8 #include <unordered_set>
14 #include "service-listener.h"
15 #include "service-constants.h"
19 * This header defines service_record, a data record maintaining information about a service,
20 * and service_set, a set of interdependent service records. It also defines some associated
21 * types and exceptions.
25 * Services have both a current state and a desired state. The desired state can be
26 * either STARTED or STOPPED. The current state can also be STARTING or STOPPING.
27 * A service can be "pinned" in either the STARTED or STOPPED states to prevent it
28 * from leaving that state until it is unpinned.
30 * The total state is a combination of the two, current and desired:
31 * STOPPED/STOPPED : stopped and will remain stopped
32 * STOPPED/STARTED : stopped (pinned), must be unpinned to start
33 * STARTING/STARTED : starting, but not yet started. Dependencies may also be starting.
34 * STARTING/STOPPED : as above, but the service will be stopped again as soon as it has
36 * STARTED/STARTED : running and will continue running.
37 * STARTED/STOPPED : started (pinned), must be unpinned to stop
38 * STOPPING/STOPPED : stopping and will stop. Dependents may be stopping.
39 * STOPPING/STARTED : as above, but the service will be re-started again once it stops.
41 * A scripted service is in the STARTING/STOPPING states during the script execution.
42 * A process service is in the STOPPING state when it has been signalled to stop, and is
43 * in the STARTING state when waiting for dependencies to start or for the exec() call in
44 * the forked child to complete and return a status.
46 * Acquisition/release:
48 * Each service has a dependent-count ("required_by"). This starts at 0, adds 1 if the
49 * service has explicitly been started (i.e. "start_explicit" is true), and adds 1 for
50 * each dependent service which is not STOPPED (including dependents with a soft dependency).
51 * When required_by transitions to 0, the service is stopped (unless it is pinned). When
52 * require_by transitions from 0, the service is started (unless pinned).
54 * So, in general, the dependent-count determines the desired state (STARTED if the count
55 * is greater than 0, otherwise STOPPED). However, a service can be issued a stop-and-take
56 * down order (via `stop(true)'); this will first stop dependent services, which may restart
57 * and cancel the stop of the former service. Finally, a service can be force-stopped, which
58 * means that its stop process cannot be cancelled (though it may still be put in a desired
59 * state of STARTED, meaning it will start immediately upon stopping).
63 * A service may be "pinned" in either STARTED or STOPPED states (or even both). Once it
64 * reaches a pinned state, a service will not leave that state, though its desired state
65 * may still be set. (Note that pinning prevents, but never causes, state transition).
67 * The priority of the different state deciders is:
70 * - desired state (which is manipulated by require/release operations)
72 * So a forced stop cannot occur until the service is not pinned started, for instance.
74 * Two-phase transition
75 * --------------------
76 * Transition between states occurs in two phases: propagation and execution. In both phases
77 * a linked-list queue is used to keep track of which services need processing; this avoids
78 * recursion (which would be of unknown depth and therefore liable to stack overflow).
80 * In the propagation phase, acquisition/release messages are processed, and desired state may be
81 * altered accordingly. Start and stop requests are also propagated in this phase. The state may
82 * be set to STARTING or STOPPING to reflect the desired state, but will never be set to STARTED
83 * or STOPPED (that happens in the execution phase).
85 * Propagation variables:
86 * prop_acquire: the service has transitioned to an acquired state and must issue an acquire
88 * prop_release: the service has transitioned to a released state and must issue a release on
91 * prop_start: the service should start
92 * prop_stop: the service should stop
94 * Note that "prop_acquire"/"prop_release" form a pair which cannot both be set at the same time
95 * which is enforced via explicit checks. For "prop_start"/"prop_stop" this occurs implicitly.
97 * In the execution phase, actions are taken to achieve the desired state. Actual state may
98 * transition according to the current and desired states. Processes can be sent signals, etc
99 * in order to stop them. A process can restart if it stops, but it does so by raising prop_start
100 * which needs to be processed in a second transition phase. Seeing as starting never causes
101 * another process to stop, the transition-execute-transition cycle always ends at the 2nd
102 * transition stage, at the latest.
