Producer/Consumer using TCP client/server

Question

The server is intended to be a multithreaded server which spawns new threads upon either a producer or consumer connection via TCP. My problem is that I'm getting stuck in a wait state once a producer client fills the queue. This snippet shows the server's handling of a producer connection. The format of the request the producer sends is PUT (item)

    reqline[0] = strtok (mesg, " \t\n");


 if ( strncmp(reqline[0], "PUT\0", 4)==0 )
           {
            item[0]=strtok(NULL," \t\n");
            pthread_create (&pro, NULL, producer, fifo);
            pthread_join (pro, NULL);


            }

So you can see I'm creating a new thread which handles the job of filling the queue/detecting when it is empty. The code within producer:

    queue *fifo;
    int i=atoi(item[0]);
    char*fullmsg="Full\n";

    fifo = (queue *)q;

    pthread_mutex_lock (fifo->mut);

         while (fifo->full) { //the problem  block

              printf ("producer: queue FULL.\n");
              send(conn_s, fullmsg,strlen(fullmsg),0);
              pthread_cond_wait (fifo->notFull, fifo->mut);
           } 

           queueAdd (fifo, 0);
           pthread_mutex_unlock (fifo->mut);
           pthread_cond_signal (fifo->notEmpty);

I believe the wait condition is the problem. The server is obviously waiting for a condition which can never be met, considering a consumer thread was not started to eat up the queue. I was thinking that I should change the condition to wait for an incoming consumer connection and then start a consumer thread. But then it seems silly to do so within this method. If I send a consumer request while in this state nothing happens.

Any suggestions are greatly appreciated. I'm not sure if this design is feasible.

"Producer" and "consumer" are supposed to be named as "server" and "client", don't they? — user529758

caf caf · Accepted Answer · 2012-03-07T11:43:58

Your problem seems to be that you're calling pthread_join() immediately after pthread_create(), which means that the main thread stops here until the producer exits - it can't ever accept a consumer connection, so the producer can't make progress once the queue is full.

Producer/Consumer using TCP client/server

1 Answers