database/database.c

   1 /* Blerg is (C) 2011 The Dominion of Awesome, and is distributed under a
   2  * BSD-style license.  Please see the COPYING file for details.
   3  */
   4 #include <stdint.h>
   5 #include <stdlib.h>
   6 #include <string.h>
   7 #include <stdio.h>
   8 #include <time.h>
   9 #include <unistd.h>
  10 #include <sys/stat.h>
  11 #include <sys/types.h>
  12 #include <sys/mman.h>
  13 #include <sys/file.h>
  14 #include <fcntl.h>
  15 #include "database.h"
  16 #include "subscription.h"
  17 #include "util.h"
  18 #include "config.h"
  19
  20 #define CHECK_VALID_BLERG(r)                               \
  21         if (blerg == NULL) {                               \
  22                 fprintf(stderr, "Invalid struct blerg\n"); \
  23                 return r;                                  \
  24         }
  25
  26 uint64_t blerg_get_record_count(struct blerg *blerg) {
  27         uint64_t count;
  28         flock(blerg->meta_fd, LOCK_SH);
  29         count = blerg->meta->sequence;
  30         flock(blerg->meta_fd, LOCK_UN);
  31         return count;
  32 }
  33
  34 /* Returns last usable record */
  35 uint64_t blerg_increment_record_count(struct blerg *blerg) {
  36         uint64_t count;
  37         flock(blerg->meta_fd, LOCK_EX);
  38         count = blerg->meta->sequence++;
  39         flock(blerg->meta_fd, LOCK_UN);
  40         return count;
  41 }
  42
  43 void blerg_segment_close(struct blerg *blerg) {
  44         if (blerg->data != NULL)
  45                 munmap((void *)blerg->data, blerg->data_size);
  46         if (blerg->data_fd != -1)
  47                 close(blerg->data_fd);
  48         if (blerg->index != NULL)
  49                 munmap((void *)blerg->index, RECORDS_PER_SEGMENT * sizeof(struct record));
  50         if (blerg->index_fd != -1)
  51                 close(blerg->index_fd);
  52 }
  53
  54 int blerg_remap_data(struct blerg *blerg) {
  55         struct stat st;
  56
  57         if (blerg->data != NULL)
  58                 munmap(blerg->data, blerg->data_size);
  59         fstat(blerg->data_fd, &st);
  60         if (st.st_size == 0) {
  61                 /* Can't map an empty data file. */
  62                 return 1;
  63         }
  64         blerg->data = (char *) mmap(NULL, st.st_size, PROT_READ, MAP_SHARED, blerg->data_fd, 0);
  65         if (blerg->data == MAP_FAILED) {
  66                 perror("Could not remap data");
  67                 return 0;
  68         }
  69         blerg->data_size = st.st_size;
  70         return 1;
  71 }
  72
  73 int blerg_segment_switch(struct blerg *blerg, int new_segment) {
  74         char filename[512];
  75         uint64_t max_sequence_no = blerg_get_record_count(blerg);
  76         struct stat st;
  77
  78         if (blerg->index != NULL && blerg->data != NULL && new_segment == blerg->current_segment) {
  79                 return 1;
  80         }
  81
  82         if (new_segment > max_sequence_no / RECORDS_PER_SEGMENT) {
  83                 fprintf(stderr, "Cannot switch to sequence beyond last record\n");
  84                 return 0;
  85         }
  86         if (new_segment < 0) {
  87                 fprintf(stderr, "Cannot switch to negative segment\n");
  88                 return 0;
  89         }
  90
  91         blerg_segment_close(blerg);
  92
  93         /* Load and map the index */
  94         snprintf(filename, 512, "%s/index%d", blerg->base_path, new_segment);
  95         blerg->index_fd = open(filename, O_RDWR | O_CREAT, 0600);
  96         if (blerg->index_fd == -1) {
  97                 perror("Could not open index");
  98                 goto open_failed_index_open;
  99         }
 100         flock(blerg->index_fd, LOCK_EX);
 101         fstat(blerg->index_fd, &st);
 102         if (st.st_size == 0) {
 103                 /* ftruncate() means never having to say you're sorry.  Sorry
 104                    in this case meaning "allocating disk space for a 1MB file
 105                    full or zeroes". */
 106                 ftruncate(blerg->index_fd, RECORDS_PER_SEGMENT * sizeof(struct record));
 107         }
 108         flock(blerg->index_fd, LOCK_UN);
 109
 110         blerg->index = (struct record *) mmap(NULL, RECORDS_PER_SEGMENT * sizeof(struct record), PROT_READ | PROT_WRITE, MAP_SHARED, blerg->index_fd, 0);
 111         if (blerg->index == MAP_FAILED) {
 112                 perror("Could not mmap index");
 113                 goto open_failed_index_mmap;
 114         }
 115
 116         /* Load data file */
 117         sprintf(filename, "%s/data%d", blerg->base_path, new_segment);
 118         blerg->data_fd = open(filename, O_RDWR | O_APPEND | O_CREAT, 0600);
