bug fix for OBJECT_NOT_FOUND error in prefetch cache due to unknown oid
[IRC.git] / Robust / src / Runtime / DSTM / interface / dstmserver.c
index 34487ff00dda826e000af1c5a0e6fd4e9fac56a0..672a955c6644129f2aa68786ba907b1be50f7cf9 100644 (file)
@@ -1,12 +1,22 @@
+/* Coordinator => Machine that initiates the transaction request call for commiting a transaction
+ * Participant => Machines that host the objects involved in a transaction commit */
+
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <pthread.h>
 #include <netdb.h>
 #include <fcntl.h>
+#include <errno.h>
+#include <string.h>
 #include "dstm.h"
 #include "mlookup.h"
 #include "llookup.h"
+#include "threadnotify.h"
+#ifdef COMPILER
+#include "thread.h"
+#endif
+
 
 #define LISTEN_PORT 2156
 #define BACKLOG 10 //max pending connections
 extern int classsize[];
 
 objstr_t *mainobjstore;
+pthread_mutex_t mainobjstore_mutex;
+pthread_mutexattr_t mainobjstore_mutex_attr; /* Attribute for lock to make it a recursive lock */
+/**********************************************************
+ * Global variables to map socketid and remote mid
+ * to  resuse sockets
+ **************************************************/
+midSocketInfo_t sockArray[NUM_MACHINES];
+int sockCount; //number of connections with all remote machines(one socket per mc)
+int sockIdFound; //track if socket file descriptor is already established
+pthread_mutex_t sockLock = PTHREAD_MUTEX_INITIALIZER; //lock to prevent global sock variables to be inconsistent
+
+/* This function initializes the main objects store and creates the 
+ * global machine and location lookup table */
 
 int dstmInit(void)
 {
-       //Initialize main object store
-       mainobjstore = objstrCreate(DEFAULT_OBJ_STORE_SIZE);    
+       mainobjstore = objstrCreate(DEFAULT_OBJ_STORE_SIZE);
+       /* Initialize attribute for mutex */
+       pthread_mutexattr_init(&mainobjstore_mutex_attr);
+       pthread_mutexattr_settype(&mainobjstore_mutex_attr, PTHREAD_MUTEX_RECURSIVE_NP);
+       pthread_mutex_init(&mainobjstore_mutex, &mainobjstore_mutex_attr);
        if (mhashCreate(HASH_SIZE, LOADFACTOR))
                return 1; //failure
        
        if (lhashCreate(HASH_SIZE, LOADFACTOR))
                return 1; //failure
+
+       if (notifyhashCreate(N_HASH_SIZE, N_LOADFACTOR))
+               return 1; //failure
        
+       //Initialize mid to socketid mapping array
+       int t;
+       sockCount = 0;
+       for(t = 0; t < NUM_MACHINES; t++) {
+               sockArray[t].mid = 0;
+               sockArray[t].sockid = 0;
+       }
+
        return 0;
 }
 
+/* This function starts the thread to listen on a socket 
+ * for tranaction calls */
 void *dstmListen()
 {
        int listenfd, acceptfd;
@@ -77,444 +116,785 @@ void *dstmListen()
        printf("Listening on port %d, fd = %d\n", LISTEN_PORT, listenfd);
        while(1)
        {
-               acceptfd = accept(listenfd, (struct sockaddr *)&client_addr, &addrlength);
-               pthread_create(&thread_dstm_accept, NULL, dstmAccept, (void *)acceptfd);
+         int retval;
+         acceptfd = accept(listenfd, (struct sockaddr *)&client_addr, &addrlength);
+         do {
+           retval=pthread_create(&thread_dstm_accept, NULL, dstmAccept, (void *)acceptfd);
+         } while(retval!=0);
+         pthread_detach(thread_dstm_accept);
        }
-       pthread_exit(NULL);
 }
-
+/* This function accepts a new connection request, decodes the control message in the connection 
+ * and accordingly calls other functions to process new requests */
 void *dstmAccept(void *acceptfd)
 {
-       int numbytes,i, val, retval;
+       int val, retval, size, sum, sockid;
        unsigned int oid;
-       char buffer[RECEIVE_BUFFER_SIZE], control,ctrl;
+       char *buffer;
+       char control,ctrl;
        char *ptr;
        void *srcObj;
        objheader_t *h;
        trans_commit_data_t transinfo;
+       unsigned short objType, *versionarry, version;
+       unsigned int *oidarry, numoid, mid, threadid;
        
-       int fd_flags = fcntl((int)acceptfd, F_GETFD), size;
+       transinfo.objlocked = NULL;
+       transinfo.objnotfound = NULL;
+       transinfo.modptr = NULL;
+       transinfo.numlocked = 0;
+       transinfo.numnotfound = 0;
+
+       /* Receive control messages from other machines */
+       recv_data((int)acceptfd, &control, sizeof(char));
 
-       printf("Recieved connection: fd = %d\n", (int)acceptfd);
-       if((retval = recv((int)acceptfd, &control, sizeof(char), 0)) <= 0) {
-               perror("Error in receiving control from coordinator\n");
-               return;
-       }
        switch(control) {
                case READ_REQUEST:
-                       if((retval = recv((int)acceptfd, &oid, sizeof(unsigned int), 0)) <= 0) {
-                               perror("Error receiving object from cooridnator\n");
-                               return;
+                       /* Read oid requested and search if available */
+                       recv_data((int)acceptfd, &oid, sizeof(unsigned int));
+                       if((srcObj = mhashSearch(oid)) == NULL) {
+                               printf("Error: Object 0x%x is not found in Main Object Store %s, %d\n", oid, __FILE__, __LINE__);
+                               pthread_exit(NULL);
                        }
-                       printf("DEBUG -> Recv READ_REQUEST from Coordinator for oid = %d\n", oid);
-                       srcObj = mhashSearch(oid);
                        h = (objheader_t *) srcObj;
-                       size = sizeof(objheader_t) + sizeof(classsize[h->type]);
+                       GETSIZE(size, h);
+                       size += sizeof(objheader_t);
+                       sockid = (int) acceptfd;
+
                        if (h == NULL) {
                                ctrl = OBJECT_NOT_FOUND;
-                               if(send((int)acceptfd, &ctrl, sizeof(char), MSG_NOSIGNAL) < sizeof(char)) {
-                                       perror("Error sending control msg to coordinator\n");
-                               }
+                               send_data(sockid, &ctrl, sizeof(char));
                        } else {
                                /* Type */
-                         char msg[]={OBJECT_FOUND, 0, 0, 0, 0};
-                         *((int *)&msg[1])=size;
-                         if(send((int)acceptfd, &msg, sizeof(msg), MSG_NOSIGNAL) < sizeof(msg)) {
-                           perror("Error sending size of object to coordinator\n");
-                         }
-                         if(send((int)acceptfd, h, size, MSG_NOSIGNAL) < size) {
-                           perror("Error in sending object\n");
-                         }
+                               char msg[]={OBJECT_FOUND, 0, 0, 0, 0};
+                               *((int *)&msg[1])=size;
+                               send_data(sockid, &msg, sizeof(msg));
+                               send_data(sockid, h, size);
                        }
                        break;
                
