src/bin/lttng-sessiond/rotation-thread.cpp

   1 /*
   2  * Copyright (C) 2017 Julien Desfossez <jdesfossez@efficios.com>
   3  * Copyright (C) 2018 Jérémie Galarneau <jeremie.galarneau@efficios.com>
   4  *
   5  * SPDX-License-Identifier: GPL-2.0-only
   6  *
   7  */
   8
   9 #define _LGPL_SOURCE
  10 #include "cmd.hpp"
  11 #include "health-sessiond.hpp"
  12 #include "lttng-sessiond.hpp"
  13 #include "notification-thread-commands.hpp"
  14 #include "rotation-thread.hpp"
  15 #include "session.hpp"
  16 #include "thread.hpp"
  17 #include "timer.hpp"
  18 #include "utils.hpp"
  19
  20 #include <common/align.hpp>
  21 #include <common/config/session-config.hpp>
  22 #include <common/defaults.hpp>
  23 #include <common/error.hpp>
  24 #include <common/eventfd.hpp>
  25 #include <common/exception.hpp>
  26 #include <common/file-descriptor.hpp>
  27 #include <common/format.hpp>
  28 #include <common/futex.hpp>
  29 #include <common/hashtable/utils.hpp>
  30 #include <common/kernel-ctl/kernel-ctl.hpp>
  31 #include <common/locked-reference.hpp>
  32 #include <common/make-unique-wrapper.hpp>
  33 #include <common/pthread-lock.hpp>
  34 #include <common/scope-exit.hpp>
  35 #include <common/time.hpp>
  36 #include <common/urcu.hpp>
  37 #include <common/utils.hpp>
  38
  39 #include <lttng/action/action-internal.hpp>
  40 #include <lttng/condition/condition-internal.hpp>
  41 #include <lttng/location-internal.hpp>
  42 #include <lttng/notification/channel-internal.hpp>
  43 #include <lttng/notification/notification-internal.hpp>
  44 #include <lttng/rotate-internal.hpp>
  45 #include <lttng/trigger/trigger.h>
  46
  47 #include <fcntl.h>
  48 #include <inttypes.h>
  49 #include <memory>
  50 #include <signal.h>
  51 #include <sys/eventfd.h>
  52 #include <sys/stat.h>
  53 #include <time.h>
  54 #include <urcu.h>
  55 #include <urcu/list.h>
  56
  57 namespace ls = lttng::sessiond;
  58
  59 /*
  60  * The timer thread enqueues jobs and wakes up the rotation thread.
  61  * When the rotation thread wakes up, it empties the queue.
  62  */
  63 struct ls::rotation_thread_timer_queue {
  64         struct lttng_pipe *event_pipe;
  65         struct cds_list_head list;
  66         pthread_mutex_t lock;
  67 };
  68
  69 namespace {
  70 struct rotation_thread_job {
  71         using uptr = std::unique_ptr<
  72                 rotation_thread_job,
  73                 lttng::memory::create_deleter_class<rotation_thread_job, lttng::free>::deleter>;
  74
  75         enum ls::rotation_thread_job_type type;
  76         struct ltt_session *session;
  77         /* List member in struct rotation_thread_timer_queue. */
  78         struct cds_list_head head;
  79 };
  80
  81 const char *get_job_type_str(enum ls::rotation_thread_job_type job_type)
  82 {
  83         switch (job_type) {
  84         case ls::rotation_thread_job_type::CHECK_PENDING_ROTATION:
  85                 return "CHECK_PENDING_ROTATION";
  86         case ls::rotation_thread_job_type::SCHEDULED_ROTATION:
  87                 return "SCHEDULED_ROTATION";
  88         default:
  89                 abort();
  90         }
  91 }
  92
  93 /*
  94  * Called with the rotation_thread_timer_queue lock held.
  95  * Return true if the same timer job already exists in the queue, false if not.
  96  */
  97 bool timer_job_exists(const ls::rotation_thread_timer_queue *queue,
  98                       ls::rotation_thread_job_type job_type,
  99                       ltt_session *session)
 100 {
 101         bool exists = false;
 102         struct rotation_thread_job *job;
 103
 104         cds_list_for_each_entry (job, &queue->list, head) {
 105                 if (job->session == session && job->type == job_type) {
 106                         exists = true;
 107                         goto end;
 108                 }
 109         }
 110 end:
 111         return exists;
 112 }
 113
 114 void check_session_rotation_pending_on_consumers(ltt_session& session, bool& _rotation_completed)
 115 {
 116         int ret = 0;
 117         struct consumer_socket *socket;
 118         struct cds_lfht_iter iter;
 119         enum consumer_trace_chunk_exists_status exists_status;
 120         uint64_t relayd_id;
 121         bool chunk_exists_on_peer = false;
 122         enum lttng_trace_chunk_status chunk_status;
 123         lttng::urcu::read_lock_guard read_lock;
 124
 125         LTTNG_ASSERT(session.chunk_being_archived);
 126
 127         /*
 128          * Check for a local pending rotation on all consumers (32-bit
 129          * user space, 64-bit user space, and kernel).
