src/aof.c

   1 #include "redis.h"
   2
   3 #include <signal.h>
   4 #include <fcntl.h>
   5 #include <sys/stat.h>
   6 #include <sys/types.h>
   7 #include <sys/time.h>
   8 #include <sys/resource.h>
   9 #include <sys/wait.h>
  10
  11 /* Called when the user switches from "appendonly yes" to "appendonly no"
  12  * at runtime using the CONFIG command. */
  13 void stopAppendOnly(void) {
  14     flushAppendOnlyFile();
  15     aof_fsync(server.appendfd);
  16     close(server.appendfd);
  17
  18     server.appendfd = -1;
  19     server.appendseldb = -1;
  20     server.appendonly = 0;
  21     /* rewrite operation in progress? kill it, wait child exit */
  22     if (server.bgsavechildpid != -1) {
  23         int statloc;
  24
  25         if (kill(server.bgsavechildpid,SIGKILL) != -1)
  26             wait3(&statloc,0,NULL);
  27         /* reset the buffer accumulating changes while the child saves */
  28         sdsfree(server.bgrewritebuf);
  29         server.bgrewritebuf = sdsempty();
  30         server.bgsavechildpid = -1;
  31     }
  32 }
  33
  34 /* Called when the user switches from "appendonly no" to "appendonly yes"
  35  * at runtime using the CONFIG command. */
  36 int startAppendOnly(void) {
  37     server.appendonly = 1;
  38     server.lastfsync = time(NULL);
  39     server.appendfd = open(server.appendfilename,O_WRONLY|O_APPEND|O_CREAT,0644);
  40     if (server.appendfd == -1) {
  41         redisLog(REDIS_WARNING,"Used tried to switch on AOF via CONFIG, but I can't open the AOF file: %s",strerror(errno));
  42         return REDIS_ERR;
  43     }
  44     if (rewriteAppendOnlyFileBackground() == REDIS_ERR) {
  45         server.appendonly = 0;
  46         close(server.appendfd);
  47         redisLog(REDIS_WARNING,"Used tried to switch on AOF via CONFIG, I can't trigger a background AOF rewrite operation. Check the above logs for more info about the error.",strerror(errno));
  48         return REDIS_ERR;
  49     }
  50     return REDIS_OK;
  51 }
  52
  53 /* Write the append only file buffer on disk.
  54  *
  55  * Since we are required to write the AOF before replying to the client,
  56  * and the only way the client socket can get a write is entering when the
  57  * the event loop, we accumulate all the AOF writes in a memory
  58  * buffer and write it on disk using this function just before entering
  59  * the event loop again. */
  60 void flushAppendOnlyFile(void) {
  61     time_t now;
  62     ssize_t nwritten;
  63
  64     if (sdslen(server.aofbuf) == 0) return;
  65
  66     /* We want to perform a single write. This should be guaranteed atomic
  67      * at least if the filesystem we are writing is a real physical one.
  68      * While this will save us against the server being killed I don't think
  69      * there is much to do about the whole server stopping for power problems
  70      * or alike */
  71      nwritten = write(server.appendfd,server.aofbuf,sdslen(server.aofbuf));
  72      if (nwritten != (signed)sdslen(server.aofbuf)) {
  73         /* Ooops, we are in troubles. The best thing to do for now is
  74          * aborting instead of giving the illusion that everything is
  75          * working as expected. */
  76          if (nwritten == -1) {
  77             redisLog(REDIS_WARNING,"Exiting on error writing to the append-only file: %s",strerror(errno));
  78          } else {
  79             redisLog(REDIS_WARNING,"Exiting on short write while writing to the append-only file: %s",strerror(errno));
  80          }
  81          exit(1);
  82     }
  83     sdsfree(server.aofbuf);
  84     server.aofbuf = sdsempty();
  85
  86     /* Don't Fsync if no-appendfsync-on-rewrite is set to yes and we have
  87      * childs performing heavy I/O on disk. */
  88     if (server.no_appendfsync_on_rewrite &&
  89         (server.bgrewritechildpid != -1 || server.bgsavechildpid != -1))
  90             return;
  91     /* Fsync if needed */
  92     now = time(NULL);
