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 _GNU_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
  30 #include <common/mi-lttng.h>
  31
  32 #include "../command.h"
  33 #include "../utils.h"
  34
  35 #include <common/defaults.h>
  36 #include <common/sessiond-comm/sessiond-comm.h>
  37 #include <common/uri.h>
  38 #include <common/utils.h>
  39 #include <lttng/snapshot.h>
  40
  41 static char *opt_output_path;
  42 static char *opt_session_name;
  43 static char *opt_url;
  44 static char *opt_ctrl_url;
  45 static char *opt_data_url;
  46 static int opt_no_consumer;
  47 static int opt_no_output;
  48 static int opt_snapshot;
  49 static unsigned int opt_live_timer;
  50
  51 enum {
  52         OPT_HELP = 1,
  53         OPT_LIST_OPTIONS,
  54         OPT_LIVE_TIMER,
  55 };
  56
  57 static struct mi_writer *writer;
  58
  59 static struct poptOption long_options[] = {
  60         /* longName, shortName, argInfo, argPtr, value, descrip, argDesc */
  61         {"help", 'h', POPT_ARG_NONE, NULL, OPT_HELP, NULL, NULL},
  62         {"output", 'o', POPT_ARG_STRING, &opt_output_path, 0, NULL, NULL},
  63         {"list-options", 0, POPT_ARG_NONE, NULL, OPT_LIST_OPTIONS, NULL, NULL},
  64         {"set-url",        'U', POPT_ARG_STRING, &opt_url, 0, 0, 0},
  65         {"ctrl-url",       'C', POPT_ARG_STRING, &opt_ctrl_url, 0, 0, 0},
  66         {"data-url",       'D', POPT_ARG_STRING, &opt_data_url, 0, 0, 0},
  67         {"no-output",       0, POPT_ARG_VAL, &opt_no_output, 1, 0, 0},
  68         {"no-consumer",     0, POPT_ARG_VAL, &opt_no_consumer, 1, 0, 0},
  69         {"snapshot",        0, POPT_ARG_VAL, &opt_snapshot, 1, 0, 0},
  70         {"live",            0, POPT_ARG_INT | POPT_ARGFLAG_OPTIONAL, 0, OPT_LIVE_TIMER, 0, 0},
  71         {0, 0, 0, 0, 0, 0, 0}
  72 };
  73
  74 /*
  75  * Please have a look at src/lib/lttng-ctl/lttng-ctl.c for more information on
  76  * why this declaration exists and used ONLY in for this command.
  77  */
  78 extern int _lttng_create_session_ext(const char *name, const char *url,
  79                 const char *datetime);
  80
  81 /*
  82  * usage
  83  */
  84 static void usage(FILE *ofp)
  85 {
  86         fprintf(ofp, "usage: lttng create [NAME] [OPTIONS] \n");
  87         fprintf(ofp, "\n");
  88         fprintf(ofp, "Without a given NAME, the default is 'auto-<yyyymmdd>-<hhmmss>'\n");
  89         fprintf(ofp, "\n");
  90         fprintf(ofp, "Options:\n");
  91         fprintf(ofp, "  -h, --help           Show this help\n");
  92         fprintf(ofp, "      --list-options   Simple listing of options\n");
  93         fprintf(ofp, "  -o, --output PATH    Specify output path for traces\n");
  94         fprintf(ofp, "      --no-output      Traces will not be outputted\n");
  95         fprintf(ofp, "      --snapshot       Set the session in snapshot mode.\n");
  96         fprintf(ofp, "                       Created in no-output mode and uses the URL,\n");
  97         fprintf(ofp, "                       if one, as the default snapshot output.\n");
  98         fprintf(ofp, "                       Every channel will be set in overwrite mode\n");
  99         fprintf(ofp, "                       and with mmap output (splice not supported).\n");
 100         fprintf(ofp, "      --live [USEC]    Set the session in live-reading mode.\n");
 101         fprintf(ofp, "                       The delay parameter in micro-seconds is the\n");
 102         fprintf(ofp, "                       maximum time the user can wait for the data\n");
 103         fprintf(ofp, "                       to be flushed. Can be set with a network\n");
 104         fprintf(ofp, "                       URL (-U or -C/-D) and must have a relayd listening.\n");
 105         fprintf(ofp, "                       By default, %u is used for the timer and the\n",
 106                                                                                         DEFAULT_LTTNG_LIVE_TIMER);
 107         fprintf(ofp, "                       network URL is set to net://127.0.0.1.\n");
 108         fprintf(ofp, "\n");
 109         fprintf(ofp, "Extended Options:\n");
 110         fprintf(ofp, "\n");
 111         fprintf(ofp, "Using these options, each API call can be controlled individually.\n");
