Robust/src/Runtime/DSTM/interface/dstmserver.c

   1 /* Coordinator => Machine that initiates the transaction request call for commiting a transaction
   2  * Participant => Machines that host the objects involved in a transaction commit */
   3
   4 #include <stdio.h>
   5 #include <stdlib.h>
   6 #include <string.h>
   7 #include <pthread.h>
   8 #include <netdb.h>
   9 #include <fcntl.h>
  10 #include "dstm.h"
  11 #include "mlookup.h"
  12 #include "llookup.h"
  13
  14 #define LISTEN_PORT 2156
  15 #define BACKLOG 10 //max pending connections
  16 #define RECEIVE_BUFFER_SIZE 2048
  17 #define PRE_BUF_SIZE 2048
  18
  19 extern int classsize[];
  20
  21 objstr_t *mainobjstore;
  22
  23 int dstmInit(void)
  24 {
  25         /* Initialize main object store */
  26         mainobjstore = objstrCreate(DEFAULT_OBJ_STORE_SIZE);
  27         /* Create machine lookup table and location lookup table */
  28         if (mhashCreate(HASH_SIZE, LOADFACTOR))
  29                 return 1; //failure
  30
  31         if (lhashCreate(HASH_SIZE, LOADFACTOR))
  32                 return 1; //failure
  33
  34         return 0;
  35 }
  36
  37 void *dstmListen()
  38 {
  39         int listenfd, acceptfd;
  40         struct sockaddr_in my_addr;
  41         struct sockaddr_in client_addr;
  42         socklen_t addrlength = sizeof(struct sockaddr);
  43         pthread_t thread_dstm_accept;
  44         int i;
  45         int setsockflag=1;
  46
  47         listenfd = socket(AF_INET, SOCK_STREAM, 0);
  48         if (listenfd == -1)
  49         {
  50                 perror("socket");
  51                 exit(1);
  52         }
  53
  54         if (setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, &setsockflag, sizeof (setsockflag)) < 0) {
  55           perror("socket");
  56           exit(1);
  57         }
  58 #ifdef MAC
  59         if (setsockopt(listenfd, SOL_SOCKET, SO_NOSIGPIPE, &setsockflag, sizeof (setsockflag)) < 0) {
  60           perror("socket");
  61           exit(1);
  62         }
  63 #endif
  64
  65         my_addr.sin_family = AF_INET;
  66         my_addr.sin_port = htons(LISTEN_PORT);
  67         my_addr.sin_addr.s_addr = INADDR_ANY;
  68         memset(&(my_addr.sin_zero), '\0', 8);
  69
  70         if (bind(listenfd, (struct sockaddr *)&my_addr, addrlength) == -1)
  71         {
  72                 perror("bind");
  73                 exit(1);
  74         }
  75
  76         if (listen(listenfd, BACKLOG) == -1)
  77         {
  78                 perror("listen");
  79                 exit(1);
  80         }
  81
  82         printf("Listening on port %d, fd = %d\n", LISTEN_PORT, listenfd);
  83         while(1)
  84         {
  85                 acceptfd = accept(listenfd, (struct sockaddr *)&client_addr, &addrlength);
  86                 pthread_create(&thread_dstm_accept, NULL, dstmAccept, (void *)acceptfd);
  87         }
  88         pthread_exit(NULL);
  89 }
  90 /* This function accepts a new connection request, decodes the control message in the connection
  91  * and accordingly calls other functions to process new requests */
  92 void *dstmAccept(void *acceptfd)
  93 {
  94         int numbytes,i, val, retval;
  95         unsigned int oid;
  96         char buffer[RECEIVE_BUFFER_SIZE], control,ctrl;
  97         char *ptr;
  98         void *srcObj;
  99         objheader_t *h;
 100         trans_commit_data_t transinfo;
 101         unsigned short objType;
 102
 103         int fd_flags = fcntl((int)acceptfd, F_GETFD), size;
 104
 105         printf("Recieved connection: fd = %d\n", (int)acceptfd);
 106         /* Receive control messages from other machines */
 107         if((retval = recv((int)acceptfd, &control, sizeof(char), 0)) <= 0) {
 108                 if (retval == 0) {
 109                         return; // Testing connection
 110                 }
 111                 perror("Error in receiving control from coordinator\n");
 112                 return;
 113         }
 114
 115         switch(control) {
 116                 case READ_REQUEST:
 117                         /* Read oid requested and search if available */
 118                         if((retval = recv((int)acceptfd, &oid, sizeof(unsigned int), 0)) <= 0) {