  93     if (server.appendfsync == APPENDFSYNC_ALWAYS ||
  94         (server.appendfsync == APPENDFSYNC_EVERYSEC &&
  95          now-server.lastfsync > 1))
  96     {
  97         /* aof_fsync is defined as fdatasync() for Linux in order to avoid
  98          * flushing metadata. */
  99         aof_fsync(server.appendfd); /* Let's try to get this data on the disk */
 100         server.lastfsync = now;
 101     }
 102 }
 103
 104 sds catAppendOnlyGenericCommand(sds buf, int argc, robj **argv) {
 105     int j;
 106     buf = sdscatprintf(buf,"*%d\r\n",argc);
 107     for (j = 0; j < argc; j++) {
 108         robj *o = getDecodedObject(argv[j]);
 109         buf = sdscatprintf(buf,"$%lu\r\n",(unsigned long)sdslen(o->ptr));
 110         buf = sdscatlen(buf,o->ptr,sdslen(o->ptr));
 111         buf = sdscatlen(buf,"\r\n",2);
 112         decrRefCount(o);
 113     }
 114     return buf;
 115 }
 116
 117 sds catAppendOnlyExpireAtCommand(sds buf, robj *key, robj *seconds) {
 118     int argc = 3;
 119     long when;
 120     robj *argv[3];
 121
 122     /* Make sure we can use strtol */
 123     seconds = getDecodedObject(seconds);
 124     when = time(NULL)+strtol(seconds->ptr,NULL,10);
 125     decrRefCount(seconds);
 126
 127     argv[0] = createStringObject("EXPIREAT",8);
 128     argv[1] = key;
 129     argv[2] = createObject(REDIS_STRING,
 130         sdscatprintf(sdsempty(),"%ld",when));
 131     buf = catAppendOnlyGenericCommand(buf, argc, argv);
 132     decrRefCount(argv[0]);
 133     decrRefCount(argv[2]);
 134     return buf;
 135 }
 136
 137 void feedAppendOnlyFile(struct redisCommand *cmd, int dictid, robj **argv, int argc) {
 138     sds buf = sdsempty();
 139     robj *tmpargv[3];
 140
 141     /* The DB this command was targetting is not the same as the last command
 142      * we appendend. To issue a SELECT command is needed. */
 143     if (dictid != server.appendseldb) {
 144         char seldb[64];
 145
 146         snprintf(seldb,sizeof(seldb),"%d",dictid);
 147         buf = sdscatprintf(buf,"*2\r\n$6\r\nSELECT\r\n$%lu\r\n%s\r\n",
 148             (unsigned long)strlen(seldb),seldb);
 149         server.appendseldb = dictid;
 150     }
 151
 152     if (cmd->proc == expireCommand) {
 153         /* Translate EXPIRE into EXPIREAT */
 154         buf = catAppendOnlyExpireAtCommand(buf,argv[1],argv[2]);
 155     } else if (cmd->proc == setexCommand) {
 156         /* Translate SETEX to SET and EXPIREAT */
 157         tmpargv[0] = createStringObject("SET",3);
 158         tmpargv[1] = argv[1];
 159         tmpargv[2] = argv[3];
 160         buf = catAppendOnlyGenericCommand(buf,3,tmpargv);
 161         decrRefCount(tmpargv[0]);
 162         buf = catAppendOnlyExpireAtCommand(buf,argv[1],argv[2]);
 163     } else {
 164         buf = catAppendOnlyGenericCommand(buf,argc,argv);
 165     }
 166
 167     /* Append to the AOF buffer. This will be flushed on disk just before
 168      * of re-entering the event loop, so before the client will get a
 169      * positive reply about the operation performed. */
 170     server.aofbuf = sdscatlen(server.aofbuf,buf,sdslen(buf));
 171
 172     /* If a background append only file rewriting is in progress we want to
 173      * accumulate the differences between the child DB and the current one
 174      * in a buffer, so that when the child process will do its work we
 175      * can append the differences to the new append only file. */
 176     if (server.bgrewritechildpid != -1)
 177         server.bgrewritebuf = sdscatlen(server.bgrewritebuf,buf,sdslen(buf));
 178
 179     sdsfree(buf);
 180 }
 181
 182 /* In Redis commands are always executed in the context of a client, so in
 183  * order to load the append only file we need to create a fake client. */
 184 struct redisClient *createFakeClient(void) {
 185     struct redisClient *c = zmalloc(sizeof(*c));
 186
 187     selectDb(c,0);
 188     c->fd = -1;
 189     c->querybuf = sdsempty();
 190     c->argc = 0;