 130          */
 131         if (!session.ust_session) {
 132                 goto skip_ust;
 133         }
 134
 135         cds_lfht_for_each_entry (
 136                 session.ust_session->consumer->socks->ht, &iter, socket, node.node) {
 137                 relayd_id = session.ust_session->consumer->type == CONSUMER_DST_LOCAL ?
 138                         -1ULL :
 139                         session.ust_session->consumer->net_seq_index;
 140
 141                 lttng::pthread::lock_guard socket_lock(*socket->lock);
 142                 ret = consumer_trace_chunk_exists(socket,
 143                                                   relayd_id,
 144                                                   session.id,
 145                                                   session.chunk_being_archived,
 146                                                   &exists_status);
 147                 if (ret) {
 148                         ERR("Error occurred while checking rotation status on consumer daemon");
 149                         goto end;
 150                 }
 151
 152                 if (exists_status != CONSUMER_TRACE_CHUNK_EXISTS_STATUS_UNKNOWN_CHUNK) {
 153                         chunk_exists_on_peer = true;
 154                         goto end;
 155                 }
 156         }
 157
 158 skip_ust:
 159         if (!session.kernel_session) {
 160                 goto skip_kernel;
 161         }
 162
 163         cds_lfht_for_each_entry (
 164                 session.kernel_session->consumer->socks->ht, &iter, socket, node.node) {
 165                 lttng::pthread::lock_guard socket_lock(*socket->lock);
 166
 167                 relayd_id = session.kernel_session->consumer->type == CONSUMER_DST_LOCAL ?
 168                         -1ULL :
 169                         session.kernel_session->consumer->net_seq_index;
 170
 171                 ret = consumer_trace_chunk_exists(socket,
 172                                                   relayd_id,
 173                                                   session.id,
 174                                                   session.chunk_being_archived,
 175                                                   &exists_status);
 176                 if (ret) {
 177                         ERR("Error occurred while checking rotation status on consumer daemon");
 178                         goto end;
 179                 }
 180
 181                 if (exists_status != CONSUMER_TRACE_CHUNK_EXISTS_STATUS_UNKNOWN_CHUNK) {
 182                         chunk_exists_on_peer = true;
 183                         goto end;
 184                 }
 185         }
 186 skip_kernel:
 187 end:
 188
 189         if (!chunk_exists_on_peer) {
 190                 uint64_t chunk_being_archived_id;
 191
 192                 chunk_status = lttng_trace_chunk_get_id(session.chunk_being_archived,
 193                                                         &chunk_being_archived_id);
 194                 LTTNG_ASSERT(chunk_status == LTTNG_TRACE_CHUNK_STATUS_OK);
 195                 DBG("Rotation of trace archive %" PRIu64
 196                     " of session \"%s\" is complete on all consumers",
 197                     chunk_being_archived_id,
 198                     session.name);
 199         }
 200
 201         _rotation_completed = !chunk_exists_on_peer;
 202         if (ret) {
 203                 ret = session_reset_rotation_state(session, LTTNG_ROTATION_STATE_ERROR);
 204                 if (ret) {
 205                         ERR("Failed to reset rotation state of session \"%s\"", session.name);
 206                 }
 207         }
 208 }
 209
 210 /*
 211  * Check if the last rotation was completed, called with session lock held.
 212  * Should only return non-zero in the event of a fatal error. Doing so will
 213  * shutdown the thread.
 214  */
 215 int check_session_rotation_pending(ltt_session& session,
 216                                    notification_thread_handle& notification_thread_handle)
 217 {
 218         int ret;
 219         struct lttng_trace_archive_location *location;
 220         enum lttng_trace_chunk_status chunk_status;
 221         bool rotation_completed = false;
 222         const char *archived_chunk_name;
 223         uint64_t chunk_being_archived_id;
 224
 225         if (!session.chunk_being_archived) {
 226                 ret = 0;
 227                 goto end;
 228         }
 229
 230         chunk_status =
 231                 lttng_trace_chunk_get_id(session.chunk_being_archived, &chunk_being_archived_id);
 232         LTTNG_ASSERT(chunk_status == LTTNG_TRACE_CHUNK_STATUS_OK);
 233
 234         DBG("Checking for pending rotation on session \"%s\", trace archive %" PRIu64,
 235             session.name,
 236             chunk_being_archived_id);
 237
 238         /*
 239          * The rotation-pending check timer of a session is launched in
 240          * one-shot mode. If the rotation is incomplete, the rotation
 241          * thread will re-enable the pending-check timer.