 119         if (blerg->data_fd == -1) {
 120                 perror("Could not open data");
 121                 goto open_failed_data_open;
 122         }
 123
 124         if (!blerg_remap_data(blerg)) {
 125                 goto open_failed_data_mmap;
 126         }
 127
 128         blerg->current_segment = new_segment;
 129
 130         return 1;
 131
 132 open_failed_data_mmap:
 133         close(blerg->data_fd);
 134 open_failed_data_open:
 135         munmap((void *)blerg->index, RECORDS_PER_SEGMENT * sizeof(struct record));
 136 open_failed_index_mmap:
 137         close(blerg->index_fd);
 138 open_failed_index_open:
 139         return 0;
 140 }
 141
 142 int blerg_exists(const char *name) {
 143         int namelen = strlen(name);
 144         char filename[512];
 145
 146         if (!valid_name(name)) {
 147                 fprintf(stderr, "Invalid name\n");
 148                 return 0;
 149         }
 150
 151         snprintf(filename, 512, "%s/%s", DATA_PATH, name);
 152         if (access(filename, F_OK) == -1)
 153                 return 0;
 154         else
 155                 return 1;
 156 }
 157
 158 struct blerg *blerg_open(const char *name) {
 159         int namelen = strlen(name);
 160         char filename[512];
 161         struct stat st;
 162         uint64_t sequence;
 163
 164         if (!valid_name(name)) {
 165                 fprintf(stderr, "Invalid name\n");
 166                 return NULL;
 167         }
 168         struct blerg *blerg = malloc(sizeof(struct blerg));
 169         if (!blerg) {
 170                 perror("Cannot allocate memory for blerg");
 171                 goto open_failed_blerg_malloc;
 172         }
 173         blerg->name = malloc(namelen + 1);
 174         memcpy(blerg->name, name, namelen + 1);
 175         blerg->meta_fd = blerg->index_fd = blerg->data_fd = -1;
 176         blerg->meta = NULL;
 177         blerg->index = NULL;
 178         blerg->data = NULL;
 179
 180         /* Make the directory if it doesn't exist */
 181         blerg->base_path = malloc(512);
 182         snprintf(blerg->base_path, 512, "%s/%s", DATA_PATH, name);
 183         if (access(blerg->base_path, F_OK) == -1)
 184                 mkdir(blerg->base_path, 0755);
 185
 186         /* Open and map metadata */
 187         snprintf(filename, 512, "%s/meta", blerg->base_path);
 188         blerg->meta_fd = open(filename, O_RDWR | O_CREAT, 0600);
 189         if (blerg->meta_fd == -1) {
 190                 perror("Could not open metadata");
 191                 goto open_failed_meta_open;
 192         }
 193         fstat(blerg->meta_fd, &st);
 194         if (st.st_size < sizeof(struct meta)) {
 195                 /* Extend the file if sizeof(struct meta) is larger than the
 196                    file. This allows seamless upgrades as long as struct meta
 197                    only adds members. */
 198                 posix_fallocate(blerg->meta_fd, 0, sizeof(struct meta));
 199         }
 200         blerg->meta = (struct meta *) mmap(NULL, sizeof(struct meta), PROT_READ | PROT_WRITE, MAP_SHARED, blerg->meta_fd, 0);
 201         if (blerg->meta == MAP_FAILED) {
 202                 perror("Could not map metadata");
 203                 goto open_failed_meta_mmap;
 204         }
 205
 206         /* Open and map index and data for the current segment */
 207         blerg->current_segment = blerg_get_record_count(blerg) / RECORDS_PER_SEGMENT;
 208         if (!blerg_segment_switch(blerg, blerg->current_segment)) {
 209                 fprintf(stderr, "Could not switch segment\n");
 210                 goto open_failed_segment_switch;
 211         }
 212
 213         return blerg;
 214
 215 open_failed_segment_switch:
 216         munmap((void *)blerg->meta, sizeof(struct meta));
 217 open_failed_meta_mmap:
 218         close(blerg->meta_fd);
 219 open_failed_meta_open:
 220         free(blerg->name);
 221         free(blerg);
 222 open_failed_blerg_malloc:
 223         return NULL;
 224 }
 225
 226 int blerg_close(struct blerg *blerg) {
 227         CHECK_VALID_BLERG(0)
 228         blerg_segment_close(blerg);
 229         munmap((void *)blerg->meta, sizeof(struct meta));
 230         close(blerg->meta_fd);
 231         free(blerg->base_path);
 232         free(blerg->name);
 233         free(blerg);
 234         return 1;
 235 }
 236
 237 int blerg_store(struct blerg *blerg, const char *data, int len) {
 238         struct stat st;
 239         int n;
 240
 241         CHECK_VALID_BLERG(-1)
 242
 243         if (len > MAX_RECORD_SIZE || len <= 0) {
 244                 fprintf(stderr, "len out of bounds\n");
 245                 return -1;