                case READ_MULT_REQUEST:
-                       printf("DEBUG-> READ_MULT_REQUEST\n");
                        break;
        
                case MOVE_REQUEST:
-                       printf("DEBUG -> MOVE_REQUEST\n");
                        break;
 
                case MOVE_MULT_REQUEST:
-                       printf("DEBUG -> MOVE_MULT_REQUEST\n");
                        break;
 
                case TRANS_REQUEST:
-                       printf("DEBUG -> Recv TRANS_REQUEST from Coordinator\n");
-                       if((val = readClientReq((int)acceptfd, &transinfo)) != 0) {
-                               printf("Error in readClientReq\n");
+                       /* Read transaction request */
+                       if((val = readClientReq(&transinfo, (int)acceptfd)) != 0) {
+                               printf("Error: In readClientReq() %s, %d\n", __FILE__, __LINE__);
+                               pthread_exit(NULL);
                        }
                        break;
+               case TRANS_PREFETCH:
+                       do {
+                               if((val = prefetchReq((int)acceptfd)) != 0) {
+                                       printf("Error: In prefetchReq() %s, %d\n", __FILE__, __LINE__);
+                                       break;
+                               }
+                               recv_data((int)acceptfd, &control, sizeof(char));
+                       } while (control == TRANS_PREFETCH);
+                       break;
+               case TRANS_PREFETCH_RESPONSE:
+                       //do {
+                               if((val = getPrefetchResponse((int) acceptfd)) != 0) {
+                                       printf("Error: In getPrefetchResponse() %s, %d\n", __FILE__, __LINE__);
+                                       pthread_exit(NULL);
+                               }
+                       //} while (control == TRANS_PREFETCH_RESPONSE);
+                       break;
+               case START_REMOTE_THREAD:
+                       recv_data((int)acceptfd, &oid, sizeof(unsigned int));
+                       objType = getObjType(oid);
+                       startDSMthread(oid, objType);
+                       break;
+
+               case THREAD_NOTIFY_REQUEST:
+                       recv_data((int)acceptfd, &numoid, sizeof(unsigned int));
+                       size = (sizeof(unsigned int) + sizeof(unsigned short)) * numoid + 2 * sizeof(unsigned int);
+                       if((buffer = calloc(1,size)) == NULL) {
+                               printf("%s() Calloc error at %s, %d\n", __func__, __FILE__, __LINE__);
+                               pthread_exit(NULL);
+                       }
 
+                       recv_data((int)acceptfd, buffer, size);
+
+                       oidarry = calloc(numoid, sizeof(unsigned int)); 
+                       memcpy(oidarry, buffer, sizeof(unsigned int) * numoid);
+                       size = sizeof(unsigned int) * numoid;
+                       versionarry = calloc(numoid, sizeof(unsigned short));
+                       memcpy(versionarry, buffer+size, sizeof(unsigned short) * numoid);
+                       size += sizeof(unsigned short) * numoid;
+                       mid = *((unsigned int *)(buffer+size));
+                       size += sizeof(unsigned int);
+                       threadid = *((unsigned int *)(buffer+size));
+                       processReqNotify(numoid, oidarry, versionarry, mid, threadid);
+                       free(buffer);
+
+                       break;
+
+               case THREAD_NOTIFY_RESPONSE:
+                       size = sizeof(unsigned short) + 2 * sizeof(unsigned int);
+                       if((buffer = calloc(1,size)) == NULL) {
+                               printf("%s() Calloc error at %s, %d\n", __func__, __FILE__, __LINE__);
+                               pthread_exit(NULL);
+                       }
+
+                       recv_data((int)acceptfd, buffer, size);
+
+                       oid = *((unsigned int *)buffer);
+                       size = sizeof(unsigned int);
+                       version = *((unsigned short *)(buffer+size));
+                       size += sizeof(unsigned short);
+                       threadid = *((unsigned int *)(buffer+size));
+                       threadNotify(oid,version,threadid);
+                       free(buffer);
+
+                       break;
                default:
-                       printf("DEBUG -> dstmAccept: Error Unknown opcode %d\n", control);
+                       printf("Error: dstmAccept() Unknown opcode %d at %s, %d\n", control, __FILE__, __LINE__);
        }
+
+       /* Close connection */
        if (close((int)acceptfd) == -1)
                perror("close");
-       else 
-               printf("Closed connection: fd = %d\n", (int)acceptfd);
-       
        pthread_exit(NULL);
-       printf("DEBUG -> Exiting dstmAccept\n");
 }
 
-int readClientReq(int acceptfd, trans_commit_data_t *transinfo) {
-       char *ptr, control, prevctrl, sendctrl, newctrl;
-       void *modptr, *header;
-       objheader_t *tmp_header;
+/* This function reads the information available in a transaction request
+ * and makes a function call to process the request */
+int readClientReq(trans_commit_data_t *transinfo, int acceptfd) {
+       char *ptr;
+       void *modptr;
+       unsigned int *oidmod, oid;
        fixed_data_t fixed;
-       int sum = 0, i, N, n, val, retval;
+       objheader_t *headaddr;
+       int sum, i, size, n, val;
+
+       oidmod = NULL;
 
-       //Reads to process the TRANS_REQUEST protocol further
-       // Read fixed_data
-       N = sizeof(fixed) - 1;
+       /* Read fixed_data_t data structure */ 
+       size = sizeof(fixed) - 1;
        ptr = (char *)&fixed;;
        fixed.control = TRANS_REQUEST;
-       do {
-               n = recv((int)acceptfd, (void *) ptr+1+sum, N-sum, 0);
-               sum += n;
-       } while(sum < N && n != 0); 
+       recv_data((int)acceptfd, ptr+1, size);
 