 191     c->argv = NULL;
 192     c->bufpos = 0;
 193     c->flags = 0;
 194     /* We set the fake client as a slave waiting for the synchronization
 195      * so that Redis will not try to send replies to this client. */
 196     c->replstate = REDIS_REPL_WAIT_BGSAVE_START;
 197     c->reply = listCreate();
 198     c->watched_keys = listCreate();
 199     listSetFreeMethod(c->reply,decrRefCount);
 200     listSetDupMethod(c->reply,dupClientReplyValue);
 201     initClientMultiState(c);
 202     return c;
 203 }
 204
 205 void freeFakeClient(struct redisClient *c) {
 206     sdsfree(c->querybuf);
 207     listRelease(c->reply);
 208     listRelease(c->watched_keys);
 209     freeClientMultiState(c);
 210     zfree(c);
 211 }
 212
 213 /* Replay the append log file. On error REDIS_OK is returned. On non fatal
 214  * error (the append only file is zero-length) REDIS_ERR is returned. On
 215  * fatal error an error message is logged and the program exists. */
 216 int loadAppendOnlyFile(char *filename) {
 217     struct redisClient *fakeClient;
 218     FILE *fp = fopen(filename,"r");
 219     struct redis_stat sb;
 220     int appendonly = server.appendonly;
 221
 222     if (redis_fstat(fileno(fp),&sb) != -1 && sb.st_size == 0)
 223         return REDIS_ERR;
 224
 225     if (fp == NULL) {
 226         redisLog(REDIS_WARNING,"Fatal error: can't open the append log file for reading: %s",strerror(errno));
 227         exit(1);
 228     }
 229
 230     /* Temporarily disable AOF, to prevent EXEC from feeding a MULTI
 231      * to the same file we're about to read. */
 232     server.appendonly = 0;
 233
 234     fakeClient = createFakeClient();
 235     while(1) {
 236         int argc, j;
 237         unsigned long len;
 238         robj **argv;
 239         char buf[128];
 240         sds argsds;
 241         struct redisCommand *cmd;
 242         int force_swapout;
 243
 244         if (fgets(buf,sizeof(buf),fp) == NULL) {
 245             if (feof(fp))
 246                 break;
 247             else
 248                 goto readerr;
 249         }
 250         if (buf[0] != '*') goto fmterr;
 251         argc = atoi(buf+1);
 252         argv = zmalloc(sizeof(robj*)*argc);
 253         for (j = 0; j < argc; j++) {
 254             if (fgets(buf,sizeof(buf),fp) == NULL) goto readerr;
 255             if (buf[0] != '$') goto fmterr;
 256             len = strtol(buf+1,NULL,10);
 257             argsds = sdsnewlen(NULL,len);
 258             if (len && fread(argsds,len,1,fp) == 0) goto fmterr;
 259             argv[j] = createObject(REDIS_STRING,argsds);
 260             if (fread(buf,2,1,fp) == 0) goto fmterr; /* discard CRLF */
 261         }
 262
 263         /* Command lookup */
 264         cmd = lookupCommand(argv[0]->ptr);
 265         if (!cmd) {
 266             redisLog(REDIS_WARNING,"Unknown command '%s' reading the append only file", argv[0]->ptr);
 267             exit(1);
 268         }
 269         /* Run the command in the context of a fake client */
 270         fakeClient->argc = argc;
 271         fakeClient->argv = argv;
 272         cmd->proc(fakeClient);
 273
 274         /* The fake client should not have a reply */
 275         redisAssert(fakeClient->bufpos == 0 && listLength(fakeClient->reply) == 0);
 276
 277         /* Clean up, ready for the next command */
 278         for (j = 0; j < argc; j++) decrRefCount(argv[j]);
 279         zfree(argv);
 280
 281         /* Handle swapping while loading big datasets when VM is on */
 282         force_swapout = 0;
 283         if ((zmalloc_used_memory() - server.vm_max_memory) > 1024*1024*32)
 284             force_swapout = 1;
 285
 286         if (server.vm_enabled && force_swapout) {
 287             while (zmalloc_used_memory() > server.vm_max_memory) {
 288                 if (vmSwapOneObjectBlocking() == REDIS_ERR) break;
 289             }
 290         }
 291     }
 292
 293     /* This point can only be reached when EOF is reached without errors.
