src/bin/lttng/commands/create.c

   1 /*
   2  * Copyright (C) 2011 - David Goulet <david.goulet@polymtl.ca>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License, version 2 only,
   6  * as published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11  * GNU General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public License along
  14  * with this program; if not, write to the Free Software Foundation, Inc.,
  15  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  16  */
  17
  18 #define _LGPL_SOURCE
  19 #include <assert.h>
  20 #include <ctype.h>
  21 #include <popt.h>
  22 #include <stdio.h>
  23 #include <stdlib.h>
  24 #include <string.h>
  25 #include <sys/stat.h>
  26 #include <sys/types.h>
  27 #include <time.h>
  28 #include <unistd.h>
  29 #include <signal.h>
  30 #include <sys/wait.h>
  31
  32 #include <common/mi-lttng.h>
  33
  34 #include "../command.h"
  35 #include "../utils.h"
  36
  37 #include <common/defaults.h>
  38 #include <common/sessiond-comm/sessiond-comm.h>
  39 #include <common/uri.h>
  40 #include <common/utils.h>
  41 #include <lttng/snapshot.h>
  42
  43 static char *opt_output_path;
  44 static char *opt_session_name;
  45 static char *opt_url;
  46 static char *opt_ctrl_url;
  47 static char *opt_data_url;
  48 static char *opt_shm_path;
  49 static int opt_no_consumer;
  50 static int opt_no_output;
  51 static int opt_snapshot;
  52 static unsigned int opt_live_timer;
  53
  54 enum {
  55         OPT_HELP = 1,
  56         OPT_LIST_OPTIONS,
  57         OPT_LIVE_TIMER,
  58 };
  59
  60 static struct mi_writer *writer;
  61
  62 static struct poptOption long_options[] = {
  63         /* longName, shortName, argInfo, argPtr, value, descrip, argDesc */
  64         {"help", 'h', POPT_ARG_NONE, NULL, OPT_HELP, NULL, NULL},
  65         {"output", 'o', POPT_ARG_STRING, &opt_output_path, 0, NULL, NULL},
  66         {"list-options", 0, POPT_ARG_NONE, NULL, OPT_LIST_OPTIONS, NULL, NULL},
  67         {"set-url",        'U', POPT_ARG_STRING, &opt_url, 0, 0, 0},
  68         {"ctrl-url",       'C', POPT_ARG_STRING, &opt_ctrl_url, 0, 0, 0},
  69         {"data-url",       'D', POPT_ARG_STRING, &opt_data_url, 0, 0, 0},
  70         {"no-output",       0, POPT_ARG_VAL, &opt_no_output, 1, 0, 0},
  71         {"no-consumer",     0, POPT_ARG_VAL, &opt_no_consumer, 1, 0, 0},
  72         {"snapshot",        0, POPT_ARG_VAL, &opt_snapshot, 1, 0, 0},
  73         {"live",            0, POPT_ARG_INT | POPT_ARGFLAG_OPTIONAL, 0, OPT_LIVE_TIMER, 0, 0},
  74         {"shm-path",        0, POPT_ARG_STRING, &opt_shm_path, 0, 0, 0},
  75         {0, 0, 0, 0, 0, 0, 0}
  76 };
  77
  78 /*
  79  * Please have a look at src/lib/lttng-ctl/lttng-ctl.c for more information on
  80  * why this declaration exists and used ONLY in for this command.
  81  */
  82 extern int _lttng_create_session_ext(const char *name, const char *url,
  83                 const char *datetime);
  84
  85 /*
  86  * Retrieve the created session and mi output it based on provided argument
  87  * This is currently a summary of what was pretty printed and is subject to
  88  * enhancements.
  89  */
  90 static int mi_created_session(const char *session_name)
  91 {
  92         int ret, i, count, found;
  93         struct lttng_session *sessions;
  94
  95         /* session_name should not be null */
  96         assert(session_name);
  97         assert(writer);
  98
  99         count = lttng_list_sessions(&sessions);
 100         if (count < 0) {
 101                 ret = count;
 102                 ERR("%s", lttng_strerror(ret));
 103                 goto error;
 104         }
 105
 106         if (count == 0) {
 107                 ERR("Error session creation failed: session %s not found", session_name);
 108                 ret = -LTTNG_ERR_SESS_NOT_FOUND;
 109                 goto end;
 110         }
 111
 112         found = 0;
 113         for (i = 0; i < count; i++) {
 114                 if (strncmp(sessions[i].name, session_name, NAME_MAX) == 0) {
 115                         found = 1;
 116                         ret = mi_lttng_session(writer, &sessions[i], 0);
 117                         if (ret) {
 118                                 goto error;
 119                         }
 120                         break;
 121                 }
 122         }
 123
 124         if (!found) {
 125                 ret = -LTTNG_ERR_SESS_NOT_FOUND;
 126         } else {
 127                 ret = CMD_SUCCESS;
 128         }
 129
 130 error:
 131         free(sessions);
 132 end:
 133         return ret;
 134 }
 135
 136 /*
 137  * For a session name, set the consumer URLs.