 242          *
 243          * The timer thread can't stop the timer itself since it is involved
 244          * in the check for the timer's quiescence.
 245          */
 246         ret = timer_session_rotation_pending_check_stop(session);
 247         if (ret) {
 248                 goto check_ongoing_rotation;
 249         }
 250
 251         check_session_rotation_pending_on_consumers(session, rotation_completed);
 252         if (!rotation_completed || session.rotation_state == LTTNG_ROTATION_STATE_ERROR) {
 253                 goto check_ongoing_rotation;
 254         }
 255
 256         /*
 257          * Now we can clear the "ONGOING" state in the session. New
 258          * rotations can start now.
 259          */
 260         chunk_status = lttng_trace_chunk_get_name(
 261                 session.chunk_being_archived, &archived_chunk_name, nullptr);
 262         LTTNG_ASSERT(chunk_status == LTTNG_TRACE_CHUNK_STATUS_OK);
 263         free(session.last_archived_chunk_name);
 264         session.last_archived_chunk_name = strdup(archived_chunk_name);
 265         if (!session.last_archived_chunk_name) {
 266                 PERROR("Failed to duplicate archived chunk name");
 267         }
 268
 269         session_reset_rotation_state(session, LTTNG_ROTATION_STATE_COMPLETED);
 270
 271         if (!session.quiet_rotation) {
 272                 location = session_get_trace_archive_location(&session);
 273                 ret = notification_thread_command_session_rotation_completed(
 274                         &notification_thread_handle,
 275                         session.id,
 276                         session.last_archived_chunk_id.value,
 277                         location);
 278                 lttng_trace_archive_location_put(location);
 279                 if (ret != LTTNG_OK) {
 280                         ERR("Failed to notify notification thread of completed rotation for session %s",
 281                             session.name);
 282                 }
 283         }
 284
 285         ret = 0;
 286 check_ongoing_rotation:
 287         if (session.rotation_state == LTTNG_ROTATION_STATE_ONGOING) {
 288                 chunk_status = lttng_trace_chunk_get_id(session.chunk_being_archived,
 289                                                         &chunk_being_archived_id);
 290                 LTTNG_ASSERT(chunk_status == LTTNG_TRACE_CHUNK_STATUS_OK);
 291
 292                 DBG("Rotation of trace archive %" PRIu64 " is still pending for session %s",
 293                     chunk_being_archived_id,
 294                     session.name);
 295                 ret = timer_session_rotation_pending_check_start(&session,
 296                                                                  DEFAULT_ROTATE_PENDING_TIMER);
 297                 if (ret) {
 298                         ERR("Failed to re-enable rotation pending timer");
 299                         ret = -1;
 300                         goto end;
 301                 }
 302         }
 303
 304 end:
 305         return ret;
 306 }
 307
 308 /* Call with the session and session_list locks held. */
 309 int launch_session_rotation(ltt_session& session)
 310 {
 311         int ret;
 312         struct lttng_rotate_session_return rotation_return;
 313
 314         DBG("Launching scheduled time-based rotation on session \"%s\"", session.name);
 315
 316         ASSERT_SESSION_LIST_LOCKED();
 317         ASSERT_LOCKED(session.lock);
 318
 319         ret = cmd_rotate_session(&session,
 320                                  &rotation_return,
 321                                  false,
 322                                  LTTNG_TRACE_CHUNK_COMMAND_TYPE_MOVE_TO_COMPLETED);
 323         if (ret == LTTNG_OK) {
 324                 DBG("Scheduled time-based rotation successfully launched on session \"%s\"",
 325                     session.name);
 326         } else {
 327                 /* Don't consider errors as fatal. */
 328                 DBG("Scheduled time-based rotation aborted for session %s: %s",
 329                     session.name,
 330                     lttng_strerror(ret));
 331         }
 332
 333         return 0;
 334 }
 335
 336 int run_job(const rotation_thread_job& job,
 337             ltt_session& session,
 338             notification_thread_handle& notification_thread_handle)
 339 {
 340         int ret;
 341
 342         switch (job.type) {
 343         case ls::rotation_thread_job_type::SCHEDULED_ROTATION:
 344                 ret = launch_session_rotation(session);
 345                 break;
 346         case ls::rotation_thread_job_type::CHECK_PENDING_ROTATION:
 347                 ret = check_session_rotation_pending(session, notification_thread_handle);
 348                 break;
 349         default:
 350                 abort();
 351         }
 352
 353         return ret;
 354 }
 355
 356 bool shutdown_rotation_thread(void *thread_data)
 357 {
 358         auto *handle = reinterpret_cast<const ls::rotation_thread *>(thread_data);
 359
 360         return handle->shutdown();
 361 }
 362 } /* namespace */
 363
 364 ls::rotation_thread_timer_queue *ls::rotation_thread_timer_queue_create()
 365 {
 366         auto queue = zmalloc<ls::rotation_thread_timer_queue>();
 367         if (!queue) {
 368                 PERROR("Failed to allocate timer rotate queue");
 369                 goto end;
 370         }
 371
 372         queue->event_pipe = lttng_pipe_open(FD_CLOEXEC | O_NONBLOCK);
 373         CDS_INIT_LIST_HEAD(&queue->list);
 374         pthread_mutex_init(&queue->lock, nullptr);
 375 end:
 376         return queue;
 377 }
 378
 379 void ls::rotation_thread_timer_queue_destroy(struct rotation_thread_timer_queue *queue)
 380 {
 381         if (!queue) {
 382                 return;
 383         }
 384
 385         lttng_pipe_destroy(queue->event_pipe);
 386
 387         {
 388                 lttng::pthread::lock_guard queue_lock(queue->lock);
 389
 390                 LTTNG_ASSERT(cds_list_empty(&queue->list));
 391         }
 392
 393         pthread_mutex_destroy(&queue->lock);
 394         free(queue);
 395 }
 396
 397 ls::rotation_thread::rotation_thread(rotation_thread_timer_queue& rotation_timer_queue,
 398                                      notification_thread_handle& notification_thread_handle) :
 399         _rotation_timer_queue(rotation_timer_queue),
 400         _notification_thread_handle(notification_thread_handle)
 401 {
 402         _quit_pipe.reset([]() {
 403                 auto raw_pipe = lttng_pipe_open(FD_CLOEXEC);
 404                 if (!raw_pipe) {
 405                         LTTNG_THROW_POSIX("Failed to rotation thread's quit pipe", errno);
 406                 }
 407
 408                 return raw_pipe;
 409         }());
 410
 411         _notification_channel.reset([]() {
 412                 auto channel = lttng_notification_channel_create(
 413                         lttng_session_daemon_notification_endpoint);
 414                 if (!channel) {
 415                         LTTNG_THROW_ERROR(
 416                                 "Failed to create notification channel of rotation thread");
 417                 }
 418
 419                 return channel;
 420         }());
 421
 422         lttng_poll_init(&_events);
 423
 424         /*
 425          * Create pollset with size 4:
 426          *      - rotation thread quit pipe,
 427          *      - rotation thread timer queue pipe,
 428          *      - notification channel sock,
 429          *      - subscribtion change event fd
 430          */
 431         if (lttng_poll_create(&_events, 4, LTTNG_CLOEXEC) < 0) {
 432                 LTTNG_THROW_ERROR("Failed to create poll object for rotation thread");
 433         }
 434
 435         if (lttng_poll_add(&_events, lttng_pipe_get_readfd(_quit_pipe.get()), LPOLLIN) < 0) {
 436                 LTTNG_THROW_ERROR("Failed to add quit pipe read fd to poll set");
 437         }
 438
 439         if (lttng_poll_add(&_events,
 440                            lttng_pipe_get_readfd(_rotation_timer_queue.event_pipe),
 441                            LPOLLIN) < 0) {
 442                 LTTNG_THROW_ERROR("Failed to add rotation timer queue event pipe fd to poll set");
 443         }
 444
 445         if (lttng_poll_add(&_events,
 446                            _notification_channel_subscribtion_change_eventfd.fd(),
 447                            LPOLLIN) < 0) {
 448                 LTTNG_THROW_ERROR(
 449                         "Failed to add rotation thread notification channel subscription change eventfd to poll set");
 450         }
 451
 452         if (lttng_poll_add(&_events, _notification_channel->socket, LPOLLIN) < 0) {
 453                 LTTNG_THROW_ERROR("Failed to add notification channel socket fd to pollset");
 454         }
 455 }
 456
 457 ls::rotation_thread::~rotation_thread()
 458 {
 459         lttng_poll_clean(&_events);
 460 }
 461
 462 void ls::rotation_thread_enqueue_job(ls::rotation_thread_timer_queue *queue,
 463                                      ls::rotation_thread_job_type job_type,
 464                                      ltt_session *session)
 465 {
 466         const char dummy = '!';
 467         struct rotation_thread_job *job = nullptr;
 468         const char *job_type_str = get_job_type_str(job_type);
 469         lttng::pthread::lock_guard queue_lock(queue->lock);
 470
 471         if (timer_job_exists(queue, job_type, session)) {
 472                 /*
 473                  * This timer job is already pending, we don't need to add
 474                  * it.