 294      * If the client is in the middle of a MULTI/EXEC, log error and quit. */
 295     if (fakeClient->flags & REDIS_MULTI) goto readerr;
 296
 297     fclose(fp);
 298     freeFakeClient(fakeClient);
 299     server.appendonly = appendonly;
 300     return REDIS_OK;
 301
 302 readerr:
 303     if (feof(fp)) {
 304         redisLog(REDIS_WARNING,"Unexpected end of file reading the append only file");
 305     } else {
 306         redisLog(REDIS_WARNING,"Unrecoverable error reading the append only file: %s", strerror(errno));
 307     }
 308     exit(1);
 309 fmterr:
 310     redisLog(REDIS_WARNING,"Bad file format reading the append only file: make a backup of your AOF file, then use ./redis-check-aof --fix <filename>");
 311     exit(1);
 312 }
 313
 314 /* Write a sequence of commands able to fully rebuild the dataset into
 315  * "filename". Used both by REWRITEAOF and BGREWRITEAOF. */
 316 int rewriteAppendOnlyFile(char *filename) {
 317     dictIterator *di = NULL;
 318     dictEntry *de;
 319     FILE *fp;
 320     char tmpfile[256];
 321     int j;
 322     time_t now = time(NULL);
 323
 324     /* Note that we have to use a different temp name here compared to the
 325      * one used by rewriteAppendOnlyFileBackground() function. */
 326     snprintf(tmpfile,256,"temp-rewriteaof-%d.aof", (int) getpid());
 327     fp = fopen(tmpfile,"w");
 328     if (!fp) {
 329         redisLog(REDIS_WARNING, "Failed rewriting the append only file: %s", strerror(errno));
 330         return REDIS_ERR;
 331     }
 332     for (j = 0; j < server.dbnum; j++) {
 333         char selectcmd[] = "*2\r\n$6\r\nSELECT\r\n";
 334         redisDb *db = server.db+j;
 335         dict *d = db->dict;
 336         if (dictSize(d) == 0) continue;
 337         di = dictGetIterator(d);
 338         if (!di) {
 339             fclose(fp);
 340             return REDIS_ERR;
 341         }
 342
 343         /* SELECT the new DB */
 344         if (fwrite(selectcmd,sizeof(selectcmd)-1,1,fp) == 0) goto werr;
 345         if (fwriteBulkLongLong(fp,j) == 0) goto werr;
 346
 347         /* Iterate this DB writing every entry */
 348         while((de = dictNext(di)) != NULL) {
 349             sds keystr = dictGetEntryKey(de);
 350             robj key, *o;
 351             time_t expiretime;
 352             int swapped;
 353
 354             keystr = dictGetEntryKey(de);
 355             o = dictGetEntryVal(de);
 356             initStaticStringObject(key,keystr);
 357             /* If the value for this key is swapped, load a preview in memory.
 358              * We use a "swapped" flag to remember if we need to free the
 359              * value object instead to just increment the ref count anyway
 360              * in order to avoid copy-on-write of pages if we are forked() */
 361             if (!server.vm_enabled || o->storage == REDIS_VM_MEMORY ||
 362                 o->storage == REDIS_VM_SWAPPING) {
 363                 swapped = 0;
 364             } else {
 365                 o = vmPreviewObject(o);
 366                 swapped = 1;
 367             }
 368             expiretime = getExpire(db,&key);
 369
 370             /* Save the key and associated value */
 371             if (o->type == REDIS_STRING) {
 372                 /* Emit a SET command */
 373                 char cmd[]="*3\r\n$3\r\nSET\r\n";
 374                 if (fwrite(cmd,sizeof(cmd)-1,1,fp) == 0) goto werr;
 375                 /* Key and value */
 376                 if (fwriteBulkObject(fp,&key) == 0) goto werr;
 377                 if (fwriteBulkObject(fp,o) == 0) goto werr;
 378             } else if (o->type == REDIS_LIST) {
 379                 /* Emit the RPUSHes needed to rebuild the list */
 380                 char cmd[]="*3\r\n$5\r\nRPUSH\r\n";
 381                 if (o->encoding == REDIS_ENCODING_ZIPLIST) {
 382                     unsigned char *zl = o->ptr;