 119                                 perror("Error receiving object from cooridnator\n");
 120                                 return NULL;
 121                         }
 122                         srcObj = mhashSearch(oid);
 123                         h = (objheader_t *) srcObj;
 124                         size = sizeof(objheader_t) + sizeof(classsize[TYPE(h)]);
 125                         if (h == NULL) {
 126                                 ctrl = OBJECT_NOT_FOUND;
 127                                 if(send((int)acceptfd, &ctrl, sizeof(char), MSG_NOSIGNAL) < sizeof(char)) {
 128                                         perror("Error sending control msg to coordinator\n");
 129                                         return NULL;
 130                                 }
 131                         } else {
 132                                 /* Type */
 133                           char msg[]={OBJECT_FOUND, 0, 0, 0, 0};
 134                           *((int *)&msg[1])=size;
 135                           if(send((int)acceptfd, &msg, sizeof(msg), MSG_NOSIGNAL) < sizeof(msg)) {
 136                                   perror("Error sending size of object to coordinator\n");
 137                                   return NULL;
 138                           }
 139                           if(send((int)acceptfd, h, size, MSG_NOSIGNAL) < size) {
 140                                   perror("Error in sending object\n");
 141                                   return NULL;
 142                           }
 143                         }
 144                         break;
 145
 146                 case READ_MULT_REQUEST:
 147                         printf("DEBUG-> READ_MULT_REQUEST\n");
 148                         break;
 149
 150                 case MOVE_REQUEST:
 151                         printf("DEBUG -> MOVE_REQUEST\n");
 152                         break;
 153
 154                 case MOVE_MULT_REQUEST:
 155                         printf("DEBUG -> MOVE_MULT_REQUEST\n");
 156                         break;
 157
 158                 case TRANS_REQUEST:
 159                         /* Read transaction request */
 160                         printf("DEBUG -> Recv TRANS_REQUEST\n");
 161                         if((val = readClientReq(&transinfo, (int)acceptfd)) != 0) {
 162                                 printf("Error in readClientReq\n");
 163                                 return;
 164                         }
 165                         break;
 166                 case TRANS_PREFETCH:
 167                         printf("DEBUG -> Recv TRANS_PREFETCH\n");
 168                         if((val = prefetchReq((int)acceptfd)) != 0) {
 169                                 printf("Error in readClientReq\n");
 170                                 return;
 171                         }
 172                         break;
 173                 case START_REMOTE_THREAD:
 174                         retval = recv((int)acceptfd, &oid, sizeof(unsigned int), 0);
 175                         if (retval <= 0)
 176                                 perror("dstmAccept(): error receiving START_REMOTE_THREAD msg");
 177                         else if (retval != sizeof(unsigned int))
 178                                 printf("dstmAccept(): incorrect msg size %d for START_REMOTE_THREAD\n",
 179                                         retval);
 180                         else
 181                         { //TODO: execute run method on this global thread object
 182                                 printf("dstmAccept(): received START_REMOTE_THREAD msg, oid=%d\n", oid);
 183                                 objType = getObjType(oid);
 184                                 printf("dstmAccept(): type of object %d is %d\n", oid, objType);
 185                         }
 186                         break;
 187
 188                 default:
 189                         printf("DEBUG -> dstmAccept: Error Unknown opcode %d\n", control);
 190         }
 191
 192         /* Close connection */
 193         if (close((int)acceptfd) == -1)
 194                 perror("close");
 195         else
 196                 printf("Closed connection: fd = %d\n", (int)acceptfd);
 197