105 struct onstart_flags_t {
106 bool rw_ready : 1; // file system should be writable once this service starts
107 bool log_ready : 1; // syslog should be available once this service starts
109 // Not actually "onstart" commands:
110 bool no_sigterm : 1; // do not send SIGTERM
111 bool runs_on_console : 1; // run "in the foreground"
112 bool starts_on_console : 1; // starts in the foreground
113 bool pass_cs_fd : 1; // pass this service a control socket connection via fd
115 onstart_flags_t() noexcept : rw_ready(false), log_ready(false),
116 no_sigterm(false), runs_on_console(false), starts_on_console(false), pass_cs_fd(false)
121 // Exception while loading a service
122 class service_load_exc
125 std::string serviceName;
126 std::string excDescription;
129 service_load_exc(std::string serviceName, std::string &&desc) noexcept
130 : serviceName(serviceName), excDescription(std::move(desc))
135 class service_not_found : public service_load_exc
138 service_not_found(std::string serviceName) noexcept
139 : service_load_exc(serviceName, "Service description not found.")
144 class service_cyclic_dependency : public service_load_exc
147 service_cyclic_dependency(std::string serviceName) noexcept
148 : service_load_exc(serviceName, "Has cyclic dependency.")
153 class service_description_exc : public service_load_exc
156 service_description_exc(std::string serviceName, std::string &&extraInfo) noexcept
157 : service_load_exc(serviceName, std::move(extraInfo))
162 class service_record;
164 class base_process_service;
166 enum class dependency_type
169 SOFT, // dependency starts in parallel, failure/stop does not affect dependent
170 WAITS_FOR, // as for SOFT, but dependent waits until dependency starts/fails before starting
171 MILESTONE // dependency must start successfully, but once started the dependency becomes soft
174 /* Service dependency record */
177 service_record * from;
181 /* Whether the 'from' service is waiting for the 'to' service to start */
183 /* Whether the 'from' service is holding an acquire on the 'to' service */
186 const dependency_type dep_type;
188 service_dep(service_record * from, service_record * to, dependency_type dep_type_p) noexcept
189 : from(from), to(to), waiting_on(false), holding_acq(false), dep_type(dep_type_p)
192 service_record * get_from() noexcept
197 service_record * get_to() noexcept
203 /* preliminary service dependency information */
207 service_record * const to;
208 dependency_type const dep_type;
210 prelim_dep(service_record *to_p, dependency_type dep_type_p) : to(to_p), dep_type(dep_type_p)
216 class service_child_watcher : public eventloop_t::child_proc_watcher_impl<service_child_watcher>
219 base_process_service * service;
220 dasynq::rearm status_change(eventloop_t &eloop, pid_t child, int status) noexcept;
222 service_child_watcher(base_process_service * sr) noexcept : service(sr) { }
225 // Watcher for the pipe used to receive exec() failure status errno
226 class exec_status_pipe_watcher : public eventloop_t::fd_watcher_impl<exec_status_pipe_watcher>
229 base_process_service * service;
230 dasynq::rearm fd_event(eventloop_t &eloop, int fd, int flags) noexcept;
232 exec_status_pipe_watcher(base_process_service * sr) noexcept : service(sr) { }
235 // service_record: base class for service record containing static information
236 // and current state of each service.
238 // This abstract base class defines the dependency behaviour of services. The actions to actually bring a
239 // service up or down are specified by subclasses in the virtual methods (see especially bring_up() and
245 using string = std::string;
246 using time_val = dasynq::time_val;
250 service_type_t record_type; /* ServiceType::DUMMY, PROCESS, SCRIPTED, INTERNAL */
251 service_state_t service_state = service_state_t::STOPPED; /* service_state_t::STOPPED, STARTING, STARTED, STOPPING */
252 service_state_t desired_state = service_state_t::STOPPED; /* service_state_t::STOPPED / STARTED */
257 onstart_flags_t onstart_flags;
259 string logfile; // log file name, empty string specifies /dev/null
261 bool auto_restart : 1; // whether to restart this (process) if it dies unexpectedly
262 bool smooth_recovery : 1; // whether the service process can restart without bringing down service
264 bool pinned_stopped : 1;
265 bool pinned_started : 1;
266 bool waiting_for_deps : 1; // if STARTING, whether we are waiting for dependencies (inc console) to start
267 // if STOPPING, whether we are waiting for dependents to stop
268 bool waiting_for_execstat : 1; // if we are waiting for exec status after fork()
269 bool start_explicit : 1; // whether we are are explicitly required to be started
271 bool prop_require : 1; // require must be propagated
272 bool prop_release : 1; // release must be propagated
273 bool prop_failure : 1; // failure to start must be propagated
277 bool restarting : 1; // re-starting after unexpected termination
279 int required_by = 0; // number of dependents wanting this service to be started
281 // list of dependencies
282 typedef std::list<service_dep> dep_list;
284 // list of dependents
285 typedef std::list<service_dep *> dpt_list;
287 dep_list depends_on; // services this one depends on
288 dpt_list dependents; // services depending on this one
290 service_set *services; // the set this service belongs to
292 std::unordered_set<service_listener *> listeners;
295 bool force_stop; // true if the service must actually stop. This is the
296 // case if for example the process dies; the service,
297 // and all its dependencies, MUST be stopped.