-       // Read list of mids
+       /* Read list of mids */
        int mcount = fixed.mcount;
-       N = mcount * sizeof(unsigned int);
+       size = mcount * sizeof(unsigned int);
        unsigned int listmid[mcount];
        ptr = (char *) listmid;
-       sum = 0;
-       do {
-               n = recv((int)acceptfd, (void *) ptr+sum, N-sum, 0);
-               sum += n;
-       } while(sum < N && n != 0);
-
-       // Read oid and version tuples
+       recv_data((int)acceptfd, ptr, size);
+       
+       /* Read oid and version tuples for those objects that are not modified in the transaction */
        int numread = fixed.numread;
-       N = numread * (sizeof(unsigned int) + sizeof(short));
-       char objread[N];
-       if(numread != 0) { // If pile contains objects to be read 
-               sum = 0;
-               do {
-                       n = recv((int)acceptfd, (void *) objread, N, 0);
-                       sum += n;
-               } while(sum < N && n != 0);
+       size = numread * (sizeof(unsigned int) + sizeof(unsigned short));
+       char objread[size];
+       if(numread != 0) { //If pile contains more than one object to be read, 
+                         // keep reading all objects
+               recv_data((int)acceptfd, objread, size);        
        }
        
-       // Read modified objects
-       if(fixed.nummod != 0) { // If pile contains modified objects 
-               if ((modptr = objstrAlloc(mainobjstore, fixed.sum_bytes)) == NULL) {
-                       printf("objstrAlloc error for modified objects %s, %d", __FILE__, __LINE__);
+       /* Read modified objects */
+       if(fixed.nummod != 0) {
+               if ((modptr = calloc(1, fixed.sum_bytes)) == NULL) {
+                       printf("calloc error for modified objects %s, %d\n", __FILE__, __LINE__);
                        return 1;
                }
-               sum = 0;
-               do { // Recv the objs that are modified at Coordinator
-                       n = recv((int)acceptfd, modptr+sum, fixed.sum_bytes-sum, 0);
-                       sum += n;
-               } while (sum < fixed.sum_bytes && n != 0);
+               size = fixed.sum_bytes;
+               recv_data((int)acceptfd, modptr, size); 
        }
 
-       //Send control message as per all votes from all oids in the machine
-       if((prevctrl = handleTransReq(acceptfd, &fixed, transinfo, listmid, objread, modptr)) == 0 ) {
-               printf("Handle req error\n");
+       /* Create an array of oids for modified objects */
+       oidmod = (unsigned int *) calloc(fixed.nummod, sizeof(unsigned int));
+       if (oidmod == NULL)
+       {
+               printf("calloc error %s, %d\n", __FILE__, __LINE__);
+               return 1;
+       }
+       ptr = (char *) modptr;
+       for(i = 0 ; i < fixed.nummod; i++) {
+         int tmpsize;
+         headaddr = (objheader_t *) ptr;
+         oid = OID(headaddr);
+         oidmod[i] = oid;
+         GETSIZE(tmpsize, headaddr);
+         ptr += sizeof(objheader_t) + tmpsize;
        }
+       
+       /*Process the information read */
+       if((val = processClientReq(&fixed, transinfo, listmid, objread, modptr, oidmod, acceptfd)) != 0) {
+               printf("Error: In processClientReq() %s, %d\n", __FILE__, __LINE__);
+               /* Free resources */
+               if(oidmod != NULL) {
+                       free(oidmod);
+               }
+               return 1;
+       }
+
+       /* Free resources */
+       if(oidmod != NULL) {
+               free(oidmod);
+       }
+
+       return 0;
+}
+
+/* This function processes the Coordinator's transaction request using "handleTransReq" 
+ * function and sends a reply to the co-ordinator.
+ * Following this it also receives a new control message from the co-ordinator and processes this message*/
+int processClientReq(fixed_data_t *fixed, trans_commit_data_t *transinfo,
+               unsigned int *listmid, char *objread, void *modptr, unsigned int *oidmod, int acceptfd) {
+       char control, sendctrl, retval;
+       objheader_t *tmp_header;
+       void *header;
+       int  i = 0, val;
 
-       //Read for new control message from Coordiator
-       if((retval = recv((int)acceptfd, &control, sizeof(char), 0)) <= 0 ) {
-               perror("Error in receiving control message");
+       /* Send reply to the Coordinator */
+       if((retval = handleTransReq(fixed, transinfo, listmid, objread, modptr,acceptfd)) == 0 ) {
+               printf("Error: In handleTransReq() %s, %d\n", __FILE__, __LINE__);
                return 1;
        }
 
+       recv_data((int)acceptfd, &control, sizeof(char));
+       
+       /* Process the new control message */
        switch(control) {
                case TRANS_ABORT:
-                       printf("DEBUG -> Recv TRANS_ABORT from Coordinator\n");
-                       //send ack to coordinator
-                       sendctrl = TRANS_SUCESSFUL;
-                       if(send((int)acceptfd, &sendctrl, sizeof(char), MSG_NOSIGNAL) < sizeof(char)) {
-                               perror("Error sending ACK to coordinator\n");
-                               return 1;
-                       }
-                       //Mark all ref counts as 1 and do garbage collection
-                       ptr = modptr;
-                       for(i = 0; i< fixed.nummod; i++) {
-                               tmp_header = (objheader_t *)ptr;
-                               tmp_header->rcount = 1;
-                               ptr += sizeof(objheader_t) + classsize[tmp_header->type];
-                       }
-                       //Unlock objects that was locked in this machine due to this transaction
+                       if (fixed->nummod > 0)
+                               free(modptr);
+                       /* Unlock objects that was locked due to this transaction */
                        for(i = 0; i< transinfo->numlocked; i++) {
-                               header = mhashSearch(transinfo->objlocked[i]);// find the header address
-                               ((objheader_t *)header)->status &= ~(LOCK);             
-                       }
-                       ptr = NULL;
-                       return 0;
-               case TRANS_COMMIT:
-                       printf("DEBUG -> Recv TRANS_COMMIT from Coordinator accept_fd = %d\n", acceptfd);
-                       if((val = transCommitProcess(transinfo, (int)acceptfd)) != 0) {
-                               printf("Error in transCommitProcess %s, %d\n", __FILE__, __LINE__);
+                               if((header = mhashSearch(transinfo->objlocked[i])) == NULL) {
+                                       printf("mhashSearch returns NULL at %s, %d\n", __FILE__, __LINE__);// find the header address
+                                       return 1;
+                               }
+                               STATUS(((objheader_t *)header)) &= ~(LOCK);             
                        }
+
+                       /* Send ack to Coordinator */
+                       sendctrl = TRANS_UNSUCESSFUL;
+                       send_data((int)acceptfd, &sendctrl, sizeof(char));
                        break;
-               case TRANS_ABORT_BUT_RETRY_COMMIT:
-                       printf("DEBUG -> Recv TRANS_ABORT_BUT_RETRY_COMMIT from Coordinator\n");
-                       //Process again after waiting for sometime and on prev control message sent
-                       sleep(2);
-                       switch(prevctrl) {
-                               case TRANS_AGREE:
-                                       sendctrl = TRANS_AGREE;
-                                       if(send((int)acceptfd, &sendctrl, sizeof(char), MSG_NOSIGNAL) < sizeof(char)) {
-                                               perror("Error sending ACK to coordinator\n");
-                                       }
-                                       break;
-                               case TRANS_SOFT_ABORT:
-                                       if((newctrl = handleTransReq(acceptfd, &fixed, transinfo, listmid, objread, modptr)) == 0 ) {
-                                               printf("Handle req error\n");
-                                       }
-                                       //If no change in previous control message that was sent then ABORT transaction
-                                       if(newctrl == TRANS_SOFT_ABORT){
-                                               //Send ABORT
-                                               newctrl = TRANS_DISAGREE;
-                                               if(send((int)acceptfd, &newctrl, sizeof(char), MSG_NOSIGNAL) < sizeof(char)) {
-                                                       perror("Error sending ACK to coordinator\n");
-                                               }
-                                               //Set the reference count of the object to 1 in mainstore for garbage collection
-                                               ptr = modptr;
-                                               for(i = 0; i< fixed.nummod; i++) {
-                                                       tmp_header = (objheader_t *) ptr;
-                                                       tmp_header->rcount = 1;
-                                                       ptr += sizeof(objheader_t) + classsize[tmp_header->type];
-                                               }
-                                               //Unlock objects that was locked in this machine due to this transaction
-                                               for(i = 0; i< transinfo->numlocked; i++) {
-                                                       ptr = mhashSearch(transinfo->objlocked[i]);// find the header address
-                                                       ((objheader_t *)ptr)->status &= ~(LOCK);                
-                                               }
-                                       } else if(newctrl == TRANS_AGREE) {
-                                               newctrl = TRANS_AGREE;
-                                               //Send new control message
-                                               if(send((int)acceptfd, &newctrl, sizeof(char), MSG_NOSIGNAL) < sizeof(char)) {
-                                                       perror("Error sending ACK to coordinator\n");
-                                               }
-                                       }
 