 475                  */
 476                 return;
 477         }
 478
 479         job = zmalloc<rotation_thread_job>();
 480         if (!job) {
 481                 PERROR("Failed to allocate rotation thread job of type \"%s\" for session \"%s\"",
 482                        job_type_str,
 483                        session->name);
 484                 return;
 485         }
 486
 487         /* No reason for this to fail as the caller must hold a reference. */
 488         (void) session_get(session);
 489
 490         job->session = session;
 491         job->type = job_type;
 492         cds_list_add_tail(&job->head, &queue->list);
 493
 494         const int write_ret =
 495                 lttng_write(lttng_pipe_get_writefd(queue->event_pipe), &dummy, sizeof(dummy));
 496         if (write_ret < 0) {
 497                 /*
 498                  * We do not want to block in the timer handler, the job has
 499                  * been enqueued in the list, the wakeup pipe is probably full,
 500                  * the job will be processed when the rotation_thread catches
 501                  * up.
 502                  */
 503                 DIAGNOSTIC_PUSH
 504                 DIAGNOSTIC_IGNORE_LOGICAL_OP
 505                 if (errno == EAGAIN || errno == EWOULDBLOCK) {
 506                         DIAGNOSTIC_POP
 507                         /*
 508                          * Not an error, but would be surprising and indicate
 509                          * that the rotation thread can't keep up with the
 510                          * current load.
 511                          */
 512                         DBG("Wake-up pipe of rotation thread job queue is full");
 513                         return;
 514                 }
 515
 516                 PERROR("Failed to wake-up the rotation thread after pushing a job of type \"%s\" for session \"%s\"",
 517                        job_type_str,
 518                        session->name);
 519                 return;
 520         }
 521 }
 522
 523 void ls::rotation_thread::_handle_job_queue()
 524 {
 525         for (;;) {
 526                 rotation_thread_job::uptr job;
 527
 528                 {
 529                         /* Take the queue lock only to pop an element from the list. */
 530                         lttng::pthread::lock_guard rotation_timer_queue_lock(
 531                                 _rotation_timer_queue.lock);
 532                         if (cds_list_empty(&_rotation_timer_queue.list)) {
 533                                 break;
 534                         }
 535
 536                         job.reset(cds_list_first_entry(
 537                                 &_rotation_timer_queue.list, typeof(rotation_thread_job), head));
 538                         cds_list_del(&job->head);
 539                 }
 540
 541                 session_lock_list();
 542                 const auto unlock_list =
 543                         lttng::make_scope_exit([]() noexcept { session_unlock_list(); });
 544
 545                 /* locked_ptr will unlock the session and release the ref held by the job. */
 546                 session_lock(job->session);
 547                 auto session = ltt_session::locked_ptr(job->session);
 548
 549                 if (run_job(*job, *session, _notification_thread_handle)) {
 550                         return;
 551                 }
 552         }
 553 }
 554
 555 void ls::rotation_thread::_handle_notification(const lttng_notification& notification)
 556 {
 557         int ret = 0;
 558         const char *condition_session_name = nullptr;
 559         enum lttng_condition_status condition_status;
 560         enum lttng_evaluation_status evaluation_status;
 561         uint64_t consumed;
 562         auto *condition = lttng_notification_get_const_condition(&notification);
 563         auto *evaluation = lttng_notification_get_const_evaluation(&notification);
 564         const auto condition_type = lttng_condition_get_type(condition);
 565
 566         if (condition_type != LTTNG_CONDITION_TYPE_SESSION_CONSUMED_SIZE) {
 567                 LTTNG_THROW_ERROR("Unexpected condition type");
 568         }
 569
 570         /* Fetch info to test. */
 571         condition_status = lttng_condition_session_consumed_size_get_session_name(
 572                 condition, &condition_session_name);
 573         if (condition_status != LTTNG_CONDITION_STATUS_OK) {
 574                 LTTNG_THROW_ERROR("Session name could not be fetched from notification");
 575         }
 576
 577         evaluation_status =
 578                 lttng_evaluation_session_consumed_size_get_consumed_size(evaluation, &consumed);
 579         if (evaluation_status != LTTNG_EVALUATION_STATUS_OK) {
 580                 LTTNG_THROW_ERROR("Failed to get consumed size from evaluation");
 581         }
 582
 583         DBG_FMT("Handling session consumed size condition: session_name=`{}`, consumed_size={}",
 584                 condition_session_name,
 585                 consumed);
 586
 587         session_lock_list();
 588         const auto unlock_list = lttng::make_scope_exit([]() noexcept { session_unlock_list(); });
 589
 590         ltt_session::locked_ptr session{ [&condition_session_name]() {
 591                 auto raw_session_ptr = session_find_by_name(condition_session_name);
 592
 593                 if (raw_session_ptr) {
 594                         session_lock(raw_session_ptr);
 595                 }
 596
 597                 return raw_session_ptr;
 598         }() };
 599         if (!session) {
 600                 DBG_FMT("Failed to find session while handling notification: notification_type={}, session name=`{}`",
 601                         lttng_condition_type_str(condition_type),
 602                         condition_session_name);
 603                 /*
 604                  * Not a fatal error: a session can be destroyed before we get
 605                  * the chance to handle the notification.