 138  */
 139 static int set_consumer_url(const char *session_name, const char *ctrl_url,
 140                 const char *data_url)
 141 {
 142         int ret;
 143         struct lttng_handle *handle;
 144
 145         assert(session_name);
 146
 147         /*
 148          * Set handle with the session_name, but no domain. This implies that
 149          * the actions taken with this handle apply on the tracing session
 150          * rather then the domain-specific session.
 151          */
 152         handle = lttng_create_handle(session_name, NULL);
 153         if (handle == NULL) {
 154                 ret = CMD_FATAL;
 155                 goto error;
 156         }
 157
 158         ret = lttng_set_consumer_url(handle, ctrl_url, data_url);
 159         if (ret < 0) {
 160                 goto error;
 161         }
 162
 163         if (ctrl_url) {
 164                 MSG("Control URL %s set for session %s", ctrl_url, session_name);
 165         }
 166
 167         if (data_url) {
 168                 MSG("Data URL %s set for session %s", data_url, session_name);
 169         }
 170
 171 error:
 172         lttng_destroy_handle(handle);
 173         return ret;
 174 }
 175
 176 static int add_snapshot_output(const char *session_name, const char *ctrl_url,
 177                 const char *data_url)
 178 {
 179         int ret;
 180         struct lttng_snapshot_output *output = NULL;
 181
 182         assert(session_name);
 183
 184         output = lttng_snapshot_output_create();
 185         if (!output) {
 186                 ret = CMD_FATAL;
 187                 goto error_create;
 188         }
 189
 190         if (ctrl_url) {
 191                 ret = lttng_snapshot_output_set_ctrl_url(ctrl_url, output);
 192                 if (ret < 0) {
 193                         goto error;
 194                 }
 195         }
 196
 197         if (data_url) {
 198                 ret = lttng_snapshot_output_set_data_url(data_url, output);
 199                 if (ret < 0) {
 200                         goto error;
 201                 }
 202         }
 203
 204         /* This call, if successful, populates the id of the output object. */
 205         ret = lttng_snapshot_add_output(session_name, output);
 206         if (ret < 0) {
 207                 goto error;
 208         }
 209
 210 error:
 211         lttng_snapshot_output_destroy(output);
 212 error_create:
 213         return ret;
 214 }
 215
 216 /*
 217  *  Create a tracing session.
 218  *  If no name is specified, a default name is generated.
 219  *
 220  *  Returns one of the CMD_* result constants.
 221  */
 222 static int create_session(void)
 223 {
 224         int ret;
 225         char *session_name = NULL, *traces_path = NULL, *alloc_path = NULL;
 226         char *alloc_url = NULL, *url = NULL, datetime[16];
 227         char session_name_date[NAME_MAX + 17], *print_str_url = NULL;
 228         time_t rawtime;
 229         struct tm *timeinfo;
 230         char shm_path[PATH_MAX] = "";
 231
 232         /* Get date and time for automatic session name/path */
 233         time(&rawtime);
 234         timeinfo = localtime(&rawtime);
 235         strftime(datetime, sizeof(datetime), "%Y%m%d-%H%M%S", timeinfo);
 236
 237         /* Auto session name creation */
 238         if (opt_session_name == NULL) {
 239                 ret = snprintf(session_name_date, sizeof(session_name_date),
 240                                 DEFAULT_SESSION_NAME "-%s", datetime);
 241                 if (ret < 0) {
 242                         PERROR("snprintf session name");
 243                         goto error;
 244                 }
 245                 session_name = session_name_date;
 246                 DBG("Auto session name set to %s", session_name_date);
 247         } else {
 248                 if (strlen(opt_session_name) > NAME_MAX) {
 249                         ERR("Session name too long. Length must be lower or equal to %d",
 250                                         NAME_MAX);
 251                         ret = LTTNG_ERR_SESSION_FAIL;
 252                         goto error;
 253                 }
 254                 /*
 255                  * Check if the session name begins with "auto-" or is exactly "auto".