 198         pthread_exit(NULL);
 199 }
 200
 201 /* This function reads the information available in a transaction request
 202  * and makes a function call to process the request */
 203 int readClientReq(trans_commit_data_t *transinfo, int acceptfd) {
 204         char *ptr;
 205         void *modptr;
 206         fixed_data_t fixed;
 207         int sum = 0, i, N, n, val;
 208
 209         /* Read fixed_data_t data structure */
 210         N = sizeof(fixed) - 1;
 211         ptr = (char *)&fixed;;
 212         fixed.control = TRANS_REQUEST;
 213         do {
 214                 n = recv((int)acceptfd, (void *) ptr+1+sum, N-sum, 0);
 215                 sum += n;
 216         } while(sum < N && n != 0);
 217
 218         /* Read list of mids */
 219         int mcount = fixed.mcount;
 220         N = mcount * sizeof(unsigned int);
 221         unsigned int listmid[mcount];
 222         ptr = (char *) listmid;
 223         sum = 0;
 224         do {
 225                 n = recv((int)acceptfd, (void *) ptr+sum, N-sum, 0);
 226                 sum += n;
 227         } while(sum < N && n != 0);
 228
 229         /* Read oid and version tuples for those objects that are not modified in the transaction */
 230         int numread = fixed.numread;
 231         N = numread * (sizeof(unsigned int) + sizeof(short));
 232         char objread[N];
 233         if(numread != 0) { //If pile contains more than one object to be read,
 234                           // keep reading all objects
 235                 sum = 0;
 236                 do {
 237                         n = recv((int)acceptfd, (void *) objread, N, 0);
 238                         sum += n;
 239                 } while(sum < N && n != 0);
 240         }
 241
 242         /* Read modified objects */
 243         if(fixed.nummod != 0) { // If pile contains more than one modified object,
 244                                 // allocate new object store and recv all modified objects
 245                                 // TODO deallocate this space
 246                 if ((modptr = objstrAlloc(mainobjstore, fixed.sum_bytes)) == NULL) {
 247                         printf("objstrAlloc error for modified objects %s, %d\n", __FILE__, __LINE__);
 248                         return 1;
 249                 }
 250                 sum = 0;
 251                 do { // Recv the objs that are modified by the Coordinator
 252                         n = recv((int)acceptfd, modptr+sum, fixed.sum_bytes-sum, 0);
 253                         sum += n;
 254                 } while (sum < fixed.sum_bytes && n != 0);
 255         }
 256
 257         /*Process the information read */
 258         if((val = processClientReq(&fixed, transinfo, listmid, objread, modptr, acceptfd)) != 0) {
 259                 printf("Error in processClientReq %s, %d\n", __FILE__, __LINE__);
 260                 return 1;
 261         }
 262
 263         return 0;
 264 }
 265
 266 /* This function processes the Coordinator's transaction request using "handleTransReq"
 267  * function and sends a reply to the co-ordinator.
 268  * Following this it also receives a new control message from the co-ordinator and processes this message*/
 269 int processClientReq(fixed_data_t *fixed, trans_commit_data_t *transinfo,
 270                 unsigned int *listmid, char *objread, void *modptr, int acceptfd) {
 271         char *ptr, control, sendctrl;
 272         objheader_t *tmp_header;
 273         void *header;
 274         int  i = 0, val, retval;
 275
 276         /* Send reply to the Coordinator */
 277         if((retval = handleTransReq(fixed, transinfo, listmid, objread, modptr,acceptfd)) == 0 ) {
 278                 printf("Handle Trans Req error %s, %d\n", __FILE__, __LINE__);
 279                 return 1;
 280         }
 281
 282         /* Read new control message from Coordiator */
 283         if((retval = recv((int)acceptfd, &control, sizeof(char), 0)) <= 0 ) {
 284                 perror("Error in receiving control message\n");
 285                 return 1;
 286         }
 287
 288         /* Process the new control message */
 289         switch(control) {
 290                 case TRANS_ABORT:
 291                         /* Set all ref counts as 1 and do garbage collection */