 606                  */
 607                 return;
 608         }
 609
 610         if (!lttng_trigger_is_equal(session->rotate_trigger,
 611                                     lttng_notification_get_const_trigger(&notification))) {
 612                 DBG("Notification does not originate from the internal size-based scheduled rotation trigger, skipping");
 613                 return;
 614         }
 615
 616         unsubscribe_session_consumed_size_rotation(*session);
 617
 618         ret = cmd_rotate_session(
 619                 session.get(), nullptr, false, LTTNG_TRACE_CHUNK_COMMAND_TYPE_MOVE_TO_COMPLETED);
 620         switch (ret) {
 621         case LTTNG_OK:
 622                 break;
 623         case -LTTNG_ERR_ROTATION_PENDING:
 624                 DBG("Rotate already pending, subscribe to the next threshold value");
 625                 break;
 626         case -LTTNG_ERR_ROTATION_MULTIPLE_AFTER_STOP:
 627                 DBG("Rotation already happened since last stop, subscribe to the next threshold value");
 628                 break;
 629         case -LTTNG_ERR_ROTATION_AFTER_STOP_CLEAR:
 630                 DBG("Rotation already happened since last stop and clear, subscribe to the next threshold value");
 631                 break;
 632         default:
 633                 LTTNG_THROW_CTL("Failed to rotate on consumed size notification",
 634                                 static_cast<lttng_error_code>(-ret));
 635         }
 636
 637         subscribe_session_consumed_size_rotation(*session, consumed + session->rotate_size);
 638 }
 639
 640 void ls::rotation_thread::_handle_notification_channel_activity()
 641 {
 642         bool notification_pending = true;
 643
 644         /*
 645          * A notification channel may have multiple notifications queued-up internally in
 646          * its buffers. This is because a notification channel multiplexes command replies
 647          * and notifications. The current protocol specifies that multiple notifications can be
 648          * received before the reply to a command.
 649          *
 650          * In such cases, the notification channel client implementation internally queues them and
 651          * provides them on the next calls to lttng_notification_channel_get_next_notification().
 652          * This is correct with respect to the public API, which is intended to be used in "blocking
 653          * mode".
 654          *
 655          * However, this internal user relies on poll/epoll to wake-up when data is available
 656          * on the notification channel's socket. As such, it can't assume that a wake-up means only
 657          * one notification is available for consumption since many of them may have been queued in
 658          * the channel's internal buffers.
 659          */
 660         while (notification_pending) {
 661                 const auto pending_status = lttng_notification_channel_has_pending_notification(
 662                         _notification_channel.get(), &notification_pending);
 663                 if (pending_status != LTTNG_NOTIFICATION_CHANNEL_STATUS_OK) {
 664                         LTTNG_THROW_ERROR("Error occurred while checking for pending notification");
 665                 }
 666
 667                 if (!notification_pending) {
 668                         return;
 669                 }
 670
 671                 /* Receive the next notification. */
 672                 lttng_notification::uptr notification;
 673                 enum lttng_notification_channel_status next_notification_status;
 674
 675                 {
 676                         struct lttng_notification *raw_notification_ptr;
 677
 678                         next_notification_status = lttng_notification_channel_get_next_notification(
 679                                 _notification_channel.get(), &raw_notification_ptr);
 680                         notification.reset(raw_notification_ptr);
 681                 }
 682
 683                 switch (next_notification_status) {
 684                 case LTTNG_NOTIFICATION_CHANNEL_STATUS_OK:
 685                         break;
 686                 case LTTNG_NOTIFICATION_CHANNEL_STATUS_NOTIFICATIONS_DROPPED:
 687                         WARN("Dropped notification detected on notification channel used by the rotation management thread.");
 688                         return;
 689                 case LTTNG_NOTIFICATION_CHANNEL_STATUS_CLOSED:
 690                         LTTNG_THROW_ERROR("Notification channel was closed");
 691                 default:
 692                         /* Unhandled conditions / errors. */
 693                         LTTNG_THROW_ERROR("Unknown notification channel status");
 694                 }
 695
 696                 _handle_notification(*notification);
 697         }
 698 }
 699
 700 void ls::rotation_thread::_thread_function() noexcept
 701 {
 702         DBG("Started rotation thread");
 703
 704         try {
 705                 _run();
 706         } catch (const std::exception& e) {
 707                 ERR_FMT("Fatal rotation thread error: {}", e.what());
 708         }
 709
 710         DBG("Thread exit");
 711 }
 712
 713 void ls::rotation_thread::_run()
 714 {
 715         rcu_register_thread();
 716         const auto unregister_rcu_thread =
 717                 lttng::make_scope_exit([]() noexcept { rcu_unregister_thread(); });
 718
 719         rcu_thread_online();
 720         const auto offline_rcu_thread =
 721                 lttng::make_scope_exit([]() noexcept { rcu_thread_offline(); });
 722
 723         health_register(the_health_sessiond, HEALTH_SESSIOND_TYPE_ROTATION);
 724         health_code_update();
 725         const auto unregister_health =
 726                 lttng::make_scope_exit([]() noexcept { health_unregister(the_health_sessiond); });
 727
 728         const auto queue_pipe_fd = lttng_pipe_get_readfd(_rotation_timer_queue.event_pipe);
 729
 730         while (true) {
 731                 health_poll_entry();
 732                 DBG("Entering poll wait");
 733                 auto poll_wait_ret = lttng_poll_wait(&_events, -1);
 734                 DBG_FMT("Poll wait returned: ret={}", poll_wait_ret);
 735                 health_poll_exit();
 736                 if (poll_wait_ret < 0) {
 737                         /*
 738                          * Restart interrupted system call.
