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service: add watchdog timestamp

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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.
This commit is contained in:
Michael Olbrich 2012-02-01 17:17:12 +01:00 committed by Lennart Poettering
parent c4aa65e714
commit a6927d7ffc
5 changed files with 67 additions and 18 deletions
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12
man/sd_notify.xml
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@ -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

42
src/dbus-service.c
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@ -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") \
@ -86,6 +88,8 @@ const char bus_service_invalidating_properties[] =
"ExecStop\0"
"ExecStopPost\0"
"ExecMain\0"
"WatchdogTimestamp\0"
"WatchdogTimestampMonotonic\0"
"MainPID\0"
"ControlPID\0"
"StatusText\0";
@ -106,32 +110,34 @@ static const BusProperty bus_exec_main_status_properties[] = {
};
static const BusProperty bus_service_properties[] = {
{ "Type", bus_service_append_type, "s", offsetof(Service, type) },
{ "Restart", bus_service_append_restart, "s", offsetof(Service, restart) },
{ "PIDFile", bus_property_append_string, "s", offsetof(Service, pid_file), true },
{ "NotifyAccess", bus_service_append_notify_access, "s", offsetof(Service, notify_access) },
{ "RestartUSec", bus_property_append_usec, "t", offsetof(Service, restart_usec) },
{ "TimeoutUSec", bus_property_append_usec, "t", offsetof(Service, timeout_usec) },
{ "Type", bus_service_append_type, "s", offsetof(Service, type) },
{ "Restart", bus_service_append_restart, "s", offsetof(Service, restart) },
{ "PIDFile", bus_property_append_string, "s", offsetof(Service, pid_file), true },
{ "NotifyAccess", bus_service_append_notify_access, "s", offsetof(Service, notify_access) },
{ "RestartUSec", bus_property_append_usec, "t", offsetof(Service, restart_usec) },
{ "TimeoutUSec", bus_property_append_usec, "t", offsetof(Service, timeout_usec) },
{ "WatchdogTimestamp", bus_property_append_usec, "t", offsetof(Service, watchdog_timestamp.realtime) },
{ "WatchdogTimestampMonotonic",bus_property_append_usec, "t", offsetof(Service, watchdog_timestamp.monotonic) },
BUS_EXEC_COMMAND_PROPERTY("ExecStartPre", offsetof(Service, exec_command[SERVICE_EXEC_START_PRE]), true ),
BUS_EXEC_COMMAND_PROPERTY("ExecStart", offsetof(Service, exec_command[SERVICE_EXEC_START]), true ),
BUS_EXEC_COMMAND_PROPERTY("ExecStartPost", offsetof(Service, exec_command[SERVICE_EXEC_START_POST]), true ),
BUS_EXEC_COMMAND_PROPERTY("ExecReload", offsetof(Service, exec_command[SERVICE_EXEC_RELOAD]), true ),
BUS_EXEC_COMMAND_PROPERTY("ExecStop", offsetof(Service, exec_command[SERVICE_EXEC_STOP]), true ),
BUS_EXEC_COMMAND_PROPERTY("ExecStopPost", offsetof(Service, exec_command[SERVICE_EXEC_STOP_POST]), true ),
{ "PermissionsStartOnly", bus_property_append_bool, "b", offsetof(Service, permissions_start_only) },
{ "RootDirectoryStartOnly", bus_property_append_bool, "b", offsetof(Service, root_directory_start_only) },
{ "RemainAfterExit", bus_property_append_bool, "b", offsetof(Service, remain_after_exit) },
{ "GuessMainPID", bus_property_append_bool, "b", offsetof(Service, guess_main_pid) },
{ "MainPID", bus_property_append_pid, "u", offsetof(Service, main_pid) },
{ "ControlPID", bus_property_append_pid, "u", offsetof(Service, control_pid) },
{ "BusName", bus_property_append_string, "s", offsetof(Service, bus_name), true },
{ "StatusText", bus_property_append_string, "s", offsetof(Service, status_text), true },
{ "PermissionsStartOnly", bus_property_append_bool, "b", offsetof(Service, permissions_start_only) },
{ "RootDirectoryStartOnly", bus_property_append_bool, "b", offsetof(Service, root_directory_start_only) },
{ "RemainAfterExit", bus_property_append_bool, "b", offsetof(Service, remain_after_exit) },
{ "GuessMainPID", bus_property_append_bool, "b", offsetof(Service, guess_main_pid) },
{ "MainPID", bus_property_append_pid, "u", offsetof(Service, main_pid) },
{ "ControlPID", bus_property_append_pid, "u", offsetof(Service, control_pid) },
{ "BusName", bus_property_append_string, "s", offsetof(Service, bus_name), true },
{ "StatusText", bus_property_append_string, "s", offsetof(Service, status_text), true },
#ifdef HAVE_SYSV_COMPAT
{ "SysVRunLevels", bus_property_append_string, "s", offsetof(Service, sysv_runlevels), true },
{ "SysVStartPriority", bus_property_append_int, "i", offsetof(Service, sysv_start_priority) },
{ "SysVPath", bus_property_append_string, "s", offsetof(Service, sysv_path), true },
{ "SysVRunLevels", bus_property_append_string, "s", offsetof(Service, sysv_runlevels), true },
{ "SysVStartPriority", bus_property_append_int, "i", offsetof(Service, sysv_start_priority) },
{ "SysVPath", bus_property_append_string, "s", offsetof(Service, sysv_path), true },
#endif
{ "FsckPassNo", bus_property_append_int, "i", offsetof(Service, fsck_passno) },
{ "FsckPassNo", bus_property_append_int, "i", offsetof(Service, fsck_passno) },
{ NULL, }
};

24
src/service.c
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@ -205,6 +205,19 @@ static void service_connection_unref(Service *s) {
unit_ref_unset(&s->accept_socket);
}
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);
@ -1476,6 +1489,9 @@ 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 && UNIT(s)->manager->n_reloading <= 0)
@ -2411,6 +2427,8 @@ static int service_serialize(Unit *u, FILE *f, FDSet *fds) {
unit_serialize_item_format(u, f, "main-exec-status-status", "%i", s->main_exec_status.status);
}
}
if (dual_timestamp_is_set(&s->watchdog_timestamp))
dual_timestamp_serialize(f, "watchdog-timestamp", &s->watchdog_timestamp);
return 0;
}
@ -2511,6 +2529,8 @@ static int service_deserialize_item(Unit *u, const char *key, const char *value,
dual_timestamp_deserialize(value, &s->main_exec_status.start_timestamp);
else if (streq(key, "main-exec-status-exit"))
dual_timestamp_deserialize(value, &s->main_exec_status.exit_timestamp);
else if (streq(key, "watchdog-timestamp"))
dual_timestamp_deserialize(value, &s->watchdog_timestamp);
else
log_debug("Unknown serialization key '%s'", key);
@ -3069,6 +3089,10 @@ 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->id);
service_reset_watchdog(s);
}
/* Notify clients about changed status or main pid */
unit_add_to_dbus_queue(u);

2
src/service.h
View File

@ -100,6 +100,8 @@ struct Service {
usec_t restart_usec;
usec_t timeout_usec;
dual_timestamp watchdog_timestamp;
ExecCommand* exec_command[_SERVICE_EXEC_COMMAND_MAX];
ExecContext exec_context;

5
src/systemd/sd-daemon.h
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@ -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_.