-                                       break;
+               case TRANS_COMMIT:
+                       /* Invoke the transCommit process() */
+                       if((val = transCommitProcess(modptr, oidmod, transinfo->objlocked, fixed->nummod, transinfo->numlocked, (int)acceptfd)) != 0) {
+                               printf("Error: In transCommitProcess() %s, %d\n", __FILE__, __LINE__);
+                               /* Free memory */
+                               if (transinfo->objlocked != NULL) {
+                                       free(transinfo->objlocked);
+                               }
+                               if (transinfo->objnotfound != NULL) {
+                                       free(transinfo->objnotfound);
+                               }
+                               return 1;
                        }
-
                        break;
+
                case TRANS_ABORT_BUT_RETRY_COMMIT_WITH_RELOCATING:
-                       //TODO expect another transrequest from client
-                       printf("DEBUG -> Recv TRANS_ABORT_BUT_RETRY_COMMIT_WITH_RELOCATING from Coordinator\n");
                        break;
                default:
-                       printf("No response to TRANS_AGREE OR DISAGREE protocol\n");
+                       printf("Error: No response to TRANS_AGREE OR DISAGREE protocol %s, %d\n", __FILE__, __LINE__);
                        //TODO Use fixed.trans_id  TID since Client may have died
                        break;
        }
-       //Free memory
-       printf("DEBUG -> Freeing...");
-       fflush(stdout);
-       if (transinfo->objmod != NULL) {
-               free(transinfo->objmod);
-               transinfo->objmod = NULL;
-       }
+
+       /* Free memory */
        if (transinfo->objlocked != NULL) {
                free(transinfo->objlocked);
-               transinfo->objlocked = NULL;
        }
        if (transinfo->objnotfound != NULL) {
                free(transinfo->objnotfound);
-               transinfo->objnotfound = NULL;
        }
+
        return 0;
 }
 
-//This function runs a decision after all objects are weighed under one of the 4 possibilities 
-//and returns the appropriate control message to the Ccordinator 
-char handleTransReq(int acceptfd, fixed_data_t *fixed, trans_commit_data_t *transinfo, unsigned int *listmid, char *objread, void *modptr) {
-       int val;
-       short version;
-       char control = 0, ctrlmissoid, *ptr;
-       int i, j = 0;
+/* This function increments counters while running a voting decision on all objects involved 
+ * in TRANS_REQUEST and If a TRANS_DISAGREE sends the response immediately back to the coordinator */
+char handleTransReq(fixed_data_t *fixed, trans_commit_data_t *transinfo, unsigned int *listmid, char *objread, void *modptr, int acceptfd) {
+       int val, i = 0, j;
+       unsigned short version;
+       char control = 0, *ptr;
        unsigned int oid;
-       unsigned int *oidnotfound, *oidlocked, *oidmod;
+       unsigned int *oidnotfound, *oidlocked;
+       void *mobj;
+       objheader_t *headptr;
 
+       /* Counters and arrays to formulate decision on control message to be sent */
        oidnotfound = (unsigned int *) calloc(fixed->numread + fixed->nummod, sizeof(unsigned int)); 
        oidlocked = (unsigned int *) calloc(fixed->numread + fixed->nummod, sizeof(unsigned int)); 
-       oidmod = (unsigned int *) calloc(fixed->nummod, sizeof(unsigned int));
-       // Counters and arrays to formulate decision on control message to be sent
-       int objnotfound = 0, objlocked = 0, objmod =0, v_nomatch = 0, v_matchlock = 0, v_matchnolock = 0;
-       int objmodnotfound = 0, nummodfound = 0;
-       void *mobj;
-       objheader_t *headptr;
+       int objnotfound = 0, objlocked = 0;
+       int v_nomatch = 0, v_matchlock = 0, v_matchnolock = 0;
+
+       /* modptr points to the beginning of the object store 
+        * created at the Pariticipant. 
+        * Object store holds the modified objects involved in the transaction request */ 
+       ptr = (char *) modptr;
        
