+/* ================================ MULTI/EXEC ============================== */
+
+/* Client state initialization for MULTI/EXEC */
+static void initClientMultiState(redisClient *c) {
+ c->mstate.commands = NULL;
+ c->mstate.count = 0;
+}
+
+/* Release all the resources associated with MULTI/EXEC state */
+static void freeClientMultiState(redisClient *c) {
+ int j;
+
+ for (j = 0; j < c->mstate.count; j++) {
+ int i;
+ multiCmd *mc = c->mstate.commands+j;
+
+ for (i = 0; i < mc->argc; i++)
+ decrRefCount(mc->argv[i]);
+ zfree(mc->argv);
+ }
+ zfree(c->mstate.commands);
+}
+
+/* Add a new command into the MULTI commands queue */
+static void queueMultiCommand(redisClient *c, struct redisCommand *cmd) {
+ multiCmd *mc;
+ int j;
+
+ c->mstate.commands = zrealloc(c->mstate.commands,
+ sizeof(multiCmd)*(c->mstate.count+1));
+ mc = c->mstate.commands+c->mstate.count;
+ mc->cmd = cmd;
+ mc->argc = c->argc;
+ mc->argv = zmalloc(sizeof(robj*)*c->argc);
+ memcpy(mc->argv,c->argv,sizeof(robj*)*c->argc);
+ for (j = 0; j < c->argc; j++)
+ incrRefCount(mc->argv[j]);
+ c->mstate.count++;
+}
+
+static void multiCommand(redisClient *c) {
+ c->flags |= REDIS_MULTI;
+ addReply(c,shared.ok);
+}
+
+static void execCommand(redisClient *c) {
+ int j;
+ robj **orig_argv;
+ int orig_argc;
+
+ if (!(c->flags & REDIS_MULTI)) {
+ addReplySds(c,sdsnew("-ERR EXEC without MULTI\r\n"));
+ return;
+ }
+
+ orig_argv = c->argv;
+ orig_argc = c->argc;
+ addReplySds(c,sdscatprintf(sdsempty(),"*%d\r\n",c->mstate.count));
+ for (j = 0; j < c->mstate.count; j++) {
+ c->argc = c->mstate.commands[j].argc;
+ c->argv = c->mstate.commands[j].argv;
+ call(c,c->mstate.commands[j].cmd);
+ }
+ c->argv = orig_argv;
+ c->argc = orig_argc;
+ freeClientMultiState(c);
+ initClientMultiState(c);
+ c->flags &= (~REDIS_MULTI);
+}
+
+/* =========================== Blocking Operations ========================= */
+
+/* Currently Redis blocking operations support is limited to list POP ops,
+ * so the current implementation is not fully generic, but it is also not
+ * completely specific so it will not require a rewrite to support new
+ * kind of blocking operations in the future.
+ *
+ * Still it's important to note that list blocking operations can be already
+ * used as a notification mechanism in order to implement other blocking
+ * operations at application level, so there must be a very strong evidence
+ * of usefulness and generality before new blocking operations are implemented.
+ *
+ * This is how the current blocking POP works, we use BLPOP as example:
+ * - If the user calls BLPOP and the key exists and contains a non empty list
+ * then LPOP is called instead. So BLPOP is semantically the same as LPOP
+ * if there is not to block.
+ * - If instead BLPOP is called and the key does not exists or the list is
+ * empty we need to block. In order to do so we remove the notification for
+ * new data to read in the client socket (so that we'll not serve new
+ * requests if the blocking request is not served). Also we put the client
+ * in a dictionary (db->blockingkeys) mapping keys to a list of clients
+ * blocking for this keys.
+ * - If a PUSH operation against a key with blocked clients waiting is
+ * performed, we serve the first in the list: basically instead to push
+ * the new element inside the list we return it to the (first / oldest)
+ * blocking client, unblock the client, and remove it form the list.
+ *
+ * The above comment and the source code should be enough in order to understand
+ * the implementation and modify / fix it later.
+ */
+
+/* Set a client in blocking mode for the specified key, with the specified
+ * timeout */
+static void blockForKeys(redisClient *c, robj **keys, int numkeys, time_t timeout) {
+ dictEntry *de;
+ list *l;
+ int j;
+
+ c->blockingkeys = zmalloc(sizeof(robj*)*numkeys);
+ c->blockingkeysnum = numkeys;
+ c->blockingto = timeout;
+ for (j = 0; j < numkeys; j++) {
+ /* Add the key in the client structure, to map clients -> keys */
+ c->blockingkeys[j] = keys[j];
+ incrRefCount(keys[j]);
+
+ /* And in the other "side", to map keys -> clients */
+ de = dictFind(c->db->blockingkeys,keys[j]);
+ if (de == NULL) {
+ int retval;
+
+ /* For every key we take a list of clients blocked for it */
+ l = listCreate();
+ retval = dictAdd(c->db->blockingkeys,keys[j],l);
+ incrRefCount(keys[j]);
+ assert(retval == DICT_OK);
+ } else {
+ l = dictGetEntryVal(de);
+ }
+ listAddNodeTail(l,c);
+ }
+ /* Mark the client as a blocked client */
+ c->flags |= REDIS_BLOCKED;
+ aeDeleteFileEvent(server.el,c->fd,AE_READABLE);
+ server.blockedclients++;
+}
+
+/* Unblock a client that's waiting in a blocking operation such as BLPOP */
+static void unblockClient(redisClient *c) {
+ dictEntry *de;
+ list *l;
+ int j;
+
+ assert(c->blockingkeys != NULL);
+ /* The client may wait for multiple keys, so unblock it for every key. */
+ for (j = 0; j < c->blockingkeysnum; j++) {
+ /* Remove this client from the list of clients waiting for this key. */
+ de = dictFind(c->db->blockingkeys,c->blockingkeys[j]);
+ assert(de != NULL);
+ l = dictGetEntryVal(de);
+ listDelNode(l,listSearchKey(l,c));
+ /* If the list is empty we need to remove it to avoid wasting memory */
+ if (listLength(l) == 0)
+ dictDelete(c->db->blockingkeys,c->blockingkeys[j]);
+ decrRefCount(c->blockingkeys[j]);
+ }
+ /* Cleanup the client structure */
+ zfree(c->blockingkeys);
+ c->blockingkeys = NULL;
+ c->flags &= (~REDIS_BLOCKED);
+ server.blockedclients--;
+ /* Ok now we are ready to get read events from socket, note that we
+ * can't trap errors here as it's possible that unblockClients() is
+ * called from freeClient() itself, and the only thing we can do
+ * if we failed to register the READABLE event is to kill the client.
