posix_mq

= posix_mq - POSIX message queues for Ruby

POSIX message queues allow local processes to exchange data in the form of messages. This API is distinct from that provided by System V message queues, but provides similar functionality.

POSIX message queues may be implemented in the kernel for fast, low-latency communication between processes on the same machine. POSIX message queues are not intended to replace userspace, network-aware message queue implementations.

== Features

• Supports message notifications via signals on all platforms

• Supports portable non-blocking operation. Under Linux 2.6.6+ and FreeBSD 7.2+, POSIX_MQ objects may even be used with event notification mechanisms such as IO.select.

• Supports notifications via block execution in a separate thread on platforms that implement SIGEV_THREAD for mq_notify(3), currently only GNU/Linux.

• Optional timeouts may be applied to send and receive operations.

• Thread-safe blocking operations under Ruby 1.9+, releases GVL before blocking operations.

• Works under Ruby 1.9 and later.

• Documented library API

• Includes a generic "posix-mq-rb" command-line tool with manpage.

• {EventMachine}[http://rubyeventmachine.com/] integration via {em-posixmq}[https://github.com/ibc/em-posixmq]

== Install

Operating system support (or library emulation) for POSIX message queues is required. Most modern GNU/Linux distributions support this out-of-the-box.

If you're using a packaged Ruby distribution, make sure you have a C compiler and the matching Ruby development libraries and headers.

If you plan on using the command-line client, a tarball installation starts up faster and is recommended. Just grab the tarball from:

https://bogomips.org/ruby_posix_mq/files/ Unpack it, and run "ruby setup.rb"

Otherwise, via RubyGems: gem install posix_mq

== Usage

The Linux mq_overview(7) {manpage}[http://kernel.org/doc/man-pages/online/pages/man7/mq_overview.7.html] provides a good overview of programming with POSIX message queues.

Under FreeBSD, you must load the {mqueuefs(5)}[http://freebsd.org/cgi/man.cgi?query=mqueuefs] kernel module before attempting to use POSIX message queues:

kldload mqueuefs

Our API matches the POSIX C API closely, see the RDoc for full API documentation. Here is an example of a process communicating with itself. In practice, processes that send will be different from processes that receive.

require 'posix_mq'
mq = POSIX_MQ.new("/foo", :rw)

# hello world
mq << "hello world"
puts mq.receive.first # => should print "hello world"

# non-blocking operation
mq.nonblock = true
begin
  mq.receive
rescue Errno::EAGAIN
end

trap(:USR1) { puts mq.receive.first }
mq.notify = :USR1
mq.send "fire USR1 handler"
# "fire USR1 handler" should be printed now

== Development

You can get the latest source via git from the following locations:

git://bogomips.org/ruby_posix_mq.git
git://repo.or.cz/ruby_posix_mq.git (mirror)

You may also browse the code from the web:

• https://bogomips.org/ruby_posix_mq.git
• http://repo.or.cz/w/ruby_posix_mq.git (gitweb)

Inline patches (from "git format-patch") to the mailing list are preferred because they allow code review and comments in the reply to the patch.

We will adhere to mostly the same conventions for patch submissions as git itself. See the Documentation/SubmittingPatches document distributed with git on patch submission guidelines to follow:

https://git.kernel.org/cgit/git/git.git/plain/Documentation/SubmittingPatches

Just don't mail the git list or maintainer with Ruby posix_mq patches.

== Contact

All feedback (bug reports, user/development discussion, patches, pull requests) go to the mailing list: mailto:[e-mail]

Send patches (from "git format-patch") with "git send-email" and do not send HTML email or attachments. We are very responsive to email and you will usually get a response within 24-72 hours.

Subscription is optional: mailto:[e-mail]

Read-only mail archives are available over HTTPS and NNTP:

https://bogomips.org/ruby-posix-mq/ nntp://news.public-inbox.org/inbox.comp.lang.ruby.posix-mq