 246         }
 247
 248         flock(blerg->index_fd, LOCK_EX);
 249         flock(blerg->data_fd, LOCK_EX);
 250
 251         uint64_t record = blerg_get_record_count(blerg);
 252         if (record == -1) {  /* Intentional signed-unsigned coercion */
 253                 fprintf(stderr, "Could not find free record\n");
 254                 return -1;
 255         }
 256         int segment = record / RECORDS_PER_SEGMENT;
 257         if (segment != blerg->current_segment)
 258                 blerg_segment_switch(blerg, segment);
 259         int seg_rec = record % RECORDS_PER_SEGMENT;
 260
 261         /* Get the position for the new data */
 262         fstat(blerg->data_fd, &st);
 263         int curpos = st.st_size;
 264
 265         /* Write data to the data log */
 266         n = write(blerg->data_fd, data, len);
 267         if (n < len) {
 268                 perror("Could not write data");
 269                 /* Truncate anything we may have written */
 270                 ftruncate(blerg->data_fd, curpos);
 271                 return -1;
 272         }
 273
 274         /* Update the index */
 275         blerg->index[seg_rec].flags = 0x0001;
 276         blerg->index[seg_rec].offset = curpos;
 277         blerg->index[seg_rec].length = len;
 278         blerg->index[seg_rec].timestamp = time(NULL);
 279
 280         /* And finally increment the record count */
 281         blerg_increment_record_count(blerg);
 282
 283         flock(blerg->data_fd, LOCK_UN);
 284         flock(blerg->index_fd, LOCK_UN);
 285
 286         /* Now do those dirty microblogging deeds */
 287         tag_scan(blerg->name, data, len, record);
 288         subscription_notify(blerg->name, record);
 289
 290         return record;
 291 }
 292
 293 int blerg_fetch(struct blerg *blerg, int record, char **data, int *length) {
 294         CHECK_VALID_BLERG(0)
 295         if (record < 0 || record >= blerg_get_record_count(blerg)) {
 296                 fprintf(stderr, "Invalid record\n");
 297                 return 0;
 298         }
 299         if (data == NULL || length == NULL) {
 300                 fprintf(stderr, "data or length is null\n");
 301                 return 0;
 302         }
 303
 304         int segment = record / RECORDS_PER_SEGMENT;
 305         if (segment != blerg->current_segment)
 306                 blerg_segment_switch(blerg, segment);
 307         int seg_rec = record % RECORDS_PER_SEGMENT;
 308
 309         if ((blerg->index[seg_rec].flags & 0x1) == 0) {
 310                 fprintf(stderr, "Invalid record\n");
 311                 return 0;
 312         }
 313
 314         int rec_offset = blerg->index[seg_rec].offset;
 315         int rec_length = blerg->index[seg_rec].length;
 316         if (rec_offset >= blerg->data_size) {
 317                 /* We're accessing an out-of-bounds record in our mmap.  Remap
 318                    and recheck. */
 319                 if (!blerg_remap_data(blerg)) {
 320                         return 0;
 321                 }
 322                 if (rec_offset >= blerg->data_size) {
 323                         fprintf(stderr, "Record offset outside of data!?");
 324                         return 0;
 325                 }
 326         }
 327
 328         *data = malloc(rec_length);
 329         if (*data == NULL) {
 330                 perror("Could not allocate string in fetch");
 331                 return 0;
 332         }
 333
 334         memcpy(*data, blerg->data + rec_offset, rec_length);
 335
 336         *length = rec_length;
 337
 338         return 1;
 339 }
 340
 341 time_t blerg_get_timestamp(struct blerg *blerg, int record) {
 342         CHECK_VALID_BLERG(0)
 343         if (record < 0 || record >= blerg_get_record_count(blerg)) {
 344                 fprintf(stderr, "Invalid record\n");
 345                 return 0;
 346         }
 347
 348         int segment = record / RECORDS_PER_SEGMENT;
 349         if (segment != blerg->current_segment)
 350                 blerg_segment_switch(blerg, segment);
 351         int seg_rec = record % RECORDS_PER_SEGMENT;
 352
 353         if ((blerg->index[seg_rec].flags & 0x1) == 0) {
 354                 fprintf(stderr, "Invalid record\n");
 355                 return 0;
 356         }
 357
 358         return blerg->index[seg_rec].timestamp;
 359 }
 360
 361 int blerg_set_subscription_mark(struct blerg *blerg) {
 362         CHECK_VALID_BLERG(0)
 363         blerg->meta->subscription_mark = subscription_count_items(blerg->name);
 364         return 1;
 365 }
 366
 367 uint64_t blerg_get_subscription_mark(struct blerg *blerg) {
 368         CHECK_VALID_BLERG(0)
 369         return blerg->meta->subscription_mark;
 370 }