-       //Process each object present in the pile 
-       ptr = modptr;
-       //printf("DEBUG -> Total objs involved in trans is %d\n",fixed->nummod + fixed->numread);
-       fflush(stdout);
-       //Process each oid in the machine pile/ group
+       /* Process each oid in the machine pile/ group per thread */
        for (i = 0; i < fixed->numread + fixed->nummod; i++) {
-               if (i < fixed->numread) {//Object is read
-                       int incr = sizeof(unsigned int) + sizeof(short);// Offset that points to next position in the objread array
+               if (i < fixed->numread) {//Objs only read and not modified
+                       int incr = sizeof(unsigned int) + sizeof(unsigned short);// Offset that points to next position in the objread array
                        incr *= i;
                        oid = *((unsigned int *)(objread + incr));
                        incr += sizeof(unsigned int);
-                       version = *((short *)(objread + incr));
-               } else {//Obj is modified
-                       headptr = (objheader_t *) ptr;
-                       oid = headptr->oid;
-                       oidmod[objmod] = oid;//Array containing modified oids
-                       objmod++;
-                       version = headptr->version;
-                       ptr += sizeof(objheader_t) + classsize[headptr->type];
+                       version = *((unsigned short *)(objread + incr));
+               } else {//Objs modified
+                 int tmpsize;
+                 headptr = (objheader_t *) ptr;
+                 oid = OID(headptr);
+                 version = headptr->version;
+                 GETSIZE(tmpsize, headptr);
+                 ptr += sizeof(objheader_t) + tmpsize;
                }
-               //Check if object is still present in the machine since the beginning of TRANS_REQUEST
-               if ((mobj = mhashSearch(oid)) == NULL) {// Obj not found
-                       //Save the oids not found for later use
-                       oidnotfound[objnotfound] = ((objheader_t *)mobj)->oid;
+               
+               /* Check if object is still present in the machine since the beginning of TRANS_REQUEST */
+
+               if ((mobj = mhashSearch(oid)) == NULL) {/* Obj not found */
+                       /* Save the oids not found and number of oids not found for later use */
+                       oidnotfound[objnotfound] = oid;
                        objnotfound++;
-               } else { // If obj found in machine (i.e. has not moved)
-                       //Check if obj is locked
-                       if ((((objheader_t *)mobj)->status & LOCK) == LOCK) {           
-                               if (version == ((objheader_t *)mobj)->version) {      // If version match
+               } else { /* If Obj found in machine (i.e. has not moved) */
+                       /* Check if Obj is locked by any previous transaction */
+                       if ((STATUS(((objheader_t *)mobj)) & LOCK) == LOCK) {           
+                               if (version == ((objheader_t *)mobj)->version) {      /* If locked then match versions */
                                        v_matchlock++;
-                               } else {//If versions don't match ..HARD ABORT
+                               } else {/* If versions don't match ...HARD ABORT */
                                        v_nomatch++;
-                                       //send TRANS_DISAGREE to Coordinator
+                                       /* Send TRANS_DISAGREE to Coordinator */
                                        control = TRANS_DISAGREE;
-                                       if((val = send(acceptfd, &control, sizeof(char),MSG_NOSIGNAL)) < sizeof(char)) {
-                                               perror("Error in sending control to the Coordinator\n");
-                                               return 0;
+                                       if (objlocked > 0) {
+                                         for(j = 0; j < objlocked; j++) {
+                                                       if((headptr = mhashSearch(oidlocked[j])) == NULL) {
+                                                               printf("mhashSearch returns NULL at %s, %d\n", __FILE__, __LINE__);
+                                                               return 0;
+                                                       }
+                                                       STATUS(headptr) &= ~(LOCK);
+                                               }
+                                               free(oidlocked);
                                        }
-                                       printf("DEBUG -> Sending TRANS_DISAGREE\n");
+                                       send_data(acceptfd, &control, sizeof(char));
                                        return control;
                                }
-                       } else {//Obj is not locked , so lock object
-                               ((objheader_t *)mobj)->status |= LOCK;
-                               //FOR TESTING
-                               sleep(1);
-                               //Save all object oids that are locked on this machine during this transaction request call
-                               oidlocked[objlocked] = ((objheader_t *)mobj)->oid;
-                               printf("DEBUG-> Obj locked are %d\n",((objheader_t *)mobj)->oid);
+                       } else {/* If Obj is not locked then lock object */
+                               STATUS(((objheader_t *)mobj)) |= LOCK;
+                               /* Save all object oids that are locked on this machine during this transaction request call */
+                               oidlocked[objlocked] = OID(((objheader_t *)mobj));
                                objlocked++;
-                               if (version == ((objheader_t *)mobj)->version) { //If versions match
+                               if (version == ((objheader_t *)mobj)->version) { /* Check if versions match */
                                        v_matchnolock++;
-                               } else { //If versions don't match
+                               } else { /* If versions don't match ...HARD ABORT */
                                        v_nomatch++;
-                                       //send TRANS_DISAGREE to Coordinator
                                        control = TRANS_DISAGREE;
-                                       if((val = send(acceptfd, &control, sizeof(char), MSG_NOSIGNAL)) < sizeof(char)) {
-                                               perror("Error in sending control to the Coordinator\n");
-                                               return 0;
+                                       if (objlocked > 0) {
+                                               for(j = 0; j < objlocked; j++) {
+                                                       if((headptr = mhashSearch(oidlocked[j])) == NULL) {
+                                                               printf("mhashSearch returns NULL at %s, %d\n", __FILE__, __LINE__);
+                                                               return 0;
+                                                       }
+                                                       STATUS(headptr) &= ~(LOCK);
+                                               }
+                                               free(oidlocked);
                                        }
-                                       printf("DEBUG -> Sending TRANS_DISAGREE\n");
+
+                                       /* Send TRANS_DISAGREE to Coordinator */
+                                       send_data(acceptfd, &control, sizeof(char));
                                        return control;
                                }
                        }
                }
        }
+       
+       /* Decide what control message to send to Coordinator */
+       if ((control = decideCtrlMessage(fixed, transinfo, &v_matchnolock, &v_matchlock, &v_nomatch, &objnotfound, &objlocked,
+                                       modptr, oidnotfound, oidlocked, acceptfd)) == 0) {
+               printf("Error: In decideCtrlMessage() %s, %d\n", __FILE__, __LINE__);
+               return 0;
+       }
+       
+       return control;
 
