Changed default number of threads to 1 instead of autoconfigured value and
added a new `auto` variable which enables autoconfiguration of thread count.
The number of threads used when autoconfiguratio fails was changed from 4 to 1.
The default value of using N threads where N is the number of CPU cores was
not optimal as the possibility of rescheduling was higher the more utility
threads there were. Due to this, N-1 is deemed to be the better autoconfigured
value for thread count.
Earlier, by default, the error and message logfiles were written to
the filesystem and trace and debug logfiles to shared memory. Now,
with just one log-file the default must be the file-system. However,
if info and debug messages are logged, then the filesystem will
become a bottle-neck.
A reasonable approach is then as follows (in the config file)
syslog=true
maxlog=false
log_to_shm=true
With this set, the maxlog file will be created to shared memory, but
nothing will be written to it, since it is disabled. However, if there
is a need to investigate something, then a dba can from maxadmin turn
on maxlog logging and also enable info and debug messages. That is, it
will be possible to enable debugging output without restarting maxscale.
Incidentally, the way the config file and command line arguments are
handled should be rewritten. Currently, it is a mess.