Handle exception thrown in nested threads from top level thr

Ruby
1

In following code, both methos get_client_symbol and sync_clients gets
called and they start their own new threads. Now, what I would like to
do is, whenever a exception is raised from the nested threads…i would
like to catch them in the toplevel thread.

Now…I have tried many things:
Thread.abort_on_exception = true
and using just rescue or rescue Exception or rescue RuntimeError,
however the exception raised in nested threads won’t get caught in the
top level thread. Any clues?

@threads << Thread.new do
child_threads = []

    begin
       child_threads << get_client_symbol(temp_client_id)
       child_threads << sync_clients(temp_client_id)
      child_threads.each {|thr| p thr.to_s; thr.join; }

     rescue Exception
       p $!
       p $!.backtrace
       # delete the values from list
       @connected_clients.synchronize do
         @connected_clients.delete(temp_client_id)
         @symbols_being_added.signal
       end #end of sync
       child_threads.each {|thr| Thread.kill(thr) if thr.alive? }
     end

  end #end of threads
2

On 18.09.2006 12:15, hemant wrote:

In following code, both methos get_client_symbol and sync_clients gets
called and they start their own new threads. Now, what I would like to
do is, whenever a exception is raised from the nested threads…i would
like to catch them in the toplevel thread.

Now…I have tried many things:
Thread.abort_on_exception = true
and using just rescue or rescue Exception or rescue RuntimeError,
however the exception raised in nested threads won’t get caught in the
top level thread. Any clues?

There is no direct way. If you think about it for a moment it’s not
possible to catch an exception thrown in another thread. But in Ruby
you can actually do that by rethrowing it in another thread. Try this:

print "Main thread : ", Thread.current.inspect, “\n”

2.times do
Thread.new(Thread.current) do |parent|
print "Child thread: ", Thread.current.inspect, “\n”

 loop do
   begin
     puts "."
     raise "Foo" if rand > 0.8
     sleep 1
   rescue Exception => e
     print "Thread     : ",
       Thread.current.inspect,
       ": ",
       e.inspect,
       "\n"
     parent.raise e
   end
 end

end
end

10.times do
begin
sleep 10
rescue Exception => e
print "Thread main: ",
Thread.current.inspect,
": ",
e.inspect,
“\n”
puts e.backtrace
end
end

Kind regards

robert