-       printf("No of objs locked = %d\n", objlocked);
-       printf("No of v_nomatch = %d\n", v_nomatch);
-       printf("No of objs v_match but are did not have locks before = %d\n", v_matchnolock);
-       printf("No of objs v_match but had locks before = %d\n", v_matchlock);
-       printf("No of objs not found = %d\n", objnotfound);
-       printf("No of objs modified but not found = %d\n", objmodnotfound);
-
-       //Decide what control message(s) to send
-       //Cond to send TRANS_AGREE
-       if(v_matchnolock == fixed->numread + fixed->nummod) {
-               //send TRANS_AGREE to Coordinator
+}
+/* This function decides what control message such as TRANS_AGREE, TRANS_DISAGREE or TRANS_SOFT_ABORT
+ * to send to Coordinator based on the votes of oids involved in the transaction */
+char decideCtrlMessage(fixed_data_t *fixed, trans_commit_data_t *transinfo, int *v_matchnolock, int *v_matchlock, 
+               int *v_nomatch, int *objnotfound, int *objlocked, void *modptr, 
+               unsigned int *oidnotfound, unsigned int *oidlocked, int acceptfd) {
+       int val;
+       char control = 0;
+
+       /* Condition to send TRANS_AGREE */
+       if(*(v_matchnolock) == fixed->numread + fixed->nummod) {
                control = TRANS_AGREE;
-               if((val = send(acceptfd, &control, sizeof(char), MSG_NOSIGNAL)) < sizeof(char)) {
-                       perror("Error in sending control to Coordinator\n");
-                       return 0;
-               }
-               printf("DEBUG -> Sending TRANS_AGREE\n");
+               /* Send control message */
+               send_data(acceptfd, &control, sizeof(char));
        }
-       //Condition to send TRANS_SOFT_ABORT
-       if((v_matchlock > 0 && v_nomatch == 0) || (objnotfound > 0 && v_nomatch == 0)) {
-               //send TRANS_SOFT_ABORT to Coordinator
+       /* Condition to send TRANS_SOFT_ABORT */
+       if((*(v_matchlock) > 0 && *(v_nomatch) == 0) || (*(objnotfound) > 0 && *(v_nomatch) == 0)) {
                control = TRANS_SOFT_ABORT;
-               char msg[]={TRANS_SOFT_ABORT, 0,0,0,0};
-               *((int*)&msg[1])=objnotfound;
-
-               printf("DEBUG -> Sending TRANS_SOFT_ABORT\n");
-               //send number of oids not found and the missing oids 
-               if((val = send(acceptfd, &msg, sizeof(msg),MSG_NOSIGNAL)) < sizeof(msg)) {
-                       perror("Error in sending no of objects that are not found\n");
-                       return 0;
-               }
-               if(objnotfound != 0) { 
-                 int size=sizeof(unsigned int)*objnotfound;
-                 if((val = send(acceptfd, oidnotfound, size ,MSG_NOSIGNAL)) < size) {
-                               perror("Error in sending objects that are not found\n");
-                               return 0;
-                       }
-               }
-       }
+
+               /* Send control message */
+               send_data(acceptfd, &control, sizeof(char));
        
-       //Do the following when TRANS_DISAGREE is sent
-       if(control == TRANS_DISAGREE) {
-               //Set the reference count of the object to 1 in mainstore for garbage collection
-               ptr = modptr;
-               for(i = 0; i< fixed->nummod; i++) {
-                       headptr = (objheader_t *) ptr;
-                       headptr->rcount = 1;
-                       ptr += sizeof(objheader_t) + classsize[headptr->type];
+               /* Send number of oids not found and the missing oids if objects are missing in the machine */
+               if(*(objnotfound) != 0) { 
+                       int msg[1];
+                       msg[0] = *(objnotfound);
+                       send_data(acceptfd, &msg, sizeof(int));
+                       int size = sizeof(unsigned int)* *(objnotfound);
+                       send_data(acceptfd, oidnotfound, size);
                }
-               //Unlock objects that was locked in the trans
-               for(i = 0; i< objlocked ; i++) {
-                       mobj = mhashSearch(oidlocked[i]);// find the header address
-                       ((objheader_t *)mobj)->status &= ~(LOCK);               
-               }       
-       }       
-
-       //Fill out the structure required for a trans commit process if pile receives a TRANS_COMMIT
-       transinfo->objmod = oidmod;
+       }
+
+       /* Fill out the trans_commit_data_t data structure. This is required for a trans commit process
+        * if Participant receives a TRANS_COMMIT */
        transinfo->objlocked = oidlocked;
        transinfo->objnotfound = oidnotfound;
        transinfo->modptr = modptr;
-       transinfo->nummod = fixed->nummod;
-       transinfo->numlocked = objlocked;
-       transinfo->numnotfound = objnotfound;
+       transinfo->numlocked = *(objlocked);
+       transinfo->numnotfound = *(objnotfound);
        
        return control;
 }
 
-//Processes oids in the TRANS_COMMIT request at the participant end and sends an ack back
-int transCommitProcess(trans_commit_data_t *transinfo, int acceptfd) {
+/* This function processes all modified objects involved in a TRANS_COMMIT and updates pointer 
+ * addresses in lookup table and also changes version number
+ * Sends an ACK back to Coordinator */
+int transCommitProcess(void *modptr, unsigned int *oidmod, unsigned int *oidlocked, int nummod, int numlocked, int acceptfd) {
        objheader_t *header;
+       objheader_t *newheader;
        int i = 0, offset = 0;
        char control;
-       //Process each modified object saved in the mainobject store
-       for(i=0; i<transinfo->nummod; i++) {
-               if((header = (objheader_t *) mhashSearch(transinfo->objmod[i])) == NULL) {
-                       printf("mhashserach returns NULL\n");
+       int tmpsize;
+
+       /* Process each modified object saved in the mainobject store */
+       for(i = 0; i < nummod; i++) {
+               if((header = (objheader_t *) mhashSearch(oidmod[i])) == NULL) {
+                       printf("Error: mhashsearch returns NULL at %s, %d\n", __FILE__, __LINE__);
+                       return 1;
                }
-               //change reference count of older address and free space in objstr ??
-               header->rcount = 1; //Not sure what would be th val
-               //change ptr address in mhash table
-               printf("DEBUG -> removing object oid = %d\n", transinfo->objmod[i]);
-               mhashRemove(transinfo->objmod[i]);
-               mhashInsert(transinfo->objmod[i], (transinfo->modptr + offset));
-               offset += sizeof(objheader_t) + classsize[header->type];
-               //update object version
-               header = (objheader_t *) mhashSearch(transinfo->objmod[i]);
+               GETSIZE(tmpsize,header);
+               pthread_mutex_lock(&mainobjstore_mutex);
+               memcpy((char*)header + sizeof(objheader_t), ((char *)modptr + sizeof(objheader_t) + offset), tmpsize);
                header->version += 1; 
+               /* If threads are waiting on this object to be updated, notify them */
+               if(header->notifylist != NULL) {
+                       notifyAll(&header->notifylist, OID(header), header->version);
+               }
+               pthread_mutex_unlock(&mainobjstore_mutex);
+               offset += sizeof(objheader_t) + tmpsize;
        }
-       for(i=0; i<transinfo->numlocked; i++) {
-               //unlock objects
-               header = (objheader_t *) mhashSearch(transinfo->objlocked[i]);
-               header->status &= ~(LOCK);
-       }
 
+       if (nummod > 0)
+               free(modptr);
+
+       /* Unlock locked objects */
+       for(i = 0; i < numlocked; i++) {
+               if((header = (objheader_t *) mhashSearch(oidlocked[i])) == NULL) {
+                       printf("Error: mhashsearch returns NULL at %s, %d\n", __FILE__, __LINE__);
+                       return 1;
+               }
+               STATUS(header) &= ~(LOCK);
+       }
        //TODO Update location lookup table
 
