trace2/tr2_dst.c

   1 #include "git-compat-util.h"
   2 #include "abspath.h"
   3 #include "sigchain.h"
   4 #include "strbuf.h"
   5 #include "trace2/tr2_dst.h"
   6 #include "trace2/tr2_sid.h"
   7 #include "trace2/tr2_sysenv.h"
   8
   9 /*
  10  * How many attempts we will make at creating an automatically-named trace file.
  11  */
  12 #define MAX_AUTO_ATTEMPTS 10
  13
  14 /*
  15  * Sentinel file used to detect when we should discard new traces to avoid
  16  * writing too many trace files to a directory.
  17  */
  18 #define DISCARD_SENTINEL_NAME "git-trace2-discard"
  19
  20 /*
  21  * When set to zero, disables directory file count checks. Otherwise, controls
  22  * how many files we can write to a directory before entering discard mode.
  23  * This can be overridden via the TR2_SYSENV_MAX_FILES setting.
  24  */
  25 static int tr2env_max_files = 0;
  26
  27 static int tr2_dst_want_warning(void)
  28 {
  29         static int tr2env_dst_debug = -1;
  30
  31         if (tr2env_dst_debug == -1) {
  32                 const char *env_value = tr2_sysenv_get(TR2_SYSENV_DST_DEBUG);
  33                 if (!env_value || !*env_value)
  34                         tr2env_dst_debug = 0;
  35                 else
  36                         tr2env_dst_debug = atoi(env_value) > 0;
  37         }
  38
  39         return tr2env_dst_debug;
  40 }
  41
  42 void tr2_dst_trace_disable(struct tr2_dst *dst)
  43 {
  44         if (dst->need_close)
  45                 close(dst->fd);
  46         dst->fd = 0;
  47         dst->initialized = 1;
  48         dst->need_close = 0;
  49 }
  50
  51 /*
  52  * Check to make sure we're not overloading the target directory with too many
  53  * files. First get the threshold (if present) from the config or envvar. If
  54  * it's zero or unset, disable this check. Next check for the presence of a
  55  * sentinel file, then check file count.
  56  *
  57  * Returns 0 if tracing should proceed as normal. Returns 1 if the sentinel file
  58  * already exists, which means tracing should be disabled. Returns -1 if there
  59  * are too many files but there was no sentinel file, which means we have
  60  * created and should write traces to the sentinel file.
  61  *
  62  * We expect that some trace processing system is gradually collecting files
  63  * from the target directory; after it removes the sentinel file we'll start
  64  * writing traces again.
  65  */
  66 static int tr2_dst_too_many_files(struct tr2_dst *dst, const char *tgt_prefix)
  67 {
  68         int file_count = 0, max_files = 0, ret = 0;
  69         const char *max_files_var;
  70         DIR *dirp;
  71         struct strbuf path = STRBUF_INIT, sentinel_path = STRBUF_INIT;
  72         struct stat statbuf;
  73
  74         /* Get the config or envvar and decide if we should continue this check */
  75         max_files_var = tr2_sysenv_get(TR2_SYSENV_MAX_FILES);
  76         if (max_files_var && *max_files_var && ((max_files = atoi(max_files_var)) >= 0))
  77                 tr2env_max_files = max_files;
  78
  79         if (!tr2env_max_files) {
  80                 ret = 0;
  81                 goto cleanup;
  82         }
  83
  84         strbuf_addstr(&path, tgt_prefix);
  85         if (!is_dir_sep(path.buf[path.len - 1])) {
  86                 strbuf_addch(&path, '/');
  87         }
  88
  89         /* check sentinel */
  90         strbuf_addbuf(&sentinel_path, &path);
  91         strbuf_addstr(&sentinel_path, DISCARD_SENTINEL_NAME);
  92         if (!stat(sentinel_path.buf, &statbuf)) {
  93                 ret = 1;
  94                 goto cleanup;
  95         }
  96
  97         /* check file count */
  98         dirp = opendir(path.buf);