 292                         ptr = modptr;
 293                         for(i = 0; i< fixed->nummod; i++) {
 294                                 tmp_header = (objheader_t *)ptr;
 295                                 tmp_header->rcount = 1;
 296                                 ptr += sizeof(objheader_t) + classsize[TYPE(tmp_header)];
 297                         }
 298                         /* Unlock objects that was locked due to this transaction */
 299                         for(i = 0; i< transinfo->numlocked; i++) {
 300                                 header = mhashSearch(transinfo->objlocked[i]);// find the header address
 301                                 STATUS(((objheader_t *)header)) &= ~(LOCK);
 302                         }
 303
 304                         /* Send ack to Coordinator */
 305                         printf("DEBUG -> Recv TRANS_ABORT\n");
 306                         sendctrl = TRANS_SUCESSFUL;
 307                         if(send((int)acceptfd, &sendctrl, sizeof(char), MSG_NOSIGNAL) < sizeof(char)) {
 308                                 perror("Error sending ACK to coordinator\n");
 309                                 return 1;
 310                         }
 311                         ptr = NULL;
 312                         break;
 313
 314                 case TRANS_COMMIT:
 315                         /* Invoke the transCommit process() */
 316                         printf("DEBUG -> Recv TRANS_COMMIT \n");
 317                         if((val = transCommitProcess(transinfo, (int)acceptfd)) != 0) {
 318                                 printf("Error in transCommitProcess %s, %d\n", __FILE__, __LINE__);
 319                                 return 1;
 320                         }
 321                         break;
 322
 323                 case TRANS_ABORT_BUT_RETRY_COMMIT_WITH_RELOCATING:
 324                         //TODO expect another transrequest from client
 325                         printf("DEBUG -> Recv TRANS_ABORT_BUT_RETRY_COMMIT_WITH_RELOCATING\n");
 326                         break;
 327                 default:
 328                         printf("No response to TRANS_AGREE OR DISAGREE protocol\n");
 329                         //TODO Use fixed.trans_id  TID since Client may have died
 330                         break;
 331         }
 332         /* Free memory */
 333         printf("DEBUG -> Freeing...\n");
 334         fflush(stdout);
 335         if (transinfo->objmod != NULL) {
 336                 free(transinfo->objmod);
 337                 transinfo->objmod = NULL;
 338         }
 339         if (transinfo->objlocked != NULL) {
 340                 free(transinfo->objlocked);
 341                 transinfo->objlocked = NULL;
 342         }
 343         if (transinfo->objnotfound != NULL) {
 344                 free(transinfo->objnotfound);
 345                 transinfo->objnotfound = NULL;
 346         }
 347         return 0;
 348 }
 349
 350 /* This function increments counters while running a voting decision on all objects involved
 351  * in TRANS_REQUEST and If a TRANS_DISAGREE sends the response immediately back to the coordinator */
 352 char handleTransReq(fixed_data_t *fixed, trans_commit_data_t *transinfo, unsigned int *listmid, char *objread, void *modptr, int acceptfd) {
 353         int val, i = 0;
 354         short version;
 355         char control = 0, *ptr;
 356         unsigned int oid;
 357         unsigned int *oidnotfound, *oidlocked, *oidmod;
 358         void *mobj;
 359         objheader_t *headptr;
 360
 361         /* Counters and arrays to formulate decision on control message to be sent */
 362         oidnotfound = (unsigned int *) calloc(fixed->numread + fixed->nummod, sizeof(unsigned int));
 363         oidlocked = (unsigned int *) calloc(fixed->numread + fixed->nummod, sizeof(unsigned int));
 364         oidmod = (unsigned int *) calloc(fixed->nummod, sizeof(unsigned int));
 365         int objnotfound = 0, objlocked = 0, objmod =0, v_nomatch = 0, v_matchlock = 0, v_matchnolock = 0;
 366         int objmodnotfound = 0, nummodfound = 0;
 367
 368         /* modptr points to the beginning of the object store
 369          * created at the Pariticipant.
