Merge pull request #4745 from joukewitteveen/notify

Improvements for notify services (including #4212)

Author: evverx

NEWS

@@ -17,6 +17,10 @@ CHANGES WITH 233 in spe
           The 'n' choice for the confirmation spawn prompt has been removed,
           because its meaning was confusing.
 
+        * Services of Type=notify require a READY=1 notification to be sent
+          during startup. If no such message is sent, the service now fails,
+          even if the main process exited with a successful exit code.
+
 CHANGES WITH 232:
 
         * The new RemoveIPC= option can be used to remove IPC objects owned by

man/systemd.exec.xml

@@ -1772,9 +1772,9 @@
         <listitem><para>Only defined for the service unit type, this environment variable is passed to all
         <varname>ExecStop=</varname> and <varname>ExecStopPost=</varname> processes, and encodes the service
         "result". Currently, the following values are defined: <literal>protocol</literal> (in case of a protocol
-        violation; if a service did not take the steps required by its configuration), <literal>timeout</literal> (in
-        case of an operation timeout), <literal>exit-code</literal> (if a service process exited with a non-zero exit
-        code; see <varname>$EXIT_CODE</varname> below for the actual exit code returned), <literal>signal</literal>
+        violation; if a service did not take the steps required by its unit configuration), <literal>timeout</literal>
+        (in case of an operation timeout), <literal>exit-code</literal> (if a service process exited with a non-zero
+        exit code; see <varname>$EXIT_CODE</varname> below for the actual exit code returned), <literal>signal</literal>
         (if a service process was terminated abnormally by a signal; see <varname>$EXIT_CODE</varname> below for the
         actual signal used for the termination), <literal>core-dump</literal> (if a service process terminated
         abnormally and dumped core), <literal>watchdog</literal> (if the watchdog keep-alive ping was enabled for the

man/systemd.service.xml

@@ -798,11 +798,14 @@
         notification socket, as accessible via the
         <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>
         call. Takes one of <option>none</option> (the default),
-        <option>main</option> or <option>all</option>. If
-        <option>none</option>, no daemon status updates are accepted
-        from the service processes, all status update messages are
-        ignored. If <option>main</option>, only service updates sent
-        from the main process of the service are accepted. If
+        <option>main</option>, <option>exec</option> or
+        <option>all</option>. If <option>none</option>, no daemon status
+        updates are accepted from the service processes, all status
+        update messages are ignored. If <option>main</option>, only
+        service updates sent from the main process of the service are
+        accepted. If <option>exec</option>, only service updates sent
+        from any of the control processes originating from one of the
+        <varname>Exec*=</varname> commands are accepted. If
         <option>all</option>, all services updates from all members of
         the service's control group are accepted. This option should
         be set to open access to the notification socket when using

src/core/service.c

@@ -1179,6 +1179,25 @@ static int service_collect_fds(Service *s, int **fds, char ***fd_names) {
         return rn_fds;
 }
 
+static bool service_exec_needs_notify_socket(Service *s, ExecFlags flags) {
+        assert(s);
+
+        /* Notifications are accepted depending on the process and
+         * the access setting of the service:
+         *     process: \ access:  NONE  MAIN  EXEC   ALL
+         *     main                  no   yes   yes   yes
+         *     control               no    no   yes   yes
+         *     other (forked)        no    no    no   yes */
+
+        if (flags & EXEC_IS_CONTROL)
+                /* A control process */
+                return IN_SET(s->notify_access, NOTIFY_EXEC, NOTIFY_ALL);
+
+        /* We only spawn main processes and control processes, so any
+         * process that is not a control process is a main process */
+        return s->notify_access != NOTIFY_NONE;
+}
+
 static int service_spawn(
                 Service *s,
                 ExecCommand *c,
@@ -1252,7 +1271,7 @@ static int service_spawn(
         if (!our_env)
                 return -ENOMEM;
 
-        if ((flags & EXEC_IS_CONTROL) ? s->notify_access == NOTIFY_ALL : s->notify_access != NOTIFY_NONE)
+        if (service_exec_needs_notify_socket(s, flags))
                 if (asprintf(our_env + n_env++, "NOTIFY_SOCKET=%s", UNIT(s)->manager->notify_socket) < 0)
                         return -ENOMEM;
 
