Tcp server with multithreading

hi.

I’m writing tcp server and I want to know:

  1. how can I block thread until some event will occur w/o overhead?
    (i.e. not timer, but something like semaphore);

  2. how can I interrupt IO::select() call from main thread?

thank you/

Daniel F. [email protected] wrote:

hi.

I’m writing tcp server and I want to know:

  1. how can I block thread until some event will occur w/o overhead?
    (i.e. not timer, but something like semaphore);

A Conditionariable, IO.select (which you already knew :),
or a blocking read on any socket or pipe.

  1. how can I interrupt IO::select() call from main thread?

Create a socketpair or pipe and and write to it from the main thread.
It’s also useful with the self-pipe trick[1]

If you’re stuck on a platform without UNIX sockets or pipes, you can
also connect to your main TCPServer (or another private one) to
wakeup from select.

[1] http://cr.yp.to/docs/selfpipe.html

A Conditionariable, IO.select (which you already knew :),
or a blocking read on any socket or pipe.

Creating a new socketpair/pipe is pretty too much imho (no matter it’s a
very
small object, but it exists and must be handled). I thought about some
kind of
semaphore, then process would look like:

in thread:

semaphore.wait_for_event

in main:

semaphore.emit_event

Create a socketpair or pipe and and write to it from the main thread.
It’s also useful with the self-pipe trick[1]

If you’re stuck on a platform without UNIX sockets or pipes, you can
also connect to your main TCPServer (or another private one) to
wakeup from select.

that makes the same trouble as described above: one more file
descriptor,
which is overhead. I knew this solution and used it in C, but I thought
ruby is able to provide some better solution.

Hi Daniel,

On Thu, Jul 9, 2009 at 8:28 PM, Daniel F. [email protected] wrote:

If you’re stuck on a platform without UNIX sockets or pipes, you can
also connect to your main TCPServer (or another private one) to
wakeup from select.

that makes the same trouble as described above: one more file
descriptor,
which is overhead. I knew this solution and used it in C, but I thought
ruby is able to provide some better solution.

Look up EventMachine - it’s what you want without re-inventing the
wheel.

John

Look up EventMachine - it’s what you want without re-inventing the
wheel.

John

thank you, thats exaclty what I need :slight_smile:

Creating a new socketpair/pipe is pretty too much imho (no matter it’s a
very
small object, but it exists and must be handled). I thought about some
kind of
semaphore, then process would look like:

in thread:

semaphore.wait_for_event

in main:

semaphore.emit_event

I’ve found the way how to do this, here is code + example:

#!/usr/bin/ruby -w

require ‘thread’

class MassSemaphoreEmulator
def initialize
@mutex=Mutex.new # we can have race condition on a variable below,
so avoid it with mutex
@waiting_threads=[]
end

def wait
@mutex.synchronize { @waiting_threads<<Thread.current } # add
current thread to waiting ones
Thread.stop
end

def signal
@mutex.synchronize do # wakeup all threads
@waiting_threads.each {|t| t.wakeup}
@waiting_threads.clear
end
end
end

semaphore=MassSemaphoreEmulator.new

threads=(1…10).map do |i|
Thread.new(i*1) do |v|
print “#{v} is waiting…\n”
semaphore.wait # wait for our mutex
print “#{v} got signal.\n”
end
end

semaphore.signal # get all waiting threads up

threads.each {|t| t.join}

I’ve also tried to do something with ConditionalVariable, but no luck,
it didn’t stop waiting threads.

now I need to find a way for interrupting select call

But overall I might suggest eventmachine or revactor for what you want.
Cheers!
=r

I’m using eventmachine atm, revactor seems to be easier and simpler, but
it requires 1.9 ruby :frowning:

  1. how can I block thread until some event will occur w/o overhead?
    (i.e. not timer, but something like semaphore);

select [or in 1.9 fibers].

  1. how can I interrupt IO::select() call from main thread?

You’d have to have some socket within it that will interrupt.

like interruptor = TCPSocket.new( ‘’, 3333)

select [interruptor], nil, nil

then in other thread
a TCPSocket.new(‘localhost’, 3333)

to interrupt

a.send ‘a’

something like that

Or if you didn’t care about thread safety you could use Thread.raise
[scary].

But overall I might suggest eventmachine or revactor for what you want.
Cheers!
=r

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