 370          * Object store holds the modified objects involved in the transaction request */
 371         ptr = modptr;
 372
 373         /* Process each oid in the machine pile/ group per thread */
 374         for (i = 0; i < fixed->numread + fixed->nummod; i++) {
 375                 if (i < fixed->numread) {//Objs only read and not modified
 376                         int incr = sizeof(unsigned int) + sizeof(short);// Offset that points to next position in the objread array
 377                         incr *= i;
 378                         oid = *((unsigned int *)(objread + incr));
 379                         incr += sizeof(unsigned int);
 380                         version = *((short *)(objread + incr));
 381                 } else {//Objs modified
 382                         headptr = (objheader_t *) ptr;
 383                         oid = OID(headptr);
 384                         oidmod[objmod] = oid;//Array containing modified oids
 385                         objmod++;
 386                         version = headptr->version;
 387                         ptr += sizeof(objheader_t) + classsize[TYPE(headptr)];
 388                 }
 389
 390                 /* Check if object is still present in the machine since the beginning of TRANS_REQUEST */
 391
 392                 if ((mobj = mhashSearch(oid)) == NULL) {/* Obj not found */
 393                         /* Save the oids not found and number of oids not found for later use */
 394                         //oidnotfound[objnotfound] = OID(((objheader_t *)mobj));
 395                         oidnotfound[objnotfound] = oid;
 396                         objnotfound++;
 397                 } else { /* If Obj found in machine (i.e. has not moved) */
 398                         /* Check if Obj is locked by any previous transaction */
 399                         if ((STATUS(((objheader_t *)mobj)) & LOCK) == LOCK) {
 400                                 if (version == ((objheader_t *)mobj)->version) {      /* If not locked then match versions */
 401                                         v_matchlock++;
 402                                 } else {/* If versions don't match ...HARD ABORT */
 403                                         v_nomatch++;
 404                                         /* Send TRANS_DISAGREE to Coordinator */
 405                                         control = TRANS_DISAGREE;
 406                                         if((val = send(acceptfd, &control, sizeof(char), MSG_NOSIGNAL)) < sizeof(char)) {
 407                                                 perror("Error in sending control to the Coordinator\n");
 408                                                 return 0;
 409                                         }
 410                                         printf("DEBUG -> Sending TRANS_DISAGREE\n");
 411                                         return control;
 412                                 }
 413                         } else {/* If Obj is not locked then lock object */
 414                                 STATUS(((objheader_t *)mobj)) |= LOCK;
 415
 416                                 /*TESTING Add random wait to make transactions run for a long time such that
 417                                  * we can test for soft abort case */
 418
 419                                 randomdelay();
 420
 421                                 /* Save all object oids that are locked on this machine during this transaction request call */
 422                                 oidlocked[objlocked] = OID(((objheader_t *)mobj));
 423                                 objlocked++;
 424                                 if (version == ((objheader_t *)mobj)->version) { /* Check if versions match */
 425                                         v_matchnolock++;
 426                                 } else { /* If versions don't match ...HARD ABORT */
 427                                         v_nomatch++;
 428                                         control = TRANS_DISAGREE;
 429                                         /* Send TRANS_DISAGREE to Coordinator */
 430                                         if((val = send(acceptfd, &control, sizeof(char), MSG_NOSIGNAL)) < sizeof(char)) {
 431                                                 perror("Error in sending control to the Coordinator\n");
 432                                                 return 0;
 433                                         }
 434                                         printf("DEBUG -> Sending TRANS_DISAGREE\n");
 435                                         return control;
 436                                 }
 437                         }
 438                 }
 439         }
 440
 441         /* Decide what control message to send to Coordinator */
 442         if ((val = decideCtrlMessage(fixed, transinfo, &v_matchnolock, &v_matchlock, &v_nomatch, &objnotfound, &objlocked,
 443                                         modptr, oidnotfound, oidlocked, oidmod, acceptfd)) == 0) {
 444                 printf("Error in decideCtrlMessage %s, %d\n", __FILE__, __LINE__);
 445                 return 0;
 446         }
 447
 448         return val;
 449
 450 }
 451 /* This function decides what control message such as TRANS_AGREE, TRANS_DISAGREE or TRANS_SOFT_ABORT
 452  * to send to Coordinator based on the votes of oids involved in the transaction */
