Eventmachine talk - Feb 2007 - EventMachine not raising exceptions properly

Well, EventMachine seem to screw up on raising exceptions. In my
particular case, I wrote a class called Common(in a file common.rb),

which can be used as both client and server and was using buftok and
forgot to do a require on buftok, and all EventMachine would tell me
about this error is:

A client connected"
/usr/local/lib/ruby/site_ruby/1.8/eventmachine.rb:801:in
`event_callback'': EventMachine::ConnectionNotBound
(EventMachine::ConnectionNotBound)
        from /usr/local/lib/ruby/site_ruby/1.8/eventmachine.rb:209:in
`release_machine''
        from /usr/local/lib/ruby/site_ruby/1.8/eventmachine.rb:209:in
`run''
        from em_slave.rb:14:in `initialize''
        from em_slave.rb:31:in `new''
        from em_slave.rb:31

Of course, it took sometime to figure out the exact problem because of
EM ate the exception.

BTW, i am experimenting with making EM and drb work together using
Slave library.


--
gnufied
-----------
There was only one Road; that it was like a great river: its springs
were at every doorstep, and every path was its tributary.

On 2/10/07, hemant <gethemant at gmail.com> wrote:
>
> Well, EventMachine seem to screw up on raising exceptions. In my
> particular case, I wrote a class called Common(in a file common.rb),
>
> which can be used as both client and server and was using buftok and
> forgot to do a require on buftok, and all EventMachine would tell me
> about this error is:
>
> A client connected"
> /usr/local/lib/ruby/site_ruby/1.8/eventmachine.rb:801:in
> `event_callback'': EventMachine::ConnectionNotBound
> (EventMachine::ConnectionNotBound)
>         from /usr/local/lib/ruby/site_ruby/1.8/eventmachine.rb:209:in
> `release_machine''
>         from /usr/local/lib/ruby/site_ruby/1.8/eventmachine.rb:209:in
> `run''
>         from em_slave.rb:14:in `initialize''
>         from em_slave.rb:31:in `new''
>         from em_slave.rb:31
>
> Of course, it took sometime to figure out the exact problem because of
> EM ate the exception.
>
> BTW, i am experimenting with making EM and drb work together using
> Slave library.


Hi Hemant. Were you able to find the begin statement in EM that ate the
exception? (I''m guessing it was a NameError or a LoadError)
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On 2/11/07, Francis Cianfrocca <garbagecat10 at gmail.com>
wrote:
> On 2/10/07, hemant <gethemant at gmail.com> wrote:
> > Well, EventMachine seem to screw up on raising exceptions. In my
> > particular case, I wrote a class called Common(in a file common.rb),
> >
> > which can be used as both client and server and was using buftok and
> > forgot to do a require on buftok, and all EventMachine would tell me
> > about this error is:
> >
> > A client connected"
> > /usr/local/lib/ruby/site_ruby/1.8/eventmachine.rb:801:in
> > `event_callback'': EventMachine::ConnectionNotBound
> > (EventMachine::ConnectionNotBound)
> >         from
> /usr/local/lib/ruby/site_ruby/1.8/eventmachine.rb:209:in
> > `release_machine''
> >         from
> /usr/local/lib/ruby/site_ruby/1.8/eventmachine.rb:209:in
> `run''
> >         from em_slave.rb:14:in `initialize''
> >         from em_slave.rb:31:in `new''
> >         from em_slave.rb:31
> >
> > Of course, it took sometime to figure out the exact problem because of
> > EM ate the exception.
> >
> > BTW, i am experimenting with making EM and drb work together using
> > Slave library.
>
>
>  Hi Hemant. Were you able to find the begin statement in EM that ate the
> exception? (I''m guessing it was a NameError or a LoadError)
>
>
Yes, It was a NameError and the problem is because of these lines in EM:


  def EventMachine::event_callback conn_binding, opcode, data
    case opcode
    when ConnectionData
      c = @conns[conn_binding] or raise ConnectionNotBound
      c.receive_data data
    when ConnectionUnbound
      if c = @conns.delete( conn_binding )
        c.unbind
      elsif c = @acceptors.delete( conn_binding )
        # no-op
      else
        raise ConnectionNotBound
      end


As, we can see, since EM catches all exceptions in the or block and
re-raises them as ConnectionUnbound exception, making things a bit
difficult.

  def receive_data data
    @tokenizer.extract(data).each do |_data|
        # process it
     end
  end

Did I answer your question Francis? or you asked something else?

btw, i did manage to fork drb processes using slave library and handle
time taking jobs as seperate processes, rather than clogging the main
EM loop. child process, can also have their own EM loop using
EventMachine.run and its working quite well.


--
gnufied
-----------
There was only one Road; that it was like a great river: its springs
were at every doorstep, and every path was its tributary.

On 2/10/07, hemant <gethemant at gmail.com> wrote:
>
>
> Yes, It was a NameError and the problem is because of these lines in EM:
>
>
>   def EventMachine::event_callback conn_binding, opcode, data
>     case opcode
>     when ConnectionData
>       c = @conns[conn_binding] or raise ConnectionNotBound
>       c.receive_data data
>     when ConnectionUnbound
>       if c = @conns.delete( conn_binding )
>         c.unbind
>       elsif c = @acceptors.delete( conn_binding )
>         # no-op
>       else
>         raise ConnectionNotBound
>       end
>
>
> As, we can see, since EM catches all exceptions in the or block and
> re-raises them as ConnectionUnbound exception, making things a bit
> difficult.
>
>   def receive_data data
>     @tokenizer.extract (data).each do |_data|
>         # process it
>      end
>   end


I''m looking for the "begin" statement that catches the
NameError that
evidently gets thrown out of your receive_data function. I wonder if
it''s
the one in EventMachine::run (line 206 in the latest version of
eventmachine.rb). Can you try adding a rescue NameError clause to that
function, just to see if it catches your error?
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On 2/11/07, Francis Cianfrocca <garbagecat10 at gmail.com>
wrote:
> On 2/10/07, hemant <gethemant at gmail.com> wrote:
>
> >
> > Yes, It was a NameError and the problem is because of these lines in
EM:
> >
> >
> >   def EventMachine::event_callback conn_binding, opcode, data
> >     case opcode
> >     when ConnectionData
> >       c = @conns[conn_binding] or raise ConnectionNotBound
> >       c.receive_data data
> >     when ConnectionUnbound
> >       if c = @conns.delete( conn_binding )
> >         c.unbind
> >       elsif c = @acceptors.delete( conn_binding )
> >         # no-op
> >       else
> >         raise ConnectionNotBound
> >       end
> >
> >
> > As, we can see, since EM catches all exceptions in the or block and
> > re-raises them as ConnectionUnbound exception, making things a bit
> > difficult.
> >
> >   def receive_data data
> >     @tokenizer.extract (data).each do |_data|
> >         # process it
> >      end
> >   end
>
>
> I''m looking for the "begin" statement that catches the
NameError that
> evidently gets thrown out of your receive_data function. I wonder if
it''s
> the one in EventMachine::run (line 206 in the latest version of
> eventmachine.rb). Can you try adding a rescue NameError clause to that
> function, just to see if it catches your error?
def EventMachine::run &block
	begin
	    initialize_event_machine
	    block and add_timer 0, block
	    run_machine
	ensure
	    release_machine
	end
end

I guess, above is the function that is catching that exception.



--
gnufied
-----------
There was only one Road; that it was like a great river: its springs
were at every doorstep, and every path was its tributary.
http://people.inxsasia.com/~hemant