/* Must be called after tpclog_iterate_begin has been called on LOG. Attempts
* to return the next most recent entry after the entry previously returned
* during the current iteration, or, immediately after tpclog_iterate_begin,
* the oldest entry in LOG, using malloc()d memory which should later be
* free()d. Returns NULL if there is an error or no more recent entry exists
* (i.e., all entries have been iterated over). */
logentry_t *tpclog_iterate_next(tpclog_t *log, logentry_t *entry) {
char filename[MAX_FILENAME];
int ret;
pthread_rwlock_rdlock(&log->lock);
if (!tpclog_iterate_has_next(log)) {
pthread_rwlock_unlock(&log->lock);
return NULL;
}
sprintf(filename, "%s/%lu%s", log->dirname, log->iterpos++, TPCLOG_FILETYPE);
ret = tpclog_load_entry(entry, filename);
pthread_rwlock_unlock(&log->lock);
return (ret < 0) ? NULL : entry;
}
/* Restore SERVER back to the state it should be in, according to the
* associated LOG. Must be called on an initialized SERVER. Only restores the
* state of the most recent TPC transaction, assuming that all previous actions
* have been written to persistent storage. Should restore SERVER to its exact
* state; e.g. if SERVER had written into its log that it received a PUTREQ but
* no corresponding COMMIT/ABORT, after calling this function SERVER should
* again be waiting for a COMMIT/ABORT. This should also ensure that as soon
* as a server logs a COMMIT, even if it crashes immediately after (before the
* KVStore has a chance to write to disk), the COMMIT will be finished upon
* rebuild. The cache need not be the same as before rebuilding.
*
* Checkpoint 2 only. */
int kvserver_rebuild_state(kvserver_t *server) {
if (server == NULL || server->state == TPC_INIT) {
return -1;
}
tpclog_iterate_begin(&server->log);
logentry_t *prev = NULL, *next = NULL;
while (tpclog_iterate_has_next(&server->log)) {
next = tpclog_iterate_next(&server->log);
if (next->type == PUTREQ || next->type == DELREQ)
prev = next;
}
if (prev == NULL && next == NULL) { // log was empty
return 0;
} else if (prev == NULL) {
prev = next;
}
server->msg = (kvmessage_t *) malloc(sizeof(kvmessage_t));
if (server->msg == NULL)
return -1;
if (next->type == COMMIT) {
server->state = TPC_READY;
if (prev->type == PUTREQ) {
if (rebuild_kvmessage(server, prev, true) == -1) {
return -1;
}
kvserver_put(server, server->msg->key, server->msg->value);
} else if (prev->type == DELREQ) {
if (rebuild_kvmessage(server, prev, false) == -1) {
return -1;
}
kvserver_del(server, server->msg->key);
}
} else if (next->type == ABORT) { // might want to avoid commiting very first time with a one-time use bool
server->state = TPC_READY;
if (prev != NULL && rebuild_kvmessage(server, prev, prev->type == PUTREQ) == -1)
return -1;
} else {
server->state = TPC_WAIT;
if (rebuild_kvmessage(server, next, next->type == PUTREQ) == -1)
return -1;
}
return tpclog_clear_log(&server->log);
}
/* Handles an incoming kvrequest REQ, and populates RES as a response. REQ and
* RES both must point to valid kvrequest_t and kvrespont_t structs,
* respectively. Assumes that the request should be handled as a TPC
* message. This should also log enough information in the server's TPC log to
* be able to recreate the current state of the server upon recovering from
* failure. See the spec for details on logic and error messages.
*/
void tpcfollower_handle_tpc(tpcfollower_t *server, kvrequest_t *req, kvresponse_t *res) {
/* TODO: Implement me! */
if (req->type == DELREQ) {
if (server->state != TPC_WAIT) {
server->state = TPC_WAIT;
} else {
res->type = ERROR;
strcpy(res->body, ERRMSG_INVALID_REQUEST);
return;
}
int del_retval = tpcfollower_del_check(server, req->key);
if (del_retval < 0) {
res->type = VOTE;
if (del_retval == ERR_KEYLEN) {
strcpy(res->body, ERRMSG_KEY_LEN);
} else if (del_retval == ERR_NOKEY) {
strcpy(res->body, ERRMSG_NO_KEY);
} else {
strcpy(res->body, ERRMSG_GENERIC_ERROR);
}
} else {
tpclog_log(&server->log, DELREQ, req->key, NULL);
res->type = VOTE;
strcpy(res->body, MSG_COMMIT);
}
} else if (req->type == PUTREQ) {
if (server->state != TPC_WAIT) {
server->state = TPC_WAIT;
} else {
res->type = ERROR;
strcpy(res->body, ERRMSG_INVALID_REQUEST);
return;
}
int put_retval = tpcfollower_put_check(server, req->key, req->val);
if (put_retval < 0) {
res->type = VOTE;
if (put_retval == ERR_KEYLEN) {
strcpy(res->body, ERRMSG_KEY_LEN);
} else if (put_retval == ERR_VALLEN) {
strcpy(res->body, ERRMSG_VAL_LEN);
} else {
strcpy(res->body, ERRMSG_GENERIC_ERROR);
}
} else {
tpclog_log(&server->log, PUTREQ, req->key, req->val);
res->type = VOTE;
strcpy(res->body, MSG_COMMIT);
}
} else if (req->type == COMMIT) {
server->state = TPC_COMMIT;
res->type = ACK;
tpclog_iterate_begin(&server->log);
logentry_t* entry = malloc(sizeof(logentry_t));
while (tpclog_iterate_has_next(&server->log)) {
entry = tpclog_iterate_next(&server->log, entry);
char* log_key = malloc(strlen(entry->data));
if (entry->type == DELREQ) {
strcpy(log_key, entry->data);
tpcfollower_del(server, log_key);
} else if (entry->type == PUTREQ) {
char* log_val = malloc(entry->length - strlen(entry->data));
strcpy(log_key, entry->data);
strcpy(log_val, entry->data + strlen(entry->data) + 1);
tpcfollower_put(server, log_key, log_val);
}
}
tpclog_clear_log(&server->log);
} else if (req->type == ABORT) {
server->state = TPC_ABORT;
res->type = ACK;
tpclog_clear_log(&server->log);
} else if (req->type == GETREQ) {
int get_retval = tpcfollower_get(server, req->key, res->body);
if (get_retval < 0) {
res->type = ERROR;
if (get_retval == ERR_KEYLEN) {
strcpy(res->body, ERRMSG_KEY_LEN);
} else if (get_retval == ERR_NOKEY) {
strcpy(res->body, ERRMSG_NO_KEY);
} else {
strcpy(res->body, ERRMSG_INVALID_REQUEST);
}
} else {
res->type = GETRESP;
}
}
}