 453 int decideCtrlMessage(fixed_data_t *fixed, trans_commit_data_t *transinfo, int *v_matchnolock, int *v_matchlock,
 454                 int *v_nomatch, int *objnotfound, int *objlocked, void *modptr,
 455                 unsigned int *oidnotfound, unsigned int *oidlocked, unsigned int *oidmod,
 456                 int acceptfd) {
 457         int val;
 458         char control = 0;
 459         /* Condition to send TRANS_AGREE */
 460         if(*(v_matchnolock) == fixed->numread + fixed->nummod) {
 461                 control = TRANS_AGREE;
 462                 /* Send control message */
 463                 if((val = send(acceptfd, &control, sizeof(char), MSG_NOSIGNAL)) < sizeof(char)) {
 464                         perror("Error in sending control to Coordinator\n");
 465                         return 0;
 466                 }
 467                 printf("DEBUG -> Sending TRANS_AGREE\n");
 468         }
 469         /* Condition to send TRANS_SOFT_ABORT */
 470         if((*(v_matchlock) > 0 && *(v_nomatch) == 0) || (*(objnotfound) > 0 && *(v_nomatch) == 0)) {
 471                 control = TRANS_SOFT_ABORT;
 472                 char msg[]={TRANS_SOFT_ABORT, 0,0,0,0};
 473                 *((int*)&msg[1])= *(objnotfound);
 474
 475                 printf("DEBUG -> Sending TRANS_SOFT_ABORT\n");
 476                 /* Send control message */
 477                 if((val = send(acceptfd, &msg, sizeof(msg),MSG_NOSIGNAL)) < sizeof(msg)) {
 478                         perror("Error in sending no of objects that are not found\n");
 479                         return 0;
 480                 }
 481                 /* Send number of oids not found and the missing oids if objects are missing in the machine */
 482                 if(*(objnotfound) != 0) {
 483                         int size = sizeof(unsigned int)* *(objnotfound);
 484                         if((val = send(acceptfd, oidnotfound, size ,MSG_NOSIGNAL)) < size) {
 485                                 perror("Error in sending objects that are not found\n");
 486                                 return 0;
 487                         }
 488                 }
 489         }
 490
 491         /* Fill out the trans_commit_data_t data structure. This is required for a trans commit process
 492          * if Participant receives a TRANS_COMMIT */
 493         transinfo->objmod = oidmod;
 494         transinfo->objlocked = oidlocked;
 495         transinfo->objnotfound = oidnotfound;
 496         transinfo->modptr = modptr;
 497         transinfo->nummod = fixed->nummod;
 498         transinfo->numlocked = *(objlocked);
 499         transinfo->numnotfound = *(objnotfound);
 500
 501         return control;
 502 }
 503
 504 /* This function processes all modified objects involved in a TRANS_COMMIT and updates pointer
 505  * addresses in lookup table and also changes version number
 506  * Sends an ACK back to Coordinator */
 507 int transCommitProcess(trans_commit_data_t *transinfo, int acceptfd) {
 508         objheader_t *header;
 509         int i = 0, offset = 0;
 510         char control;
 511         /* Process each modified object saved in the mainobject store */
 512         for(i=0; i<transinfo->nummod; i++) {
 513                 if((header = (objheader_t *) mhashSearch(transinfo->objmod[i])) == NULL) {
 514                         printf("mhashsearch returns NULL at %s, %d\n", __FILE__, __LINE__);
 515                 }
 516                 /* Change reference count of older address and free space in objstr ?? */
 517                 header->rcount = 1; //Not sure what would be the val
 518
 519                 /* Change ptr address in mhash table */
 520                 printf("DEBUG -> removing object oid = %d\n", transinfo->objmod[i]);
 521                 mhashRemove(transinfo->objmod[i]);
 522                 mhashInsert(transinfo->objmod[i], (transinfo->modptr + offset));
 523                 offset += sizeof(objheader_t) + classsize[TYPE(header)];
 524
 525                 /* Update object version number */
 526                 header = (objheader_t *) mhashSearch(transinfo->objmod[i]);
 527                 header->version += 1;
 528         }
 529         /* Unlock locked objects */
 530         for(i=0; i<transinfo->numlocked; i++) {
 531                 header = (objheader_t *) mhashSearch(transinfo->objlocked[i]);
 532                 STATUS(header) &= ~(LOCK);
 533         }
 534
 535         //TODO Update location lookup table
 536
 537         /* Send ack to coordinator */
 538         control = TRANS_SUCESSFUL;
 539         printf("DEBUG-> TRANS_SUCESSFUL\n");
 540         if(send((int)acceptfd, &control, sizeof(char), MSG_NOSIGNAL) < sizeof(char)) {
 541                 perror("Error sending ACK to coordinator\n");
 542         }
 543
 544         return 0;
 545 }
 546
 547 int prefetchReq(int acceptfd) {
 548         int i, length, sum, n, numbytes, numoffset, N, objnotfound = 0, size, count = 0;
 549         unsigned int oid, index = 0;
 550         char *ptr, buffer[PRE_BUF_SIZE];
 551         void *mobj;
 552         unsigned int objoid;
 553         char *header, control;
 554         objheader_t * head;
 555
 556         /* Repeatedly recv the oid and offset pairs sent for prefetch */
 557         while(numbytes = recv((int)acceptfd, &length, sizeof(int), 0) != 0) {
 558                 count++;
 559                 if(length == -1)
 560                         break;
 561                 sum = 0;