 112         fprintf(ofp, "\n");
 113         fprintf(ofp, "  -U, --set-url=URL    Set URL destination of the trace data.\n");
 114         fprintf(ofp, "                       It is persistent for the session lifetime.\n");
 115         fprintf(ofp, "                       This will set both data and control URL.\n");
 116         fprintf(ofp, "  -C, --ctrl-url=URL   Set control path URL. (Must use -D also)\n");
 117         fprintf(ofp, "  -D, --data-url=URL   Set data path URL. (Must use -C also)\n");
 118         fprintf(ofp, "\n");
 119         fprintf(ofp, "Please refer to the man page (lttng(1)) for more information on network\n");
 120         fprintf(ofp, "streaming mechanisms and explanation of the control and data port\n");
 121         fprintf(ofp, "You must have a running remote lttng-relayd for network streaming\n");
 122         fprintf(ofp, "\n");
 123         fprintf(ofp, "URL format is has followed:\n");
 124         fprintf(ofp, "\n");
 125         fprintf(ofp, "  proto://[HOST|IP][:PORT1[:PORT2]][/TRACE_PATH]\n");
 126         fprintf(ofp, "\n");
 127         fprintf(ofp, "  Supported protocols are (proto):\n");
 128         fprintf(ofp, "  > file://...\n");
 129         fprintf(ofp, "    Local filesystem full path.\n");
 130         fprintf(ofp, "\n");
 131         fprintf(ofp, "  > net[6]://...\n");
 132         fprintf(ofp, "    This will use the default network transport layer which is\n");
 133         fprintf(ofp, "    TCP for both control (PORT1) and data port (PORT2).\n");
 134         fprintf(ofp, "    The default ports are respectively 5342 and 5343.\n");
 135         fprintf(ofp, "\n");
 136         fprintf(ofp, "  > tcp[6]://...\n");
 137         fprintf(ofp, "    Can only be used with -C and -D together\n");
 138         fprintf(ofp, "\n");
 139         fprintf(ofp, "NOTE: IPv6 address MUST be enclosed in brackets '[]' (rfc2732)\n");
 140         fprintf(ofp, "\n");
 141         fprintf(ofp, "Examples:\n");
 142         fprintf(ofp, "    # lttng create -U net://192.168.1.42\n");
 143         fprintf(ofp, "    Uses TCP and default ports for the given destination.\n");
 144         fprintf(ofp, "    # lttng create -U net6://[fe80::f66d:4ff:fe53:d220]\n");
 145         fprintf(ofp, "    Uses TCP, default ports and IPv6.\n");
 146         fprintf(ofp, "    # lttng create s1 -U net://myhost.com:3229\n");
 147         fprintf(ofp, "    Set the consumer to the remote HOST on port 3229 for control.\n");
 148         fprintf(ofp, "\n");
 149 }
 150
 151 /*
 152  * Retrieve the created session and mi output it based on provided argument
 153  * This is currently a summary of what was pretty printed and is subject to
 154  * enhancements.
 155  */
 156 static int mi_created_session(const char *session_name)
 157 {
 158         int ret, i, count, found;
 159         struct lttng_session *sessions;
 160
 161         /* session_name should not be null */
 162         assert(session_name);
 163         assert(writer);
 164
 165         count = lttng_list_sessions(&sessions);
 166         if (count < 0) {
 167                 ret = count;
 168                 ERR("%s", lttng_strerror(ret));
 169                 goto error;
 170         }
 171
 172         if (count == 0) {
 173                 ERR("Error session creation failed: session %s not found", session_name);
 174                 ret = -LTTNG_ERR_SESS_NOT_FOUND;
 175                 goto end;
 176         }
 177
 178         found = 0;
 179         for (i = 0; i < count; i++) {
 180                 if (strncmp(sessions[i].name, session_name, NAME_MAX) == 0) {
 181                         found = 1;
 182                         ret = mi_lttng_session(writer, &sessions[i], 0);
 183                         if (ret) {
 184                                 goto error;
 185                         }
 186                         break;
 187                 }
 188         }
 189
 190         if (!found) {
 191                 ret = -LTTNG_ERR_SESS_NOT_FOUND;
 192         } else {
 193                 ret = CMD_SUCCESS;
 194         }
 195
 196 error:
 197         free(sessions);
 198 end:
 199         return ret;
 200 }
 201
 202 /*
 203  * For a session name, set the consumer URLs.
