7
>
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