 256                  * Both are reserved for the default session name. See bug #449 to
 257                  * understand why we need to check both here.
 258                  */
 259                 if ((strncmp(opt_session_name, DEFAULT_SESSION_NAME "-",
 260                                         strlen(DEFAULT_SESSION_NAME) + 1) == 0) ||
 261                                 (strncmp(opt_session_name, DEFAULT_SESSION_NAME,
 262                                         strlen(DEFAULT_SESSION_NAME)) == 0 &&
 263                                 strlen(opt_session_name) == strlen(DEFAULT_SESSION_NAME))) {
 264                         ERR("%s is a reserved keyword for default session(s)",
 265                                         DEFAULT_SESSION_NAME);
 266                         ret = CMD_ERROR;
 267                         goto error;
 268                 }
 269                 session_name = opt_session_name;
 270                 ret = snprintf(session_name_date, sizeof(session_name_date),
 271                                 "%s-%s", session_name, datetime);
 272                 if (ret < 0) {
 273                         PERROR("snprintf session name");
 274                         goto error;
 275                 }
 276         }
 277
 278         if ((!opt_ctrl_url && opt_data_url) || (opt_ctrl_url && !opt_data_url)) {
 279                 ERR("You need both control and data URL.");
 280                 ret = CMD_ERROR;
 281                 goto error;
 282         }
 283
 284         if (opt_output_path != NULL) {
 285                 traces_path = utils_expand_path(opt_output_path);
 286                 if (traces_path == NULL) {
 287                         ret = CMD_ERROR;
 288                         goto error;
 289                 }
 290
 291                 /* Create URL string from the local file system path */
 292                 ret = asprintf(&alloc_url, "file://%s", traces_path);
 293                 if (ret < 0) {
 294                         PERROR("asprintf url path");
 295                         ret = CMD_FATAL;
 296                         goto error;
 297                 }
 298                 /* URL to use in the lttng_create_session() call */
 299                 url = alloc_url;
 300                 print_str_url = traces_path;
 301         } else if (opt_url) { /* Handling URL (-U opt) */
 302                 url = opt_url;
 303                 print_str_url = url;
 304         } else if (opt_data_url && opt_ctrl_url) {
 305                 /*
 306                  * With both control and data, we'll be setting the consumer URL after
 307                  * session creation thus use no URL.
 308                  */
 309                 url = NULL;
 310         } else if (!opt_no_output) {
 311                 char *tmp_path;
 312
 313                 /* Auto output path */
 314                 tmp_path = utils_get_home_dir();
 315                 if (tmp_path == NULL) {
 316                         ERR("HOME path not found.\n \
 317                                         Please specify an output path using -o, --output PATH");
 318                         ret = CMD_FATAL;
 319                         goto error;
 320                 }
 321                 alloc_path = strdup(tmp_path);
 322                 if (!alloc_path) {
 323                         PERROR("allocating alloc_path");
 324                         ret = CMD_FATAL;
 325                         goto error;
 326                 }
 327                 ret = asprintf(&alloc_url,
 328                                 "file://%s/" DEFAULT_TRACE_DIR_NAME "/%s",
 329                                 alloc_path, session_name_date);
 330                 if (ret < 0) {
 331                         PERROR("asprintf trace dir name");
 332                         ret = CMD_FATAL;
 333                         goto error;
 334                 }
 335
 336                 url = alloc_url;
 337                 print_str_url = alloc_url + strlen("file://");
 338         } else {
 339                 /* No output means --no-output or --snapshot mode. */
 340                 url = NULL;
 341         }
 342
 343         /* Use default live URL if NO url is/are found. */
 344         if ((opt_live_timer && !opt_url) && (opt_live_timer && !opt_data_url)) {
 345                 ret = asprintf(&alloc_url, "net://127.0.0.1");
 346                 if (ret < 0) {
 347                         PERROR("asprintf default live URL");
 348                         ret = CMD_FATAL;
 349                         goto error;
 350                 }
 351                 url = alloc_url;
 352                 print_str_url = url;
 353         }
 354
 355         if (opt_snapshot && opt_live_timer) {
 356                 ERR("Snapshot and live modes are mutually exclusive.");
 357                 ret = CMD_ERROR;
 358                 goto error;
 359         }
 360
 361         if (opt_snapshot) {
 362                 /* No output by default. */