@@ -2579,11 +2598,16 @@ static void service_notify_cgroup_empty_event(Unit *u) {
                  * SIGCHLD for. */
 
         case SERVICE_START:
-        case SERVICE_START_POST:
-                if (s->type == SERVICE_NOTIFY)
+                if (s->type == SERVICE_NOTIFY) {
                         /* No chance of getting a ready notification anymore */
                         service_enter_signal(s, SERVICE_FINAL_SIGTERM, SERVICE_FAILURE_PROTOCOL);
-                else if (s->pid_file_pathspec) {
+                        break;
+                }
+
+                /* Fall through */
+
+        case SERVICE_START_POST:
+                if (s->pid_file_pathspec) {
                         /* Give up hoping for the daemon to write its PID file */
                         log_unit_warning(u, "Daemon never wrote its PID file. Failing.");
 
@@ -3056,7 +3080,18 @@ static void service_notify_message(Unit *u, pid_t pid, char **tags, FDSet *fds)
                 if (s->main_pid != 0)
                         log_unit_warning(u, "Got notification message from PID "PID_FMT", but reception only permitted for main PID "PID_FMT, pid, s->main_pid);
                 else
-                        log_unit_debug(u, "Got notification message from PID "PID_FMT", but reception only permitted for main PID which is currently not known", pid);
+                        log_unit_warning(u, "Got notification message from PID "PID_FMT", but reception only permitted for main PID which is currently not known", pid);
+                return;
+        } else if (s->notify_access == NOTIFY_EXEC && pid != s->main_pid && pid != s->control_pid) {
+                if (s->main_pid != 0 && s->control_pid != 0)
+                        log_unit_warning(u, "Got notification message from PID "PID_FMT", but reception only permitted for main PID "PID_FMT" and control PID "PID_FMT,
+                                         pid, s->main_pid, s->control_pid);
+                else if (s->main_pid != 0)
+                        log_unit_warning(u, "Got notification message from PID "PID_FMT", but reception only permitted for main PID "PID_FMT, pid, s->main_pid);
+                else if (s->control_pid != 0)
+                        log_unit_warning(u, "Got notification message from PID "PID_FMT", but reception only permitted for control PID "PID_FMT, pid, s->control_pid);
+                else
+                        log_unit_warning(u, "Got notification message from PID "PID_FMT", but reception only permitted for main PID and control PID which are currently not known", pid);
                 return;
         } else
                 log_unit_debug(u, "Got notification message from PID "PID_FMT" (%s)", pid, isempty(cc) ? "n/a" : cc);
@@ -3066,6 +3101,8 @@ static void service_notify_message(Unit *u, pid_t pid, char **tags, FDSet *fds)
         if (e && IN_SET(s->state, SERVICE_START, SERVICE_START_POST, SERVICE_RUNNING, SERVICE_RELOAD)) {
                 if (parse_pid(e, &pid) < 0)
                         log_unit_warning(u, "Failed to parse MAINPID= field in notification message: %s", e);
+                else if (pid == s->control_pid)
+                        log_unit_warning(u, "A control process cannot also be the main process");
                 else {
                         service_set_main_pid(s, pid);
                         unit_watch_pid(UNIT(s), pid);
@@ -3381,6 +3418,7 @@ DEFINE_STRING_TABLE_LOOKUP(service_exec_command, ServiceExecCommand);
 static const char* const notify_access_table[_NOTIFY_ACCESS_MAX] = {
         [NOTIFY_NONE] = "none",
         [NOTIFY_MAIN] = "main",
+        [NOTIFY_EXEC] = "exec",
         [NOTIFY_ALL] = "all"
 };
 

src/core/service.h

@@ -65,6 +65,7 @@ typedef enum NotifyAccess {
         NOTIFY_NONE,
         NOTIFY_ALL,
         NOTIFY_MAIN,
+        NOTIFY_EXEC,
         _NOTIFY_ACCESS_MAX,
         _NOTIFY_ACCESS_INVALID = -1
 } NotifyAccess;

src/shared/bus-unit-util.c

@@ -764,6 +764,7 @@ static const struct {
         const char *result, *explanation;
 } explanations [] = {
         { "resources",   "of unavailable resources or another system error" },
+        { "protocol",    "the service did not take the steps required by its unit configuration" },
         { "timeout",     "a timeout was exceeded" },
         { "exit-code",   "the control process exited with error code" },
         { "signal",      "a fatal signal was delivered to the control process" },