299 int term_signal = -1; // signal to use for process termination
301 string socket_path; // path to the socket for socket-activation service
302 int socket_perms; // socket permissions ("mode")
303 uid_t socket_uid = -1; // socket user id or -1
304 gid_t socket_gid = -1; // socket group id or -1
306 // Implementation details
308 pid_t pid = -1; // PID of the process. If state is STARTING or STOPPING,
309 // this is PID of the service script; otherwise it is the
310 // PID of the process itself (process service).
311 int exit_status; // Exit status, if the process has exited (pid == -1).
312 int socket_fd = -1; // For socket-activation services, this is the file
313 // descriptor for the socket.
315 // Data for use by service_set
319 lld_node<service_record> console_queue_node;
321 // Propagation and start/stop queues
322 lls_node<service_record> prop_queue_node;
323 lls_node<service_record> stop_queue_node;
328 void emergency_stop() noexcept;
330 // Service has actually stopped (includes having all dependents
331 // reaching STOPPED state).
332 void stopped() noexcept;
334 // Service has successfully started
335 void started() noexcept;
337 // Service failed to start (only called when in STARTING state).
338 // dep_failed: whether failure is recorded due to a dependency failing
339 void failed_to_start(bool dep_failed = false) noexcept;
341 void run_child_proc(const char * const *args, const char *logfile, bool on_console, int wpipefd,
344 // A dependency has reached STARTED state
345 void dependency_started() noexcept;
347 void all_deps_started(bool haveConsole = false) noexcept;
349 // Open the activation socket, return false on failure
350 bool open_socket() noexcept;
352 // Start all dependencies, return true if all have started
353 bool start_check_dependencies() noexcept;
355 // Check whether all dependencies have started (i.e. whether we can start now)
356 bool check_deps_started() noexcept;
358 // Whether a STOPPING service can immediately transition to STARTED.
359 bool can_interrupt_stop() noexcept
361 return waiting_for_deps && ! force_stop;
364 // A dependent has reached STOPPED state
365 void dependent_stopped() noexcept;
367 // check if all dependents have stopped
368 bool stop_check_dependents() noexcept;
370 // issue a stop to all dependents, return true if they are all already stopped
371 bool stop_dependents() noexcept;
373 void require() noexcept;
374 void release() noexcept;
375 void release_dependencies() noexcept;
377 // Check if service is, fundamentally, stopped.
378 bool is_stopped() noexcept
380 return service_state == service_state_t::STOPPED
381 || (service_state == service_state_t::STARTING && waiting_for_deps);
384 void notify_listeners(service_event_t event) noexcept
386 for (auto l : listeners) {
387 l->service_event(this, event);
391 // Queue to run on the console. 'acquired_console()' will be called when the console is available.
392 // Has no effect if the service has already queued for console.
393 void queue_for_console() noexcept;
395 // Release console (console must be currently held by this service)
396 void release_console() noexcept;
398 bool do_auto_restart() noexcept;
400 // Started state reached
401 bool process_started() noexcept;
403 // Called on transition of desired state from stopped to started (or unpinned stop)
404 void do_start() noexcept;
406 // Called on transition of desired state from started to stopped (or unpinned start)
407 void do_stop() noexcept;
409 // Set the service state
410 void set_state(service_state_t new_state) noexcept
412 service_state = new_state;
415 // Virtual functions, to be implemented by service implementations:
417 // Do any post-dependency startup; return false on failure
418 virtual bool bring_up() noexcept;
420 // All dependents have stopped, and this service should proceed to stop.
421 virtual void bring_down() noexcept;
423 // Whether a STARTING service can immediately transition to STOPPED (as opposed to
424 // having to wait for it reach STARTED and then go through STOPPING).
425 virtual bool can_interrupt_start() noexcept
427 return waiting_for_deps;
430 // Whether a STARTING service can transition to its STARTED state, once all
431 // dependencies have started.
432 virtual bool can_proceed_to_start() noexcept
437 // Interrupt startup. Returns true if service start is fully cancelled; returns false if cancel order
438 // issued but service has not yet responded (state will be set to STOPPING).