 363                 const char *snapshot_url = NULL;
 364
 365                 if (opt_url) {
 366                         snapshot_url = url;
 367                 } else if (!opt_data_url && !opt_ctrl_url) {
 368                         /* This is the session path that we need to use as output. */
 369                         snapshot_url = url;
 370                 }
 371                 ret = lttng_create_session_snapshot(session_name, snapshot_url);
 372         } else if (opt_live_timer) {
 373                 const char *pathname;
 374
 375                 if (opt_relayd_path) {
 376                         pathname = opt_relayd_path;
 377                 } else {
 378                         pathname = INSTALL_BIN_PATH "/lttng-relayd";
 379                 }
 380                 if (!opt_url && !opt_data_url && !check_relayd() &&
 381                                 spawn_relayd(pathname, 0) < 0) {
 382                         goto error;
 383                 }
 384                 ret = lttng_create_session_live(session_name, url, opt_live_timer);
 385         } else {
 386                 ret = _lttng_create_session_ext(session_name, url, datetime);
 387         }
 388         if (ret < 0) {
 389                 /* Don't set ret so lttng can interpret the sessiond error. */
 390                 switch (-ret) {
 391                 case LTTNG_ERR_EXIST_SESS:
 392                         WARN("Session %s already exists", session_name);
 393                         break;
 394                 default:
 395                         break;
 396                 }
 397                 goto error;
 398         }
 399
 400         if (opt_ctrl_url && opt_data_url) {
 401                 if (opt_snapshot) {
 402                         ret = add_snapshot_output(session_name, opt_ctrl_url,
 403                                         opt_data_url);
 404                 } else {
 405                         /* Setting up control URI (-C or/and -D opt) */
 406                         ret = set_consumer_url(session_name, opt_ctrl_url, opt_data_url);
 407                 }
 408                 if (ret < 0) {
 409                         /* Destroy created session because the URL are not valid. */
 410                         lttng_destroy_session(session_name);
 411                         goto error;
 412                 }
 413         }
 414
 415         if (opt_shm_path) {
 416                 ret = snprintf(shm_path, sizeof(shm_path),
 417                                 "%s/%s", opt_shm_path, session_name_date);
 418                 if (ret < 0) {
 419                         PERROR("snprintf shm_path");
 420                         goto error;
 421                 }
 422
 423                 ret = lttng_set_session_shm_path(session_name, shm_path);
 424                 if (ret < 0) {
 425                         lttng_destroy_session(session_name);
 426                         goto error;
 427                 }
 428         }
 429
 430         MSG("Session %s created.", session_name);
 431         if (print_str_url && !opt_snapshot) {
 432                 MSG("Traces will be written in %s", print_str_url);
 433
 434                 if (opt_live_timer) {
 435                         MSG("Live timer set to %u usec", opt_live_timer);
 436                 }
 437         } else if (opt_snapshot) {
 438                 if (print_str_url) {
 439                         MSG("Default snapshot output set to: %s", print_str_url);
 440                 }
 441                 MSG("Snapshot mode set. Every channel enabled for that session will "
 442                                 "be set in overwrite mode and mmap output.");
 443         }
 444         if (opt_shm_path) {
 445                 MSG("Session %s set to shm_path: %s.", session_name,
 446                         shm_path);
 447         }
 448
 449         /* Mi output */
 450         if (lttng_opt_mi) {
 451                 ret = mi_created_session(session_name);
 452                 if (ret) {
 453                         ret = CMD_ERROR;
 454                         goto error;
 455                 }
 456         }
 457
 458         /* Init lttng session config */
 459         ret = config_init(session_name);
 460         if (ret < 0) {
 461                 ret = CMD_ERROR;
 462                 goto error;
 463         }
 464
 465         ret = CMD_SUCCESS;
 466
 467 error:
 468         free(alloc_url);
 469         free(traces_path);
 470         free(alloc_path);
 471
 472         if (ret < 0) {
 473                 ERR("%s", lttng_strerror(ret));
 474         }
 475         return ret;
 476 }
 477
 478 /*
 479  *  spawn_sessiond
 480  *
 481  *  Spawn a session daemon by forking and execv.
 482  */
 483 static int spawn_sessiond(char *pathname)
 484 {
 485         int ret = 0;
 486         pid_t pid;
 487
 488         MSG("Spawning a session daemon");
 489         pid = fork();
 490         if (pid == 0) {
 491                 /*
 492                  * Spawn session daemon in daemon mode.