  99         while (file_count < tr2env_max_files && dirp && readdir(dirp))
 100                 file_count++;
 101         if (dirp)
 102                 closedir(dirp);
 103
 104         if (file_count >= tr2env_max_files) {
 105                 dst->too_many_files = 1;
 106                 dst->fd = open(sentinel_path.buf, O_WRONLY | O_CREAT | O_EXCL, 0666);
 107                 ret = -1;
 108                 goto cleanup;
 109         }
 110
 111 cleanup:
 112         strbuf_release(&path);
 113         strbuf_release(&sentinel_path);
 114         return ret;
 115 }
 116
 117 static int tr2_dst_try_auto_path(struct tr2_dst *dst, const char *tgt_prefix)
 118 {
 119         int too_many_files;
 120         const char *last_slash, *sid = tr2_sid_get();
 121         struct strbuf path = STRBUF_INIT;
 122         size_t base_path_len;
 123         unsigned attempt_count;
 124
 125         last_slash = strrchr(sid, '/');
 126         if (last_slash)
 127                 sid = last_slash + 1;
 128
 129         strbuf_addstr(&path, tgt_prefix);
 130         if (!is_dir_sep(path.buf[path.len - 1]))
 131                 strbuf_addch(&path, '/');
 132         strbuf_addstr(&path, sid);
 133         base_path_len = path.len;
 134
 135         too_many_files = tr2_dst_too_many_files(dst, tgt_prefix);
 136         if (!too_many_files) {
 137                 for (attempt_count = 0; attempt_count < MAX_AUTO_ATTEMPTS; attempt_count++) {
 138                         if (attempt_count > 0) {
 139                                 strbuf_setlen(&path, base_path_len);
 140                                 strbuf_addf(&path, ".%d", attempt_count);
 141                         }
 142
 143                         dst->fd = open(path.buf, O_WRONLY | O_CREAT | O_EXCL, 0666);
 144                         if (dst->fd != -1)
 145                                 break;
 146                 }
 147         } else if (too_many_files == 1) {
 148                 strbuf_release(&path);
 149                 if (tr2_dst_want_warning())
 150                         warning("trace2: not opening %s trace file due to too "
 151                                 "many files in target directory %s",
 152                                 tr2_sysenv_display_name(dst->sysenv_var),
 153                                 tgt_prefix);
 154                 return 0;
 155         }
 156
 157         if (dst->fd == -1) {
 158                 if (tr2_dst_want_warning())
 159                         warning("trace2: could not open '%.*s' for '%s' tracing: %s",
 160                                 (int) base_path_len, path.buf,
 161                                 tr2_sysenv_display_name(dst->sysenv_var),
 162                                 strerror(errno));
 163
 164                 tr2_dst_trace_disable(dst);
 165                 strbuf_release(&path);
 166                 return 0;
 167         }
 168
 169         strbuf_release(&path);
 170
 171         dst->need_close = 1;
 172         dst->initialized = 1;
 173
 174         return dst->fd;
 175 }
 176
 177 static int tr2_dst_try_path(struct tr2_dst *dst, const char *tgt_value)
 178 {
 179         int fd = open(tgt_value, O_WRONLY | O_APPEND | O_CREAT, 0666);
 180         if (fd == -1) {
 181                 if (tr2_dst_want_warning())
 182                         warning("trace2: could not open '%s' for '%s' tracing: %s",
 183                                 tgt_value,
 184                                 tr2_sysenv_display_name(dst->sysenv_var),
 185                                 strerror(errno));
 186
 187                 tr2_dst_trace_disable(dst);
 188                 return 0;
 189         }
 190
 191         dst->fd = fd;
 192         dst->need_close = 1;