 204  */
 205 static int set_consumer_url(const char *session_name, const char *ctrl_url,
 206                 const char *data_url)
 207 {
 208         int ret;
 209         struct lttng_handle *handle;
 210         struct lttng_domain dom;
 211
 212         assert(session_name);
 213
 214         /*
 215          * Set handle with the session name and the domain set to 0. This means to
 216          * the session daemon that the next action applies on the tracing session
 217          * rather then the domain specific session.
 218          */
 219         memset(&dom, 0, sizeof(dom));
 220
 221         handle = lttng_create_handle(session_name, &dom);
 222         if (handle == NULL) {
 223                 ret = CMD_FATAL;
 224                 goto error;
 225         }
 226
 227         ret = lttng_set_consumer_url(handle, ctrl_url, data_url);
 228         if (ret < 0) {
 229                 goto error;
 230         }
 231
 232         if (ctrl_url) {
 233                 MSG("Control URL %s set for session %s", ctrl_url, session_name);
 234         }
 235
 236         if (data_url) {
 237                 MSG("Data URL %s set for session %s", data_url, session_name);
 238         }
 239
 240 error:
 241         lttng_destroy_handle(handle);
 242         return ret;
 243 }
 244
 245 static int add_snapshot_output(const char *session_name, const char *ctrl_url,
 246                 const char *data_url)
 247 {
 248         int ret;
 249         struct lttng_snapshot_output *output = NULL;
 250
 251         assert(session_name);
 252
 253         output = lttng_snapshot_output_create();
 254         if (!output) {
 255                 ret = CMD_FATAL;
 256                 goto error_create;
 257         }
 258
 259         if (ctrl_url) {
 260                 ret = lttng_snapshot_output_set_ctrl_url(ctrl_url, output);
 261                 if (ret < 0) {
 262                         goto error;
 263                 }
 264         }
 265
 266         if (data_url) {
 267                 ret = lttng_snapshot_output_set_data_url(data_url, output);
 268                 if (ret < 0) {
 269                         goto error;
 270                 }
 271         }
 272
 273         /* This call, if successful, populates the id of the output object. */
 274         ret = lttng_snapshot_add_output(session_name, output);
 275         if (ret < 0) {
 276                 goto error;
 277         }
 278
 279 error:
 280         lttng_snapshot_output_destroy(output);
 281 error_create:
 282         return ret;
 283 }
 284
 285 /*
 286  *  Create a tracing session.
 287  *  If no name is specified, a default name is generated.
 288  *
 289  *  Returns one of the CMD_* result constants.
 290  */
 291 static int create_session(void)
 292 {
 293         int ret;
 294         char *session_name = NULL, *traces_path = NULL, *alloc_path = NULL;
 295         char *alloc_url = NULL, *url = NULL, datetime[16];
 296         char session_name_date[NAME_MAX + 17], *print_str_url = NULL;
 297         time_t rawtime;
 298         struct tm *timeinfo;
 299
 300         /* Get date and time for automatic session name/path */
 301         time(&rawtime);
 302         timeinfo = localtime(&rawtime);
 303         strftime(datetime, sizeof(datetime), "%Y%m%d-%H%M%S", timeinfo);
 304
 305         /* Auto session name creation */
 306         if (opt_session_name == NULL) {
 307                 ret = snprintf(session_name_date, sizeof(session_name_date),
 308                                 DEFAULT_SESSION_NAME "-%s", datetime);
 309                 if (ret < 0) {
 310                         PERROR("snprintf session name");
 311                         goto error;
 312                 }
 313                 session_name = session_name_date;
 314                 DBG("Auto session name set to %s", session_name_date);
 315         } else {
 316                 if (strlen(opt_session_name) > NAME_MAX) {
 317                         ERR("Session name too long. Length must be lower or equal to %d",
 318                                         NAME_MAX);
 319                         ret = LTTNG_ERR_SESSION_FAIL;
 320                         goto error;
 321                 }
 322                 /*
 323                  * Check if the session name begins with "auto-" or is exactly "auto".