 562                 index = sizeof(unsigned int); // Index starts with sizeof  unsigned int because the
 563                                               // first 4 bytes are saved to send the
 564                                               // size of the buffer (that is computed at the end of the loop)
 565                 oid = recv((int)acceptfd, &oid, sizeof(unsigned int), 0);
 566                 numoffset = (length - (sizeof(int) + sizeof(unsigned int)))/ sizeof(short);
 567                 N = numoffset * sizeof(short);
 568                 short offset[numoffset];
 569                 ptr = (char *)&offset;
 570                 /* Recv the offset values per oid */
 571                 do {
 572                         n = recv((int)acceptfd, (void *)ptr+sum, N-sum, 0);
 573                         sum += n;
 574                 } while(sum < N && n != 0);
 575
 576                 /* Process each oid */
 577                 /* Check if object is still present in the machine since the beginning of TRANS_PREFETCH */
 578                 if ((mobj = mhashSearch(oid)) == NULL) {/* Obj not found */
 579                         /* Save the oids not found in buffer for later use */
 580                         *(buffer + index) = OBJECT_NOT_FOUND;
 581                         index += sizeof(char);
 582                         memcpy(buffer+index, &oid, sizeof(unsigned int));
 583                         index += sizeof(unsigned int);
 584                 } else { /* If Obj found in machine (i.e. has not moved) */
 585                         /* send the oid, it's size, it's header and data */
 586                         header = (char *) mobj;
 587                         head = (objheader_t *) header;
 588                         size = sizeof(objheader_t) + sizeof(classsize[TYPE(head)]);
 589                         *(buffer + index) = OBJECT_FOUND;
 590                         index += sizeof(char);
 591                         memcpy(buffer+index, &oid, sizeof(unsigned int));
 592                         index += sizeof(unsigned int);
 593                         memcpy(buffer+index, &size, sizeof(int));
 594                         index += sizeof(int);
 595                         memcpy(buffer + index, header, size);
 596                         index += size;
 597                         /* Calculate the oid corresponding to the offset value */
 598                         for(i = 0 ; i< numoffset ; i++) {
 599                                 objoid = *((int *)(header + sizeof(objheader_t) + offset[i]));
 600                                 if((header = (char *) mhashSearch(objoid)) == NULL) {
 601                                         /* Obj not found, send oid */
 602                                         *(buffer + index) = OBJECT_NOT_FOUND;
 603                                         index += sizeof(char);
 604                                         memcpy(buffer+index, &oid, sizeof(unsigned int));
 605                                         index += sizeof(unsigned int);
 606                                         break;
 607                                 } else {/* Obj Found */
 608                                         /* send the oid, it's size, it's header and data */
 609                                         head = (objheader_t *) header;
 610                                         size = sizeof(objheader_t) + sizeof(classsize[TYPE(head)]);
 611                                         *(buffer + index) = OBJECT_FOUND;
 612                                         index += sizeof(char);
 613                                         memcpy(buffer+index, &oid, sizeof(unsigned int));
 614                                         index += sizeof(unsigned int);
 615                                         memcpy(buffer+index, &size, sizeof(int));
 616                                         index += sizeof(int);
 617                                         memcpy(buffer + index, header, size);
 618                                         index += size;
 619                                         continue;
 620                                 }
 621                         }
 622                 }
 623                 /* Check for overflow in the buffer */
 624                 if (index >= PRE_BUF_SIZE) {
 625                         printf("Char buffer is overflowing\n");
 626                         return 1;
 627                 }
 628                 /* Send Prefetch response control message only once*/
 629                 if(count == 1) {
 630                         control = TRANS_PREFETCH_RESPONSE;
 631                         if((numbytes = send(acceptfd, &control, sizeof(char), MSG_NOSIGNAL)) < sizeof(char)) {
 632                                 perror("Error in sending PREFETCH RESPONSE to Coordinator\n");
 633                                 return 1;
 634                         }
 635                 }
 636
 637                 /* Add the buffer size into buffer as a parameter */
 638                 memcpy(buffer, &index, sizeof(unsigned int));
 639                 /* Send the entire buffer with its size and oids found and not found */
 640                 if(send((int)acceptfd, &buffer, sizeof(index - 1), MSG_NOSIGNAL) < sizeof(index -1)) {
 641                         perror("Error sending oids found\n");
 642                         return 1;
 643                 }
 644         }
 645         return 0;
 646 }