 383                     unsigned char *p = ziplistIndex(zl,0);
 384                     unsigned char *vstr;
 385                     unsigned int vlen;
 386                     long long vlong;
 387
 388                     while(ziplistGet(p,&vstr,&vlen,&vlong)) {
 389                         if (fwrite(cmd,sizeof(cmd)-1,1,fp) == 0) goto werr;
 390                         if (fwriteBulkObject(fp,&key) == 0) goto werr;
 391                         if (vstr) {
 392                             if (fwriteBulkString(fp,(char*)vstr,vlen) == 0)
 393                                 goto werr;
 394                         } else {
 395                             if (fwriteBulkLongLong(fp,vlong) == 0)
 396                                 goto werr;
 397                         }
 398                         p = ziplistNext(zl,p);
 399                     }
 400                 } else if (o->encoding == REDIS_ENCODING_LINKEDLIST) {
 401                     list *list = o->ptr;
 402                     listNode *ln;
 403                     listIter li;
 404
 405                     listRewind(list,&li);
 406                     while((ln = listNext(&li))) {
 407                         robj *eleobj = listNodeValue(ln);
 408
 409                         if (fwrite(cmd,sizeof(cmd)-1,1,fp) == 0) goto werr;
 410                         if (fwriteBulkObject(fp,&key) == 0) goto werr;
 411                         if (fwriteBulkObject(fp,eleobj) == 0) goto werr;
 412                     }
 413                 } else {
 414                     redisPanic("Unknown list encoding");
 415                 }
 416             } else if (o->type == REDIS_SET) {
 417                 char cmd[]="*3\r\n$4\r\nSADD\r\n";
 418
 419                 /* Emit the SADDs needed to rebuild the set */
 420                 if (o->encoding == REDIS_ENCODING_INTSET) {
 421                     int ii = 0;
 422                     int64_t llval;
 423                     while(intsetGet(o->ptr,ii++,&llval)) {
 424                         if (fwrite(cmd,sizeof(cmd)-1,1,fp) == 0) goto werr;
 425                         if (fwriteBulkObject(fp,&key) == 0) goto werr;
 426                         if (fwriteBulkLongLong(fp,llval) == 0) goto werr;
 427                     }
 428                 } else if (o->encoding == REDIS_ENCODING_HT) {
 429                     dictIterator *di = dictGetIterator(o->ptr);
 430                     dictEntry *de;
 431                     while((de = dictNext(di)) != NULL) {
 432                         robj *eleobj = dictGetEntryKey(de);
 433                         if (fwrite(cmd,sizeof(cmd)-1,1,fp) == 0) goto werr;
 434                         if (fwriteBulkObject(fp,&key) == 0) goto werr;
 435                         if (fwriteBulkObject(fp,eleobj) == 0) goto werr;
 436                     }
 437                     dictReleaseIterator(di);
 438                 } else {
 439                     redisPanic("Unknown set encoding");
 440                 }
 441             } else if (o->type == REDIS_ZSET) {
 442                 /* Emit the ZADDs needed to rebuild the sorted set */
 443                 zset *zs = o->ptr;
 444                 dictIterator *di = dictGetIterator(zs->dict);
 445                 dictEntry *de;
 446
 447                 while((de = dictNext(di)) != NULL) {
 448                     char cmd[]="*4\r\n$4\r\nZADD\r\n";
 449                     robj *eleobj = dictGetEntryKey(de);
 450                     double *score = dictGetEntryVal(de);
 451
 452                     if (fwrite(cmd,sizeof(cmd)-1,1,fp) == 0) goto werr;
 453                     if (fwriteBulkObject(fp,&key) == 0) goto werr;
 454                     if (fwriteBulkDouble(fp,*score) == 0) goto werr;
 455                     if (fwriteBulkObject(fp,eleobj) == 0) goto werr;
 456                 }
 457                 dictReleaseIterator(di);