 324                  * Both are reserved for the default session name. See bug #449 to
 325                  * understand why we need to check both here.
 326                  */
 327                 if ((strncmp(opt_session_name, DEFAULT_SESSION_NAME "-",
 328                                         strlen(DEFAULT_SESSION_NAME) + 1) == 0) ||
 329                                 (strncmp(opt_session_name, DEFAULT_SESSION_NAME,
 330                                         strlen(DEFAULT_SESSION_NAME)) == 0 &&
 331                                 strlen(opt_session_name) == strlen(DEFAULT_SESSION_NAME))) {
 332                         ERR("%s is a reserved keyword for default session(s)",
 333                                         DEFAULT_SESSION_NAME);
 334                         ret = CMD_ERROR;
 335                         goto error;
 336                 }
 337                 session_name = opt_session_name;
 338                 ret = snprintf(session_name_date, sizeof(session_name_date),
 339                                 "%s-%s", session_name, datetime);
 340                 if (ret < 0) {
 341                         PERROR("snprintf session name");
 342                         goto error;
 343                 }
 344         }
 345
 346         if ((!opt_ctrl_url && opt_data_url) || (opt_ctrl_url && !opt_data_url)) {
 347                 ERR("You need both control and data URL.");
 348                 ret = CMD_ERROR;
 349                 goto error;
 350         }
 351
 352         if (opt_output_path != NULL) {
 353                 traces_path = utils_expand_path(opt_output_path);
 354                 if (traces_path == NULL) {
 355                         ret = CMD_ERROR;
 356                         goto error;
 357                 }
 358
 359                 /* Create URL string from the local file system path */
 360                 ret = asprintf(&alloc_url, "file://%s", traces_path);
 361                 if (ret < 0) {
 362                         PERROR("asprintf url path");
 363                         ret = CMD_FATAL;
 364                         goto error;
 365                 }
 366                 /* URL to use in the lttng_create_session() call */
 367                 url = alloc_url;
 368                 print_str_url = traces_path;
 369         } else if (opt_url) { /* Handling URL (-U opt) */
 370                 url = opt_url;
 371                 print_str_url = url;
 372         } else if (opt_data_url && opt_ctrl_url) {
 373                 /*
 374                  * With both control and data, we'll be setting the consumer URL after
 375                  * session creation thus use no URL.
 376                  */
 377                 url = NULL;
 378         } else if (!opt_no_output) {
 379                 char *tmp_path;
 380
 381                 /* Auto output path */
 382                 tmp_path = utils_get_home_dir();
 383                 if (tmp_path == NULL) {
 384                         ERR("HOME path not found.\n \
 385                                         Please specify an output path using -o, --output PATH");
 386                         ret = CMD_FATAL;
 387                         goto error;
 388                 }
 389                 alloc_path = strdup(tmp_path);
 390                 if (!alloc_path) {
 391                         PERROR("allocating alloc_path");
 392                         ret = CMD_FATAL;
 393                         goto error;
 394                 }
 395                 ret = asprintf(&alloc_url,
 396                                 "file://%s/" DEFAULT_TRACE_DIR_NAME "/%s",
 397                                 alloc_path, session_name_date);
 398                 if (ret < 0) {
 399                         PERROR("asprintf trace dir name");
 400                         ret = CMD_FATAL;
 401                         goto error;
 402                 }
 403
 404                 url = alloc_url;
 405                 print_str_url = alloc_url + strlen("file://");
 406         } else {
 407                 /* No output means --no-output or --snapshot mode. */
 408                 url = NULL;
 409         }
 410
 411         /* Use default live URL if NO url is/are found. */
 412         if ((opt_live_timer && !opt_url) && (opt_live_timer && !opt_data_url)) {
 413                 ret = asprintf(&alloc_url, "net://127.0.0.1");
 414                 if (ret < 0) {
 415                         PERROR("asprintf default live URL");
