Function serveClientBlockedOnList

src/t_list.cpp:880–932

This is a helper function for handleClientsBlockedOnKeys(). Its work * is to serve a specific client (receiver) that is blocked on 'key' * in the context of the specified 'db', doing the following: * * 1) Provide the client with the 'value' element. * 2) If the dstkey is not NULL (we are serving a BLMOVE) also push the * 'value' element on the destination list (the "push" side of the comm

 * BLMOVE that fails to push the value to the destination key as it is
 * of the wrong type. */
int serveClientBlockedOnList(client *receiver, robj *key, robj *dstkey, redisDb *db, robj *value, int wherefrom, int whereto)
{
    robj *argv[5];
    std::unique_lock<fastlock> ul(receiver->lock);

    if (dstkey == NULL) {
        /* Propagate the [LR]POP operation. */
        argv[0] = (wherefrom == LIST_HEAD) ? shared.lpop :
                                             shared.rpop;
        argv[1] = key;
        propagate((wherefrom == LIST_HEAD) ?
            cserver.lpopCommand : cserver.rpopCommand,
            db->id,argv,2,PROPAGATE_AOF|PROPAGATE_REPL);
       
        /* BRPOP/BLPOP */
        addReplyArrayLen(receiver,2);
        addReplyBulk(receiver,key);
        addReplyBulk(receiver,value);

        /* Notify event. */
        const char *event = (wherefrom == LIST_HEAD) ? "lpop" : "rpop";
        notifyKeyspaceEvent(NOTIFY_LIST,event,key,receiver->db->id);
    } else {
        /* BLMOVE */
        robj *dstobj =
            lookupKeyWrite(receiver->db,dstkey);
        if (!(dstobj &&
             checkType(receiver,dstobj,OBJ_LIST)))
        {
            lmoveHandlePush(receiver,dstkey,dstobj,value,whereto);
            /* Propagate the LMOVE/RPOPLPUSH operation. */
            int isbrpoplpush = (receiver->lastcmd->proc == brpoplpushCommand);
            argv[0] = isbrpoplpush ? shared.rpoplpush : shared.lmove;
            argv[1] = key;
            argv[2] = dstkey;
            argv[3] = getStringObjectFromListPosition(wherefrom);
            argv[4] = getStringObjectFromListPosition(whereto);
            propagate(isbrpoplpush ? cserver.rpoplpushCommand : cserver.lmoveCommand,
                db->id,argv,(isbrpoplpush ? 3 : 5),
                PROPAGATE_AOF|
                PROPAGATE_REPL);

            /* Notify event ("lpush" or "rpush" was notified by lmoveHandlePush). */
            notifyKeyspaceEvent(NOTIFY_LIST,wherefrom == LIST_TAIL ? "rpop" : "lpop",
                                key,receiver->db->id);
        } else {
            /* BLMOVE failed because of wrong
             * destination type. */
            return C_ERR;
        }
    }
    return C_OK;
}

/* Blocking RPOP/LPOP */
void blockingPopGenericCommand(client *c, int where) {