 739                          */
 740                         if (errno == EINTR) {
 741                                 continue;
 742                         }
 743
 744                         LTTNG_THROW_POSIX("Error encountered during lttng_poll_wait", errno);
 745                 }
 746
 747                 const auto fd_count = poll_wait_ret;
 748                 for (int i = 0; i < fd_count; i++) {
 749                         const auto fd = LTTNG_POLL_GETFD(&_events, i);
 750                         const auto revents = LTTNG_POLL_GETEV(&_events, i);
 751
 752                         DBG_FMT("Handling descriptor activity: fd={}, events={:b}", fd, revents);
 753
 754                         if (revents & LPOLLERR) {
 755                                 LTTNG_THROW_ERROR(
 756                                         fmt::format("Polling returned an error on fd: fd={}", fd));
 757                         }
 758
 759                         if (fd == _notification_channel->socket ||
 760                             fd == _notification_channel_subscribtion_change_eventfd.fd()) {
 761                                 try {
 762                                         _handle_notification_channel_activity();
 763                                 } catch (const lttng::ctl::error& e) {
 764                                         /*
 765                                          * The only non-fatal error (rotation failed), others
 766                                          * are caught at the top-level.
 767                                          */
 768                                         DBG_FMT("Control error occurred while handling activity on notification channel socket: {}",
 769                                                 e.what());
 770                                         continue;
 771                                 }
 772
 773                                 if (fd == _notification_channel_subscribtion_change_eventfd.fd()) {
 774                                         _notification_channel_subscribtion_change_eventfd
 775                                                 .decrement();
 776                                 }
 777                         } else {
 778                                 /* Job queue or quit pipe activity. */
 779
 780                                 /*
 781                                  * The job queue is serviced if there is
 782                                  * activity on the quit pipe to ensure it is
 783                                  * flushed and all references held in the queue
 784                                  * are released.
 785                                  */
 786                                 _handle_job_queue();
 787                                 if (fd == queue_pipe_fd) {
 788                                         char buf;
 789
 790                                         if (lttng_read(fd, &buf, 1) != 1) {
 791                                                 LTTNG_THROW_POSIX(
 792                                                         fmt::format(
 793                                                                 "Failed to read from wakeup pipe: fd={}",
 794                                                                 fd),
 795                                                         errno);
 796                                         }
 797                                 } else {
 798                                         DBG("Quit pipe activity");
 799                                         return;
 800                                 }
 801                         }
 802                 }
 803         }
 804 }
 805
 806 bool ls::rotation_thread::shutdown() const noexcept
 807 {
 808         const int write_fd = lttng_pipe_get_writefd(_quit_pipe.get());
 809
 810         return notify_thread_pipe(write_fd) == 1;
 811 }
 812
 813 void ls::rotation_thread::launch_thread()
 814 {
 815         auto thread = lttng_thread_create(
 816                 "Rotation",
 817                 [](void *ptr) {
 818                         auto handle = reinterpret_cast<rotation_thread *>(ptr);
 819
 820                         handle->_thread_function();
 821                         return static_cast<void *>(nullptr);
 822                 },
 823                 shutdown_rotation_thread,
 824                 nullptr,
 825                 this);
 826         if (!thread) {
 827                 LTTNG_THROW_ERROR("Failed to launch rotation thread");
 828         }
 829
 830         lttng_thread_put(thread);
 831 }
 832
 833 void ls::rotation_thread::subscribe_session_consumed_size_rotation(ltt_session& session,
 834                                                                    std::uint64_t size)
 835 {
 836         const struct lttng_credentials session_creds = {
 837                 .uid = LTTNG_OPTIONAL_INIT_VALUE(session.uid),
 838                 .gid = LTTNG_OPTIONAL_INIT_VALUE(session.gid),
 839         };
 840
 841         ASSERT_LOCKED(session.lock);
 842
 843         auto rotate_condition = lttng::make_unique_wrapper<lttng_condition, lttng_condition_put>(