439 virtual bool interrupt_start() noexcept;
443 service_record(service_set *set, string name)
444 : service_state(service_state_t::STOPPED), desired_state(service_state_t::STOPPED),
445 auto_restart(false), smooth_recovery(false),
446 pinned_stopped(false), pinned_started(false), waiting_for_deps(false),
447 waiting_for_execstat(false), start_explicit(false),
448 prop_require(false), prop_release(false), prop_failure(false),
449 prop_start(false), prop_stop(false), restarting(false), force_stop(false)
453 record_type = service_type_t::DUMMY;
458 service_record(service_set *set, string name, service_type_t record_type_p,
459 const std::list<prelim_dep> &deplist_p)
460 : service_record(set, name)
464 this->record_type = record_type_p;
466 for (auto & pdep : deplist_p) {
467 auto b = depends_on.emplace(depends_on.end(), this, pdep.to, pdep.dep_type);
468 pdep.to->dependents.push_back(&(*b));
472 virtual ~service_record() noexcept
476 // Get the type of this service record
477 service_type_t get_type() noexcept
482 // begin transition from stopped to started state or vice versa depending on current and desired state
483 void execute_transition() noexcept;
485 void do_propagation() noexcept;
487 // Console is available.
488 void acquired_console() noexcept;
490 // Get the target (aka desired) state.
491 service_state_t get_target_state() noexcept
493 return desired_state;
496 // Set logfile, should be done before service is started
497 void set_log_file(string logfile)
499 this->logfile = logfile;
502 // Set whether this service should automatically restart when it dies
503 void set_auto_restart(bool auto_restart) noexcept
505 this->auto_restart = auto_restart;
508 void set_smooth_recovery(bool smooth_recovery) noexcept
510 this->smooth_recovery = smooth_recovery;
513 // Set "on start" flags (commands)
514 void set_flags(onstart_flags_t flags) noexcept
516 this->onstart_flags = flags;
519 // Set an additional signal (other than SIGTERM) to be used to terminate the process
520 void set_extra_termination_signal(int signo) noexcept
522 this->term_signal = signo;
525 void set_pid_file(string &&pid_file) noexcept
527 this->pid_file = std::move(pid_file);
530 void set_socket_details(string &&socket_path, int socket_perms, uid_t socket_uid, uid_t socket_gid) noexcept
532 this->socket_path = std::move(socket_path);
533 this->socket_perms = socket_perms;
534 this->socket_uid = socket_uid;
535 this->socket_gid = socket_gid;
538 const std::string &get_name() const noexcept { return service_name; }
539 service_state_t get_state() const noexcept { return service_state; }
541 void start(bool activate = true) noexcept; // start the service
542 void stop(bool bring_down = true) noexcept; // stop the service
544 void forced_stop() noexcept; // force-stop this service and all dependents
546 // Pin the service in "started" state (when it reaches the state)
547 void pin_start() noexcept
549 pinned_started = true;
552 // Pin the service in "stopped" state (when it reaches the state)
553 void pin_stop() noexcept
555 pinned_stopped = true;
558 // Remove both "started" and "stopped" pins. If the service is currently pinned
559 // in either state but would naturally be in the opposite state, it will immediately
560 // commence starting/stopping.
561 void unpin() noexcept;
563 bool isDummy() noexcept
565 return record_type == service_type_t::DUMMY;
568 // Add a listener. A listener must only be added once. May throw std::bad_alloc.
569 void addListener(service_listener * listener)
571 listeners.insert(listener);
574 // Remove a listener.
575 void removeListener(service_listener * listener) noexcept
577 listeners.erase(listener);
581 inline auto extract_prop_queue(service_record *sr) -> decltype(sr->prop_queue_node) &
583 return sr->prop_queue_node;
586 inline auto extract_stop_queue(service_record *sr) -> decltype(sr->stop_queue_node) &
588 return sr->stop_queue_node;
591 inline auto extract_console_queue(service_record *sr) -> decltype(sr->console_queue_node) &
593 return sr->console_queue_node;
597 * A service_set, as the name suggests, manages a set of services.
599 * Other than the ability to find services by name, the service set manages various queues.
600 * One is the queue for processes wishing to acquire the console. There is also a set of
601 * processes that want to start, and another set of those that want to stop. These latter
602 * two "queues" (not really queues since their order is not important) are used to prevent too
603 * much recursion and to prevent service states from "bouncing" too rapidly.
605 * A service that wishes to start or stop puts itself on the start/stop queue; a service that
606 * needs to propagate changes to dependent services or dependencies puts itself on the
607 * propagation queue. Any operation that potentially manipulates the queues must be followed
608 * by a "process queues" order (processQueues() method).
610 * Note that processQueues always repeatedly processes both queues until they are empty. The
611 * process is finite because starting a service can never cause services to stop, unless they
612 * fail to start, which should cause them to stop semi-permanently.