 458             } else if (o->type == REDIS_HASH) {
 459                 char cmd[]="*4\r\n$4\r\nHSET\r\n";
 460
 461                 /* Emit the HSETs needed to rebuild the hash */
 462                 if (o->encoding == REDIS_ENCODING_ZIPMAP) {
 463                     unsigned char *p = zipmapRewind(o->ptr);
 464                     unsigned char *field, *val;
 465                     unsigned int flen, vlen;
 466
 467                     while((p = zipmapNext(p,&field,&flen,&val,&vlen)) != NULL) {
 468                         if (fwrite(cmd,sizeof(cmd)-1,1,fp) == 0) goto werr;
 469                         if (fwriteBulkObject(fp,&key) == 0) goto werr;
 470                         if (fwriteBulkString(fp,(char*)field,flen) == 0)
 471                             goto werr;
 472                         if (fwriteBulkString(fp,(char*)val,vlen) == 0)
 473                             goto werr;
 474                     }
 475                 } else {
 476                     dictIterator *di = dictGetIterator(o->ptr);
 477                     dictEntry *de;
 478
 479                     while((de = dictNext(di)) != NULL) {
 480                         robj *field = dictGetEntryKey(de);
 481                         robj *val = dictGetEntryVal(de);
 482
 483                         if (fwrite(cmd,sizeof(cmd)-1,1,fp) == 0) goto werr;
 484                         if (fwriteBulkObject(fp,&key) == 0) goto werr;
 485                         if (fwriteBulkObject(fp,field) == 0) goto werr;
 486                         if (fwriteBulkObject(fp,val) == 0) goto werr;
 487                     }
 488                     dictReleaseIterator(di);
 489                 }
 490             } else {
 491                 redisPanic("Unknown object type");
 492             }
 493             /* Save the expire time */
 494             if (expiretime != -1) {
 495                 char cmd[]="*3\r\n$8\r\nEXPIREAT\r\n";
 496                 /* If this key is already expired skip it */
 497                 if (expiretime < now) continue;
 498                 if (fwrite(cmd,sizeof(cmd)-1,1,fp) == 0) goto werr;
 499                 if (fwriteBulkObject(fp,&key) == 0) goto werr;
 500                 if (fwriteBulkLongLong(fp,expiretime) == 0) goto werr;
 501             }
 502             if (swapped) decrRefCount(o);
 503         }
 504         dictReleaseIterator(di);
 505     }
 506
 507     /* Make sure data will not remain on the OS's output buffers */
 508     fflush(fp);
 509     aof_fsync(fileno(fp));
 510     fclose(fp);
 511
 512     /* Use RENAME to make sure the DB file is changed atomically only
 513      * if the generate DB file is ok. */
 514     if (rename(tmpfile,filename) == -1) {
 515         redisLog(REDIS_WARNING,"Error moving temp append only file on the final destination: %s", strerror(errno));
 516         unlink(tmpfile);
 517         return REDIS_ERR;
 518     }
 519     redisLog(REDIS_NOTICE,"SYNC append only file rewrite performed");
 520     return REDIS_OK;
 521
 522 werr:
 523     fclose(fp);
 524     unlink(tmpfile);
 525     redisLog(REDIS_WARNING,"Write error writing append only file on disk: %s", strerror(errno));
 526     if (di) dictReleaseIterator(di);
 527     return REDIS_ERR;
 528 }
 529
 530 /* This is how rewriting of the append only file in background works:
 531  *
 532  * 1) The user calls BGREWRITEAOF
 533  * 2) Redis calls this function, that forks():
 534  *    2a) the child rewrite the append only file in a temp file.
 535  *    2b) the parent accumulates differences in server.bgrewritebuf.
 536  * 3) When the child finished '2a' exists.
 537  * 4) The parent will trap the exit code, if it's OK, will append the
 538  *    data accumulated into server.bgrewritebuf into the temp file, and
 539  *    finally will rename(2) the temp file in the actual file name.
 540  *    The the new file is reopened as the new append only file. Profit!