 416                         ret = CMD_FATAL;
 417                         goto error;
 418                 }
 419                 url = alloc_url;
 420                 print_str_url = url;
 421         }
 422
 423         if (opt_snapshot && opt_live_timer) {
 424                 ERR("Snapshot and live modes are mutually exclusive.");
 425                 ret = CMD_ERROR;
 426                 goto error;
 427         }
 428
 429         if (opt_snapshot) {
 430                 /* No output by default. */
 431                 const char *snapshot_url = NULL;
 432
 433                 if (opt_url) {
 434                         snapshot_url = url;
 435                 } else if (!opt_data_url && !opt_ctrl_url) {
 436                         /* This is the session path that we need to use as output. */
 437                         snapshot_url = url;
 438                 }
 439                 ret = lttng_create_session_snapshot(session_name, snapshot_url);
 440         } else if (opt_live_timer) {
 441                 const char *pathname;
 442
 443                 if (opt_relayd_path) {
 444                         pathname = opt_relayd_path;
 445                 } else {
 446                         pathname = INSTALL_BIN_PATH "/lttng-relayd";
 447                 }
 448                 if (!opt_url && !opt_data_url && !check_relayd() &&
 449                                 spawn_relayd(pathname, 0) < 0) {
 450                         goto error;
 451                 }
 452                 ret = lttng_create_session_live(session_name, url, opt_live_timer);
 453         } else {
 454                 ret = _lttng_create_session_ext(session_name, url, datetime);
 455         }
 456         if (ret < 0) {
 457                 /* Don't set ret so lttng can interpret the sessiond error. */
 458                 switch (-ret) {
 459                 case LTTNG_ERR_EXIST_SESS:
 460                         WARN("Session %s already exists", session_name);
 461                         break;
 462                 default:
 463                         break;
 464                 }
 465                 goto error;
 466         }
 467
 468         if (opt_ctrl_url && opt_data_url) {
 469                 if (opt_snapshot) {
 470                         ret = add_snapshot_output(session_name, opt_ctrl_url,
 471                                         opt_data_url);
 472                 } else {
 473                         /* Setting up control URI (-C or/and -D opt) */
 474                         ret = set_consumer_url(session_name, opt_ctrl_url, opt_data_url);
 475                 }
 476                 if (ret < 0) {
 477                         /* Destroy created session because the URL are not valid. */
 478                         lttng_destroy_session(session_name);
 479                         goto error;
 480                 }
 481         }
 482
 483         MSG("Session %s created.", session_name);
 484         if (print_str_url && !opt_snapshot) {
 485                 MSG("Traces will be written in %s", print_str_url);
 486
 487                 if (opt_live_timer) {
 488                         MSG("Live timer set to %u usec", opt_live_timer);
 489                 }
 490         } else if (opt_snapshot) {
 491                 if (print_str_url) {
 492                         MSG("Default snapshot output set to: %s", print_str_url);
 493                 }
 494                 MSG("Snapshot mode set. Every channel enabled for that session will "
 495                                 "be set in overwrite mode and mmap output.");
 496         }
 497
 498         /* Mi output */
 499         if (lttng_opt_mi) {
 500                 ret = mi_created_session(session_name);
 501                 if (ret) {
 502                         ret = CMD_ERROR;
 503                         goto error;
 504                 }
 505         }
 506
 507         /* Init lttng session config */
 508         ret = config_init(session_name);
 509         if (ret < 0) {
 510                 ret = CMD_ERROR;
 511                 goto error;
 512         }
 513
 514         ret = CMD_SUCCESS;
 515
 516 error:
 517         free(alloc_url);
 518         free(traces_path);
 519         free(alloc_path);
 520
 521         if (ret < 0) {
 522                 ERR("%s", lttng_strerror(ret));
 523         }
 524         return ret;
 525 }
 526
 527 /*
 528  *  The 'create <options>' first level command
 529  *
 530  *  Returns one of the CMD_* result constants.