618 std::list<service_record *> records;
619 bool restart_enabled; // whether automatic restart is enabled (allowed)
621 shutdown_type_t shutdown_type = shutdown_type_t::CONTINUE; // Shutdown type, if stopping
623 // Services waiting for exclusive access to the console
624 dlist<service_record, extract_console_queue> console_queue;
626 // Propagation and start/stop "queues" - list of services waiting for processing
627 slist<service_record, extract_prop_queue> prop_queue;
628 slist<service_record, extract_stop_queue> stop_queue;
634 restart_enabled = true;
637 virtual ~service_set()
639 for (auto * s : records) {
644 // Start the specified service. The service will be marked active.
645 void start_service(service_record *svc)
651 // Stop the specified service. Its active mark will be cleared.
652 void stop_service(service_record *svc)
658 // Locate an existing service record.
659 service_record *find_service(const std::string &name) noexcept;
661 // Load a service description, and dependencies, if there is no existing
662 // record for the given name.
664 // ServiceLoadException (or subclass) on problem with service description
665 // std::bad_alloc on out-of-memory condition
666 virtual service_record *load_service(const char *name)
668 auto r = find_service(name);
670 throw service_not_found(name);
675 // Start the service with the given name. The named service will begin
676 // transition to the 'started' state.
678 // Throws a ServiceLoadException (or subclass) if the service description
679 // cannot be loaded or is invalid;
680 // Throws std::bad_alloc if out of memory.
681 void start_service(const char *name)
684 service_record *record = load_service(name);
685 service_set::start_service(record);
688 void add_service(service_record *svc)
690 records.push_back(svc);
693 void remove_service(service_record *svc)
695 std::remove(records.begin(), records.end(), svc);
698 // Get the list of all loaded services.
699 const std::list<service_record *> &list_services() noexcept
704 // Stop the service with the given name. The named service will begin
705 // transition to the 'stopped' state.
706 void stop_service(const std::string &name) noexcept;
708 // Add a service record to the state propagation queue. The service record will have its
709 // do_propagation() method called when the queue is processed.
710 void add_prop_queue(service_record *service) noexcept
712 if (! prop_queue.is_queued(service)) {
713 prop_queue.insert(service);
717 // Add a service record to the stop queue. The service record will have its
718 // execute_transition() method called when the queue is processed.
719 void add_transition_queue(service_record *service) noexcept
721 if (! stop_queue.is_queued(service)) {
722 stop_queue.insert(service);
726 // Process state propagation and start/stop queues, until they are empty.
727 void process_queues() noexcept
729 while (! stop_queue.is_empty() || ! prop_queue.is_empty()) {
730 while (! prop_queue.is_empty()) {
731 auto next = prop_queue.pop_front();
732 next->do_propagation();
734 while (! stop_queue.is_empty()) {
735 auto next = stop_queue.pop_front();
736 next->execute_transition();
741 // Set the console queue tail (returns previous tail)
742 void append_console_queue(service_record * newTail) noexcept
744 bool was_empty = console_queue.is_empty();
745 console_queue.append(newTail);
747 enable_console_log(false);
751 // Pull and dispatch a waiter from the console queue
752 void pull_console_queue() noexcept
754 if (console_queue.is_empty()) {
755 enable_console_log(true);
758 service_record * front = console_queue.pop_front();
759 front->acquired_console();
763 void unqueue_console(service_record * service) noexcept
765 if (console_queue.is_queued(service)) {
766 console_queue.unlink(service);
770 // Notification from service that it is active (state != STOPPED)
771 // Only to be called on the transition from inactive to active.
772 void service_active(service_record *) noexcept;
774 // Notification from service that it is inactive (STOPPED)
775 // Only to be called on the transition from active to inactive.
776 void service_inactive(service_record *) noexcept;
778 // Find out how many services are active (starting, running or stopping,
780 int count_active_services() noexcept
782 return active_services;
785 void stop_all_services(shutdown_type_t type = shutdown_type_t::HALT) noexcept
787 restart_enabled = false;
788 shutdown_type = type;
789 for (std::list<service_record *>::iterator i = records.begin(); i != records.end(); ++i) {
796 void set_auto_restart(bool restart) noexcept
798 restart_enabled = restart;
801 bool get_auto_restart() noexcept
803 return restart_enabled;
806 shutdown_type_t getShutdownType() noexcept
808 return shutdown_type;
812 class dirload_service_set : public service_set
814 const char *service_dir; // directory containing service descriptions
817 dirload_service_set(const char *service_dir_p) : service_set(), service_dir(service_dir_p)
821 service_record *load_service(const char *name) override;