 844                 lttng_condition_session_consumed_size_create());
 845         if (!rotate_condition) {
 846                 LTTNG_THROW_POSIX("Failed to create session consumed size condition object", errno);
 847         }
 848
 849         auto condition_status =
 850                 lttng_condition_session_consumed_size_set_threshold(rotate_condition.get(), size);
 851         if (condition_status != LTTNG_CONDITION_STATUS_OK) {
 852                 LTTNG_THROW_ERROR(fmt::format(
 853                         "Could not set session consumed size condition threshold: size={}", size));
 854         }
 855
 856         condition_status = lttng_condition_session_consumed_size_set_session_name(
 857                 rotate_condition.get(), session.name);
 858         if (condition_status != LTTNG_CONDITION_STATUS_OK) {
 859                 LTTNG_THROW_ERROR(fmt::format(
 860                         "Could not set session consumed size condition session name: name=`{}`",
 861                         session.name));
 862         }
 863
 864         auto notify_action = lttng::make_unique_wrapper<lttng_action, lttng_action_put>(
 865                 lttng_action_notify_create());
 866         if (!notify_action) {
 867                 LTTNG_THROW_POSIX("Could not create notify action", errno);
 868         }
 869
 870         LTTNG_ASSERT(!session.rotate_trigger);
 871         /* trigger acquires its own reference to condition and action on success. */
 872         auto trigger = lttng::make_unique_wrapper<lttng_trigger, lttng_trigger_put>(
 873                 lttng_trigger_create(rotate_condition.get(), notify_action.get()));
 874         if (!trigger) {
 875                 LTTNG_THROW_POSIX("Could not create size-based rotation trigger", errno);
 876         }
 877
 878         /* Ensure this trigger is not visible to external users. */
 879         lttng_trigger_set_hidden(trigger.get());
 880         lttng_trigger_set_credentials(trigger.get(), &session_creds);
 881
 882         auto nc_status = lttng_notification_channel_subscribe(_notification_channel.get(),
 883                                                               rotate_condition.get());
 884         if (nc_status != LTTNG_NOTIFICATION_CHANNEL_STATUS_OK) {
 885                 LTTNG_THROW_ERROR("Could not subscribe to session consumed size notification");
 886         }
 887
 888         /*
 889          * Ensure any notification queued during the subscription are consumed by queueing an
 890          * event.
 891          */
 892         _notification_channel_subscribtion_change_eventfd.increment();
 893
 894         const auto register_ret = notification_thread_command_register_trigger(
 895                 &_notification_thread_handle, trigger.get(), true);
 896         if (register_ret != LTTNG_OK) {
 897                 LTTNG_THROW_CTL(
 898                         fmt::format(
 899                                 "Failed to register trigger for automatic size-based rotation: session_name{}, size={}",
 900                                 session.name,
 901                                 size),
 902                         register_ret);
 903         }
 904
 905         /* Ownership transferred to the session. */
 906         session.rotate_trigger = trigger.release();
 907 }
 908
 909 void ls::rotation_thread::unsubscribe_session_consumed_size_rotation(ltt_session& session)
 910 {
 911         LTTNG_ASSERT(session.rotate_trigger);
 912
 913         const auto remove_session_trigger = lttng::make_scope_exit([&session]() noexcept {
 914                 lttng_trigger_put(session.rotate_trigger);
 915                 session.rotate_trigger = nullptr;
 916         });
 917
 918         const auto unsubscribe_status = lttng_notification_channel_unsubscribe(
 919                 _notification_channel.get(),
 920                 lttng_trigger_get_const_condition(session.rotate_trigger));
 921         if (unsubscribe_status != LTTNG_NOTIFICATION_CHANNEL_STATUS_OK) {
 922                 LTTNG_THROW_ERROR(fmt::format(
 923                         "Failed to unsubscribe from consumed size condition used to control automatic size-based rotations: session_name=`{}` return_code={}",
 924                         session.name,
 925                         static_cast<int>(unsubscribe_status)));
 926         }
 927
 928         /*
 929          * Ensure any notification queued during the un-subscription are consumed by queueing an
 930          * event.
 931          */
 932         _notification_channel_subscribtion_change_eventfd.increment();
 933
 934         const auto unregister_status = notification_thread_command_unregister_trigger(
 935                 &_notification_thread_handle, session.rotate_trigger);
 936         if (unregister_status != LTTNG_OK) {
 937                 LTTNG_THROW_CTL(
 938                         fmt::format(
 939                                 "Failed to unregister trigger for automatic size-based rotation: session_name{}",
 940                                 session.name),
 941                         unregister_status);
 942         }
 943 }