 493                  */
 494                 execlp(pathname, "lttng-sessiond",
 495                                 "--daemonize", NULL);
 496                 /* execlp only returns if error happened */
 497                 if (errno == ENOENT) {
 498                         ERR("No session daemon found. Use --sessiond-path.");
 499                 } else {
 500                         PERROR("execlp");
 501                 }
 502                 kill(getppid(), SIGTERM);       /* wake parent */
 503                 exit(EXIT_FAILURE);
 504         } else if (pid > 0) {
 505                 /*
 506                  * In daemon mode (--daemonize), sessiond only exits when
 507                  * it's ready to accept commands.
 508                  */
 509                 for (;;) {
 510                         int status;
 511                         pid_t wait_pid_ret = waitpid(pid, &status, 0);
 512
 513                         if (wait_pid_ret < 0) {
 514                                 if (errno == EINTR) {
 515                                         continue;
 516                                 }
 517                                 PERROR("waitpid");
 518                                 ret = -errno;
 519                                 goto end;
 520                         }
 521
 522                         if (WIFSIGNALED(status)) {
 523                                 ERR("Session daemon was killed by signal %d",
 524                                                 WTERMSIG(status));
 525                                 ret = -1;
 526                                 goto end;
 527                         } else if (WIFEXITED(status)) {
 528                                 DBG("Session daemon terminated normally (exit status: %d)",
 529                                                 WEXITSTATUS(status));
 530
 531                                 if (WEXITSTATUS(status) != 0) {
 532                                         ERR("Session daemon terminated with an error (exit status: %d)",
 533                                                         WEXITSTATUS(status));
 534                                         ret = -1;
 535                                         goto end;
 536                                 }
 537                                 break;
 538                         }
 539                 }
 540
 541                 goto end;
 542         } else {
 543                 PERROR("fork");
 544                 ret = -1;
 545                 goto end;
 546         }
 547
 548 end:
 549         return ret;
 550 }
 551
 552 /*
 553  *  launch_sessiond
 554  *
 555  *  Check if the session daemon is available using
 556  *  the liblttngctl API for the check. If not, try to
 557  *  spawn a daemon.
 558  */
 559 static int launch_sessiond(void)
 560 {
 561         int ret;
 562         char *pathname = NULL;
 563
 564         ret = lttng_session_daemon_alive();
 565         if (ret) {
 566                 /* Sessiond is alive, not an error */
 567                 ret = 0;
 568                 goto end;
 569         }
 570
 571         /* Try command line option path */
 572         pathname = opt_sessiond_path;
 573
 574         /* Try LTTNG_SESSIOND_PATH env variable */
 575         if (pathname == NULL) {
 576                 pathname = getenv(DEFAULT_SESSIOND_PATH_ENV);
 577         }
 578
 579         /* Try with configured path */
 580         if (pathname == NULL) {
 581                 if (CONFIG_SESSIOND_BIN[0] != '\0') {
 582                         pathname = CONFIG_SESSIOND_BIN;
 583                 }
 584         }
 585
 586         /* Try the default path */
 587         if (pathname == NULL) {
 588                 pathname = INSTALL_BIN_PATH "/lttng-sessiond";
 589         }
 590
 591         DBG("Session daemon binary path: %s", pathname);
 592
 593         /* Check existence and permissions */
 594         ret = access(pathname, F_OK | X_OK);
 595         if (ret < 0) {
 596                 ERR("No such file or access denied: %s", pathname);
 597                 goto end;
 598         }
 599
 600         ret = spawn_sessiond(pathname);
 601 end:
 602         if (ret) {
 603                 ERR("Problem occurred while launching session daemon (%s)",
 604                                 pathname);
 605         }
 606         return ret;
 607 }
 608
 609 /*
 610  *  The 'create <options>' first level command
 611  *
 612  *  Returns one of the CMD_* result constants.
