MYSQL UDF sockets - mysql

Question

I've created a MySQL User defined function to open a unix domain type socket.
My problem is that if I call my function directly like so:
SELECT socketOpen("/path/to/file", "message");
It always executes in <10ms. So that is nice. But since I don't want to manually call this function everytime, I've created a stored procedure which does an insert into database and then calls this function.
The problem I'm facing is that the stored procedure usually takes <10ms, but somestimes takes over 1s. Even 5s. I don't understand how this happens. Is there a caching problem or something ?
Below is the code is use, stripped of error checking for clarity:
char *socketOpen(UDF_INIT *initid __attribute__((unused)),
UDF_ARGS *args, char *result, unsigned long *length,
char *is_null, char *error __attribute__((unused)))
{
int sockfd, portno, n, servlen;
struct sockaddr_un serv_addr;
struct hostent *server;
char socket_path[100];
char message[100];
memcpy(socket_path,args->args[0],args->lengths[0]);
socket_path[args->lengths[0]] = 0;
memcpy(message,args->args[1],args->lengths[1]);
message[args->lengths[1]] = 0;
sockfd = socket(AF_UNIX, SOCK_STREAM, 0);
bzero((char *) &serv_addr, sizeof(serv_addr));
serv_addr.sun_family = AF_UNIX;
strcpy(serv_addr.sun_path, args->args[0]);
servlen=strlen(serv_addr.sun_path) + sizeof(serv_addr.sun_family);
connect(sockfd,(struct sockaddr *) &serv_addr, servlen);
n = write(sockfd, message, strlen(message));
bzero(message,100);
n = read(sockfd, message, 100);
close(sockfd);
strcpy(result, message);
*length = strlen(message);
return result;
}
I would appreciate your insight into this problem. Thank you.

Answer 1

Since I've got no replies and I've fixed the problem I would like to share my solution to the problem.
The cause of the problem was quite different than I ancipated.
The machine of running the above code was Raspberry pi, which slowness I did not take into account. As it turns out most of the delay was caused by the UPDATE statement in the procedure. As soon as I changed the table ENGINE to MyISAM everything went smooth from then on.
Altough while testing the code there was sometimes still a slight delay. I've fixed that with making the socket non-blocking. That means that if something will go wrong the socket will never be opened, but I figure that is better than blocking indefinetely.