-       //send ack to coordinator
+       /* Send ack to coordinator */
        control = TRANS_SUCESSFUL;
-       //FOR TESTING
-       printf("DEBUG-> Transaction is SUCCESSFUL \n");
-       if(send((int)acceptfd, &control, sizeof(char), MSG_NOSIGNAL) < sizeof(char)) {
-               perror("Error sending ACK to coordinator\n");
-       }
-       
+       send_data((int)acceptfd, &control, sizeof(char));
+       return 0;
+}
+
+/* This function recevies the oid and offset tuples from the Coordinator's prefetch call.
+ * Looks for the objects to be prefetched in the main object store.
+ * If objects are not found then record those and if objects are found
+ * then use offset values to prefetch references to other objects */
+
+int prefetchReq(int acceptfd) {
+       int i, size, objsize, numbytes = 0, isArray = 0, numoffset = 0;
+       int length, sd = -1;
+       char *recvbuffer, *sendbuffer, control;
+       unsigned int oid, mid;
+       short *offsetarry;
+       objheader_t *header;
+       struct sockaddr_in remoteAddr;
+
+       do {
+               recv_data((int)acceptfd, &length, sizeof(int));
+               if(length != -1) {
+                       size = length - sizeof(int);
+                       if((recvbuffer = calloc(1, size)) == NULL) {
+                               printf("Calloc error at %s,%d\n", __FILE__, __LINE__);
+                               return -1;
+                       }
+                       recv_data((int)acceptfd, recvbuffer, size);
+                       oid = *((unsigned int *) recvbuffer);
+                       mid = *((unsigned int *) (recvbuffer + sizeof(unsigned int)));
+                       size = size - (2 * sizeof(unsigned int));
+                       numoffset = size / sizeof(short);
+                       if((offsetarry = calloc(numoffset, sizeof(short))) == NULL) {
+                               printf("Calloc error at %s,%d\n", __FILE__, __LINE__);
+                               free(recvbuffer);
+                               return -1;
+                       }
+                       memcpy(offsetarry, recvbuffer + (2 * sizeof(unsigned int)), size);
+                       free(recvbuffer);
+#if 0
+                       pthread_mutex_lock(&sockLock);
+                       sockIdFound = 0;
+                       pthread_mutex_unlock(&sockLock);
+                       for(i = 0; i < NUM_MACHINES; i++) {
+                               if(sockArray[i].mid == mid) {
+                                       sd = sockArray[i].sockid;
+                                       pthread_mutex_lock(&sockLock);
+                                       sockIdFound = 1;
+                                       pthread_mutex_unlock(&sockLock);
+                                       break;
+                               }
+                       }
+
+                       if(sockIdFound == 0) {
+                               if(sockCount < NUM_MACHINES) {
+
+#endif
+                                       /* Create socket to send information */
+                                       if ((sd = socket(AF_INET, SOCK_STREAM, 0)) < 0){
+                                               perror("prefetchReq():socket()");
+                                               return -1;
+                                       }
+                                       bzero(&remoteAddr, sizeof(remoteAddr));
+                                       remoteAddr.sin_family = AF_INET;
+                                       remoteAddr.sin_port = htons(LISTEN_PORT);
+                                       remoteAddr.sin_addr.s_addr = htonl(mid);
+
+                                       if (connect(sd, (struct sockaddr *)&remoteAddr, sizeof(remoteAddr)) < 0){
+                                               printf("Error: prefetchReq():error %d connecting to %s:%d\n", errno,
+                                                               inet_ntoa(remoteAddr.sin_addr), LISTEN_PORT);
+                                               close(sd);
+                                               return -1;
+                                       }
+
+#if 0
+                                       sockArray[sockCount].mid = mid;
+                                       sockArray[sockCount].sockid = sd;
+                                       pthread_mutex_lock(&sockLock);
+                                       sockCount++;
+                                       pthread_mutex_unlock(&sockLock);
+                               } else {
+                                       //TODO Fix for connecting to more than 2 machines && close socket
+                                       printf("%s(): Error: Currently works for only 2 machines\n", __func__);
+                                       return -1;
+                               }
+                       }
+#endif
+
+                       /*Process each oid */
+                       if ((header = mhashSearch(oid)) == NULL) {/* Obj not found */
+                               /* Save the oids not found in buffer for later use */
+                               size = sizeof(int) + sizeof(char) + sizeof(unsigned int) ;
+                               if((sendbuffer = calloc(1, size)) == NULL) {
+                                       printf("Calloc error at %s,%d\n", __FILE__, __LINE__);
+                                       free(offsetarry);
+                                       close(sd);
+                                       return -1;
+                               }
+                               *((int *) sendbuffer) = size;
+                               *((char *)(sendbuffer + sizeof(int))) = OBJECT_NOT_FOUND;
+                               *((unsigned int *)(sendbuffer + sizeof(int) + sizeof(char))) = oid;
+
+                               control = TRANS_PREFETCH_RESPONSE;
+                               if(sendPrefetchResponse(sd, &control, sendbuffer, &size) != 0) {
+                                       free(offsetarry);
+                                       printf("Error: %s() in sending prefetch response at %s, %d\n",
+                                                       __func__, __FILE__, __LINE__);
+                                       close(sd);
+                                       return -1;
+                               }
+                       } else { /* Object Found */
+                               int incr = 0;
+                               GETSIZE(objsize, header);
+                               size = sizeof(int) + sizeof(char) + sizeof(unsigned int) + sizeof(objheader_t) + objsize;
+                               if((sendbuffer = calloc(1, size)) == NULL) {
+                                       printf("Calloc error at %s,%d\n", __FILE__, __LINE__);
+                                       free(offsetarry);
+                                       close(sd);
+                                       return -1;
+                               }
+                               *((int *) (sendbuffer + incr)) = size;
+                               incr += sizeof(int);
+                               *((char *)(sendbuffer + incr)) = OBJECT_FOUND;
+                               incr += sizeof(char);
+                               *((unsigned int *)(sendbuffer+incr)) = oid;
+                               incr += sizeof(unsigned int);
+                               memcpy(sendbuffer + incr, header, objsize + sizeof(objheader_t));
+
+                               control = TRANS_PREFETCH_RESPONSE;
+                               if(sendPrefetchResponse(sd, &control, sendbuffer, &size) != 0) {
+                                       free(offsetarry);
+                                       printf("Error: %s() in sending prefetch response at %s, %d\n",
+                                                       __func__, __FILE__, __LINE__);
+                                       close(sd);
+                                       return -1;
+                               }
+
+                               /* Calculate the oid corresponding to the offset value */
+                               for(i = 0 ; i< numoffset ; i++) {
+                                       /* Check for arrays  */
+                                       if(TYPE(header) > NUMCLASSES) {
+                                               isArray = 1;
+                                       }
+                                       if(isArray == 1) {
+                                               int elementsize = classsize[TYPE(header)];
+                                               struct ArrayObject *ao = (struct ArrayObject *) (((char *)header) + sizeof(objheader_t));
+                                               unsigned short length = ao->___length___;
+                                               /* Check if array out of bounds */
+                                               if(offsetarry[i]< 0 || offsetarry[i] >= length) {
+                                                       break;
+                                               }
+                                               oid = *((unsigned int *)(((char *)header) + sizeof(objheader_t) + sizeof(struct ArrayObject) + (elementsize*offsetarry[i])));
+                                       } else {
+                                               oid = *((unsigned int *)(((char *)header) + sizeof(objheader_t) + offsetarry[i]));
+                                       }
+
+                                       if((header = mhashSearch(oid)) == NULL) {
+                                               size = sizeof(int) + sizeof(char) + sizeof(unsigned int) ;
+                                               if((sendbuffer = calloc(1, size)) == NULL) {
+                                                       printf("Calloc error at %s,%d\n", __FILE__, __LINE__);
+                                                       free(offsetarry);
+                                                       close(sd);
+                                                       return -1;
+                                               }
+                                               *((int *) sendbuffer) = size;
+                                               *((char *)(sendbuffer + sizeof(int))) = OBJECT_NOT_FOUND;
+                                               *((unsigned int *)(sendbuffer + sizeof(int) + sizeof(char))) = oid;
+
+                                               control = TRANS_PREFETCH_RESPONSE;
+                                               if(sendPrefetchResponse(sd, &control, sendbuffer, &size) != 0) {
+                                                       free(offsetarry);
+                                                       printf("Error: %s() in sending prefetch response at %s, %d\n",
+                                                                       __FILE__, __LINE__);
+                                                       close(sd);
+                                                       return -1;
+                                               }
+                                               break;
+                                       } else {/* Obj Found */
+                                               int incr = 0;
+                                               GETSIZE(objsize, header);
+                                               size = sizeof(int) + sizeof(char) + sizeof(unsigned int) + sizeof(objheader_t) + objsize;
+                                               if((sendbuffer = calloc(1, size)) == NULL) {
+                                                       printf("Calloc error at %s,%d\n", __func__, __FILE__, __LINE__);
+                                                       free(offsetarry);
+                                                       close(sd);
+                                                       return -1;
+                                               }
+                                               *((int *) (sendbuffer + incr)) = size;
+                                               incr += sizeof(int);
+                                               *((char *)(sendbuffer + incr)) = OBJECT_FOUND;
+                                               incr += sizeof(char);
+                                               *((unsigned int *)(sendbuffer+incr)) = oid;
+                                               incr += sizeof(unsigned int);
+                                               memcpy(sendbuffer + incr, header, objsize + sizeof(objheader_t));
+
+                                               control = TRANS_PREFETCH_RESPONSE;
+                                               if(sendPrefetchResponse(sd, &control, sendbuffer, &size) != 0) {
+                                                       free(offsetarry);
+                                                       printf("Error: %s() in sending prefetch response at %s, %d\n",
+                                                                       __func__, __FILE__, __LINE__);
+                                                       close(sd);
+                                                       return -1;
+                                               }
+                                       }
+                                       isArray = 0;
+                               }
+                               free(offsetarry);
+                       }
+                       close(sd);
+               }
+       } while (length != -1);
        return 0;
 }
 
