trace2/tr2_dst.c

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