syslog in mysql function

I experimented with sending UDP messages from MySQL functions, but ended up with simple syslogging UDF

I played a bit with various interaction with outer world ideas in MySQL UDFs and ended up with something what was really really simple – a single libc call. I did shamelessly steal bare bones and simply added a single line of code in it:

#include <mysql.h>
#include <string.h>
#include <syslog.h>

my_bool logger_init(UDF_INIT *initid, UDF_ARGS *args, char *message) {
        initid->maybe_null=0;
        return 0;
}

long long logger(UDF_INIT *initid, UDF_ARGS *args, char *is_null, char *error) {
        if (args->arg_count != 1) {
                strcpy(error, "LOGGER(): needs message");
                return 1;
        }

        if (args->arg_type[0] != STRING_RESULT) {
                strcpy(error, "LOGGER() message should be string");
                return 1;
        }

        syslog(LOG_INFO,"%s",args->args[0]);
        *is_null = 0;
        *error = 0;

        return 0;
}

Of course, I had to compile it:

gcc -I /usr/include/mysql/ -shared -o syslogudf.so syslogudf.c

And later load it:

mysql> create function logger returns integer soname 'syslogudf.so';
Query OK, 0 rows affected (0.00 sec)

One more thing… testing:

mysql> select logger(concat(user()," wishes you ",
    -> if(rand()>0.3,"good","bad")," luck"));
+---------------------------------------------------------------------------+
| logger(concat(user()," wishes you ",if(rand()>0.3,"good","bad")," luck")) |
+---------------------------------------------------------------------------+
|                                                                         0 |
+---------------------------------------------------------------------------+
1 row in set (0.00 sec)

So now our systems administrator will see:

$ tail -1 /var/log/messages
Dec 12 01:09:22 flake mysqld-max: root@localhost wishes you bad luck

Oops!