Another subtlety occurs on the last line in the program. Why do we call
join on each of the threads we created?
When a Ruby program terminates, all running threads are killed,
regardless of their states. However, you can wait for a particular
thread to finish by calling that thread's
Thread#join
method.
The calling thread will block until the given thread is finished. By
calling
join on each of the requestor threads, you can make
sure that all three requests have completed before you terminate the
main program.
In addition to
join, there are a few other handy routines that are
used to manipulate threads. First of all, the current thread is
always accessible using
Thread.current
. You can obtain a list
of all threads using
Thread.list
, which returns a list of
all
Thread objects that are runnable or stopped. To determine the
status of a particular thread, you can use
Thread#status
and
Thread#alive?
.
Also, you can adjust the priority of a thread using
Thread#priority=
. Higher-priority threads will run before
lower-priority threads. We'll talk more about thread scheduling, and
stopping and starting threads, in just a bit.