 193         dst->initialized = 1;
 194
 195         return dst->fd;
 196 }
 197
 198 #ifndef NO_UNIX_SOCKETS
 199 #define PREFIX_AF_UNIX "af_unix:"
 200 #define PREFIX_AF_UNIX_STREAM "af_unix:stream:"
 201 #define PREFIX_AF_UNIX_DGRAM "af_unix:dgram:"
 202
 203 static int tr2_dst_try_uds_connect(const char *path, int sock_type, int *out_fd)
 204 {
 205         int fd;
 206         struct sockaddr_un sa;
 207
 208         fd = socket(AF_UNIX, sock_type, 0);
 209         if (fd == -1)
 210                 return -1;
 211
 212         sa.sun_family = AF_UNIX;
 213         strlcpy(sa.sun_path, path, sizeof(sa.sun_path));
 214
 215         if (connect(fd, (struct sockaddr *)&sa, sizeof(sa)) == -1) {
 216                 int saved_errno = errno;
 217                 close(fd);
 218                 errno = saved_errno;
 219                 return -1;
 220         }
 221
 222         *out_fd = fd;
 223         return 0;
 224 }
 225
 226 #define TR2_DST_UDS_TRY_STREAM (1 << 0)
 227 #define TR2_DST_UDS_TRY_DGRAM  (1 << 1)
 228
 229 static int tr2_dst_try_unix_domain_socket(struct tr2_dst *dst,
 230                                           const char *tgt_value)
 231 {
 232         unsigned int uds_try = 0;
 233         int fd;
 234         const char *path = NULL;
 235
 236         /*
 237          * Allow "af_unix:[<type>:]<absolute_path>"
 238          *
 239          * Trace2 always writes complete individual messages (without
 240          * chunking), so we can talk to either DGRAM or STREAM type sockets.
 241          *
 242          * Allow the user to explicitly request the socket type.
 243          *
 244          * If they omit the socket type, try one and then the other.
 245          */
 246
 247         if (skip_prefix(tgt_value, PREFIX_AF_UNIX_STREAM, &path))
 248                 uds_try |= TR2_DST_UDS_TRY_STREAM;
 249
 250         else if (skip_prefix(tgt_value, PREFIX_AF_UNIX_DGRAM, &path))
 251                 uds_try |= TR2_DST_UDS_TRY_DGRAM;
 252
 253         else if (skip_prefix(tgt_value, PREFIX_AF_UNIX, &path))
 254                 uds_try |= TR2_DST_UDS_TRY_STREAM | TR2_DST_UDS_TRY_DGRAM;
 255
 256         if (!path || !*path) {
 257                 if (tr2_dst_want_warning())
 258                         warning("trace2: invalid AF_UNIX value '%s' for '%s' tracing",
 259                                 tgt_value,
 260                                 tr2_sysenv_display_name(dst->sysenv_var));
 261
 262                 tr2_dst_trace_disable(dst);
 263                 return 0;
 264         }
 265
 266         if (!is_absolute_path(path) ||
 267             strlen(path) >= sizeof(((struct sockaddr_un *)0)->sun_path)) {
 268                 if (tr2_dst_want_warning())
 269                         warning("trace2: invalid AF_UNIX path '%s' for '%s' tracing",
 270                                 path, tr2_sysenv_display_name(dst->sysenv_var));
 271
 272                 tr2_dst_trace_disable(dst);
 273                 return 0;
 274         }
 275
 276         if (uds_try & TR2_DST_UDS_TRY_STREAM) {
 277                 if (!tr2_dst_try_uds_connect(path, SOCK_STREAM, &fd))
 278                         goto connected;
 279                 if (errno != EPROTOTYPE)
 280                         goto error;
 281         }
 282         if (uds_try & TR2_DST_UDS_TRY_DGRAM) {
 283                 if (!tr2_dst_try_uds_connect(path, SOCK_DGRAM, &fd))
 284                         goto connected;
 285         }
 286
 287 error:
 288         if (tr2_dst_want_warning())
 289                 warning("trace2: could not connect to socket '%s' for '%s' tracing: %s",
 290                         path, tr2_sysenv_display_name(dst->sysenv_var),
 291                         strerror(errno));