+int sendPrefetchResponse(int sd, char *control, char *sendbuffer, int *size) {
+       int numbytes = 0;
+
+       send_data(sd, control, sizeof(char));
+       /* Send the buffer with its size */
+       int length = *(size);
+       send_data(sd, sendbuffer, length);
+       free(sendbuffer);
+       return 0;
+}
+
+void processReqNotify(unsigned int numoid, unsigned int *oidarry, unsigned short *versionarry, unsigned int mid, unsigned int threadid) {
+       objheader_t *header;
+       unsigned int oid;
+       unsigned short newversion;
+       char msg[1+  2 * sizeof(unsigned int) + sizeof(unsigned short)];
+       int sd;
+       struct sockaddr_in remoteAddr;
+       int bytesSent;
+       int size;
+
+       int i = 0;
+       while(i < numoid) {
+               oid = *(oidarry + i);
+               if((header = (objheader_t *) mhashSearch(oid)) == NULL) {
+                       printf("Error: mhashsearch returns NULL at %s, %d\n", __FILE__, __LINE__);
+                       return;
+               } else {
+                       /* Check to see if versions are same */
+checkversion:
+                       if ((STATUS(header) & LOCK) != LOCK) {          
+                               //FIXME make locking atomic
+                               STATUS(header) |= LOCK;
+                               newversion = header->version;
+                               if(newversion == *(versionarry + i)) {
+                                       //Add to the notify list 
+                                       if((header->notifylist = insNode(header->notifylist, threadid, mid)) == NULL) {
+                                               printf("Error: Obj notify list points to NULL %s, %d\n", __FILE__, __LINE__); 
+                                               return;
+                                       }
+                                       STATUS(header) &= ~(LOCK);              
+                               } else {
+                                       STATUS(header) &= ~(LOCK);              
+                                       if ((sd = socket(AF_INET, SOCK_STREAM, 0)) < 0){
+                                               perror("processReqNotify():socket()");
+                                               return;
+                                       }
+                                       bzero(&remoteAddr, sizeof(remoteAddr));
+                                       remoteAddr.sin_family = AF_INET;
+                                       remoteAddr.sin_port = htons(LISTEN_PORT);
+                                       remoteAddr.sin_addr.s_addr = htonl(mid);
+
+                                       if (connect(sd, (struct sockaddr *)&remoteAddr, sizeof(remoteAddr)) < 0){
+                                               printf("Error: processReqNotify():error %d connecting to %s:%d\n", errno,
+                                                               inet_ntoa(remoteAddr.sin_addr), LISTEN_PORT);
+                                               close(sd);
+                                               return;
+                                       } else {
+                                               //Send Update notification
+                                               msg[0] = THREAD_NOTIFY_RESPONSE;
+                                               *((unsigned int *)&msg[1]) = oid;
+                                               size = sizeof(unsigned int);
+                                               *((unsigned short *)(&msg[1]+size)) = newversion;
+                                               size += sizeof(unsigned short);
+                                               *((unsigned int *)(&msg[1]+size)) = threadid;
+                                               size = 1+ 2*sizeof(unsigned int) + sizeof(unsigned short);
+                                               send_data(sd, msg, size);
+                                       }
+                                       close(sd);
+                               }
+                       } else {
+                               randomdelay();
+                               goto checkversion;
+                       }
+               }
+               i++;
+       }
+       free(oidarry);
+       free(versionarry);
+}