 531  */
 532 int cmd_create(int argc, const char **argv)
 533 {
 534         int opt, ret = CMD_SUCCESS, command_ret = CMD_SUCCESS, success = 1;
 535         char *opt_arg = NULL;
 536         static poptContext pc;
 537
 538         pc = poptGetContext(NULL, argc, argv, long_options, 0);
 539         poptReadDefaultConfig(pc, 0);
 540
 541         while ((opt = poptGetNextOpt(pc)) != -1) {
 542                 switch (opt) {
 543                 case OPT_HELP:
 544                         usage(stdout);
 545                         goto end;
 546                 case OPT_LIST_OPTIONS:
 547                         list_cmd_options(stdout, long_options);
 548                         goto end;
 549                 case OPT_LIVE_TIMER:
 550                 {
 551                         unsigned long v;
 552
 553                         errno = 0;
 554                         opt_arg = poptGetOptArg(pc);
 555                         if (!opt_arg) {
 556                                 /* Set up default values. */
 557                                 opt_live_timer = (uint32_t) DEFAULT_LTTNG_LIVE_TIMER;
 558                                 DBG("Session live timer interval set to default value %d",
 559                                                 opt_live_timer);
 560                                 break;
 561                         }
 562
 563                         v = strtoul(opt_arg, NULL, 0);
 564                         if (errno != 0 || !isdigit(opt_arg[0])) {
 565                                 ERR("Wrong value in --live parameter: %s", opt_arg);
 566                                 ret = CMD_ERROR;
 567                                 goto end;
 568                         }
 569                         if (v != (uint32_t) v) {
 570                                 ERR("32-bit overflow in --live parameter: %s", opt_arg);
 571                                 ret = CMD_ERROR;
 572                                 goto end;
 573                         }
 574                         opt_live_timer = (uint32_t) v;
 575                         DBG("Session live timer interval set to %d", opt_live_timer);
 576                         break;
 577                 }
 578                 default:
 579                         usage(stderr);
 580                         ret = CMD_UNDEFINED;
 581                         goto end;
 582                 }
 583         }
 584
 585         if (opt_no_consumer) {
 586                 MSG("The option --no-consumer is obsolete. Use --no-output now.");
 587                 ret = CMD_WARNING;
 588                 goto end;
 589         }
 590
 591         /* MI initialization */
 592         if (lttng_opt_mi) {
 593                 writer = mi_lttng_writer_create(fileno(stdout), lttng_opt_mi);
 594                 if (!writer) {
 595                         ret = -LTTNG_ERR_NOMEM;
 596                         goto end;
 597                 }
 598
 599                 /* Open command element */
 600                 ret = mi_lttng_writer_command_open(writer,
 601                                 mi_lttng_element_command_create);
 602                 if (ret) {
 603                         ret = CMD_ERROR;
 604                         goto end;
 605                 }
 606
 607                 /* Open output element */
 608                 ret = mi_lttng_writer_open_element(writer,
 609                                 mi_lttng_element_command_output);
 610                 if (ret) {
 611                         ret = CMD_ERROR;
 612                         goto end;
 613                 }
 614         }
 615         opt_session_name = (char*) poptGetArg(pc);
 616
 617         command_ret = create_session();
 618         if (command_ret) {
 619                 success = 0;
 620         }
 621
 622         if (lttng_opt_mi) {
 623                 /* Close  output element */
 624                 ret = mi_lttng_writer_close_element(writer);
 625                 if (ret) {
 626                         ret = CMD_ERROR;
 627                         goto end;
 628                 }
 629
 630                 /* Success ? */
 631                 ret = mi_lttng_writer_write_element_bool(writer,
 632                                 mi_lttng_element_command_success, success);
 633                 if (ret) {
 634                         ret = CMD_ERROR;
 635                         goto end;
 636                 }
 637
 638                 /* Command element close */
 639                 ret = mi_lttng_writer_command_close(writer);
 640                 if (ret) {
 641                         ret = CMD_ERROR;
 642                         goto end;
 643                 }
 644         }
 645
 646 end:
 647         /* Mi clean-up */
 648         if (writer && mi_lttng_writer_destroy(writer)) {
 649                 /* Preserve original error code */
 650                 ret = ret ? ret : -LTTNG_ERR_MI_IO_FAIL;
 651         }
 652
 653         /* Overwrite ret if an error occurred in create_session() */
 654         ret = command_ret ? command_ret : ret;
 655
 656         poptFreeContext(pc);
 657         return ret;
 658 }