 613  */
 614 int cmd_create(int argc, const char **argv)
 615 {
 616         int opt, ret = CMD_SUCCESS, command_ret = CMD_SUCCESS, success = 1;
 617         char *opt_arg = NULL;
 618         static poptContext pc;
 619
 620         pc = poptGetContext(NULL, argc, argv, long_options, 0);
 621         poptReadDefaultConfig(pc, 0);
 622
 623         while ((opt = poptGetNextOpt(pc)) != -1) {
 624                 switch (opt) {
 625                 case OPT_HELP:
 626                         SHOW_HELP();
 627                         goto end;
 628                 case OPT_LIST_OPTIONS:
 629                         list_cmd_options(stdout, long_options);
 630                         goto end;
 631                 case OPT_LIVE_TIMER:
 632                 {
 633                         unsigned long v;
 634
 635                         errno = 0;
 636                         opt_arg = poptGetOptArg(pc);
 637                         if (!opt_arg) {
 638                                 /* Set up default values. */
 639                                 opt_live_timer = (uint32_t) DEFAULT_LTTNG_LIVE_TIMER;
 640                                 DBG("Session live timer interval set to default value %d",
 641                                                 opt_live_timer);
 642                                 break;
 643                         }
 644
 645                         v = strtoul(opt_arg, NULL, 0);
 646                         if (errno != 0 || !isdigit(opt_arg[0])) {
 647                                 ERR("Wrong value in --live parameter: %s", opt_arg);
 648                                 ret = CMD_ERROR;
 649                                 goto end;
 650                         }
 651                         if (v != (uint32_t) v) {
 652                                 ERR("32-bit overflow in --live parameter: %s", opt_arg);
 653                                 ret = CMD_ERROR;
 654                                 goto end;
 655                         }
 656                         if (v == 0) {
 657                                 ERR("Live timer interval must be greater than zero");
 658                                 ret = CMD_ERROR;
 659                                 goto end;
 660                         }
 661                         opt_live_timer = (uint32_t) v;
 662                         DBG("Session live timer interval set to %d", opt_live_timer);
 663                         break;
 664                 }
 665                 default:
 666                         ret = CMD_UNDEFINED;
 667                         goto end;
 668                 }
 669         }
 670
 671         if (opt_no_consumer) {
 672                 MSG("The option --no-consumer is obsolete. Use --no-output now.");
 673                 ret = CMD_WARNING;
 674                 goto end;
 675         }
 676
 677         /* Spawn a session daemon if needed */
 678         if (!opt_no_sessiond) {
 679                 ret = launch_sessiond();
 680                 if (ret) {
 681                         ret = CMD_ERROR;
 682                         goto end;
 683                 }
 684         }
 685
 686         /* MI initialization */
 687         if (lttng_opt_mi) {
 688                 writer = mi_lttng_writer_create(fileno(stdout), lttng_opt_mi);
 689                 if (!writer) {
 690                         ret = -LTTNG_ERR_NOMEM;
 691                         goto end;
 692                 }
 693
 694                 /* Open command element */
 695                 ret = mi_lttng_writer_command_open(writer,
 696                                 mi_lttng_element_command_create);
 697                 if (ret) {
 698                         ret = CMD_ERROR;
 699                         goto end;
 700                 }
 701
 702                 /* Open output element */
 703                 ret = mi_lttng_writer_open_element(writer,
 704                                 mi_lttng_element_command_output);
 705                 if (ret) {
 706                         ret = CMD_ERROR;
 707                         goto end;
 708                 }
 709         }
 710         opt_session_name = (char*) poptGetArg(pc);
 711
 712         command_ret = create_session();
 713         if (command_ret) {
 714                 success = 0;
 715         }
 716
 717         if (lttng_opt_mi) {
 718                 /* Close  output element */
 719                 ret = mi_lttng_writer_close_element(writer);
 720                 if (ret) {
 721                         ret = CMD_ERROR;
 722                         goto end;
 723                 }
 724
 725                 /* Success ? */
 726                 ret = mi_lttng_writer_write_element_bool(writer,
 727                                 mi_lttng_element_command_success, success);
 728                 if (ret) {
 729                         ret = CMD_ERROR;
 730                         goto end;
 731                 }
 732
 733                 /* Command element close */
 734                 ret = mi_lttng_writer_command_close(writer);
 735                 if (ret) {
 736                         ret = CMD_ERROR;
 737                         goto end;
 738                 }
 739         }
 740
 741 end:
 742         /* Mi clean-up */
 743         if (writer && mi_lttng_writer_destroy(writer)) {
 744                 /* Preserve original error code */
 745                 ret = ret ? ret : -LTTNG_ERR_MI_IO_FAIL;
 746         }
 747
 748         /* Overwrite ret if an error occurred in create_session() */
 749         ret = command_ret ? command_ret : ret;
 750
 751         poptFreeContext(pc);
 752         return ret;
 753 }