 292
 293         tr2_dst_trace_disable(dst);
 294         return 0;
 295
 296 connected:
 297         dst->fd = fd;
 298         dst->need_close = 1;
 299         dst->initialized = 1;
 300
 301         return dst->fd;
 302 }
 303 #endif
 304
 305 static void tr2_dst_malformed_warning(struct tr2_dst *dst,
 306                                       const char *tgt_value)
 307 {
 308         warning("trace2: unknown value for '%s': '%s'",
 309                 tr2_sysenv_display_name(dst->sysenv_var), tgt_value);
 310 }
 311
 312 int tr2_dst_get_trace_fd(struct tr2_dst *dst)
 313 {
 314         const char *tgt_value;
 315
 316         /* don't open twice */
 317         if (dst->initialized)
 318                 return dst->fd;
 319
 320         dst->initialized = 1;
 321
 322         tgt_value = tr2_sysenv_get(dst->sysenv_var);
 323
 324         if (!tgt_value || !strcmp(tgt_value, "") || !strcmp(tgt_value, "0") ||
 325             !strcasecmp(tgt_value, "false")) {
 326                 dst->fd = 0;
 327                 return dst->fd;
 328         }
 329
 330         if (!strcmp(tgt_value, "1") || !strcasecmp(tgt_value, "true")) {
 331                 dst->fd = STDERR_FILENO;
 332                 return dst->fd;
 333         }
 334
 335         if (strlen(tgt_value) == 1 && isdigit(*tgt_value)) {
 336                 dst->fd = atoi(tgt_value);
 337                 return dst->fd;
 338         }
 339
 340         if (is_absolute_path(tgt_value)) {
 341                 if (is_directory(tgt_value))
 342                         return tr2_dst_try_auto_path(dst, tgt_value);
 343                 else
 344                         return tr2_dst_try_path(dst, tgt_value);
 345         }
 346
 347 #ifndef NO_UNIX_SOCKETS
 348         if (starts_with(tgt_value, PREFIX_AF_UNIX))
 349                 return tr2_dst_try_unix_domain_socket(dst, tgt_value);
 350 #endif
 351
 352         /* Always warn about malformed values. */
 353         tr2_dst_malformed_warning(dst, tgt_value);
 354         tr2_dst_trace_disable(dst);
 355         return 0;
 356 }
 357
 358 int tr2_dst_trace_want(struct tr2_dst *dst)
 359 {
 360         return !!tr2_dst_get_trace_fd(dst);
 361 }
 362
 363 void tr2_dst_write_line(struct tr2_dst *dst, struct strbuf *buf_line)
 364 {
 365         int fd = tr2_dst_get_trace_fd(dst);
 366         ssize_t bytes;
 367
 368         strbuf_complete_line(buf_line); /* ensure final NL on buffer */
 369
 370         /*
 371          * We do not use write_in_full() because we do not want
 372          * a short-write to try again.  We are using O_APPEND mode
 373          * files and the kernel handles the atomic seek+write. If
 374          * another thread or git process is concurrently writing to
 375          * this fd or file, our remainder-write may not be contiguous
 376          * with our initial write of this message.  And that will
 377          * confuse readers.  So just don't bother.
 378          *
 379          * It is assumed that TRACE2 messages are short enough that
 380          * the system can write them in 1 attempt and we won't see
 381          * a short-write.
 382          *
 383          * If we get an IO error, just close the trace dst.
 384          */
 385         sigchain_push(SIGPIPE, SIG_IGN);
 386         bytes = write(fd, buf_line->buf, buf_line->len);
 387         sigchain_pop(SIGPIPE);
 388         if (bytes >= 0)
 389                 return;
 390
 391         tr2_dst_trace_disable(dst);
 392         if (tr2_dst_want_warning())
 393                 warning("unable to write trace to '%s': %s",
 394                         tr2_sysenv_display_name(dst->sysenv_var),
 395                         strerror(errno));
 396 }