+ * Still the following function should never fail in the real world as
+ * we are sure the file descriptor is sane, and we exit on out of mem. */
+ aeCreateFileEvent(server.el, c->fd, AE_READABLE, readQueryFromClient, c);
+ /* As a final step we want to process data if there is some command waiting
+ * in the input buffer. Note that this is safe even if unblockClient()
+ * gets called from freeClient() because freeClient() will be smart
+ * enough to call this function *after* c->querybuf was set to NULL. */
+ if (c->querybuf && sdslen(c->querybuf) > 0) processInputBuffer(c);
+}
+
+/* This should be called from any function PUSHing into lists.
+ * 'c' is the "pushing client", 'key' is the key it is pushing data against,
+ * 'ele' is the element pushed.
+ *
+ * If the function returns 0 there was no client waiting for a list push
+ * against this key.
+ *
+ * If the function returns 1 there was a client waiting for a list push
+ * against this key, the element was passed to this client thus it's not
+ * needed to actually add it to the list and the caller should return asap. */
+static int handleClientsWaitingListPush(redisClient *c, robj *key, robj *ele) {
+ struct dictEntry *de;
+ redisClient *receiver;
+ list *l;
+ listNode *ln;
+
+ de = dictFind(c->db->blockingkeys,key);
+ if (de == NULL) return 0;
+ l = dictGetEntryVal(de);
+ ln = listFirst(l);
+ assert(ln != NULL);
+ receiver = ln->value;
+
+ addReplySds(receiver,sdsnew("*2\r\n"));
+ addReplyBulkLen(receiver,key);
+ addReply(receiver,key);
+ addReply(receiver,shared.crlf);
+ addReplyBulkLen(receiver,ele);
+ addReply(receiver,ele);
+ addReply(receiver,shared.crlf);
+ unblockClient(receiver);
+ return 1;
+}
+
+/* Blocking RPOP/LPOP */
+static void blockingPopGenericCommand(redisClient *c, int where) {
+ robj *o;
+ time_t timeout;
+ int j;
+
+ for (j = 1; j < c->argc-1; j++) {
+ o = lookupKeyWrite(c->db,c->argv[j]);
+ if (o != NULL) {
+ if (o->type != REDIS_LIST) {
+ addReply(c,shared.wrongtypeerr);
+ return;
+ } else {
+ list *list = o->ptr;
+ if (listLength(list) != 0) {
+ /* If the list contains elements fall back to the usual
+ * non-blocking POP operation */
+ robj *argv[2], **orig_argv;
+ int orig_argc;
+
+ /* We need to alter the command arguments before to call
+ * popGenericCommand() as the command takes a single key. */
+ orig_argv = c->argv;
+ orig_argc = c->argc;
+ argv[1] = c->argv[j];
+ c->argv = argv;
+ c->argc = 2;
+
+ /* Also the return value is different, we need to output
+ * the multi bulk reply header and the key name. The
+ * "real" command will add the last element (the value)
+ * for us. If this souds like an hack to you it's just
+ * because it is... */
+ addReplySds(c,sdsnew("*2\r\n"));
+ addReplyBulkLen(c,argv[1]);
+ addReply(c,argv[1]);
+ addReply(c,shared.crlf);
+ popGenericCommand(c,where);
+
+ /* Fix the client structure with the original stuff */
+ c->argv = orig_argv;
+ c->argc = orig_argc;
+ return;
+ }
+ }
+ }
+ }
+ /* If the list is empty or the key does not exists we must block */
+ timeout = strtol(c->argv[c->argc-1]->ptr,NULL,10);
+ if (timeout > 0) timeout += time(NULL);
+ blockForKeys(c,c->argv+1,c->argc-2,timeout);
+}
+
+static void blpopCommand(redisClient *c) {
+ blockingPopGenericCommand(c,REDIS_HEAD);
+}
+
+static void brpopCommand(redisClient *c) {
+ blockingPopGenericCommand(c,REDIS_TAIL);
+}
+
projects / redis.git / blobdiff