Slave-0.2.0

Ruby
1

SYNOPSIS

the Slave class forks a process and starts a drb server in the child
using
any object as the server. the process is detached so it is not
required
(nor possible) to wait on the child pid. a Heartbeat is set up
between the
parent and child processes so that the child will exit of the parent
exits
for any reason - preventing orphaned slaves from running
indefinitely. the
purpose of Slaves is to be able to easily set up a collection of
objects
communicating via drb protocols instead of having to use IPC.

typical usage:

 obj = AnyClass::new

 slave = Slave::new obj

 p slave.object                  # handle on drb object
 p slave.uri                     # uri of the drb object
 p slave.socket                  # unix domain socket path for drb

object
p slave.psname # title shown in ps/top

other usage:

set the pulse_rate used for the Heartbeat

 slave = Slave::new MyClass::new, 'pulse_rate' => 10

same

 Slave::pulse_rate = 10
 slave = Slave::new MyClass::new

same

 ENV['SLAVE_PULSE_RATE'] = 10
 slave = Slave::new MyClass::new

to avoid having a copy of the object in both the parent and child use
the
block form

 slave = Slave::new{ Server::new }  # copy only in child!
 server = slave.object

if both an object AND a block are passed the object is passed to the
block
in the child process

 slave = Slave::new(Server::new){|server| p 'in child!' }

slaves may be configured via the environment, the Slave class, or via
the
ctor for object itself. attributes which may be configured include

 * socket_creation_attempts
 * pulse_rate
 * psname
 * debug

HISTORY

0.2.0:
incorporated joel vanderWerf’s patch such that, if no object is
passed the
block is used to create one ONLY in the child. this avoids having
a copy
in both parent and child is that needs to be avoided due to, for
instance,
resource consumption.

0.0.1:
- patch from Logan C. adds block form to slave new, block is
run in the
child

 - added a few more samples/*

 - added Slave#wait

 - added status information to slaves

 - added close-on-exec flag to pipes in parent process

0.0.0:
- initial version

enjoy.

-a

2

On Sep 23, 2006, at 3:52 PM, [email protected] wrote:

parent exits
for any reason - preventing orphaned slaves from running
indefinitely. the
purpose of Slaves is to be able to easily set up a collection of
objects
communicating via drb protocols instead of having to use IPC.

-a

This is a great library Ara, I am writing a library that wraps up

the slave lib into another interface for controlling jobs with timers
and a few other things. So the master process holds a thread pool
with references to slave classes in it so that you can set a limit on
the number of running slaves. Using it to offload jobs from a rails
app to not hold up the http flow. I have a question though. What
would be the cleanest way to have a slave class signal that it is
finished working and needs to be kill’ed. I know there is the
shutdown method that you could call from the master process to
shutdown a slave. But is there something similar that can be called
from a slave process? Or should I just let the slave process exit!
and let the heartbeat cleanup after the dead slaves?

Thanks
-Ezra

3

On Sun, 24 Sep 2006, Ezra Z. wrote:

just let the slave process exit! and let the heartbeat cleanup after
the dead slaves?

hmmm. good question. i could add a feature where at_exit handlers
could be
added, somthing like

s = Slave.new( :at_exit => lambda{}){ do_child_stuff }

would that be sufficient?

-a

4

On Sep 24, 2006, at 8:57 AM, [email protected] wrote:

not hold up the http flow. I have a question though. What would

-a
Ara-

Yeah that would work fine I think. So that would call the lambda

when the child process calls exit! ? Is there any way for a slave to
call back to the parent process? Or is there a way to get the drb uri
of the parent from the child?

Thanks for slave and all your other codeforpeople ;) I have learned

a lot by reading through your code and by googling “cat a.rb” :wink:

Cheers-
-Ezra