 541  */
 542 int rewriteAppendOnlyFileBackground(void) {
 543     pid_t childpid;
 544
 545     if (server.bgrewritechildpid != -1) return REDIS_ERR;
 546     if (server.vm_enabled) waitEmptyIOJobsQueue();
 547     if ((childpid = fork()) == 0) {
 548         /* Child */
 549         char tmpfile[256];
 550
 551         if (server.vm_enabled) vmReopenSwapFile();
 552         if (server.ipfd > 0) close(server.ipfd);
 553         if (server.sofd > 0) close(server.sofd);
 554         snprintf(tmpfile,256,"temp-rewriteaof-bg-%d.aof", (int) getpid());
 555         if (rewriteAppendOnlyFile(tmpfile) == REDIS_OK) {
 556             _exit(0);
 557         } else {
 558             _exit(1);
 559         }
 560     } else {
 561         /* Parent */
 562         if (childpid == -1) {
 563             redisLog(REDIS_WARNING,
 564                 "Can't rewrite append only file in background: fork: %s",
 565                 strerror(errno));
 566             return REDIS_ERR;
 567         }
 568         redisLog(REDIS_NOTICE,
 569             "Background append only file rewriting started by pid %d",childpid);
 570         server.bgrewritechildpid = childpid;
 571         updateDictResizePolicy();
 572         /* We set appendseldb to -1 in order to force the next call to the
 573          * feedAppendOnlyFile() to issue a SELECT command, so the differences
 574          * accumulated by the parent into server.bgrewritebuf will start
 575          * with a SELECT statement and it will be safe to merge. */
 576         server.appendseldb = -1;
 577         return REDIS_OK;
 578     }
 579     return REDIS_OK; /* unreached */
 580 }
 581
 582 void bgrewriteaofCommand(redisClient *c) {
 583     if (server.bgrewritechildpid != -1) {
 584         addReplyError(c,"Background append only file rewriting already in progress");
 585         return;
 586     }
 587     if (rewriteAppendOnlyFileBackground() == REDIS_OK) {
 588         addReplyStatus(c,"Background append only file rewriting started");
 589     } else {
 590         addReply(c,shared.err);
 591     }
 592 }
 593
 594 void aofRemoveTempFile(pid_t childpid) {
 595     char tmpfile[256];
 596
 597     snprintf(tmpfile,256,"temp-rewriteaof-bg-%d.aof", (int) childpid);
 598     unlink(tmpfile);
 599 }
 600
 601 /* A background append only file rewriting (BGREWRITEAOF) terminated its work.
 602  * Handle this. */
 603 void backgroundRewriteDoneHandler(int statloc) {
 604     int exitcode = WEXITSTATUS(statloc);
 605     int bysignal = WIFSIGNALED(statloc);
 606
 607     if (!bysignal && exitcode == 0) {
 608         int fd;
 609         char tmpfile[256];
 610
 611         redisLog(REDIS_NOTICE,
 612             "Background append only file rewriting terminated with success");
 613         /* Now it's time to flush the differences accumulated by the parent */
 614         snprintf(tmpfile,256,"temp-rewriteaof-bg-%d.aof", (int) server.bgrewritechildpid);
 615         fd = open(tmpfile,O_WRONLY|O_APPEND);
 616         if (fd == -1) {
 617             redisLog(REDIS_WARNING, "Not able to open the temp append only file produced by the child: %s", strerror(errno));
 618             goto cleanup;
 619         }
 620         /* Flush our data... */
 621         if (write(fd,server.bgrewritebuf,sdslen(server.bgrewritebuf)) !=
 622                 (signed) sdslen(server.bgrewritebuf)) {
 623             redisLog(REDIS_WARNING, "Error or short write trying to flush the parent diff of the append log file in the child temp file: %s", strerror(errno));
 624             close(fd);
 625             goto cleanup;
 626         }
 627         redisLog(REDIS_NOTICE,"Parent diff flushed into the new append log file with success (%lu bytes)",sdslen(server.bgrewritebuf));
 628         /* Now our work is to rename the temp file into the stable file. And
 629          * switch the file descriptor used by the server for append only. */
 630         if (rename(tmpfile,server.appendfilename) == -1) {
 631             redisLog(REDIS_WARNING,"Can't rename the temp append only file into the stable one: %s", strerror(errno));
 632             close(fd);
 633             goto cleanup;
 634         }
 635         /* Mission completed... almost */
 636         redisLog(REDIS_NOTICE,"Append only file successfully rewritten.");
 637         if (server.appendfd != -1) {
 638             /* If append only is actually enabled... */
 639             close(server.appendfd);
 640             server.appendfd = fd;
 641             if (server.appendfsync != APPENDFSYNC_NO) aof_fsync(fd);
 642             server.appendseldb = -1; /* Make sure it will issue SELECT */
 643             redisLog(REDIS_NOTICE,"The new append only file was selected for future appends.");
 644         } else {
 645             /* If append only is disabled we just generate a dump in this
 646              * format. Why not? */
 647             close(fd);
 648         }
 649     } else if (!bysignal && exitcode != 0) {
 650         redisLog(REDIS_WARNING, "Background append only file rewriting error");
 651     } else {
 652         redisLog(REDIS_WARNING,
 653             "Background append only file rewriting terminated by signal %d",
 654             WTERMSIG(statloc));
 655     }
 656 cleanup:
 657     sdsfree(server.bgrewritebuf);
 658     server.bgrewritebuf = sdsempty();
 659     aofRemoveTempFile(server.bgrewritechildpid);
 660     server.bgrewritechildpid = -1;
 661 }